High-power large-energy femtosecond chirped pulse amplification system based on in-band pumping

Abstract

The invention discloses a high-power large-energy femtosecond chirped pulse amplification system based on in-band pumping, and the system comprises an optical signal input device which is used for inputting a femtosecond chirped pulse signal to be amplified; the main amplification device comprises a single crystal optical fiber with a single-pass structure, and is used for carrying out main amplification on the pre-amplified femtosecond chirped pulse signal and outputting the amplified femtosecond chirped pulse signal; the double-end in-band pumping device comprises a first pumping light source, a second pumping light source, a first dichroscope and a second dichroscope, pumping light generated by the first pumping light source is injected into one end of the single crystal optical fiber through the first dichroscope, and pumping light generated by the second pumping light source is injected into the other end of the single crystal optical fiber through the second dichroscope. Pump light generated by the second pump light source is injected into the other end of the single crystal optical fiber through the second dichroscope, so that double-end in-band pumping is achieved. By adopting a double-end in-band pumping mode, the laser output efficiency is improved, the quantum loss of the laser is reduced, and the thermal load of the laser is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of femtosecond lasers, and relates to a high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping, and specifically to a hybrid high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping Yb:YAG single crystal optical fiber. Background Art

[0002] The output power of fiber lasers is restricted by many factors.

[0003] First, the brightness of the pump source determines the intensity of the pump light that can be input into the doped fiber, which in turn affects the gain and output of the fiber laser.

[0004] Secondly, nonlinear effects will reduce the performance of fiber lasers. Among them, stimulated Raman scattering (SRS) is the main nonlinear effect of broadband fiber lasers, which will cause the laser power to shift to the long-wave direction and reduce the conversion efficiency of the laser. At the same time, the reverse-transmitted Raman light will damage the fiber devices, limiting the further increase of power.

[0005] Thirdly, the thermal load of the gain fiber is also a factor that cannot be ignored. The thermal load of the ytterbium-doped fiber laser mainly comes from the quantum loss generated by the laser transition. The thermal load will increase the temperature of the fiber and affect the stability of the laser.

[0006] Finally, the thermally induced mode instability effect is a key obstacle to high-power fiber lasers based on large mode area fibers. It causes the proportion of high-order modes in the fiber to increase and the laser beam quality to deteriorate after the output laser reaches a certain power.

[0007] In addition, the photon darkening effect of the gain fiber will also affect the power stability of high-power fiber lasers. The photon darkening effect will cause the output power of the laser to gradually decay as the operating time increases. Summary of the invention

[0008] In order to solve the problems of poor beam quality, low output energy and high system integration complexity in the existing high-power and high-energy femtosecond fiber amplification system under high-power femtosecond output conditions, the present invention provides a hybrid high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumped Yb:YAG single crystal fiber, which adopts a double-end co-band pumping method to improve laser output efficiency, reduce laser quantum loss and reduce the thermal load of the laser.

[0009] The present invention discloses a high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumping, comprising:

[0010] An optical signal input device, used for inputting a femtosecond chirped pulse signal to be amplified;

[0011] A pre-amplifier, used for pre-amplifying a femtosecond chirped pulse signal;

[0012] A main amplifier, comprising a single-pass structured single crystal optical fiber, for performing main amplification on the pre-amplified femtosecond chirped pulse signal and outputting the amplified femtosecond chirped pulse signal;

[0013] A double-ended same-band pumping device, the double-ended same-band pumping device comprising a first pumping light source, a second pumping light source, a first dichroic mirror and a second dichroic mirror, the pumping light generated by the first pumping light source is injected into one end of the single crystal optical fiber through the first dichroic mirror, and the pumping light generated by the second pumping light source is injected into the other end of the single crystal optical fiber through the second dichroic mirror, so as to realize double-ended same-band pumping;

[0014] The isolator is used to isolate the input femtosecond chirp pulse signal and the output femtosecond chirp pulse signal to prevent the reversely transmitted light from influencing the system.

[0015] As a further improvement of the present invention, a beam scaling component is provided between the first pump light source and the first dichroic mirror and between the second pump light source and the second dichroic mirror. The pump light generated by the first pump light source is scaled by the beam scaling component and then injected into one end of the single crystal optical fiber through the first dichroic mirror. The pump light generated by the second pump light source is scaled by the beam scaling component and then injected into the other end of the single crystal optical fiber through the second dichroic mirror, so as to realize double-end same-band pumping.

[0016] As a further improvement of the present invention, the pre-amplification device is composed of a silicate glass optical fiber amplifier.

