Light and small type wide-temperature-amplitude laser for space application

Abstract

The invention discloses a light and small wide-temperature-amplitude laser for space application. The light and small wide-temperature-amplitude laser comprises a laser base, a laser shell and a laser resonant cavity. The laser base and the laser shell are combined to form a sealed cavity; the laser resonant cavity is located in the sealed cavity and comprises an LD array, an LD coupling assembly, a laser crystal, a polarization element, an electro-optical Q switch, a quarter-wave plate and an output mirror which are sequentially arranged, and pump light emitted by the LD array sequentially passes through the coupling assembly, the laser crystal and the polarization element and is emitted through the quarter-wave plate and the output mirror when the electro-optical Q switch is turned on. The weight of the laser can be greatly reduced, the size of the laser is reduced, meanwhile, wide-temperature-amplitude work can be achieved, and the work power consumption of the laser is reduced.

Description

Technical Field

[0001] The invention relates to a light and small-sized wide-temperature-range laser for space application, belonging to the technical field of all-solid-state lasers. Background Art

[0002] As an active remote sensing detection technology, space laser radar is widely used in space target detection, terrain detection, atmospheric detection, space confrontation and other fields. As the core unit of space laser radar, space laser is used to emit active detection light source. Its performance index and reliability have a decisive influence on the performance of laser radar. When the laser is in the space environment, it will face the test of harsh space environment such as radiation, vacuum, pollution, temperature, and the impact of vibration and impact on the optical and mechanical performance of the laser during spacecraft launch. In order to improve the optical and mechanical stability of the laser, most space lasers adopt the following scheme: in the optical design, two orthogonal Paul prisms are used as the cavity mirrors of the laser to improve the anti-detuning ability of the laser. In the structural design, a shock-absorbing design is adopted to install the sensitive device separately on the isolation board. The overall mechanical stability is improved by structural reinforcement. The above scheme has the problem that the optical and structural volume of the laser resonant cavity are large, resulting in the weight of most space all-solid-state lasers being more than 3kg.

[0003] However, for space application payloads, especially small satellite platforms, their volume, weight and power consumption are limited, so there is an urgent need for lightweight, low-power laser products. However, the current design routes of space lasers launched at home and abroad are large in size and weight, which makes it difficult to adapt to the application needs of light and small payloads. Summary of the invention

[0004] The purpose of the present invention is to overcome the above defects and provide a light and small laser with a wide temperature range for space applications, which solves the technical problem that the existing lasers are large in size and weight and difficult to adapt to the application requirements of light and small loads. The present invention can significantly reduce the weight and volume of the laser, while achieving wide temperature range operation and reducing the operating power consumption of the laser.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention discloses a light and small-sized wide temperature range laser for space application, which adopts LD array direct end-face pumping to reduce the volume and weight of the pump end; at the same time, the end-face pumping can make full use of the long-range absorption of the laser crystal to realize the wide temperature range operation of the laser, improve the laser conversion efficiency, and reduce the laser power consumption; the cavity length is compressed by directly plating a full reflection film on the surface of the gain medium, the connector adopts a sintering method, and the lens adopts a welding method to reduce the volume and weight of the whole machine, and improve the sealing reliability, the structural design adopts an optical-mechanical integrated design, the structural base is an optical mounting seat, and the compactness of the structure is improved. The laser base adopts a flexible unloading cantilever support structure, which greatly reduces the influence of the space mechanical environment and the temperature environment on the stability of the laser structure. At the same time, in order to further improve the life and reliability of the space application laser, all external devices of the laser are metal sealed and filled with clean air to reduce the probability of pollution and damage to the internal optical components.

[0007] The present invention discloses a light and small-sized wide temperature range laser for space application, comprising: a laser base, a laser housing and a laser resonant cavity;

[0008] The laser base and the laser housing are combined to form a sealed cavity;

[0009] The laser resonant cavity is located inside a sealed cavity, and includes an LD array, an LD coupling component, a laser crystal, a polarization element, an electro-optical Q switch, a quarter-wave plate, and an output mirror arranged in sequence. The pump light emitted by the LD array passes through the coupling component, the laser crystal, and the polarization element in sequence, and is emitted through the quarter-wave plate and the output mirror when the electro-optical Q switch is turned on.

[0010] Furthermore, the light emitting plane of the LD array is parallel to the crystal end face of the laser crystal.

[0011] Furthermore, the LD array is a stacked array of diode lasers;

[0012] The number of stacked arrays is determined by the laser single pulse energy and the size of the laser crystal.

