CN116937304A - An all-fiber Raman laser - Google Patents

Abstract

The application discloses an all-fiber Raman laser, which comprises: a pumping pulse fiber laser seed source (1) which outputs broadband mode locking pulse laser with positive chirp and is connected with a first pumping/signal fiber combiner (4); the output end of the first semiconductor laser pumping source (3) is connected to the first pumping/signal optical fiber combiner (4), and the output of the first pumping/signal optical fiber combiner (4) is connected to the second pumping/signal optical fiber combiner (8) through a first gain optical fiber (5); a second semiconductor laser pump source (7) with its output connected to the second pump/signal fiber combiner (8); and the output end of the second pump/signal optical fiber beam combiner (8) is connected with a second gain optical fiber (9), and the generated ultrafast Raman laser is spatially output after passing through a Raman pulse separator (10). The laser provided by the application can inhibit harmful nonlinear effects, improve the conversion efficiency and realize micro-focal-level ultra-fast Raman laser output.

Description

An all-fiber Raman laser

Technical field

The present application relates to the field of laser technology, and in particular to an all-fiber Raman laser.

Background technique

Fiber as a Raman gain medium can produce laser wavelengths that cannot be covered by rare earth doped gain media. Theoretically, by selecting the appropriate pump laser wavelength, any wavelength within the transmission window of the Raman gain fiber can be generated through the Raman effect. At present, Raman fiber lasers based on the Raman effect have achieved high power output in the kilowatt range and wavelength coverage from visible to mid-infrared in the field of continuous and long pulse lasers. In the field of picosecond and femtosecond ultrafast lasers, Raman fiber lasers are also developing rapidly thanks to their applications in industry, biomedicine, scientific research and other fields. The generation methods of ultrafast Raman fiber laser mainly include mode locking, synchronous pumping, nonlinear optical gain modulation and self-Raman seeding method. Among these methods, mode-locked and synchronously pumped ultrafast Raman fiber lasers are based on optical resonator structures, and the pulse energy is limited to the nanojoule level. Synchronous pumping even requires optical or electrical delay lines to realize optical resonators. The cavity length is precisely matched to the repetition frequency of the pump pulse laser, which increases the cost and complexity of the system. Although nonlinear optical gain modulation can generate ultrafast Raman laser seeds without relying on optical resonators and delay lines, further improvement of Raman laser energy still requires the introduction of delay lines, thereby increasing system cost and complexity.

A more effective method to generate ultrafast Raman fiber laser is the self-Raman seed method, which uses a rare earth doped gain fiber to directly amplify the ultrafast pump pulse laser. At this time, the rare earth doped fiber acts as the pump pulse laser and pull The dual role of the Man pulse laser amplifier, in which the ultrafast Raman laser seed is played by the long-wave pulse component generated by self-phase modulation or the long-wave pulse component of the pump pulse, without the need for an additional optical resonator. In addition, the ultrafast Raman laser and pump Pulsed lasers also enable passive synchronization without the need for additional delay lines. At present, this method uses an all-fiber structure to achieve a Raman conversion efficiency (ratio of Raman pulse energy to total energy) of greater than 80% in a rare earth-doped gain fiber with negative dispersion. However, due to the limitation of harmful nonlinear effects, Raman The pulse energy is limited to the nanojoule level. In rare earth-doped gain fibers with positive dispersion, although the harmful nonlinear effects can be weakened, the Raman conversion efficiency is usually less than 50%, and the pulse energy also stays at the nanojoule level. , it can be seen that the output energy of all-fiber ultrafast Raman laser has limited its application in related fields.

Currently, the output energy of all-fiber ultrafast Raman lasers based on the self-Raman seeding method is limited to the nanojoule level due to harmful nonlinear effects and limitations in conversion efficiency.

Contents of the invention

Embodiments of the present application provide an all-fiber Raman laser to suppress harmful nonlinear effects, improve conversion efficiency, and achieve ultrafast Raman laser output at the microfocus level.

Embodiments of the present application provide an all-fiber Raman laser, including:

The pump pulse fiber laser seed source 1 outputs a broadband mode-locked pulse laser with positive chirp and is connected to the first pump/signal fiber combiner 4;

The output end of the first semiconductor laser pump source 3 is connected to the first pump/signal fiber combiner 4 , and the output of the first pump/signal fiber combiner 4 is connected through the first gain fiber 5 second pump/signal fiber combiner 8;

The second semiconductor laser pump source 7 has its output end connected to the second pump/signal fiber combiner 8;

The output end of the second pump/signal fiber combiner 8 is connected to the second gain fiber 9, and the generated Raman laser is spatially output after passing through the Raman pulse splitter 10, wherein the first gain fiber 5, the The second gain fiber 9 is a rare earth doped gain fiber with positive dispersion.

