CN118380847A - Deep ultraviolet laser device and generation method - Google Patents
Deep ultraviolet laser device and generation method Download PDFInfo
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- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
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Abstract
本发明公开了一种深紫外激光装置及生成方法，装置包括：依次连接的种子光源组件、放大组件及倍频组件；种子光源组件产生并输出种子光，种子光的波长为输出目标激光的波长的预设倍数；种子光的类型为单频连续光或单频脉冲光，波长为1480‑2160nm，光谱宽度不大于0.5nm；放大组件包括至少两个依次连接的全光纤结构放大器，用于接收并放大种子光的功率，输出高功率种子光；倍频组件用于基于预设倍数对高功率种子光进行多级频率放大，形成并输出目标激光，频率放大的级数不小于3，目标激光的波长为185‑270nm，目标激光的功率不小于1μW。本发明在预定波长附近实现各项功率和噪声等性能均达到最佳的深紫外激光输出。
The present invention discloses a deep ultraviolet laser device and a generation method, the device includes: a seed light source component, an amplifying component and a frequency doubling component connected in sequence; the seed light source component generates and outputs a seed light, the wavelength of the seed light is a preset multiple of the wavelength of the output target laser; the type of the seed light is a single-frequency continuous light or a single-frequency pulse light, the wavelength is 1480-2160nm, and the spectrum width is not more than 0.5nm; the amplifying component includes at least two all-fiber structure amplifiers connected in sequence, which are used to receive and amplify the power of the seed light and output high-power seed light; the frequency doubling component is used to perform multi-stage frequency amplification on the high-power seed light based on the preset multiple, form and output the target laser, the frequency amplification level is not less than 3, the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1μW. The present invention realizes the deep ultraviolet laser output with the best performance of various power and noise near the predetermined wavelength.
Description
Technical Field
The invention belongs to the technical field of lasers, and particularly relates to a deep ultraviolet laser device and a generation method.
Background
The concept of lasers was first proposed by gauss et al and later evolved into different types of gas, semiconductor and solid state lasers. The wavelength of the laser is gradually expanded from visible light to ultraviolet spectrum, such as 193nm laser, so as to meet the requirements of different application fields. Along with the continuous innovation of the laser in the aspects of output power, wavelength stability, beam quality and the like, the application field is gradually expanded. Among them, 193nm laser is used as a key device in the field of semiconductor manufacturing, and its main characteristics include: wavelength characteristics: 193nm is in the ultraviolet spectral range, has shorter wavelength, and can realize high-resolution pattern patterning. Optical design: the laser adopts special optical design, and can realize high-power and narrow-linewidth output. And (3) material selection: the laser medium is usually made of materials such as argon fluoride, lithium fluoride and the like, and can realize high-efficiency laser emission at 193nm wavelength. Application field: 193nm laser is widely applied to links such as photoetching technology, photoresist exposure and the like in semiconductor manufacturing.
As can be seen from the above, lasers with different wavelengths are widely used in different fields, and thus, there is a great demand for the accuracy of the generated laser wavelength and structural stability, for example, the patent CN105191026a discloses a laser for generating an output wavelength of about 193.4nm, which comprises a fundamental wave laser, an optical parameter generator, a fifth harmonic generator and a mixing module. The optical parameter generator coupled to the fundamental laser can generate a down-converted signal. The fifth harmonic generator, which may be coupled to the optical parameter generator or the fundamental laser, may generate fifth harmonics. The mixing module coupled to the optical parameter generator and the fifth harmonic generator may generate a laser output at a frequency equal to a sum of frequencies of the fifth harmonic and the down-converted signal. After four nonlinear frequency conversion is needed, the laser wavelength is converted from infrared to 193nm, the structure is complex, nonlinear frequency conversion processes such as optical parameter generation, frequency multiplication, sum frequency and the like are needed, and the cost and the scheme execution difficulty are improved.
Therefore, how to reduce the structural complexity and the difficulty of laser generation of a laser on the basis of improving the stability and accuracy of output laser is a problem to be solved by those skilled in the art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a deep ultraviolet laser device and a generation method. The deep ultraviolet laser output with optimal performances such as various powers, noise and the like can be realized near the preset wavelength.
In a first aspect, the present invention provides a deep ultraviolet laser apparatus, specifically including: the seed light source component, the amplifying component and the frequency doubling component are connected in sequence;
The seed light source component generates and outputs seed light, and the wavelength of the seed light is a preset multiple of the wavelength of the target laser output by the deep ultraviolet laser device;
The seed light is single-frequency continuous light or single-frequency pulse light, the wavelength of the seed light is 1480-2160nm, and the spectrum width of the seed light is not more than 0.5nm;
The amplifying assembly comprises at least two amplifiers which are connected in sequence, each amplifier is of an all-fiber structure and is used for receiving and amplifying the power of the seed light and outputting high-power seed light;
the frequency multiplication component is used for carrying out multistage frequency amplification on the high-power seed light based on preset multiples to form and output target laser, the stage number of the frequency amplification is not less than 3, the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W.
Further, the wavelength of the seed light is 1546.944 + -8 nm, and the wavelength of the target laser is 193.3680 + -1 nm.
Further, the seed light source component comprises one of a fiber laser, a semiconductor laser or a solid-state laser.
Further, the seed light source component further comprises a gain modulation module and/or an intensity modulation module.
Further, the amplifying assembly comprises a pre-amplifier and a main amplifier, and the pre-amplifier and the main amplifier are used for carrying out at least one-stage power amplification;
Each stage of all-fiber structure of the pre-amplifier and the main amplifier comprises: the optical combiner inputs pump light output by the pump diode into the gain optical fiber, amplifies the power of seed light input into the gain optical fiber, and outputs high-power seed light through the isolator;
the optical combiner is a wavelength division multiplexer of a single-mode fiber or a multi-cladding optical fiber combiner.
Further, the pre-amplifier and/or the main amplifier also comprises an intensity modulation module.
Further, the frequency multiplication assembly comprises a primary frequency multiplication module, a secondary frequency multiplication module and a tertiary frequency multiplication module which are sequentially connected, and the primary frequency multiplication module, the secondary frequency multiplication module and the tertiary frequency multiplication module are all used for amplifying at least twice the frequency.