[0013] Furthermore, the LD coupling component is an optical waveguide device, which is used to shape the pump light emitted by the LD array and couple it into the laser crystal.

[0014] Furthermore, the laser crystal is made of Nd:YAG material, wherein Nd 3+ The doping concentration is 0.6at.%~1.1at.%;

[0015] The incident end of the laser crystal is coated with a film that fully reflects the oscillation light, the four sides are roughened, and the output end is coated with a film that fully reflects the pump light;

[0016] The length of the laser crystal is 10 mm to 25 mm.

[0017] Further, the polarizing element is a polarizing beam splitter prism or a polarizing plate;

[0018] The angle between the normal to the polarizer and the optical axis of the laser crystal is the Brewster angle;

[0019] The incident surface of the polarization beam splitter prism is parallel to the end face of the laser crystal.

[0020] Further, the laser resonant cavity is mounted on the laser base via a flexible cantilever support structure;

[0021] The flexible cantilever support structure is a T-shaped structure, including a cantilever support and a base cantilever;

[0022] The cantilever support is connected to the laser base and is used to support the base cantilever;

[0023] The base cantilever is connected to the cantilever support, two ends of the base cantilever are respectively located on both sides of the cantilever support, and the laser crystal and the output mirror are respectively installed on the two ends of the base cantilever.

[0024] Furthermore, a window mirror is provided on the laser housing;

[0025] The window mirror is directly welded to the laser housing by metal sealing, or the window mirror is welded to the flange, and the flange is installed on the laser housing by metal sealing;

[0026] Welding leakage rate ≤1×10 -9 Pa·m 3 ·s -1 .

[0027] Furthermore, a sintered connector is provided on the laser base;

[0028] The sintered connector is directly sintered on the laser base, or the sintered connector is sintered on the flange, and the flange is installed on the laser base through a metal seal;

[0029] Sintering leakage rate ≤1×10 -9 Pa·m 3 ·s -1 .

[0030] Furthermore, the laser base and the laser housing are combined by metal sealing or welding to form a sealed cavity, and the sealing leakage rate is ≤1×10 -8 Pa·m 3 ·s -1 ;

[0031] The sealed cavity is filled with clean air at a pressure of ≤1.5 atmospheres.

[0032] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0033] (1) The present invention creatively proposes a light and small laser with a wide temperature range for space application, which adopts an optical-mechanical integrated design, and the structural base is the optical element mounting seat, thereby improving the compactness of the structure;

[0034] (2) The present invention adopts the LD direct end-face pumping method, combined with the long-range absorption of the long laser crystal to achieve wide temperature range operation of the laser, and the temperature adaptation range can reach (T0±10)℃;

[0035] (3) The laser base of the present invention adopts a flexible unloading cantilever support structure, which greatly reduces the influence of the spatial mechanical environment and the temperature environment on the stability of the laser structure, reduces the sensitivity of the laser's sensitive optical elements, and increases the compactness of the structure, greatly reduces the weight of the laser, reduces the volume of the laser, and truly realizes the lightweight and compact design of the laser;

[0036] (4) The laser crystal of the present invention uses a method of directly coating the surface of the gain medium with a total reflection film to compress the cavity length, further improving the miniaturization of the laser;

[0037] (5) The present invention adopts the connector sintering and lens welding method to reduce the volume and weight of the whole machine and improve the sealing reliability;

[0038] (6) All external components of the laser of the present invention are metal sealed and filled with clean air, which reduces the probability of contamination and damage to the internal optical components, and is beneficial to improving the life and reliability of the laser for space applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the overall configuration diagram of the laser device of the present invention;

[0040] Figure 2 is a cross-sectional view of the laser structure of the present invention;

[0041] Figure 3 This is a structural diagram of the laser base of the present invention;

[0042] Reference numerals:

[0043] 1- inflation valve; 2- laser housing; 3- LD array; 4- coupling assembly; 5- laser crystal; 6- polarization element; 7- electro-optic Q switch; 8- quarter wave plate; 9- output mirror; 10- window mirror; 11- sintered connector; 12- laser base; 13- cantilever support; 14- base cantilever. DETAILED DESCRIPTION