[0017] As a further improvement of the present invention, the single crystal optical fiber is a Yb:YAG single crystal optical fiber.

[0018] As a further improvement of the present invention, the length of the Yb:YAG single crystal optical fiber is 10 to 20 cm, the nonlinear effect is small, and it can withstand high peak power.

[0019] As a further improvement of the present invention, the isolator includes a first polarizer, a 1 / 2 wave plate, a Faraday rotator and a second polarizer which are sequentially arranged along the laser transmission direction.

[0020] As a further improvement of the present invention, the isolator also includes a transmission mirror and a reflection mirror arranged in sequence along the laser transmission direction, and the transmission mirror is arranged between the second polarizer and the reflection mirror, and is used to collimate the input femtosecond chirped pulse signal and inject it into the single crystal optical fiber, and to extract the output femtosecond chirped pulse signal from the single crystal optical fiber.

[0021] As a further improvement of the present invention, the wavelength of the first pump light source and the second pump light source is 1018 nm, which is close to the peak wavelength of the emission spectrum of the Yb:YAG single crystal optical fiber, thereby reducing the quantum loss and improving the quantum conversion efficiency.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention utilizes a pre-amplifier cascaded with a main amplifier consisting of a single-crystal optical fiber with a first-stage single-pass structure to achieve amplification of femtosecond chirped pulse signals; wherein the single-crystal optical fiber adopts double-ended same-band pumping, so that the main amplifier has a compact structure, high quantum conversion efficiency, and less thermal effect; therefore, the entire system can achieve femtosecond chirped pulse amplification with a compact structure, high beam quality, and large output energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic structural diagram of a high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping disclosed in an embodiment of the present invention.

[0025] In the figure:

[0026] 1. The first polarizer;

[0027] 2. 1 / 2 wave plate;

[0028] 3. Faraday rotator;

[0029] 4. Second polarizer;

[0030] 5. Transmission mirror;

[0031] 6. Reflector;

[0032] 7. The first dichroic mirror;

[0033] 8. Yb:YAG single crystal optical fiber;

[0034] 9. Second dichroic mirror;

[0035] 10. The first pump light source;

[0036] 11. Second pump light source;

[0037] 12. Beam scaling component. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0040] like Figure 1 As shown, the present invention provides a hybrid high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumped Yb:YAG single crystal fiber, which can improve the slope efficiency and output power of the fiber laser, reduce thermal effects, and obtain high-quality beams; at the same time, due to the flexible structure of the system, the present invention is also applicable to other rare earth element single-doped or co-doped structure lasers; the amplification system specifically includes:

[0041] An optical signal input device, used for inputting a femtosecond chirped pulse signal to be amplified;

[0042] A pre-amplifier, which is composed of a silicate glass fiber amplifier and is used to pre-amplify the femtosecond chirped pulse signal;

[0043] A main amplifier device, the main amplifier device includes a Yb:YAG single crystal optical fiber 8 with a single-pass structure, and is used to perform main amplification on the pre-amplified femtosecond chirped pulse signal and output the amplified femtosecond chirped pulse signal;

[0044] A double-ended same-band pumping device includes a first pumping light source 10, a second pumping light source 11, a first dichroic mirror 7 and a second dichroic mirror 9. The pumping light generated by the first pumping light source 10 is scaled by a beam scaling component 12 and then injected into one end of a Yb:YAG single crystal fiber 8 through the first dichroic mirror 7. The pumping light generated by the second pumping light source 11 is scaled by a beam scaling component 12 and then injected into the other end of the Yb:YAG single crystal fiber 8 through the second dichroic mirror 9 to achieve double-ended same-band pumping. The double-ended same-band pumping method can obtain a higher output power. The length of the Yb:YAG single crystal fiber 8 is 10 to 20 cm, the nonlinear effect is small, and it can withstand high peak power. The wavelength of the first pumping light source 10 and the second pumping light source 11 is 1018 nm, which is close to the peak wavelength of the emission spectrum of the Yb:YAG single crystal fiber, reducing the quantum loss and improving the quantum conversion efficiency.

[0045] An isolator is used to isolate an input femtosecond chirp pulse signal from an output femtosecond chirp pulse signal to prevent the reversely transmitted light from affecting the system; wherein the isolator comprises a first polarizer 1, a 1 / 2 wave plate 2, a Faraday rotator 3, a second polarizer 4, a transmission mirror 5 and a reflection mirror 6 which are sequentially arranged along the laser transmission direction, and is used to collimate the input femtosecond chirp pulse signal and inject it into a single crystal optical fiber, and to extract the output femtosecond chirp pulse signal from the single crystal optical fiber.

