CN104852266A - Intracavity-frequency-multiplication-optic-parameter-oscillator-based femto-second near-infrared laser light source and method - Google Patents

Abstract

The invention discloses a femtosecond near-infrared laser light source and method based on an intracavity frequency-doubling optical parametric oscillator, which includes an all-solid-state femtosecond mode-locked Yb laser, an isolator, a half-wave plate, a focusing lens, and a first concave surface placed in sequence. mirror, first PPLN crystal, second concave mirror, third concave mirror, second PPLN crystal, fourth concave mirror and output coupling mirror. The invention utilizes the advantages of high output power, compact structure and low cost of the all-solid-state mode-locked femtosecond Yb laser to realize continuously tunable coherent femtosecond near-infrared lasers with wavelengths of 1.4-1.8 μm and 0.7-0.9 μm; compared to The traditional mode-locked Ti:Sapphire laser produces a 0.7-0.9 μm near-infrared laser source. The femtosecond near-infrared source based on an intracavity frequency-doubling optical parametric oscillator provided by the present invention has the advantages of simple structure, stable performance, and low price.

Description

Femtosecond near-infrared laser source and method based on intracavity frequency doubling optical parametric oscillator

technical field

The invention belongs to the field of ultrafast laser technology, and in particular relates to a femtosecond near-infrared laser light source and method based on an intracavity frequency doubling optical parametric oscillator.

Background technique

After decades of research on the generation of femtosecond laser pulses, people have successfully used the principles of Kerr lens mode-locking (KLM) and SESAM passive mode-locking to obtain near-infrared femtosecond pulses from visible light to about 2 μm in many kinds of gain media. pulse. Compared with lasers that use population inversion to provide laser gain, femtosecond optical parametric oscillators (OPO) use pump light, signal The principle of mutual coupling of light and idle light energy to generate ultrashort laser pulses has unique advantages: First, the femtosecond OPO pumped by synchronous pumping can use the same crystal and the same femtosecond pumping source to simultaneously Generate femtosecond pulse output of multiple wavelengths; secondly, femtosecond OPO has a tuning range from visible light to mid-infrared, which greatly expands the output wavelength range of lasers based on the mode-locking principle, and its wavelength is continuously tunable; in addition, Since the parametric interaction has a very wide parametric bandwidth, which is not limited to the energy level bandwidth of atoms or molecules, theoretically a narrower pulse output than that of pump light can be obtained. With the maturity of Ti:Sapphire KLM mode-locking technology, the femtosecond OPO with femtosecond Ti:Sapphire oscillator as the pumping source has been developed rapidly. It has been reported at home and abroad that the use of different gain media, fundamental frequency and double frequency Ti:Sapphire pump Pu's femtosecond OPO. The first domestic femtosecond OPO using femtosecond Ti:Sapphire oscillator to achieve synchronous pumping was in 2007 (document 1.J.Zhu et al.Chin.Phys.Lett.24(9)2603(2007)), followed by successive Realized high-power Ti:Sapphire pumped dual-wavelength femtosecond OPO (document 2.L.Xuet al.Opt.Lett.37(9)1436(2012)) and intracavity frequency-doubling femtosecond OPO (document 3.J. Zhu et al. ChinPhys. B 22(5)054210). Although the use of Ti:sapphire laser to pump femtosecond OPO has the advantages of stable operation and good beam quality, but because the Ti:sapphire oscillator requires an expensive 532nm laser as the pump source, the cost of the entire system is very high, which limits the use in many popular applications. Industry research and application. Therefore, the development of low-cost laser diode-pumped all-solid-state mode-locked femtosecond Yb lasers as the pump source for femtosecond OPO can greatly save costs on the one hand, and on the other hand femtosecond Yb lasers can output higher average power. Thus, a higher-power tunable near-mid-infrared laser can be obtained. Therefore, it is of great significance and value to establish a synchronously pumped femtosecond optical parametric oscillator using an all-solid-state mode-locked femtosecond Yb laser as a pump source. In addition, the 0.7-0.9 μm near-infrared ultrafast laser light source has important applications in many important fields such as biophotonics, optical microscopy and non-Stokes Raman spectroscopy. At present, the mainstream 0.7-0.9μm near-infrared ultra-short laser source is Ti:Sapphire femtosecond mode-locked laser. As mentioned above, although Ti:Sapphire femtosecond mode-locked laser has various advantages, it needs expensive 532nm The laser is used as the pump source, so the cost of the whole system is very high, and both the 532nm pump source and the Ti:sapphire laser need to be water-cooled, which determines that its volume is relatively large and not compact enough. Therefore, it is imperative to propose a low-cost, simple-structured 0.7-0.9 μm ultrafast mid-infrared laser source.

