Titanium sapphire bonded crystal low-temperature cooling module for laser with high peak power and high repetition frequency

Abstract

The invention relates to a titanium sapphire bonded crystal low-temperature cooling module for laser with high peak power and high repetition frequency. The titanium sapphire bonded crystal low-temperature cooling module is characterized by mainly comprising a titanium sapphire bonded crystal, a heat sink crystal frame, a vacuum chamber with an air exhaust interface and an optical window, a low-temperature cooling chamber with a cooling medium inlet / outlet interface and the like. The titanium sapphire bonding crystal is installed on the heat sink crystal frame, one end of the titanium sapphire bonding crystal and one end of the heat sink crystal frame are arranged in a vacuum chamber with an air exhaust connector and an optical window, and the light passing face of the titanium sapphire bonding crystal is opposite to the optical window on the vacuum chamber. And the other end of the heat sink crystal frame is arranged in a low-temperature cooling chamber with a cooling medium inlet / outlet interface. According to the invention, the generation of transverse parasitic oscillation in the titanium sapphire bonded crystal can be inhibited, ultralow-temperature cooling of the titanium sapphire bonded crystal can be realized, and the repetition frequency and peak power of laser pulses output by an ultra-strong and ultra-short laser system can be further improved.

Description

TECHNICAL FIELD

[0001] The application relates to a laser crystal cooling technology of a solid laser amplifier, in particular to a low-temperature cooling module of a titanium sapphire bonded crystal for high-peak-power and high-repetition-frequency laser (1PW / 10Hz and above). BACKGROUND

[0002] With the development of the chirped pulse amplification (CPA) technology, the peak power of laser pulses is continuously improved, and has reached the level of petawatt (PW) or even more than 10PW. During the energy amplification of laser pulses, the pump light energy in the titanium sapphire crystal is partially converted into residual heat and spontaneous emission. The residual heat changes the refractive index distribution in the crystal, causes thermal lens effect and the like, and further affects the beam quality of the laser. The spontaneous emission is amplified between the side surfaces of the crystal, which may cause transverse parasitic oscillation and further affect the laser amplification efficiency. Therefore, in the laser system, a low-temperature cooling device is needed to suppress the thermal lens effect caused by the residual heat, and a special material is needed to suppress the transverse parasitic oscillation caused by the spontaneous emission. A common method for suppressing the transverse parasitic oscillation is to use an index matching liquid containing an absorber (Optics Letters, 2012, 37(11): 1913-1915). Since the index matching liquid has a similar refractive index to the titanium sapphire crystal, the reflectivity of the titanium sapphire crystal side surface to the spontaneous emission can be reduced, and the absorber can further absorb the spontaneous emission transmitted by the titanium sapphire crystal side surface. However, for a high-peak-power and high-repetition-frequency laser system, the titanium sapphire crystal needs to work in an extremely low temperature environment (such as below 150K), at which the physical properties of the index matching liquid will change, and the index matching liquid cannot effectively play a role.

[0003] Therefore, it is urgent to develop a crystal low-temperature cooling module suitable for high-peak-power and high-repetition-frequency laser, so as to overcome the adverse effects of the residual heat and the spontaneous emission in the crystal during the laser amplification process. SUMMARY

[0004] The application provides a titanium sapphire bonded crystal low-temperature cooling module for high-peak-power and high-repetition-frequency laser. By using the module, the effects of the residual heat and the spontaneous emission in the crystal on the laser amplification process can be overcome, the generation of transverse parasitic oscillation in the titanium sapphire bonded crystal can be suppressed, and the titanium sapphire bonded crystal can be cooled at an ultra-low temperature, which is beneficial to improving the repetition frequency and the peak power of the output laser pulse of the ultrastrong and ultrashort laser system.

[0005] The technical solution of the application is as follows:

[0006] A titanium-sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser, characterized in that it comprises a titanium-sapphire bonded crystal, a heat sink crystal holder, a vacuum chamber with a gas exhaust interface and an optical window, and a cryogenic cooling chamber with a cooling medium inlet and outlet interface. The titanium-sapphire bonded crystal is mounted on the heat sink crystal holder, one end of the titanium-sapphire bonded crystal and the heat sink crystal holder is placed in the vacuum chamber with a gas exhaust interface and an optical window, the light transmission surface of the titanium-sapphire bonded crystal is opposite to the optical window in the vacuum chamber, and the other end of the heat sink crystal holder is placed in the cryogenic cooling chamber with a cooling medium inlet and outlet interface.

[0007] The titanium-sapphire bonded crystal is composed of a titanium-sapphire crystal and a doped-absorbing-particle sapphire crystal bonded around the side of the titanium-sapphire crystal (non-light transmission surface). The doped-absorbing-particle sapphire crystal has a refractive index matching that of the titanium-sapphire crystal and can absorb the radiation light transmitted from the side of the titanium-sapphire crystal.

[0008] Compared with the prior art, the present application has the following significant features:

[0009] 1. The doped-absorbing-particle sapphire crystal with a refractive index substantially the same as that of the titanium-sapphire crystal is bonded, which can absorb spontaneous radiation light and inhibit the formation of transverse parasitic oscillation in the titanium-sapphire crystal.

