Laser amplifier based on composite ceramic structure

Abstract

The invention relates to a laser amplifier based on a composite ceramic structure. The laser amplifier comprises a single-frequency seed light unit (1), an optical isolator (2), a light beam shaping unit (3), a composite structure ceramic crystal (5), a pump light coupling unit (6) and an LD stack array (7) which are arranged in sequence. The high-power laser amplifier is used for solving the problems that the high-power laser amplifier is heated unevenly and amplified spontaneous radiation and self-oscillation are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser, in particular to a laser amplifier based on composite ceramic structure. BACKGROUND

[0002] With the vigorous development of atomic physics, quantum information, precision measurement and other fields, high-power single-frequency laser has great application prospects in space high-speed communication, high-precision detection, time-frequency transfer, laser radar and other fields, and is an important research direction that countries compete to develop. Directly obtaining hundreds of watts of single-frequency continuous output has great challenges in laser linewidth narrowing and beam quality control, and the scheme of using a narrow-linewidth seed laser combined with a power amplifier can reduce the difficulty, which is also the mainstream realization scheme of high-power single-frequency laser at present.

[0003] With the maturity of ground equipment, many applications will be extended to astronomical and space fields, such as quantum communication, space gravitational wave detection, deep space ranging, etc., which puts higher requirements on the performance of high-power single-frequency continuous laser. In addition to requiring high beam quality, high power and narrow linewidth output, the laser also needs to have long service life, low energy consumption and radiation resistance. When using a traditional uniformly doped Nd:YAG or Nd:YVO4 crystal as a gain medium, under high-power pumping, the early absorption of the doped ions at the incident end of the crystal to the pump laser causes the absorption of the pump laser to be weak at the rear end of the crystal, thereby causing the thermal distribution in the crystal to be uneven along the laser propagation direction.

[0004] The temperature gradient caused by the uneven thermal distribution produces a serious thermal lens effect in the crystal, which greatly reduces the light output efficiency, beam quality and output power stability of the laser.

[0005] Therefore, it is still an urgent problem to design a laser amplifier based on a composite ceramic structure. SUMMARY

[0006] The present application provides a composite structure ceramic laser amplifier to solve the problem of uneven heating of high-power laser and reduce self-excited oscillation in the amplification process.

[0007] The laser amplifier based on the composite ceramic structure provided by the embodiment of the present application comprises a single-frequency seed light unit, an optical isolator, a beam shaping unit, a composite structure ceramic crystal, a pump light coupling unit and an LD array arranged in sequence.

[0008] Further, a 45° mirror is further arranged between the beam shaping unit and the composite structure ceramic crystal.

[0009] Further, the single-frequency seed light unit is used to provide seed light with single frequency, narrow linewidth and good beam quality.

[0010] Further, the optical isolator is used for unidirectional transmission of the seed light, ensuring that the seed light does not backflow.

[0011] Further, the beam shaping unit is used for shaping the seed light, so that the seed light fills the composite structure ceramic crystal in the horizontal direction, and the seed light is shaped to a predetermined radius in the vertical direction.

[0012] Further, the composite structure ceramic crystal is a Nd:YAG composite ceramic crystal.

[0013] Further, the pump light coupling unit is used for making the pump light beam uniformly distributed and fill the slab gain medium of the composite structure ceramic crystal in the horizontal direction after coupling, and fill the central part of the gain medium in the vertical direction.

[0014] Further, the LD stack is used for providing high-power pump light.

[0015] Further, the composite structure ceramic crystal comprises a low-gain region part and a high-gain region part, and the high-gain region part is also provided with concentration step doping.

[0016] Further, the low-gain region part and the high-gain region part are arranged along the vertical direction, and the high-gain region part is provided with concentration step doping along the horizontal direction.

[0017] The embodiment of the present application provides a composite structure ceramic laser amplifier for solving the problems of uneven heating of a high-power laser and reducing amplified spontaneous emission, concentration step doping exists in two directions of the composite structure ceramic crystal, the thermal effect of the gain medium can be effectively reduced, and the amplified spontaneous emission and self-excited oscillation of the amplifier can be effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 FIG. 1 is a structural schematic diagram of a laser amplifier based on a composite ceramic structure according to an embodiment of the present application;

[0020] Figure 2 FIG. 2 is a structural schematic diagram of a composite structure ceramic crystal according to an embodiment of the present application.