Contents of the invention

The purpose of the present invention is to provide a femtosecond near-infrared laser light source and method based on an intracavity frequency-doubling optical parametric oscillator, aiming to solve the problems of existing near-infrared femtosecond lasers such as uncompact structure, high price, and non-continuous wavelength. Adjustable question.

The present invention is achieved in this way, a femtosecond near-infrared laser light source based on an intracavity frequency-doubling optical parametric oscillator, the femtosecond near-infrared laser light source based on an intracavity frequency-doubling optical parametric oscillator includes all solid-state femtosecond laser sources placed in sequence Mode-locked Yb laser, isolator, half-wave plate, focusing lens, first concave mirror, first PPLN crystal, second concave mirror, third concave mirror, second PPLN crystal, fourth concave mirror and output coupling mirror;

The all-solid-state femtosecond mode-locked Yb laser is used to generate a pump laser with a femtosecond pulse width;

The isolator is used to isolate the part of the mode-locked laser returning from the parametric oscillator, avoiding returning the laser to interfere with the mode-locking state of the Yb oscillator, and avoiding returning the laser to interfere with the mode-locking state of the Yb oscillator;

The half-wave plate is used to adjust the polarization state of the pumping mode-locked laser, realize the phase matching of the pumping light, the signal light and the idle light, and change the polarization direction of the pumping laser;

The focusing lens is used to focus the pumping mode-locked laser light onto the first PPLN crystal;

The first concave mirror and the second concave mirror are used to form a confocal tight-focus cavity;

The first PPLN crystal is located between the first concave mirror and the second concave mirror, and is used to realize high-efficiency parametric oscillation and wavelength tuning;

The third concave mirror and the fourth concave mirror are used to form a confocal structure to reduce the spot size on the second PPLN crystal, wherein the fourth concave mirror also plays the role of returning and reflecting the parametric signal light in the original way, for It constitutes an end mirror of the parametric resonant cavity and outputs all frequency-doubled light;

The second PPLN crystal is located between the third concave mirror and the fourth concave mirror, and is used to realize high-efficiency frequency doubling and wavelength tuning;

The output mirror is used to place the output signal light on a one-dimensional precision translation stage.

Further, the all-solid-state femtosecond mode-locked Yb laser is a semiconductor saturable absorber mirror passively mode-locked femtosecond oscillator of a Yb-doped gain medium pumped by LD, with a center wavelength around 1 μm, and the output average power of the pump laser is greater than 500mW, pulse width less than 300fs, repetition frequency about 80MHz.

Further, both sides of the focusing lens are coated with a dielectric film that is anti-reflective to the pump laser wavelength, and the focal length is 100mm or 75mm.

Further, one side of the first concave mirror and the second concave mirror is coated with an anti-reflection coating of 1000nm-1100nm, and the other side is coated with a high-reflection coating of 1400nm-1800nm, and the radius of curvature is R=100mm.

Further, the first PPLN crystal is a periodically poled lithium niobate crystal doped with 5% MgO, with a cross-section of 1 mm×8 mm, a length of 1 mm, and seven polarization periods, respectively 28/28.5, 29/29.5/30/30.5/31m, the length of each polarization period is 1mm, the interval between two polarization periods is 0.2mm, there are 0.1mm unpolarized areas at both ends of the crystal; They are respectively coated with anti-reflection coatings for 1000nm～1100nm/1400nm～1900nm/2300nm～4000nm.