Further, the primary frequency doubling module, the secondary frequency doubling module and the tertiary frequency doubling module comprise at least one frequency doubling element, the frequency doubling element comprises at least one of a nonlinear optical crystal and a nonlinear waveguide, the length of each frequency doubling element in the primary frequency doubling module and the secondary frequency doubling module is 1-70mm, and the length of each frequency doubling element in the tertiary frequency doubling module is 0.1-70mm;
the high-power seed light forms primary frequency multiplication laser after passing through a primary frequency multiplication module, the primary frequency multiplication laser forms secondary frequency multiplication laser after passing through a secondary frequency multiplication module, and the secondary frequency multiplication laser forms target laser after passing through a tertiary frequency multiplication module.
Further, the seed light is single-frequency continuous light, the first-stage frequency multiplication module, the second-stage frequency multiplication module and the third-stage frequency multiplication module are respectively a single-pass frequency multiplication component, a multi-pass frequency multiplication component or a resonance frequency multiplication component, the resonance frequency multiplication component comprises a frequency locking unit and at least one resonance frequency multiplication element, and the frequency locking unit is in the type of PDH frequency locking, HC frequency locking, lock in or jitter locking and the like.
Further, the deep ultraviolet laser device also comprises a frequency stabilizing component, and the frequency stabilizing component is connected with at least one of the seed light source component, the amplifying component and the frequency doubling component;
The frequency stabilization component comprises a reference source and a frequency stabilization unit, wherein the reference source comprises an atomic spectrum, a molecular spectrum, an ion spectrum, a crystal space hole burning, an optical reference cavity, an optical frequency comb, an optical fiber delay line, a laser source with constant frequency and the like, and the frequency stabilization component locks the output light of the seed light source component, the amplifying component or the frequency multiplication component with the reference source based on a constant frequency difference.
In a second aspect, the present invention further provides a deep ultraviolet laser generating method, which adopts the above deep ultraviolet laser device, and specifically includes the following steps:
Determining that the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W;
determining a preset multiple between the wavelength of the seed light and the wavelength of the target laser;
controlling a seed light source component to generate and output seed light, wherein the wavelength of the seed light is 1480-2160nm, and the spectrum width of the seed light is not more than 0.5nm;
Inputting seed light into an amplifying assembly, amplifying the seed light in the amplifying assembly in power, and outputting high-power seed light;
the high-power seed light enters a frequency multiplication component with the preset frequency amplification progression to carry out frequency amplification, the frequency amplification progression is not less than 3, and the target laser is formed and output.
The invention provides a deep ultraviolet laser device and a generating method, which at least comprise the following beneficial effects:
(1) The seed light source component, the amplifying component and the frequency doubling component which are sequentially connected can obtain high-performance seed light and high-power fundamental frequency light in a laser conventional wave band, and then the nonlinear frequency conversion technology is utilized to convert the wavelength, so that the deep ultraviolet laser output with optimal performances such as various powers, noise and the like is realized at a target wavelength (near 193 nm).
(2) The single-frequency fixed external cavity semiconductor laser has the characteristics of compact structure, good stability, narrow linewidth and large modulation bandwidth, and has great improvement effect on the environment interference resistance capability, laser linewidth, power stability and laser wavelength locking effect of the whole deep ultraviolet laser device.
(3) The amplifying components are all optical fiber structures, and the pre-amplifier and the main amplifier have the characteristics of high conversion efficiency, compact structure and difficult influence by external environment, can amplify the power of seed light emitted by the seed light source component from milliwatt level to tens of watt level, and can optimize or maintain the intensity noise and the frequency noise of the seed light to obtain low-noise high-power seed light.
(4) The wavelength of laser can be converted from a mature 1.5 mu m wave band of a seed light technology and a high-power laser technology to a deep ultraviolet wave band through multistage frequency multiplication formed by the frequency multiplication component, so that the problem that a laser gain medium is lacking in the deep ultraviolet wave band is effectively solved, and particularly, a single-frequency light source with high coherence, narrow linewidth and low noise can be obtained near 193 nm. And the resonant frequency doubling technology is adopted, so that the frequency doubling efficiency can be improved, and the requirement on fundamental frequency optical power is reduced, thereby effectively improving the overall conversion efficiency.
Drawings
FIG. 1 is a schematic diagram of a deep ultraviolet laser device according to the present invention;
FIG. 2 is a schematic diagram of an all-fiber structure in an amplifying assembly according to an embodiment of the present invention;
Fig. 3 is a schematic diagram of a frequency stabilizing module according to an embodiment of the present invention;
fig. 4 is a schematic flow chart of a deep ultraviolet laser generating method provided by the invention.
Detailed Description
In order to better understand the above technical solutions, the following detailed description will be given with reference to the accompanying drawings and specific embodiments. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, the "plurality" generally includes at least two.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such product or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a commodity or device comprising such elements.
As shown in fig. 1, the present invention provides a deep ultraviolet laser device, which specifically includes: the seed light source component, the amplifying component and the frequency doubling component are connected in sequence;
The seed light source component generates and outputs seed light, and the wavelength of the seed light is a preset multiple of the wavelength of the target laser output by the deep ultraviolet laser device;
The seed light is single-frequency continuous light or single-frequency pulse light, the wavelength of the seed light is 1480-2160nm, and the spectrum width of the seed light is not more than 0.5nm;
The amplifying assembly comprises at least two amplifiers which are connected in sequence, each amplifier is of an all-fiber structure and is used for receiving and amplifying the power of the seed light and outputting high-power seed light;
the frequency multiplication component is used for carrying out multistage frequency amplification on the high-power seed light based on preset multiples to form and output target laser, the stage number of the frequency amplification is not less than 3, the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W.
The seed light source component comprises one of a fiber laser, a semiconductor laser or a solid laser.
The laser type emitted by the seed light source component can be single-frequency continuous light or single-frequency pulse light according to the emission mode classification of the light source component. Single frequency continuous light refers to continuous laser light of a single longitudinal mode. The seed light source assembly further includes a gain modulation module and/or an intensity modulation module. The single-frequency continuous laser can also be converted into single-frequency pulse light by gain modulation, intensity modulation or other modes. The single-frequency pulse light is to convert the single-frequency continuous light into a pulse laser by modulating the single-frequency continuous light. The specific modulation method includes pumping signal modulation of the seed light or time domain intensity modulation of the seed light after the seed light is output through an intensity modulator.