[0044] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0045] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0046] In order to solve the application demand of space payload for light, small and low-power lasers, the present invention provides a light, small and wide temperature range laser for space application, which adopts LD array direct end-face pumping to reduce the volume and weight of the pump module; the end-face pumping form makes full use of the long-range absorption of the laser crystal to realize the wide temperature range operation of the laser, improve the laser conversion efficiency and reduce the laser power consumption; the cavity length is compressed by directly plating the full reflection film on the surface of the gain medium, and the connector sintering and lens welding methods are adopted to reduce the volume and weight of the whole machine and improve the sealing reliability; the structural design adopts the optical-mechanical integration design, and the structural base is the optical element mounting seat to improve the compactness of the structure; the laser base adopts a flexible unloading cantilever support structure to greatly reduce the influence of the space mechanical environment and temperature environment on the stability of the laser structure. At the same time, in order to further improve the life and reliability of the space application laser, all external components of the laser are metal sealed and filled with clean air to reduce the probability of pollution and damage to the internal optical components.

[0047] The present invention discloses a light and small laser with a wide temperature range for space application, comprising a laser base 12, a laser housing 2 forming a sealed structure with the laser base, and a laser resonant cavity composed of optical components placed on the laser base 12; in a specific embodiment, it also includes a sintered connector 11 placed on the laser base, a window mirror 10 placed on the laser housing 2, and an inflation valve 1.

[0048] The laser adopts the working system of LD array 3 direct end-face pumping to miniaturize the resonant cavity configuration.

[0049] The laser resonant cavity comprises an LD array 3, an LD coupling component 4, a laser crystal 5, a polarization element 6, an electro-optical Q switch 7, a quarter wave plate 8, and an output mirror 9 which are arranged in sequence.

[0050] The LD array is a stacked array diode laser, the number of stacked arrays is determined by the laser single pulse energy and the laser crystal size, preferably, there are 5 to 10 arrays.

[0051] The coupling component is preferably an optical waveguide, which is used to shape the pump light emitted by the LD and couple it into the laser crystal 5. The size of the optical waveguide is determined by the size of the light-emitting surface of the LD array 3 and the aperture of the laser crystal 5.

[0052] The laser crystal is preferably made of Nd:YAG material, wherein Nd 3+The doping concentration is 0.6at.% to 1.1at.%; the incident end of the laser crystal is plated with a total reflection film for oscillation light, which serves as the total reflection surface of the laser resonant cavity. The four sides of the laser crystal are roughened to avoid parasitic oscillation in the cavity. In order to achieve wide temperature range operation, the length of the laser crystal is 10mm to 25mm, and the output end is plated with a total reflection film for pump light, so that the pump light is fully absorbed in the laser crystal.

[0053] The polarizing element is preferably a polarizing beam splitter prism or a polarizing plate, and the angle between the optical axis of the polarizing plate and the optical axis of the laser crystal is the Brewster angle.

[0054] The laser base preferably adopts a flexible cantilever support structure to isolate and place two sensitive elements of the laser resonant cavity, thereby reducing the influence of thermal elastic deformation caused by external forced displacement and temperature gradient on the laser resonant cavity.

[0055] The base flexible cantilever support structure is that only the cantilever support of the base cantilever is connected to the laser base. The laser crystal and the output mirror are placed at both ends of the base cantilever respectively. With this structural form, the thermoelastic deformation caused by the external forced displacement and the temperature change of the whole machine will cause the base to deform, but the deformation will not be transmitted to the base cantilever, effectively isolating the influence of the structural deformation on the laser resonant cavity.

[0056] Preferably, the window mirror is welded to the laser housing or flange by metal welding, and the flange is mounted on the housing by metal sealing, and the welding leakage rate is ≤1×10 -9 Pa·m 3 ·s -1 .

[0057] Preferably, the sintered connector is a power supply pin directly sintered on the base or flange, and the flange is installed on the housing by metal sealing. The sintering leakage rate is ≤1×10 -9 Pa·m 3 ·s -1 .

[0058] Preferably, the laser housing and the laser base are sealed by metal sealing or welding, and the sealing leakage rate of the whole machine is ≤1×10 -8 Pa·m 3 ·s -1 The laser is filled with clean air at ≤1.5 atmospheres, which reduces the pollution inside the laser housing and improves the reliability of the laser.

[0059] In summary, the present invention adopts a laser optical-mechanical integrated design, the optical elements are directly mounted on the structural base, and a flexible cantilever structure is adopted, which reduces the sensitivity of the laser sensitive optical elements and increases the compactness of the structure. Compared with other laser structural designs that often use structural reinforcement to cope with external forced displacement and temperature gradients, and use a low thermal expansion coefficient as the structural mounting base, the weight of the laser is greatly reduced, the volume of the laser is reduced, and the lightweight design of the laser is truly realized.