Optionally, a first fiber isolator 2 is provided between the pump pulse fiber laser seed source 1 and the first pump/signal fiber combiner 4, and the first gain fiber 5 and the third A second fiber isolator 6 is disposed between the two pump/signal fiber combiners 8, and the operating wavelengths of the first fiber isolator 2 and the second fiber isolator 6 are consistent with the pump pulse fiber laser. The output wavelength of seed source 1 is consistent.

Optionally, the first gain fiber 5 and the second gain fiber 9 are Yb-doped double-clad fibers, which have positive dispersion at both the pump pulse wavelength and the Raman pulse wavelength, and have specified Core diameter and fiber length.

Optionally, the first semiconductor laser pump source 3 and the second semiconductor laser pump source 7 are both fiber-coupled 976nm semiconductor lasers, and the maximum output power of the second semiconductor laser pump source 7 is greater than the The maximum output power of the first semiconductor laser pump source 3.

Optionally, the working wavelength of the input ends of the first pump/signal fiber combiner 4 and the second pump/signal fiber combiner 8 is consistent with the output wavelength of the pump pulse fiber laser seed source 1 .

Optionally, the pump pulse fiber laser seed source 1 has a laser center wavelength of 1020-1080 nm, a spectral bandwidth greater than 10 nm, and a pulse width greater than 5 ps.

Optionally, each component of the Raman laser uses optical fiber fusion welding to achieve an all-fiber structure.

The embodiment of the present application uses a picosecond pump pulse laser with broadband positive chirp as the seed source, and a rare earth doped gain fiber with positive dispersion as the amplifier. On the one hand, it suppresses harmful nonlinear effects, and on the other hand, it increases the relationship between Raman pulses and The walk-off length of the pump pulse increases the conversion efficiency, and ultimately enables ultrafast Raman laser output at the microjoule level.

The above description is only an overview of the technical solutions of the present application. In order to have a clearer understanding of the technical means of the present application, they can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and understandable. , the specific implementation methods of the present application are specifically listed below.

Description of the drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be construed as limiting the application. Also throughout the drawings, the same reference characters are used to designate the same components. In the attached picture:

Figure 1 is a schematic diagram of the overall structure of an all-fiber Raman laser according to an embodiment of the present application;

Figure 2 shows the spectra of application examples of all-fiber Raman lasers in this application under different output powers;

Figure 3 shows the autocorrelation curve of an application example of the all-fiber Raman laser of this application when the ultrafast Raman pulse laser energy is 2.56 μJ.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a thorough understanding of the disclosure, and to fully convey the scope of the disclosure to those skilled in the art.

An embodiment of the present application provides an all-fiber Raman laser, as shown in Figure 1, including:

The pump pulse fiber laser seed source 1 outputs a broadband mode-locked pulse laser with positive chirp and is connected to the first pump/signal fiber combiner 4.

The output end of the first semiconductor laser pump source 3 is connected to the first pump/signal fiber combiner 4 , and the output of the first pump/signal fiber combiner 4 is connected through the first gain fiber 5 Second pump/signal fiber combiner 8.

The output end of the second semiconductor laser pump source 7 is connected to the second pump/signal fiber combiner 8 .

The output end of the second pump/signal fiber combiner 8 is connected to the second gain fiber 9, and the generated ultrafast Raman laser is spatially output after passing through the Raman pulse splitter 10, wherein the first gain fiber 5, The second gain fiber 9 is a rare earth doped gain fiber with positive dispersion.

In some embodiments, each component of the Raman laser uses optical fiber fusion welding to achieve an all-fiber structure.

In the embodiment of this application, the first optical fiber isolator 2, the first semiconductor pump source 3, the first pump/signal optical fiber combiner 4, and the first gain optical fiber 5 form a first-stage pump/Raman pulse amplifier. The initial Raman pulse seed is served by the long-wave pulse component generated by self-phase modulation or the long-wave pulse component of the pump pulse. The second fiber isolator 6, the second semiconductor laser pump source 7, the second pump/signal fiber combiner 8, and the second rare earth doped gain fiber 9 form a second stage pump/Raman pulse amplifier. stage amplifier, the pump pulse laser is efficiently converted into Raman pulse laser, and is output after passing through the Raman pulse splitter 10.

The embodiment of the present application uses a picosecond pump pulse laser with broadband positive chirp as the seed source, and a rare earth doped gain fiber with positive dispersion as the amplifier. On the one hand, it suppresses harmful nonlinear effects, and on the other hand, it increases the relationship between Raman pulses and The walk-off length of the pump pulse increases the conversion efficiency, and ultimately enables ultrafast Raman laser output at the microjoule level.