[0021] 1, single frequency seed light unit, 2, optical isolator, 3, light beam shaping unit, 4, 45° reflector, 5, composite structure ceramic crystal, 6, pump light coupling unit, 7, LD laser stack. DETAILED DESCRIPTION

[0022] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be part of the complete specification. In the drawings, the shape or thickness of the embodiment can be exaggerated and simplified or facilitated. Moreover, parts of the structure in the drawings will be described separately, and it should be noted that the elements not shown or not described by text in the drawings are in the form known to those skilled in the art.

[0023] The description of the embodiments here, any reference to direction and orientation, is only for the convenience of description, and cannot be understood as any limitation on the scope of protection of the present application. The following description of the preferred embodiment will refer to a combination of features, which can exist independently or in combination, and the present application is not particularly limited to the preferred embodiment. The scope of the present application is defined by the claims.

[0024] For multi-section gradient-doped neodymium ion laser gain medium, composite structure laser ceramic has more application potential, not only short processing cycle and low processing cost, but also can greatly homogenize the temperature distribution inside the gain medium, improve the light output efficiency and output power, and suppress the parasitic oscillation problem that easily occurs in the all-solid-state amplifier, reduce the intensity noise of the laser, and the laser ceramic itself has radiation resistance, which is very suitable for developing space lasers.

[0025] As shown in Figure 1 The laser amplifier based on the composite ceramic structure of the embodiment of the present application comprises a single frequency seed light unit 1, an optical isolator 2, a light beam shaping unit 3, a 45° reflector 4, a composite structure ceramic crystal 5, a pump light coupling unit 6 and an LD stack 7 arranged in sequence. Among them, the single frequency seed light unit 1 is the master oscillator part, responsible for providing small signal seed light with high beam quality, and the composite structure ceramic crystal 5 is the amplifier part, responsible for amplifying the seed light.

[0026] The single frequency seed light unit 1 is used to provide single frequency seed light meeting the requirements, and the seed light needs to have the advantages of narrow linewidth and good beam quality.

[0027] The optical isolator 2 is used to make the seed light pass in one direction, so as to prevent the laser from flowing back to the seed laser and damaging the laser.

[0028] Beam shaping unit 3 is used for shaping the seed light in vertical and horizontal directions, so that the seed light fills the whole Nd:YAG composite ceramic crystal in the horizontal direction as much as possible, thereby improving the extraction efficiency, and the seed light is shaped to a specified radius in the vertical direction, thereby achieving better mode matching with the pump light.

[0029] LD stack 7 is used for providing sufficient pump laser for the amplifier part.

[0030] Pump light coupling unit 6 is used for shaping the pump laser provided by the LD stack 7, so that the emitted pump laser is uniformly distributed in the horizontal direction, effectively reducing the thermal effect, and filling the whole slab gain medium in the horizontal direction; in the vertical direction, the size of the pump light spot is changed, so that the pump light is matched with the intracavity mode of the amplification cavity.

[0031] As shown in Figure 2 The composite structure ceramic crystal 5 includes a low-gain area part A and a high-gain area part B, wherein the high-gain area part B is also step-doped from left to right, and the doping concentration gradually increases from left to right. The purpose of this is that when the seed light of a small signal directly passes through the high-gain area part B, the upper level inversion particle number is relatively large, which will aggravate the self-oscillation and the amplified spontaneous emission to a certain extent, and inhibit the amplification of the seed light, so that the extraction efficiency of the amplifier is reduced. Therefore, the ceramic with low doping concentration (the low-gain area part A) and the ceramic with relatively high doping concentration (the high-gain area part B) are sintered together, so that the seed light is first amplified in the low-gain area, and the upper level inversion particle number is small in the low-gain area, and the self-oscillation and the amplified spontaneous emission are weak, and then the seed light is further amplified in the high-gain area part B. This can effectively reduce the self-oscillation and the spontaneous emission in the amplification process; at the same time, the high-gain area part B is also step-doped from left to right, and the doping concentration gradually increases from left to right. This is because for a uniformly doped crystal, the absorption of the crystal to the pump light gradually decreases along the light transmission direction of the pump light, resulting in uneven temperature distribution. However, for the step-doped crystal with gradually increasing doping concentration from left to right, the absorption of the crystal to the pump light is relatively uniform along the light transmission direction of the pump light, so that the heat distribution of the gain medium is more uniform, thereby the ceramic gain medium can withstand higher pump power. The conversion efficiency of the amplified laser is improved.