Taking the seed light source component to emit single-frequency continuous light as an example:
The fiber laser may be a single frequency distributed feedback fiber laser, which is an all-fiber structure that produces seed light by directly writing a fiber bragg grating with a phase shift on the erbium-doped fiber. Specifically, the absorption coefficient of the fiber core of the erbium-doped fiber at 1530nm is not less than 2.5dB/m, the length of the grating is 25-55mm, the phase shift value is 0.2-1.8 pi, the refractive index modulation period in the grating is 981.7-1092.3nm, the phase shift position is positioned in the range of shifting the grating length from the center of the grating to two sides by 0-25% of the length of the grating, and when the phase shift is not positioned in the center of the grating region, the deflection end of the phase shift is the main laser output end. The wavelength range of the direct output laser of the grating is 1546.944 +/-8 nm, the linewidth is smaller than 10kHz, the power is larger than 50 mu W, and the output laser is polarized light.
The single frequency distributed feedback fiber laser consists of a fiber Bragg grating (DFB FBG) with phase shift, a Pump diode (Pump), a Wavelength Division Multiplexer (WDM), an isolator (Isolator) and an electro-optic modulator (EOM) which are inscribed on an erbium-doped fiber. The standard structure is backward pumping (forward pumping and bi-directional pumping can also be used). The wavelength of the pump diode is 900-1030nm or 1450-1540nm, and the power is more than 100mW. The pump light generated by the pump diode enters the grating through the wavelength division multiplexer to generate seed light. The generated seed light passes through the wavelength division multiplexer and then passes through the isolator to realize output. The seed light output by the isolator can be amplified in power, the amplified power is larger than 5mW, and the output seed light is then input into the preamplifier through one or more electro-optical modulators. Wherein the electro-optic modulator is used for generating sidebands for locking cavity modes of the resonant cavity and laser frequencies in subsequent resonant frequency doubling.
The types of semiconductor lasers are two types: the single-frequency fixed external cavity semiconductor laser is based on a semiconductor gain chip, and realizes seed light output in an external feedback and filtering mode.
The transmission frequency of the filtering component and the gain wave band of the gain chip determine the precise wavelength for generating laser, and the PN junction structure and the applied current of the gain chip and the resonant cavity structure determine the power for outputting seed light. The structural parameters of the gain chip and the transmission peak width of the filtering component determine the line width of seed light, and the total cavity length is smaller than 20mm; the single-frequency fixed external cavity semiconductor laser can also comprise an electro-optic modulator, and the seed light output can pass through the electro-optic modulator as required after passing through the isolator, wherein the electro-optic modulator is used for generating sidebands and locking cavity modes of the resonant cavity and laser frequency in subsequent resonant frequency multiplication, namely PDH frequency locking in the resonant frequency multiplication. The output laser wavelength range of the single-frequency fixed external cavity semiconductor laser is 1480-2160nm, preferably 1546.944 +/-8 nm, the line width is smaller than 20kHz, the power is larger than 5mW, and the output laser is polarized light. The high reflection film reflectivity of the gain chip is more than 90%; the single transmission peak transmission bandwidth of the filtering component is not more than 0.5nm; the reflectivity of the output part is 1-99%. The gain chip directly outputs power not smaller than 0.5mW when the current is 300 mA.
And secondly, the single-frequency adjustable external cavity semiconductor laser is based on a laser diode with a built-in semiconductor gain chip, and seed light output is realized in an external feedback and filtering mode. The structure of the light source comprises a Laser Diode (LD), a plurality of lenses, an optical filter, a half mirror, an output isolator and an electro-optic modulator. The filter transmission frequency and the gain band of the laser diode determine the exact wavelength at which the laser is generated, and the direct output power of the laser diode is greater than 1 mu W at 300 mA. Tuning of the laser wavelength can be achieved by adjusting the placement angle of the optical filter. The PN junction structure and applied current of the gain chip in the laser diode and the resonant cavity structure determine the power of the output seed light. The structural parameters of the gain chip and the transmission peak width of the optical filter determine the line width of seed light, and the total cavity length is smaller than 20mm. The output laser has a wavelength range of 1546.944 +/-8 nm, a linewidth of less than 100kHz, a power of more than 5mW, and is polarized light, the output laser is output after passing through the isolator, and can pass through the electro-optic modulator according to the requirement after output, and the electro-optic modulator is used for generating sidebands and can be used for locking cavity modes of the resonant cavity and laser frequency in subsequent resonant frequency multiplication.
Multiple frequency multiplication is required from the seed light to the target laser, but the laser power is reduced during the frequency multiplication by the frequency multiplication means, and thus the laser power needs to be amplified before the frequency multiplication is performed.
The invention is described by taking seed light with any wavelength within 1546.944 +/-8 nm output by a seed light source component as an example, firstly, the seed light is subjected to power pre-amplification by a pre-amplifier, the output power can be more than 100mW, and then the seed light enters into main amplification to be further subjected to power amplification, and the output power can reach 90W.
Then, the seed light sequentially passes through multiple stages of frequency multiplication, for example, when three stages of frequency multiplication are adopted, the seed light firstly enters a first stage of frequency multiplication module, the fundamental frequency light and the frequency multiplication light pass through the frequency multiplication crystal for a limited time, the output power can reach 60W, the wavelength is in the range of 773.472 +/-4 nm, the output power of a second stage of frequency multiplication module can reach 45W, the wavelength is in the range of 386.736 +/-2 nm, the three stages of frequency multiplication module is resonant frequency multiplication, the output power is larger than 1 mu W, and the wavelength is in the range of 193.368+/-1 nm.
The third-level frequency doubling module is provided with a cavity locking module to realize the matching of the cavity mode of the resonant frequency doubling cavity and the laser frequency, and is also provided with a frequency stabilizing component to lock the laser frequency of the seed light source, and finally the output 193nm laser frequency is locked.