[0060] The laser is pumped by direct end-face pumping of LD, combined with the long-range absorption of long laser crystals to achieve wide temperature range operation of the laser. The weight of the laser is ≤500g, the temperature adaptability range can reach (T0±10)℃, the output laser repetition frequency is (1~20)Hz, the single pulse energy is (10~30)mJ, the pulse width is (4~7)ns, and the laser divergence angle is (2~4)mrad. The present invention further combines the flexible cantilever structure to greatly increase the stability of the laser structure. Compared with the conventional space laser operating temperature within ±2℃, it truly realizes wide temperature range operation and reduces the laser operating power consumption.

[0061] Example:

[0062] like Figure 1 , Figure 2 As shown, a light and small-sized wide temperature range laser for space application includes a laser base 12, a laser housing 2 forming a sealed structure with the laser base, a laser resonant cavity composed of optical components placed on the laser base (an LD array 3, an LD coupling component 4, a laser crystal 5, a polarization element 6, an electro-optical Q switch 7, a quarter wave plate 8, and an output mirror 9 are placed in sequence), a sintered connector 11 placed on the laser base, a window mirror 10 placed on the laser housing, and an inflation valve 1.

[0063] The laser adopts the working system of LD array 3 direct end-face pumping, which makes the laser resonant cavity configuration miniaturized.

[0064] The pump light band of LD array 3 is 808nm, and the pump light power is 800W. The pump light is shaped by coupling component 4 and then coupled into laser crystal 5. The size of the coupling component is determined by the size of the LD light emitting surface and the aperture of the laser crystal.

[0065] Laser crystal 5 is Nd:YAG, where Nd 3+ The doping concentration is 0.6at.% to 1.1at.%; one end of the laser crystal is coated with a 1064nm total reflection film as the total reflection surface of the laser resonant cavity, and the four sides of the laser crystal are roughened to avoid parasitic oscillation in the cavity. In order to achieve wide temperature range operation of the laser, the length of the laser crystal is 15mm, and the output end is coated with an 808nm total reflection film to ensure that the pump light is fully absorbed in the laser crystal.

[0066] The polarization element 6 is a polarizing plate, and the angle between the optical axis of the polarizing plate and the optical axis of the laser crystal is the Brewster angle.

[0067] In order to achieve a light and compact design of the whole machine, an optical-mechanical integrated design is adopted, and the optical elements of the resonant cavity are installed on the laser base 12.

[0068] like Figure 3 As shown, in order to cope with the influence of space mechanics and thermal environment, the installation of the resonant cavity optical element on the laser base is realized through a flexible unloading cantilever support structure. The flexible unloading cantilever support structure includes a cantilever support 13 and a base cantilever 14. Only the cantilever support 13 is connected to the laser base 12. The two sensitive elements of the laser resonant cavity, the laser crystal 5 and the output mirror 9, are respectively placed at the two ends of the base cantilever 14 to reduce the influence of the external forced displacement and the thermoelastic deformation caused by the temperature gradient on the laser resonant cavity. After simulation analysis, the flexible support structure unloads about 90% of the influence of the forced displacement and the thermoelastic deformation on the relative position of the optical element, thereby improving the reliability of the laser in the space environment.

[0069] The window mirror 10 is formed by welding the lens metal to the flange. To cope with the space radiation environment, the lens is a radiation-resistant sapphire lens. The flange is sealed to the laser housing 2 through an indium wire. The window mirror sealing leakage rate is ≤1×10 -9 Pa·m 3 ·s -1 .

[0070] The sintered connector 11 adopts glass sintering method to sinter the power supply pins of LD and electro-optical Q switch on the flange and seal it on the laser base 12 through indium wire. The leakage rate of the sintered connector is ≤1×10 -9 Pa·m 3 ·s -1 .

[0071] The gas filling valve 1 is sealed on the laser housing 2 through an indium wire, and the gas valve leakage rate is ≤1×10 -9 Pa·m 3 ·s -1 .

[0072] The laser housing 2 and the laser base 1 are sealed by indium wire. The laser is filled with clean air at 1.2 atmospheres through the air valve 1. The leakage rate of the whole machine is ≤1×10 -8 Pa·m 3 ·s -1 .