[0032] The laser amplifier based on the composite ceramic structure of the embodiment of the application uses the following principles:

[0033] The LD stack 7 emits high-power pump light, which is shaped by the pump light coupling unit 6, fills the gain medium of the composite structure ceramic crystal 5 in the horizontal direction and presents uniform distribution, and fills the ceramic central part in the vertical direction. At the same time, the pump light is incident on the gain medium of the composite structure ceramic crystal 5 through the pump light coupling unit 6 to realize population inversion. The single-frequency seed light unit 1 provides a single-frequency and good beam quality Nd:YAG laser beam (i.e. seed light). The seed light is incident on the beam shaping unit 3 through the optical isolator 2. The seed light is shaped to fill the composite structure ceramic crystal 5 as much as possible in the horizontal direction, so as to improve the extraction efficiency as much as possible, and the seed light is shaped to a specified width in the vertical direction, so as to realize mode matching with the pump light. Specifically, after the seed light is reflected by the 45° reflector 4, it enters the Nd:YAG composite ceramic, is pre-amplified by the low-gain region part A, and is further amplified by the high-gain region part B. In this way, the thermal effect of the ceramic can be effectively reduced, and the spontaneous radiation and self-oscillation in the amplification process can be suppressed, so as to facilitate the amplification process, improve the extraction efficiency, and improve the output power.

[0034] The composite structure laser ceramic has application potential for the multi-section gradient-doped neodymium ion laser gain medium, and can not only shorten the processing period and reduce the processing cost, but also can homogenize the internal temperature distribution of the gain medium, improve the light extraction efficiency and output power, suppress the parasitic oscillation problem easily occurring in the all-solid-state amplifier, reduce the intensity noise of the laser, and has great application prospects in the fields of space high-speed communication, high-precision detection, time-frequency transmission, laser radar and the like.

[0035] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A laser amplifier based on a composite ceramic structure, characterized in that: It comprises a single-frequency seed light unit (1), an optical isolator (2), a beam shaping unit (3), a composite structure ceramic crystal (5), a pump light coupling unit (6) and an LD stack array (7) which are arranged in sequence.

2. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: A 45° reflecting mirror (4) is also provided between the beam shaping unit (3) and the composite structure ceramic crystal (5).

3. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The single-frequency seed light unit (1) is used to provide seed light with single frequency, narrow line width and good beam quality.

4. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The optical isolator (2) is used to enable the seed light to be transmitted in one direction, thereby ensuring that the seed light does not flow back.

5. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The beam shaping unit (3) is used to shape the seed light so that the seed light fills the composite structure ceramic crystal (5) in the horizontal direction, and to shape the seed light to a predetermined radius in the vertical direction.

6. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The composite structure ceramic crystal (5) is a Nd:YAG composite ceramic crystal.

7. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The pump light coupling unit (6) is used to make the pump light beam evenly distributed in the horizontal direction after coupling and fill the slab gain medium of the composite structure ceramic crystal (5), and fill the central part of the gain medium in the vertical direction.

8. The laser amplifier based on a composite ceramic structure according to claim 1, characterized in that: The LD stack array (7) is used to provide high-power pump light.

9. The laser amplifier based on a composite ceramic structure according to any one of claims 1 to 8, characterized in that: The composite structure ceramic crystal (5) comprises a low-gain region (A) and a high-gain region (B), and the high-gain region (B) itself is also configured with a concentration step doping arrangement.

10. The laser amplifier based on a composite ceramic structure according to claim 9, characterized in that: The low-gain region portion (A) and the high-gain region portion (B) are arranged along a vertical direction, and the high-gain region portion (B) itself is configured to be doped with a concentration step along a horizontal direction.

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