The reasons for the power reduction during frequency doubling mainly include:
1. Nonlinear efficiency: frequency multiplication is a nonlinear optical process, and two fundamental frequency photons are combined into one frequency-multiplied photon, the efficiency of which is lower than 100%, because part of fundamental frequency photons cannot successfully participate in the frequency-multiplication process, resulting in that even if the input fundamental frequency power is high, the output frequency-multiplied power is reduced due to the limitation of conversion efficiency.
2. Phase matching conditions: in order to achieve efficient frequency doubling, certain phase matching conditions must be met, which require matching of propagation speeds of the fundamental frequency light and the frequency-doubled light in the nonlinear optical crystal. If the phase matching condition is not satisfied, the frequency multiplication efficiency thereof is lowered, resulting in a decrease in output power.
3. Thermal effect: high power lasers generate heat when transported in nonlinear optical crystals, resulting in an increase in the crystal temperature. Temperature variations affect the refractive index and nonlinear coefficient of the crystal, thereby affecting frequency doubling efficiency. In some cases, thermal effects may cause crystal damage, further reducing frequency doubling efficiency.
4. Absorption and scattering losses: the nonlinear optical crystal itself may have a certain absorption to fundamental frequency light or frequency-doubled light, and impurities or defects inside the crystal may also cause scattering loss. These losses reduce the optical energy passing through the crystal and thus reduce the frequency multiplied output power.
5. Laser damage threshold: nonlinear optical crystals have a certain threshold of tolerance limit for laser power beyond which the crystal may be damaged, such as by optical breakdown or thermally induced damage. Such damage may damage the crystal structure, reduce frequency multiplication efficiency, and may result in a reduction in output power.
6. Focusing and beam quality: the focusing condition of the laser beam and the beam quality also affect the frequency doubling efficiency. If the focusing is not fine enough or the beam quality is not good, uneven distribution of light energy in the crystal may be caused, thereby reducing frequency doubling efficiency.
Based on the problem of power reduction in the frequency doubling process, the invention sets an amplifying component before the frequency doubling component to realize laser power amplification.
Specifically, the amplifying assembly comprises a pre-amplifier and a main amplifier, the seed optical power amplified by the pre-amplifier is not less than 100mW, and the seed optical power amplified by the main amplifier is not more than 90W;
The pre-amplifier and the main amplifier are all fiber structures with at least one stage of amplification. As shown in fig. 2, each stage of amplifying all-fiber structure includes: pump diode, beam combiner, gain fiber, isolator. The beam combiner inputs the pump light output by the pump diode into the gain fiber, amplifies the seed light input into the gain fiber, and if more pump light remains, the pump filter is needed to filter the redundant pump light, and the high-power seed light is output through the isolator after the amplification;
The length of the gain fiber in each stage of amplification is not more than 30m, the beam combiner is a wavelength division multiplexer of a single-mode fiber or a multimode fiber beam combiner, and the transmittance of pump light and seed light in the wavelength division multiplexer is not less than 80 percent.
In the all-fiber structure, the pump diode is an energy source of the laser, and the particle number inversion distribution is realized by emitting near infrared light, so that necessary energy is provided for the generation of laser. The beam combiner is used for effectively combining the pump light and the seed light so that the pump light energy enters the gain fiber. The beam combiner can bear high-power pump light, and meanwhile, the transmission efficiency of the seed light is maintained. The gain fiber is a core part for realizing power amplification, and is internally doped with rare earth elements capable of amplifying optical signals. When the pump light is absorbed, rare earth ions in the gain fiber can transition from an excited state to a ground state, and photons with the same frequency as the seed light are released, so that the passing seed light is amplified. The pump filter is used for filtering out unnecessary pump light in the laser output. Because the wavelength of the pump light is different from the wavelength of the laser output, the pump filter can ensure that only the laser output is transmitted, and the pump light is effectively filtered, so that the pump light is prevented from interfering with a system or an application. An isolator is an optical element that ensures that the laser light propagates in only one direction, preventing reflection of the laser light back to the gain fiber or pump diode, which can cause instability or compromise the efficiency of the laser.
In deep ultraviolet laser devices, a pre-amplifier is used to amplify the power of the seed light to a moderate level, which can improve efficiency without having an excessive impact on the device stability. If the seed optical power is directly amplified to a very high level, thermal management problems may occur, especially in the gain medium, which may affect the normal operation of the amplifier, even burn out the amplifier. By staged amplification, the power can be increased stepwise without exceeding the thermal damage threshold of the medium.
There is an associative correspondence in the type settings of the synergistic fiber, pump diode, combiner. When the gain fiber is erbium-doped single-clad fiber, the pump diode outputs single-mode fiber, the power is larger than 200mW, the wavelength is in the range of 900-1030nm and 1450-1540nm, the gain fiber absorbs more than 0.5dB/m at the core of 1530nm, the beam combiner is a wavelength division multiplexer, the pump light transmittance is larger than 80%, and the signal light transmittance is larger than 80%;
When the gain fiber is erbium-doped double-cladding fiber, the pump diode outputs by multimode fiber, the power is more than 800mW, the wavelength is in the range of 900-1030nm and 1450-1540nm, and the absorption of the gain fiber at 1530nm cladding is more than 0.16dB/m; the pump light transmittance of the beam combiner is more than 80%, and the signal light transmittance is more than 80%.
In a certain embodiment, for the main amplifier, the gain fiber is erbium-doped double-clad fiber, the pump diode is multimode fiber output, the power is more than 5W, the wavelength is in the range of 900-1030nm and 1450-1540nm, and the absorption of the gain fiber at 1530nm cladding is more than 0.16dB/m; the pump light transmittance of the beam combiner is more than 80%, the signal light transmittance is more than 80%, and the fiber cores of the gain fiber and the energy-transmitting fiber are more than or equal to 8 mu m.
The frequency multiplication assembly specifically comprises a primary frequency multiplication module, a secondary frequency multiplication module and a tertiary frequency multiplication module which are sequentially connected, and the primary frequency multiplication module, the secondary frequency multiplication module and the tertiary frequency multiplication module are all used for amplifying at least twice the frequency.