[0073] The optical path of the laser of the present invention is as follows:

[0074] The pump light emitted by the LD array 3 enters the LD coupling component 4. After the LD coupling component 4 shapes the pump light beam, it is coupled into the laser crystal 5. After the pump light is fully absorbed in the laser crystal 5, it enters the polarization element 6 to form polarized light. After passing through the electro-optical Q switch 7 and the quarter-wave plate 8, it is output by the output mirror 9. The laser forms a resonant cavity through the incident end of the laser crystal 5 and the output mirror. The intracavity loss of the laser resonant cavity is controlled by the switch of the electro-optical Q switch 7. When the electro-optical Q switch 7 is turned on, the loss of the electro-optical Q switch 7 is reduced to form laser oscillation. The laser passes through the quarter-wave plate 8 and is output by the output mirror 9 to the window mirror 10.

[0075] The laser of the present invention has an output repetition rate of 10 Hz, a single pulse energy of 30 mJ, a pulse width of 5 ns, and a laser divergence of 3 mrad. The simulated on-orbit mechanical environment test and thermal vacuum test have been completed, and no change has been observed in the indicators, thus passing the verification of the simulated on-orbit environment.

[0076] The laser of the present invention weighs only 400g and has a normal operating temperature range of (25±10)°C, meeting the requirements of lightness, small size and wide temperature range for space lasers.

[0077] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0078] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A light and small laser with a wide temperature range for space application, characterized in that: include: A laser base (12), a laser housing (2) and a laser resonant cavity; The laser base (12) and the laser housing (2) are combined to form a sealed cavity; The laser resonant cavity is located inside a sealed cavity, and comprises an LD array (3), an LD coupling component (4), a laser crystal (5), a polarization element (6), an electro-optical Q switch (7), a quarter wave plate (8) and an output mirror (9) which are arranged in sequence. The pump light emitted by the LD array (3) passes through the coupling component (4), the laser crystal (5) and the polarization element (6) in sequence, and is emitted through the quarter wave plate (8) and the output mirror (9) when the electro-optical Q switch (7) is turned on.

2. A light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: The light emitting array surface of the LD array (3) is parallel to the crystal end surface of the laser crystal (5).

3. A light and small laser with a wide temperature range for space application according to claim 1, characterized in that: The LD array (3) is a stacked array diode laser; The number of stacked arrays is determined according to the single pulse energy of the laser and the size of the laser crystal (5).

4. A light and small laser with a wide temperature range for space application according to claim 1, characterized in that: The LD coupling component (4) is an optical waveguide device used for shaping the pump light emitted by the LD array (3) and coupling it into the laser crystal (5).

5. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: The laser crystal (5) is made of Nd:YAG material, wherein Nd 3+ The doping concentration is 0.6at.%~1.1at.%; The incident end of the laser crystal (5) is coated with an oscillation light total reflection film, the four side surfaces are roughened, and the output end is coated with a pump light total reflection film; The length of the laser crystal (5) is 10 mm to 25 mm.

6. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: The polarizing element (6) is a polarizing beam splitter prism or a polarizing plate; The angle between the normal line of the polarizer and the optical axis of the laser crystal (5) is the Brewster angle; The incident surface of the polarization beam splitting prism is parallel to the end surface of the laser crystal (5).

7. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: The laser resonant cavity is mounted on a laser base (12) via a flexible cantilever support structure; The flexible cantilever support structure is a T-shaped structure, comprising a cantilever support (13) and a base cantilever (14); The cantilever support (13) is connected to the laser base (12) and is used to support the base cantilever (14); The base cantilever (14) is connected to the cantilever support (13), the two ends of the base cantilever (14) are respectively located on both sides of the cantilever support (13), and the laser crystal (5) and the output mirror (9) are respectively installed on the two ends of the base cantilever (14).

8. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: A window mirror (10) is provided on the laser housing (2); The window mirror (10) is directly welded to the laser housing (2) by means of metal sealing, or the window mirror (10) is welded to a flange, and the flange is mounted on the laser housing (2) by means of metal sealing; Welding leakage rate ≤1×10 -9 Pa·m 3 ·s -1 .

9. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: A sintered connector is provided on the laser base (12); The sintered connector is directly sintered on the laser base (12), or the sintered connector is sintered on a flange, and the flange is installed on the laser base (12) by metal sealing; Sintering leakage rate ≤1×10 -9 Pa·m 3 ·s -1 .

10. The light and small-sized wide temperature range laser for space application according to claim 1, characterized in that: The laser base (12) and the laser housing (2) are combined by metal sealing or welding to form a sealed cavity, and the sealing leakage rate is ≤1×10 -8 Pa·m 3 ·s -1 ; The sealed cavity is filled with clean air at a pressure of ≤1.5 atmospheres.

Images