Further, one side of the third concave mirror and the fourth concave mirror is coated with an antireflection coating of 700nm to 900nm, and the other side is coated with a high reflection coating of 1400nm to 1800nm, and the radius of curvature is R=100mm;

The second PPLN crystal is a periodically poled lithium niobate crystal doped with 5% MgO, with a light cross-section of 1mm×6mm, a light length of 1mm, and five polarization periods, respectively 19.5/19.7/19.9/ 20.1/20.3m, the length of each polarization period is 1mm, the interval between two polarization periods is 0.2mm, and there are 0.1mm unpolarized areas at both ends; /1400nm～1900nm AR coating;

The side of the output mirror facing the inside of the resonant cavity is coated with a dielectric film with an output coupling rate in the signal light band, and the other side is coated with an anti-reflection dielectric film in the signal light band.

Another object of the present invention is to provide a method for generating femtosecond near-infrared laser light using a femtosecond near-infrared laser source based on an intracavity frequency-doubling optical parametric oscillator. The method for generating femtosecond near-infrared laser includes:

The all-solid-state femtosecond mode-locked Yb laser generates a femtosecond pulse width pump laser, which passes through an optical isolator and a half-wave plate, and then is focused into the first PPLN crystal by a focusing lens;

The first concave mirror, the second concave mirror, the third concave mirror, the fourth concave mirror and the output mirror constitute a parametric oscillation resonator; the second PPLN crystal is placed in the center of the confocal structure formed by the third concave mirror and the fourth concave mirror Intra-cavity frequency doubling is generated; the first concave mirror and the second concave mirror form a confocal tight-focus cavity, so that the signal beam waist size on the first PPLN crystal matches the beam waist size of the pump light;

The third concave mirror and the fourth concave mirror form another confocal structure to reduce the spot size of the signal light on the second PPLN crystal to obtain high-efficiency frequency doubling in the cavity, and the generated frequency doubling light is all output through the fourth concave mirror ;

The output mirror outputs a part of the signal light, and returns the other part of the signal light through the original path to realize the cavity length tuning of the parametric resonant cavity.

Another object of the present invention is to provide a laser radar using the femtosecond near-infrared laser light source based on an intracavity frequency doubling optical parametric oscillator.

Another object of the present invention is to provide an ultrafast optical communication using the femtosecond near-infrared laser light source based on an intracavity frequency doubling optical parametric oscillator.

Another object of the present invention is to provide an ultrafast spectroscopy using the femtosecond near-infrared laser light source based on the intracavity frequency doubling optical parametric oscillator.

The femtosecond near-infrared laser source and method based on the intracavity frequency doubling optical parametric oscillator provided by the present invention can conveniently realize the wavelength at 1.4 - 1.8μm (signal light) and 0.7-0.9μm (frequency doubled light) continuously tunable coherent femtosecond near-infrared laser; compared to the traditional mode-locked Ti:Sapphire laser to generate 0.7-0.9μm near-infrared laser light source. The femtosecond near-infrared light source based on the intracavity frequency-doubling optical parametric oscillator provided by the present invention has the advantages of simple structure, stable performance, and low price, and better solves the problems of existing femtosecond lasers such as uncompact structure and relatively low price. The problem that the height and wavelength cannot be continuously adjusted.

Description of drawings

Fig. 1 is a schematic structural diagram of a femtosecond near-infrared laser light source based on an intracavity frequency doubling optical parametric oscillator provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of signal light wavelength tuning provided by an embodiment of the present invention;

3 is a schematic diagram of the relationship between signal optical power and wavelength provided by an embodiment of the present invention;

Fig. 4 is a schematic diagram of wavelength tuning of frequency-doubled light provided by an embodiment of the present invention;

5 is a schematic diagram of the output signal optical pulse width measured by an intensity autocorrelator provided by an embodiment of the present invention;

Fig. 6 is a schematic diagram of the output frequency-doubled light pulse width measured by an intensity autocorrelator provided by an embodiment of the present invention;

In the figure: 1. All-solid-state femtosecond mode-locked Yb laser; 2. Isolator; 3. Half-wave plate; 4. Focusing lens; 5. The first concave mirror; 6. The first PPLN crystal; 7. The second concave mirror ; 8, the third concave mirror; 9, the second PPLN crystal; 10, the fourth concave mirror; 11, the output coupling mirror.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The femtosecond near-infrared laser light source generated by the intracavity frequency-doubling optical parametric oscillator of the present invention can output continuously tunable coherent femtosecond near-infrared lasers with wavelengths of 1.4 μm to 1.8 μm and 0.7 μm to 0.9 μm. The femtosecond light source It has important potential applications in lidar, biological imaging, ultrafast spectroscopy, ultrafast optical communication and other fields.