The first-stage frequency multiplication module and the second-stage frequency multiplication module are single-pass frequency multiplication components, multi-pass frequency multiplication components or resonance frequency multiplication components, the first-stage frequency multiplication module comprises at least one first frequency multiplication element, the length of each first frequency multiplication element is 1-70mm, and the first frequency multiplication element comprises at least one of nonlinear optical crystals and nonlinear waveguides, such as PPLN, KDP, KTP, LBO, BBO, CLBO, PPLN, PPSLT, PPKTP, PPKDP, CLT and the like.
The high-power seed light forms primary frequency doubling laser after passing through the primary frequency doubling module, and the power of the primary frequency doubling laser is not more than 60W. The first-order frequency multiplication laser forms second-order frequency multiplication laser after passing through a second-order frequency multiplication module, and the second-order frequency multiplication module comprises at least one second frequency multiplication element, and the length of each second frequency multiplication element is 1-70mm. The second frequency doubling element likewise comprises at least one of a nonlinear optical crystal, a nonlinear waveguide, e.g., LBO, BBO, CLBO, PPSLT, NSBBF, etc. The power of the second-order frequency multiplication laser is not more than 45W.
The high-power seed light output by the main amplifier is firstly subjected to primary frequency multiplication by a primary frequency multiplication module, and the wavelength of the high-power seed light is converted from a 1546.944 +/-8 nm range to 773.472 +/-4 nm. The primary frequency multiplication module is single-pass or multi-pass frequency multiplication, the fundamental frequency light and the frequency multiplication light pass through the frequency multiplication crystal or the nonlinear waveguide (the first frequency multiplication element) for a limited time, and frequency conversion occurs when passing through the frequency multiplication crystal or the nonlinear waveguide each time. The incidence and emergence surfaces of the frequency doubling crystal or the nonlinear waveguide are plated with high-transmittance films or are subjected to Brewster angle cutting treatment, and the transmittance is more than 95%. The primary frequency multiplication module can comprise one or more frequency multiplication crystals and nonlinear waveguides, and each frequency multiplication crystal or nonlinear waveguide is subjected to temperature control to improve the frequency conversion efficiency and the output power stability. The specific structure can be cascade, folding, cascade plus folding, etc. The maximum value of the output power of the first-order frequency-doubled laser is 60W.
The second-level frequency multiplication module converts the wavelength of the seed light passing through the first-level frequency multiplication module from 773.472 +/-4 nm to 386.736 +/-2 nm. The frequency multiplication crystal is a core component for realizing frequency multiplication and is a nonlinear optical medium. In the frequency doubling crystal, two fundamental frequency photons (lasers) are combined into one frequency doubling photon through nonlinear interaction, and the frequency of the frequency doubling photon is twice that of the original fundamental frequency light, so that second harmonic generation is realized. Nonlinear waveguides can be used to guide the beam, ensuring that the beam remains properly shaped and sized.
The three-stage frequency doubling module is a single-pass, multi-pass or resonant frequency doubling component and comprises at least one third frequency doubling element, and the length of each third frequency doubling element is 0.1-70mm; the third frequency doubling element also comprises at least one of a nonlinear optical crystal and a nonlinear waveguide, such as KBBF, ABF and the like, and the second-order frequency doubling laser forms target laser after passing through the third-order frequency doubling module, wherein the power of the target laser is larger than 1 mu W. The first frequency doubling element, the second frequency doubling element and the third frequency doubling element are nonlinear optical crystals and nonlinear waveguides, but the frequency conversion wave bands are different, so that the types of the frequency doubling elements are different.
The incident and emergent surfaces of the third frequency tripling elements are plated with high-transmittance films or cut at Brewster angle, the fundamental frequency light transmittance is required to be greater than 95%, the frequency doubling light transmittance is greater than 90%, and each third frequency tripling element in the third frequency tripling module is subjected to temperature control to improve the frequency conversion efficiency and the output power stability. When the three-stage frequency doubling module is a resonant frequency doubling component, a resonant cavity of the resonant frequency doubling component contains PZT (piezoelectric ceramics), a PDH technology is adopted to lock a resonant cavity mode and laser frequency, and the maximum value of the output 386.736 +/-2 nm frequency doubling optical power is 45W.
The third-level frequency multiplication module converts the wavelength of the seed light passing through the second-level frequency multiplication module from 386.736 +/-2 nm to 193.368+/-1 nm, and the fundamental frequency light oscillates in the resonant cavity to improve the power density by adopting a resonant frequency multiplication mode. The type of the resonant frequency doubling element is KBBF (lithium triborate crystal), the length is in the range of 15-35mm, the incident and emergent surfaces are plated with high-permeability films or cut at Brewster angle, and the light transmittance of fundamental frequency light and frequency doubling light is more than 95%. The resonant cavity contains PZT (piezoelectric ceramics), the PDH technology is adopted to lock the cavity mode and the laser frequency, and the output 193.368+/-1 nm frequency multiplication optical power is larger than 5mW.
When the laser of the seed light source component is a single-frequency distributed feedback fiber laser, an EOM (electro-optical modulator) in the seed light source component is modulated to generate a frequency sideband, and the cavity mode of the resonant cavity and the laser frequency are locked through a PDH (Pound-Drever-Hall) technology, so that stable and efficient frequency multiplication laser output is realized.
When the laser of the seed light source component is a single-frequency fixed external cavity semiconductor laser, a single-frequency adjustable external cavity semiconductor laser or a single-frequency distributed feedback semiconductor laser, frequency sidebands are generated by modulating gain chip current or EOM in the seed light source component, error signals are formed, and the cavity mode and the laser frequency of the resonant cavity are locked by changing the length of the resonant cavity through PDH technology and real-time tuning of PZT, so that stable and efficient frequency multiplication laser output is realized.
The deep ultraviolet laser device also comprises a frequency stabilizing component which is connected with at least one of the seed light source component, the amplifying component and the frequency doubling component;
The frequency stabilization assembly comprises a reference source and a frequency stabilization unit, wherein the reference source comprises an absorption tank, an optical reference cavity, an optical frequency comb, an optical fiber delay line and a laser source with constant frequency, and the frequency stabilization assembly unit locks the output light of the seed light source assembly, the amplifying assembly or the frequency multiplication assembly with the reference source based on constant frequency difference.