In some embodiments, a first fiber isolator 2 is provided between the pump pulse fiber laser seed source 1 and the first pump/signal fiber combiner 4, and the first gain fiber 5 is connected to the first gain fiber 5. A second optical fiber isolator 6 is disposed between the second pump/signal optical fiber combiners 8, and the operating wavelengths of the first optical fiber isolator 2 and the second optical fiber isolator 6 are different from the pump pulse. The output wavelength of fiber laser seed source 1 is consistent.

In some embodiments, the first gain fiber 5 and the second gain fiber 9 are Yb-doped double-clad fibers, which have positive dispersion at both the pump pulse wavelength and the Raman pulse wavelength, and have respective Specified core diameter and fiber length. In some specific applications, the core diameters of the first gain fiber 5 and the second gain fiber 9 may be 14 μm and 30 μm respectively, and the fiber lengths may be 1.5 m and 1.9 m respectively, or they may be other specified core diameters. and fiber length.

In some embodiments, the first semiconductor laser pump source 3 and the second semiconductor laser pump source 7 are both fiber-coupled 976nm semiconductor lasers, and the maximum output power of the second semiconductor laser pump source 7 is greater than The maximum output power of the first semiconductor laser pump source 3.

In some embodiments, the operating wavelengths of the input ends of the first pump/signal fiber combiner 4 and the second pump/signal fiber combiner 8 are different from the output of the pump pulse fiber laser seed source 1 The wavelength is the same.

In some embodiments, the pump pulse fiber laser seed source 1 has a laser center wavelength of 1020 nm to 1080 nm, a spectral broadband (half-maximum width) greater than 10 nm, and a pulse width greater than 5 ps.

The embodiment of the present application also proposes an application example of an all-fiber Raman laser, including: a pump pulse fiber laser seed source 1, a first fiber isolator 2, a first semiconductor laser pump source 3, a first pump/signal Fiber combiner 4, first gain fiber 5, second fiber isolator 6, second semiconductor laser pump source 7, second pump/signal fiber combiner 8, second gain fiber 9, Raman pulse separation Device 10.

Among them, the input end and the output end of the first fiber isolator 2 are respectively connected to the output end of the ultrafast pump pulse fiber laser seed source 1 and the signal input end of the first pump/signal fiber combiner 4. The first pump The signal output end of the Pu/signal optical fiber combiner 4 is connected to the input end of the first rare earth doped gain fiber 5, and the input end and output end of the second optical fiber isolator 6 are respectively connected to the output end of the first gain fiber 5 and the third The signal input end of the second pump/signal fiber combiner 8 is connected, the signal output end of the second pump/signal fiber combiner 8 is connected to the input end of the second gain fiber 9, the first and second semiconductor laser pumps Pu sources 3 and 7 are connected to the pump input ends of the first and second pump/signal fiber combiners 4 and 8 respectively. The connection methods of the above devices are all fiber fusion welding to achieve an all-fiber structure.

Among them, the first fiber isolator 2, the first semiconductor pump source 3, the first pump/signal fiber combiner 4, and the first rare earth doped gain fiber 5 form the first stage pump/Raman pulse amplifier. The Raman pulse seed is served by the long-wave pulse component generated by self-phase modulation or the long-wave pulse component of the pump pulse. The second fiber isolator 6, the second semiconductor laser pump source 7, the second pump/signal fiber combiner 8, and the second rare earth doped gain fiber 9 form a second stage pump/Raman pulse amplifier. stage amplifier, the pump pulse laser is efficiently converted into Raman pulse laser, and is output after passing through the Raman pulse splitter 10.

In this application example, the ultrafast pump pulse fiber laser seed source 1 outputs a mode-locked pulse laser with positive chirp. Its laser center wavelength is 1033.7nm, the spectral broadband (half-maximum width) is 17.5nm, and the pulse width is 7.7ps.

The operating wavelengths of the first optical fiber isolator 2 and the second optical fiber isolator 6 are both 1030 nm. The first semiconductor laser pump source 3 is a fiber-coupled 976nm semiconductor laser with a maximum output power of 9W. The second semiconductor laser pump source 7 is two fiber-coupled 976nm semiconductor lasers with a single maximum output power of 100W. The operating wavelength of the pump input end of the first pump/signal fiber combiner 4 and the second pump/signal fiber combiner 8 is 976 nm, and the operating wavelength of the signal input end is 1030 nm. The first gain fiber 5 and the second gain fiber 9 are Yb-doped double-clad fibers, with core diameters of 14 μm and 30 μm respectively, and fiber lengths of 1.5 m and 1.9 m respectively.