The application principle of the present invention will be described in detail below in conjunction with FIG. 1 .

As shown in Figure 1, the femtosecond near-infrared laser light source based on the intracavity frequency doubling optical parametric oscillator in the embodiment of the present invention is mainly composed of: an all-solid-state femtosecond mode-locked Yb laser 1, an isolator 2, a half-wave plate 3, and a focusing lens 4. A first concave mirror 5, a first PPLN crystal 6, a second concave mirror 7, a third concave mirror 8, a second PPLN crystal 9, a fourth concave mirror 10, and an output coupling mirror 11.

All-solid-state femtosecond mode-locked Yb laser 1 is a semiconductor saturable absorber mirror (SESAM) passively mode-locked femtosecond oscillator pumped by an LD-pumped Yb-doped gain medium. The center wavelength is around 1 μm. According to the Yb gain medium Different, the central wavelength is different, the average output power of the pump laser is greater than 500mW, the pulse width is less than 300fs, and the repetition frequency is about 80MHz.

The isolator 2 is used to isolate part of the mode-locked laser returning from the parametric oscillator, so as to prevent the returning laser from interfering with the mode-locking state of the Yb oscillator.

The half-wave plate 3 is used to adjust the polarization state of the pump mode-locked laser light, so as to realize the phase matching of the pump light, the signal light and the idle light.

The focusing lens 4 is used to focus the pumping mode-locked laser light onto the first PPLN crystal. The two sides of the lens are coated with a dielectric film that is anti-reflective to the wavelength of the pumping laser light, and the focal length is 100mm or 75mm.

The first concave mirror 5 and the second concave mirror 7 are used to form a confocal tight-focus cavity, so that the signal beam waist size on the first PPLN crystal matches the beam waist size of the pump light to achieve high parametric Conversion efficiency: Both concave mirrors are coated with antireflection coating (R<3%) of 1000nm～1100nm and high reflection coating of 1400nm～1800nm (R>99.8%), and the radius of curvature is R=100mm.

The first PPLN crystal 6 is a periodically poled lithium niobate crystal doped with 5% MgO. The crystal light cross section is 1mm×8mm, the light length is 1mm, and there are seven polarization periods on the crystal, which are 28/28.5 /29.5/30/30.5/31m, the length of each polarization period is 1mm, the interval between two polarization periods is 0.2mm, and there are 0.1mm unpolarized regions at both ends of the crystal; Coated with antireflection coating for 1000nm～1100nm(R<1%)/1400nm～1900nm(R<1%)/2300nm～4000nm(R<10%). The crystal is placed on a five-dimensional translation stage, which can fine-tune the azimuth and XYZ direction position to achieve high-efficiency parametric oscillation and wavelength tuning.

The third concave mirror 8 and the fourth concave mirror 10 are used to form a confocal structure so that the signal beam waist on the second PPLN crystal is as small as possible to achieve high intracavity frequency doubling efficiency. The two concave mirrors are coated with an anti-reflection coating of 700nm-900nm (R<3%) and a high-reflection coating of 1400nm-1800nm (R>99.8%), and the radius of curvature is R=100mm.

The second PPLN crystal 9 is a periodically poled lithium niobate crystal doped with 5% MgO. The crystal cross-section is 1mm×6mm, and the length of the light is 1mm. There are five polarization periods on the crystal, respectively 19.5/ 19.7/19.9/20.1/20.3m, the length of each polarization period is 1mm, the interval between two polarization periods is 0.2mm, and there are 0.1mm unpolarized areas at both ends of the crystal; Coated with anti-reflection coating for 700nm～900nm (R<1%)/1400nm～1900nm (R<1%); the crystal is placed on a five-dimensional translation stage, which can fine-tune the azimuth and XYZ direction position to achieve high efficiency times frequency and wavelength tuning.

The output mirror 11, with an output rate of 2% at 1220nm to 1750nm, is used to output signal light and is placed on a one-dimensional precision translation stage, which can precisely change the cavity length of the parametric resonant cavity to match the cavity length of the Yb resonant cavity.

The application principle of the present invention will be further described below in conjunction with specific embodiments.