In a certain embodiment, the frequency stabilization component is connected to the seed light source component, the frequency stabilization unit is connected to the seed light source component, the reference source generates reference frequency laser with preset wavelength and inputs the reference frequency laser to the frequency stabilization unit, and the frequency stabilization unit controls the seed light source component to output seed light with stable wavelength based on the reference frequency laser.
As shown in fig. 3, the frequency stabilizing unit includes: the device comprises a frequency stabilization beam combiner, a first photoelectric detector (PD 1), a frequency divider, a frequency phase detector and a first servo element (servo 1) which are connected in sequence;
The reference source comprises a reference laser, a beam splitter, an optoelectronic modulator (EOM), an absorption cell, a second photoelectric detector (PD 2), a mixer, a low-pass filter and a second servo element (servo 2) which are sequentially connected in a ring shape, wherein the beam splitter is also connected with a frequency-stabilizing beam combiner, and the optoelectronic modulator is also connected with the mixer;
The reference laser outputs reference frequency laser, the reference frequency laser forms a first path of reference frequency laser and a second path of reference frequency laser through the beam splitter, the first path of reference frequency laser enters the frequency-stabilizing beam combiner, and the second path of reference frequency laser returns to the reference laser after passing through the photoelectric modulator, the absorption tank, the second photoelectric detector, the mixer, the low-pass filter and the second servo element, so that the reference laser outputs the reference frequency laser which is all the preset wavelength laser with locked wavelength;
the laser with preset wavelength and the seed light form constant frequency difference at the phase frequency detector.
The frequency stabilizing component is used for locking the wavelength of laser output by the seed light source component, so that the locking of the 193nm laser output wavelength of the final deep ultraviolet laser is realized, and the wavelength after locking is within the range of 193.368+/-1 nm.
In the frequency stabilizing assembly, a frequency stabilizing combiner is used to combine the light beams from different sources into a single light beam. The beam splitter is used to split the beam into multiple portions, each of which may be used for different measurement or control purposes. The sensors for detecting light intensity of the PD1 and the PD2 may convert the optical signals into electrical signals for subsequent operations. The frequency divider is used to divide the frequency of the laser light into a lower frequency. The phase frequency detector is used for measuring and comparing the frequency and phase difference of two light waves. For ensuring stability of the laser and locking to a specific frequency. The error signal generated by the frequency divider and the reference signal is input to servo 1. An electro-optic modulator is a device that changes the nature of an optical wave by applying a voltage, and may be used to modulate the frequency, phase, or intensity of a laser.
The absorption cell may be selected from HCN absorption cells, which are containers containing a specific absorption medium for absorbing light of a specific wavelength. HCN molecules have specific absorption lines that correspond to specific spectral wavelengths. When the frequency of the laser matches one of these absorption lines, the laser will be absorbed by the HCN molecules. By precisely controlling the frequency of the laser light, saturated absorption of these absorption lines can be achieved, thereby reducing the loss of the laser light in the absorption cell.
The mixer is used for mixing the electric signal output by the PD2 with the modulated signal after phase shifting to generate new frequency components (one frequency component is the sum of the two components and one frequency component is the difference of the two components), and then, through low-pass filtering, only the electric signal with the difference of the two frequencies is left. The servo 1 and the servo 2 are part of automatic control and are used for adjusting the seed light source assembly according to the feedback signal so as to keep the stability and the accuracy of laser. The low-pass filter is used for filtering high-frequency noise, retaining low-frequency signals and ensuring the smoothness and stability of system control signals.
The seed light source component is processed by the frequency stabilization component as follows:
Seed light source components and reference lasers in a deep ultraviolet laser with the target laser of 193nm can realize seed light output near 1546.944 nm. The seed light output by the reference laser is divided into two paths through the beam splitter, wherein the first path and the seed light source component output a combined beam, and the second path passes through the EOM. The EOM receives the modulated signal such that the splitting of the reference laser produces frequency sidebands after passing. The laser after EOM enters into an HCN absorption tank, and the corresponding wavelength of a2 mu 3P6 line in an H 13C14 N molecular absorption spectrum is 1546.690nm.
The laser signal output by the absorption cell is converted into an electric signal by the PD2, then mixed with a modulation signal to obtain a sum frequency signal and a difference frequency signal, the difference frequency signal is fed back to the servo 2 after low-pass filtering, and then the servo 2 outputs a frequency locking signal to the reference laser, so that the laser wavelength of the reference laser can be locked at 1546.690nm.
The reference laser and the seed light source component after the wavelength locking are combined into the same optical fiber through the frequency stabilization beam combiner and then input into the PD1, so that beat frequency signals with two laser frequency differences are obtained, and then the beat frequency signals are subjected to frequency division by eight frequency dividers to be subjected to frequency reduction. The reference signal outputs a stable signal with the frequency of 4GHz, the stable signal and the beat signal after frequency reduction are input into the frequency and phase discriminator together, an error signal is generated and input into the servo 1, the servo 1 outputs a frequency locking signal to the seed light source component, and the laser frequency of the seed light source component is locked. At this time, the difference between the output laser frequencies of the seed light source component and the reference laser is locked at 32GHz. Since the reference laser wavelength is locked at 1546.690nm, the seed light source assembly output seed light wavelength can be locked at 1546.944nm when the seed light source assembly laser frequency is less than the reference laser.
The frequency stabilizing component can be connected to the amplifying component and the frequency doubling component, namely, the frequency stabilizing component can search a reference source in the range of fundamental frequency light, frequency doubling laser of the primary frequency doubling module, frequency doubling laser of the secondary frequency doubling module and frequency doubling laser of the tertiary frequency doubling module, feed back and lock fundamental frequency light wavelength, and finally realize the wavelength locking of any level of seed light. The specific principle and connection manner are similar to those of the seed light source assembly, and will not be described herein.
The deep ultraviolet laser device provided by the invention can also process single-frequency pulse light emitted by the seed light source component (the seed light source component at the moment comprises a seed light laser and an intensity modulator) to obtain target laser, and a specific light path process is as follows:
the seed light laser (which can be one of a fiber laser, a semiconductor laser or a solid laser) can realize seed light output, the wavelength range is 1546.944 +/-8 nm, the spectrum width is smaller than 0.5nm, and the power is larger than 1 mu W.