[0046] The present invention uses the same-band pump and has the following advantages:

[0047] 1. The brightness of the pump source is significantly improved.

[0048] 2. Compared with LD direct pumping, the wavelength of the pump light with the same pumping band is closer to the wavelength of the signal light emitted by the laser, which reduces the quantum loss in the laser conversion process.

[0049] The reduction of quantum loss can effectively reduce the heat load in the gain fiber, relieve the pressure of thermal management, improve the efficiency of the laser, and increase the threshold of thermal mode instability. 3. Reduce the photon darkening rate and extend the service life of the gain fiber.

[0050] The present invention uses a Yb:YAG rod-shaped crystal (Yb:YAG single crystal optical fiber 8) for the main amplifier part. The Yb:YAG rod-shaped crystal is short in length, has a small nonlinear effect, and can avoid the influence of the self-focusing effect by optimizing the structural design of the amplifier, so it can withstand very high peak power. By combining the advantages of the ytterbium-doped fiber laser, such as high single-pass gain, good beam quality, good heat dissipation performance, and compact structure, with the advantages of the Yb:YAG rod-shaped crystal amplifier, such as weak nonlinear effect and high peak power tolerance, a compact and low-cost ultrashort pulse laser can be obtained.

[0051] The method of using the present invention comprises:

[0052] The femtosecond chirped pulse signal generated by the optical signal input device is collimated by the first polarizer 1, the 1 / 2 wave plate 2, the Faraday rotator 3, the second polarizer 4, the transmission mirror 5 and the reflection mirror 6 in sequence, and then injected into the Yb:YAG single crystal optical fiber 8 by the first dichroic mirror 7; the pump light generated by the first pump light source 10 is scaled by the beam scaling component 12 and then injected into one end of the Yb:YAG single crystal optical fiber 8 through the first dichroic mirror 7, and the pump light generated by the second pump light source 11 is scaled by the beam scaling component 12 and then injected into the other end of the Yb:YAG single crystal optical fiber 8 through the second dichroic mirror 9, so as to realize the double-ended same-band pumping amplification effect of the laser.

[0053] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumping, characterized in that: include: An optical signal input device, used for inputting a femtosecond chirped pulse signal to be amplified; A pre-amplifier, used for pre-amplifying a femtosecond chirped pulse signal; A main amplifier, comprising a single-pass structured single crystal optical fiber, for performing main amplification on the pre-amplified femtosecond chirped pulse signal and outputting the amplified femtosecond chirped pulse signal; A double-ended same-band pumping device, the double-ended same-band pumping device comprising a first pumping light source, a second pumping light source, a first dichroic mirror and a second dichroic mirror, the pumping light generated by the first pumping light source is injected into one end of the single crystal optical fiber through the first dichroic mirror, and the pumping light generated by the second pumping light source is injected into the other end of the single crystal optical fiber through the second dichroic mirror, so as to realize double-ended same-band pumping; The isolator is used to isolate an input femtosecond chirped pulse signal from an output femtosecond chirped pulse signal.

2. The high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping according to claim 1, characterized in that: The pre-amplification device is composed of a silicate glass optical fiber amplifier.

3. The high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping according to claim 1, characterized in that: The single crystal optical fiber is Yb:YAG single crystal optical fiber.

4. The high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumping as claimed in claim 3, characterized in that: The length of the Yb:YAG single crystal optical fiber is 10 to 20 cm.

5. The high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumping according to claim 1, characterized in that: A beam scaling component is provided between the first pump light source and the first dichroic mirror and between the second pump light source and the second dichroic mirror.

6. The high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping according to claim 1, characterized in that: The isolator comprises a first polarizer, a half wave plate, a Faraday rotator and a second polarizer which are sequentially arranged along the laser transmission direction.

7. The high-power and high-energy femtosecond chirped pulse amplification system based on in-band pumping according to claim 6, characterized in that: The isolator also includes a transmission mirror and a reflection mirror arranged in sequence along the laser transmission direction. The transmission mirror is arranged between the second polarizer and the reflection mirror and is used to collimate the input femtosecond chirped pulse signal and then inject it into the single crystal optical fiber.

8. The high-power and high-energy femtosecond chirped pulse amplification system based on co-band pumping according to claim 1, characterized in that: The wavelength of the first pump light source and the second pump light source is 1018 nm, which is close to the peak wavelength of the emission spectrum of the Yb:YAG single crystal optical fiber.

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