Specific embodiments of the present invention:

In Fig. 1, an all-solid-state femtosecond mode-locked Yb laser 1 is used to generate a pump laser with a femtosecond pulse width. After passing through an optical isolator 2 and a half-wave plate 3, it is focused by a focusing lens 4 and enters the first PPLN crystal 6. Middle; the first concave mirror 5, the second concave mirror 7, the third concave mirror 8, the fourth concave mirror 10 and the output mirror 11 constitute a parametric oscillation resonant cavity; the second PPLN crystal 9 is placed in the third concave mirror 8 and the fourth The center of the confocal structure formed by the concave mirror 10 is used to generate frequency doubling in the cavity; wherein the first concave mirror 5 and the second concave mirror 7 form a confocal tight-focus cavity, so that the signal beam on the first PPLN crystal 6 The waist size matches the beam waist size of the pump light; the third concave mirror 8 and the fourth concave mirror 10 form another confocal structure to reduce the signal light spot size on the second PPLN crystal 9, and obtain a high-efficiency cavity Internal frequency doubling, the generated frequency doubling light is all output through the fourth concave mirror 10; the output mirror 11 outputs a part of the signal light, and the other part of the signal light returns to the original path, and at the same time, the cavity length tuning of the parametric resonator can be realized; when the phase matching, Under the conditions of cavity length matching, stable cavity conditions and reaching the signal light oscillation threshold, the optical parametric oscillator can realize stable operation, the signal light propagates back and forth in the parametric resonant cavity, and couples out a part of the signal every time it reaches the output coupling mirror 11 When the light energy reaches the second PPLN crystal 9 , frequency-doubled light is generated, which is output from the fourth concave mirror 10 .

According to the physical principle of synchronously pumped femtosecond OPO, the wavelength of the signal light can be tuned by the following methods: 1. Changing the wavelength of the pumping light; 2. Changing the polarization period of the PPLN crystal; 3. Changing the temperature of the PPLN crystal; 4. , Change the cavity length of the OPO resonant cavity. Through the above steps, the coherent femtosecond near-infrared laser output with signal light running at 1.4-1.8m can be continuously tunable, and while the tunable signal light is obtained, the polarization period or temperature of the second PPLN crystal 9 can be changed accordingly, The corresponding 0.7-0.9um continuously tunable coherent femtosecond near-infrared laser output can be obtained at the same time.

The laser gain medium of the all-solid-state femtosecond mode-locked Yb laser is Yb:LYSO crystal, the average output power is 2W, the pulse width is 300fs, the center wavelength is 1042nm, and the repetition frequency is **MHz.

In the present invention, by adjusting the cavity length of the OPO resonant cavity, the tuning range of signal light from 1428nm to 1763nm and frequency doubled light from 767nm to 874nm is obtained; the signal light spectrum tuning curve is shown in FIG. 2 . The output power is between 100mW and 400mW depending on the wavelength of the signal light, as shown in Figure 3; the tuning curve of the frequency-doubled light is shown in Figure 4; Typical pulse widths are 465fs and 313fs, respectively, as shown in Figure 5 and Figure 6, and the corresponding wavelengths of signal light and frequency-doubled light are 1511nm and 792nm.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (10)

1. one kind based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, describedly comprise all solid state femtosecond locked mode Yb laser, isolator, half-wave plate, condenser lens, the first concave mirror, a PPLN crystal, the second concave mirror, the 3rd concave mirror, the 2nd PPLN crystal, the 4th concave mirror and the output coupling mirror placed successively based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source;

Described all solid state femtosecond locked mode Yb laser, for generation of the pumping laser of femto-second pulse duration;

Described isolator, for isolating the part mode-locked laser returned from parametric oscillator, avoids return laser light to disturb Yb oscillator mode-lock status;

Described half-wave plate, for adjusting the polarization state of pumping mode-locked laser, realizes the phase matched of pump light, flashlight and idle light;

Described condenser lens, for focusing on a PPLN crystal by pumping mode-locked laser;

Described first concave mirror and the second concave mirror, for the formation of confocal tight focusing lumen type;

A described PPLN crystal, is placed in the middle of the first concave mirror and the second concave mirror, for realizing high efficiency parametric oscillation and wavelength tuning;

Described 3rd concave mirror and the 4th concave mirror, for the formation of confocal arrangement;

Described 2nd PPLN crystal, is placed in the middle of the 3rd concave mirror and the 4th concave mirror, for realizing efficient frequency doubling and wavelength tuning;

Described outgoing mirror, for being placed on an one-dimensional precise translation stage by output signal light.