Figure 2 shows the spectrum of the high-energy all-fiber ultrafast Raman laser at different output powers in this application example. As shown in Figure 2, the central wavelength of ultrafast Raman pulse laser gradually red-shifts from 1080nm to 1120nm as the output power increases, and the Raman conversion efficiency (ratio of Raman pulse energy to total energy) gradually increases. When the Man wavelength is 1120nm, its Raman conversion efficiency is as high as 89.5%. The average power of the ultrafast Raman pulse output at this time is 93W, and the corresponding pulse energy is 2.56μJ.

Figure 3 shows the autocorrelation curve of the high-energy all-fiber ultrafast Raman laser in this application example when the ultrafast Raman pulse laser energy is 2.56μJ. It can be seen that the pulse width is 19.2ps, and the corresponding peak power is as high as 133kW. Meet the application needs in industry, biomedicine, scientific research and other fields.

The embodiment of this application adopts the self-Raman seeding method, using a picosecond pump pulse laser with broadband positive chirping as the seed source, and a rare earth-doped gain fiber with positive dispersion as the amplifier, which effectively suppresses harmful nonlinear effects and improves efficiency. The Raman conversion efficiency increases the energy of the all-fiber ultrafast Raman laser to the microjoule level. The laser has a compact structure and low cost, which can better meet its application in industry, biomedicine, scientific research and other fields.

It should be noted that in the various embodiments of the present application, the terms "comprising", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only Includes those elements and also includes other elements not expressly listed or inherent in such process, method, article or apparatus. Without further limitation, an element defined by the statement "comprises a..." does not exclude the presence of additional identical elements in a process, method, article or apparatus that includes that element.

The above serial numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above-mentioned specific implementations. The above-mentioned specific implementations are only illustrative and not restrictive. Those of ordinary skill in the art will Inspired by this application, many forms can be made without departing from the purpose of this application and the scope protected by the claims, and these all fall within the protection of this application.

Claims (7)

1. An all-fiber Raman laser, characterized by: The pump pulse fiber laser seed source (1) outputs a broadband mode-locked pulse laser with positive chirp and is connected to the first pump/signal fiber combiner (4); The first semiconductor laser pump source (3) has an output end connected to the first pump/signal fiber combiner (4), and the output of the first pump/signal fiber combiner (4) passes through the A gain fiber (5) is connected to the second pump/signal fiber combiner (8); A second semiconductor laser pump source (7), the output end of which is connected to the second pump/signal fiber combiner (8); The output end of the second pump/signal fiber combiner (8) is connected to the second gain fiber (9), and the generated Raman laser is spatially output after passing through the Raman pulse splitter (10), wherein the first The gain fiber (5) and the second gain fiber (9) are rare earth doped gain fibers with positive dispersion. 2. The all-fiber Raman laser according to claim 1, characterized in that, the pump pulse fiber laser seed source (1) and the first pump/signal fiber combiner (4) are arranged between There is a first fiber isolator (2), and a second fiber isolator (6) is provided between the first gain fiber (5) and the second pump/signal fiber combiner (8), and the The operating wavelength of the first fiber isolator (2) and the second fiber isolator (6) is consistent with the output wavelength of the pump pulse fiber laser seed source (1). 3. The all-fiber Raman laser according to claim 1, characterized in that the first gain fiber (5) and the second gain fiber (9) are Yb-doped double-clad fibers, which are used in the pump Both the Pu pulse wavelength and the Raman pulse wavelength have positive dispersion, and have specified core diameter and fiber length respectively. 4. The all-fiber Raman laser according to claim 1, characterized in that the first semiconductor laser pump source (3) and the second semiconductor laser pump source (7) are both 976nm semiconductors coupled by optical fibers. Laser, the maximum output power of the second semiconductor laser pump source (7) is greater than the maximum output power of the first semiconductor laser pump source (3). 5. The all-fiber Raman laser according to claim 4, characterized in that the first pump/signal fiber combiner (4) and the second pump/signal fiber combiner (8) The working wavelength of the input end is consistent with the output wavelength of the pump pulse fiber laser seed source (1). 6. The all-fiber Raman laser according to claim 1, characterized in that the pump pulse fiber laser seed source (1) has a laser center wavelength of 1020-1080 nm, a spectral bandwidth greater than 10 nm, and a pulse width greater than 5 ps. 7. The all-fiber Raman laser according to claim 1, characterized in that each component of the Raman laser adopts optical fiber fusion welding to achieve an all-fiber structure.