The intensity modulator may be an acousto-optic modulator, an electro-optic intensity modulator, a semiconductor optical amplifier, or the like, and converts laser light output from the seed optical laser into pulse laser light in combination with a modulation signal. When the electro-optic intensity modulator is adopted, the laser output by the seed light laser can be converted into single-frequency pulse laser with the pulse width of 3ns and the repetition frequency of 20 MHz.
The pre-amplifier and the main amplifier are all-fiber structures amplified by at least one stage, and each stage of all-fiber structure comprises: the device comprises a pump diode, a beam combiner, a gain optical fiber and an isolator, wherein the beam combiner inputs pump light output by the pump diode into the gain optical fiber, power amplification is carried out on single-frequency pulse laser input into the gain optical fiber, if more pump light exists, the pump light still needs to be filtered by the pump filter, and high-power seed light is output by the isolator after amplification;
the length of the gain fiber is not more than 30m, the beam combiner is a wavelength division multiplexer of a single-mode fiber or a multimode fiber beam combiner, and the transmittance of pump light and single-frequency pulse laser in the wavelength division multiplexer is not less than 80%.
When the gain fiber is erbium-doped single-clad fiber, the pump diode outputs a single-mode fiber, the power is larger than 200mW, the wavelength is in the range of 900-1030nm and 1450-1540nm, the gain fiber absorbs more than 0.5dB/m at the 1530nm fiber core, the beam combiner is a wavelength division multiplexer, the pump light transmittance is larger than 80%, and the single-frequency pulse laser transmittance is larger than 80%; when the gain fiber is erbium-doped double-cladding fiber, the pump diode outputs the multimode fiber, the power is more than 800mW, the wavelength is in the range of 900-1030nm and 1450-1540nm, and the absorption of the gain fiber at 1530nm cladding is more than 0.16dB/m; the pump light transmittance of the beam combiner is more than 80%, and the single-frequency pulse laser transmittance is more than 80%.
The gain fiber of the main amplifier is erbium-doped double-cladding fiber, the pump diode outputs by multimode fiber, the power is more than 5W, the wavelength is in the range of 900-1030nm and 1450-1540nm, and the absorption of the gain fiber is more than 0.16dB/m at 1530nm cladding; the pump light transmittance of the beam combiner is more than 80%, the single-frequency pulse laser transmittance is more than 80%, and the cores of the gain fiber and the energy-transmitting fiber are more than or equal to 10 mu m.
The frequency doubling component can comprise a primary frequency doubling module, a secondary frequency doubling module and a tertiary frequency doubling module which are sequentially connected, and the primary frequency doubling module, the secondary frequency doubling module and the tertiary frequency doubling module are all used for frequency doubling amplification.
The high-power seed light output by the main amplifier is firstly subjected to a first-stage frequency multiplication module by the first-stage frequency multiplication module, and the wavelength of the high-power seed light is converted from a 1546.944 +/-8 nm range to 773.472 +/-4 nm. The primary frequency multiplication module is single-pass or multi-pass frequency multiplication, the fundamental frequency light and the frequency multiplication light pass through the frequency multiplication crystal or the nonlinear waveguide (the first frequency multiplication element) for a limited time, and frequency conversion occurs when passing through the frequency multiplication crystal or the nonlinear waveguide each time. The incidence and emergence surfaces of the frequency doubling crystal or the nonlinear waveguide are plated with high-transmittance films, and the transmittance is more than 95%. The primary frequency multiplication module can comprise one or more frequency multiplication crystals and nonlinear waveguides, and each frequency multiplication crystal or nonlinear waveguide is subjected to temperature control to improve the frequency conversion efficiency and the output power stability. The specific structure can be cascade, folding, cascade plus folding, etc. The maximum value of the output power of the first-order frequency-doubled laser is 60W. The second-level frequency multiplication module converts the wavelength of the seed light passing through the first-level frequency multiplication module from 773.472 +/-4 nm to 386.736 +/-2 nm. The frequency multiplication crystal or the nonlinear waveguide is a core component for realizing frequency multiplication and is a nonlinear optical medium. In the frequency doubling crystal, two fundamental frequency photons (lasers) are combined into one frequency doubling photon through nonlinear interaction, and the frequency of the frequency doubling photon is twice that of the original fundamental frequency light, so that second harmonic generation is realized. Nonlinear waveguides can be used to guide the beam, ensuring that the beam remains properly shaped and sized.
The three-stage frequency multiplication module is a single-pass frequency multiplication component or a multi-pass frequency multiplication component and comprises at least one third-stage frequency multiplication element, and the length of each third-stage frequency multiplication element is 0.1-70mm; the resonant frequency doubling element in the three-stage frequency doubling module is a nonlinear optical crystal or nonlinear waveguide, the two-stage frequency doubling laser forms target laser after passing through the three-stage frequency doubling module, and the power of the target laser is not less than 1 mu W.
The deep ultraviolet laser device provided by the invention can at least achieve the following effects through the seed light source component, the frequency stabilizing component, the preamplifier, the main amplifier, the primary frequency doubling module, the secondary frequency doubling module and the tertiary frequency doubling module which are arranged:
(1) The seed light source component, the amplifying component and the frequency doubling component which are sequentially connected can obtain high-performance seed light in a laser conventional wave band, then the nonlinear frequency conversion technology is utilized to convert the wavelength, and the frequency stabilizing component is combined to lock the laser wavelength, so that the optimal deep ultraviolet laser output of various performances such as various powers, noise and the like can be realized at a target wavelength (near 193 nm).
(2) The single-frequency fixed external cavity semiconductor laser has the characteristics of compact structure, good stability, narrow linewidth and large modulation bandwidth, and has great improvement effect on the environment interference resistance capability, laser linewidth, power stability and laser wavelength locking effect of the whole laser device.
(3) The amplifying assembly is of an all-fiber structure, and the pre-amplifier and the main amplifier have the characteristics of high conversion efficiency, compact structure and difficult influence by external environment, can amplify the power of seed light emitted by the seed light source assembly from milliwatt level to tens of watt level, and can optimize or maintain the intensity noise of the seed light to obtain low-noise high-power seed light.