2. as claimed in claim 1 based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, described all solid state femtosecond locked mode Yb laser is the semiconductor saturable absorbing mirror passive mode locking femtosecond oscillator of the Yb doping gain media of LD pumping, centre wavelength is near 1 μm, the output average power of pumping laser is greater than 500mW, and pulse duration is less than 300fs, repetition rate is 80MHz.

3. as claimed in claim 1 based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, described condenser lens two sides is coated with the anti-reflection deielectric-coating of pumping laser wavelength, and focal length is 100mm or 75mm.

4. as claimed in claim 1 based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, the one side of described first concave mirror and the second concave mirror is coated with the anti-reflection film of 1000nm ~ 1100nm, another side is coated with the high-reflecting film of 1400nm ~ 1800nm, and radius of curvature is R=100mm.

5. as claimed in claim 1 based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, a described PPLN crystal is the periodically poled lithium niobate crystal of doping 5%MgO, logical optical cross-section is 1mm × 8mm, logical light length is 1mm, has seven polarization cycles, is respectively 28/28.5/29/29.5/30/30.5/31m, the length of every polarization cycle is 1mm, be spaced apart 0.2mm between two polarization cycles, and respectively there is the non-polarized area of 0.1mm at crystal two ends; Crystal two leads to light face and is coated with anti-reflection film to 1000nm ~ 1100nm/1400nm ~ 1900nm/2300nm ~ 4000nm respectively.

6. as claimed in claim 1 based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, the one side of described 3rd concave mirror and the 4th concave mirror is coated with the anti-reflection film of 700nm ~ 900nm, another side is coated with the high-reflecting film of 1400nm ~ 1800nm, and radius of curvature is R=100mm;

Described 2nd PPLN crystal is the periodically poled lithium niobate crystal of doping 5%MgO, logical optical cross-section is 1mm × 6mm, logical light length is 1mm, there are five polarization cycles, be respectively 19.5/19.7/19.9/20.1/20.3m, the length of every polarization cycle is 1mm, be spaced apart 0.2mm between two polarization cycles, and respectively there is the non-polarized area of 0.1mm at two ends; Two logical light faces are coated with the anti-reflection film to 700nm ~ 900nm/1400nm ~ 1900nm respectively;

Described outgoing mirror is coated with towards the one side in resonant cavity has at flashlight wave band the deielectric-coating exporting coupling efficiency, and another side is coated with the anti-reflection deielectric-coating of flashlight wave band.

7. utilize the method producing femtosecond near-infrared laser based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source, it is characterized in that, the method for described generation femtosecond near-infrared laser comprises:

All solid state femtosecond locked mode Yb laser produces the pumping laser of femto-second pulse duration, and after optical isolator and half-wave plate, line focus lens focus enters in a PPLN crystal;

First concave mirror, the second concave mirror, the 3rd concave mirror, the 4th concave mirror and outgoing mirror form parametric oscillation resonant cavity; The center that 2nd PPLN crystal is placed in the confocal arrangement of the 3rd concave mirror and the formation of the 4th concave mirror produces intracavity frequency doubling; First concave mirror and the second concave mirror form confocal tight focusing lumen type, and the beam waist of the flashlight beam waist on a PPLN crystal and pump light is matched;

3rd concave mirror and the 4th concave mirror form another confocal arrangement to reduce the flashlight spot size on the 2nd PPLN crystal, obtain high efficiency intracavity frequency doubling, and the frequency doubled light of generation is all exported by the 4th concave mirror;

Outgoing mirror exports a part of flashlight, and to return to the chamber simultaneously realizing parametric reasonance chamber long tuning on another part flashlight former road.

8. one kind utilizes the laser radar based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source described in claim 1-7 any one.

9. one kind utilizes the ultrafast optical communication based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source described in claim 1-7 any one.

10. one kind utilizes the Ultrafast spectrum based on intracavity frequency doubling optical parametric oscillator femtosecond near-infrared laser light source described in claim 1-7 any one.