[0010] 2. The module can realize ultra-low temperature cooling of the titanium-sapphire bonded crystal, overcome the influence of residual heat and spontaneous radiation light in the crystal on the laser amplification process, and is beneficial to further improve the repetition rate and peak power of ultrastrong ultra-short laser pulses. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Front view of the titanium-sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser.

[0012] Figure 2 Side view of the titanium-sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser.

[0013] Figure 3 Front view of the titanium-sapphire bonded crystal structure. DETAILED DESCRIPTION

[0014] The present application will be further described below through examples and drawings to enable those skilled in the art to fully understand and implement the present application, but the protection scope of the present application should not be limited thereby.

[0015] Please refer to Figure 1 and Figure 2 , Figure 1 and Figure 2The drawings are the front view and side view of the titanium-sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser. The titanium-sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser comprises the following parts:

[0016] The titanium-sapphire bonded crystal 1 is bonded by a titanium-sapphire crystal 101 and a sapphire crystal 102 doped with absorption particles, as shown in the drawing. The front and back surfaces of the titanium-sapphire crystal 101 are light transmission surfaces, and the sapphire crystal 102 doped with absorption particles is bonded around the side surface (non-light transmission surface) of the titanium-sapphire crystal 101. The sapphire crystal 102 doped with absorption particles matches the refractive index of the titanium-sapphire crystal 101 and can absorb the radiation light transmitted by the side surface of the titanium-sapphire crystal 101. The absorption particles can be selected from iron ions or copper ions. Figure 3

[0017] The heat sink crystal holder 2 is used to fix the titanium-sapphire bonded crystal 1 and realize efficient heat conduction.

[0018] The vacuum chamber 3 is equipped with exhaust interfaces 301 and 302, and opposite first and second optical window pieces 303 and 304, and is used to maintain a low-thermal-interference optical environment.

[0019] The cryogenic cooling chamber 4 is provided with cooling medium in-out interfaces 401 and 402, and realizes ultra-low temperature cooling through a cooling medium (such as liquid nitrogen).

[0020] Preparation of the titanium-sapphire bonded crystal 1 in the embodiment:

[0021] The titanium-sapphire crystal 101 is used as a gain medium, which has a wide tuning range and a high damage threshold.

[0022] The sapphire crystal 102 doped with iron ions or copper ions has a refractive index matching the titanium-sapphire crystal, and can efficiently absorb parasitic radiation light.

[0023] The contact surface of the titanium-sapphire crystal 101 and the doped sapphire crystal 102 is super-precision polished (surface roughness <1 nm). Direct bonding or optical cementing technology is used to ensure that the bonding interface is free of bubbles and scattering defects. After bonding, the whole is annealed (temperature 800-1000℃) to enhance the interface bonding strength.

[0024] Workflow of the embodiment:

[0025] 1. Start the vacuum pump set, and through the exhaust interfaces 301 and 302, the vacuum chamber 3 is pumped to the working vacuum degree;

[0026] 2. Start the liquid nitrogen circulation system, and through the cooling medium in-out interfaces 401 and 402, the cryogenic cooling chamber 4 is pre-cooled to the target temperature.

[0027] ​3. Pump light is injected into the titanium sapphire bonded crystal 1 through the optical window 303, and the amplified laser light is output from the window 304. Residual heat is conducted through the heat sink crystal holder 2 to the cryogenic cooling chamber 4 for dissipation. Side parasitic radiation light is absorbed by the doped sapphire crystal 102, suppressing transverse parasitic oscillation.

[0028] 4. The vacuum degree is checked periodically through the gas exhaust interface 301, 302, and the cooling medium is supplemented to maintain the low temperature environment.

Claims

1. A Ti:Sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate lasers, characterized in that: include: A titanium sapphire bonded crystal (1) is formed by bonding a titanium sapphire crystal (101) and a sapphire crystal (102) doped with absorption particles, wherein the sapphire crystal (102) doped with absorption particles is bonded around the side surface (non-light-transmitting surface) of the titanium sapphire crystal (101), and its refractive index matches the refractive index of the titanium sapphire crystal (101), and is used to absorb radiation light transmitted from the side surface of the titanium sapphire crystal (101); A vacuum chamber (3) is provided with gas extraction and exhaust interfaces (301 and 302), and a first optical window (303) and a second optical window (304) are provided opposite to each other, and the titanium sapphire bonded crystal (1) is placed in the vacuum chamber (3), with its light-transmitting surface facing the first optical window (303) and the second optical window (304); A low-temperature cooling chamber (4) is provided with cooling medium inlet and outlet ports (401 and 402); A heat sink crystal frame (2), one end of which is placed in the vacuum chamber (3) for fixing the titanium sapphire bonded crystal (1), and the other end of which is placed in the low-temperature cooling chamber (4) for ultra-low-temperature cooling of the titanium sapphire bonded crystal (1).

2. The Ti:Sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser according to claim 1, characterized in that: The absorbing particles in the sapphire crystal (102) doped with absorbing particles are iron ions or copper ions.

3. The Ti:Sapphire bonded crystal cryogenic cooling module for high peak power and high repetition rate laser according to claim 1, characterized in that: A heat insulation design is adopted between the low-temperature cooling chamber (4) and the vacuum chamber (3) to reduce the impact of heat exchange on the vacuum environment.

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