(4) The multi-stage frequency multiplication formed by the frequency multiplication component can convert the wavelength of laser from a 1.5 mu m wave band of seed light technology and high-power laser to a deep ultraviolet wave band, so that the problem that a laser gain medium is lacking in the deep ultraviolet wave band is effectively solved, and particularly, a single-frequency light source with high coherence, narrow line width and low noise can be obtained near 193 nm. And the resonant frequency doubling technology is adopted, so that the frequency doubling efficiency can be improved, and the requirement on fundamental frequency optical power is reduced, thereby effectively improving the overall conversion efficiency.
As shown in fig. 4, the present invention further provides a deep ultraviolet laser generating method, which adopts the above deep ultraviolet laser device, and specifically includes the following steps:
Determining that the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W;
determining a preset multiple between the wavelength of the seed light and the wavelength of the target laser;
controlling a seed light source component to generate and output seed light, wherein the wavelength of the seed light is 1480-2160nm;
Inputting seed light into an amplifying assembly, amplifying the seed light in the amplifying assembly in power, and outputting high-power seed light;
the high-power seed light enters a frequency multiplication component with the preset frequency amplification progression to carry out frequency amplification, the frequency amplification progression is not less than 3, and the target laser is formed and output.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. The deep ultraviolet laser device is characterized by comprising the following components in detail: the seed light source component, the amplifying component and the frequency doubling component are connected in sequence;
The seed light source component generates and outputs seed light, and the wavelength of the seed light is a preset multiple of the wavelength of the target laser output by the deep ultraviolet laser device;
The seed light is single-frequency continuous light or single-frequency pulse light, the wavelength of the seed light is 1480-2160nm, and the spectrum width of the seed light is not more than 0.5nm;
The amplifying assembly comprises at least two amplifiers which are connected in sequence, each amplifier is of an all-fiber structure and is used for receiving and amplifying the power of the seed light and outputting high-power seed light;
the frequency multiplication component is used for carrying out multistage frequency amplification on the high-power seed light based on preset multiples to form and output target laser, the stage number of the frequency amplification is not less than 3, the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W.
2. The deep ultraviolet laser device of claim 1, wherein the seed light source assembly comprises one of a fiber laser, a semiconductor laser, or a solid state laser.
3. The deep ultraviolet laser device of claim 1 or 2, wherein the seed light source assembly further comprises a gain modulation module and/or an intensity modulation module.
4. The deep ultraviolet laser device of claim 1, wherein the amplifying assembly comprises a pre-amplifier and a main amplifier, each of the pre-amplifier and the main amplifier performing at least one stage of power amplification;
Each stage of all-fiber structure of the pre-amplifier and the main amplifier comprises: the optical combiner inputs pump light output by the pump diode into the gain optical fiber, amplifies the power of seed light input into the gain optical fiber, and outputs high-power seed light through the isolator;
the optical combiner is a wavelength division multiplexer of a single-mode fiber or a multi-cladding optical fiber combiner.
5. The deep ultraviolet laser device of claim 1, further comprising an intensity modulation module in the pre-amplifier and/or the main amplifier.
6. The deep ultraviolet laser device of claim 1, wherein the frequency doubling component comprises a primary frequency doubling module, a secondary frequency doubling module and a tertiary frequency doubling module which are sequentially connected, and the primary frequency doubling module, the secondary frequency doubling module and the tertiary frequency doubling module all amplify at least twice the frequency.
7. The deep ultraviolet laser device according to claim 6, wherein the primary frequency doubling module, the secondary frequency doubling module and the tertiary frequency doubling module each comprise at least one frequency doubling element, the frequency doubling elements comprise at least one of nonlinear optical crystals and nonlinear waveguides, the length of each frequency doubling element in the primary frequency doubling module and the secondary frequency doubling module is 1-70mm, and the length of each frequency doubling element in the tertiary frequency doubling module is 0.1-70mm;
the high-power seed light forms primary frequency multiplication laser after passing through a primary frequency multiplication module, the primary frequency multiplication laser forms secondary frequency multiplication laser after passing through a secondary frequency multiplication module, and the secondary frequency multiplication laser forms target laser after passing through a tertiary frequency multiplication module.
8. The deep ultraviolet laser device according to claim 7, wherein the seed light is single-frequency continuous light, the first-order frequency doubling module, the second-order frequency doubling module and the third-order frequency doubling module are single-pass frequency doubling components, multi-pass frequency doubling components or resonance frequency doubling components respectively, the resonance frequency doubling components comprise frequency locking units and at least one resonance frequency doubling element, and the frequency locking units are PDH frequency locking, HC frequency locking, lockin or jitter locking.
9. The deep ultraviolet laser device according to claim 1, further comprising a frequency stabilization assembly, wherein the frequency stabilization assembly is coupled to at least one of the seed light source assembly, the amplifying assembly, and the frequency doubling assembly;
The frequency stabilization component comprises a reference source and a frequency stabilization unit, wherein the reference source comprises an atomic spectrum, a molecular spectrum, an ion spectrum, a crystal space hole burning, an optical reference cavity, an optical frequency comb, an optical fiber delay line and a laser source with constant frequency, and the frequency stabilization component locks the output light of the seed light source component, the amplifying component or the frequency multiplication component with the reference source based on constant frequency difference.
10. A deep ultraviolet laser generating method, characterized in that the deep ultraviolet laser device according to any one of claims 1-9 is adopted, comprising the following steps:
Determining that the wavelength of the target laser is 185-270nm, and the power of the target laser is not less than 1 mu W;
determining a preset multiple between the wavelength of the seed light and the wavelength of the target laser;
controlling a seed light source component to generate and output seed light, wherein the wavelength of the seed light is 1480-2160nm, and the spectrum width of the seed light is not more than 0.5nm;
Inputting seed light into an amplifying assembly, amplifying the seed light in the amplifying assembly in power, and outputting high-power seed light;
the high-power seed light enters a frequency multiplication component with the preset frequency amplification progression to carry out frequency amplification, the frequency amplification progression is not less than 3, and the target laser is formed and output.
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