Laser device and artificial satellite

Abstract

Provided is a laser device comprising: an accommodation unit in which a resonator is accommodated; an excitation light source that is provided to the exterior of the accommodation unit and that includes a fiber cable for outputting excitation light; and a fixation unit for fixing an emission end of the fiber cable at the exterior of the accommodation unit and causing, by spatial transmission, the excitation light from the emission end to be incident on the resonator inside the accommodation unit. The accommodation unit may comprise an incidence window that allows the excitation light to pass.

Description

Laser device and artificial satellite

[0001] The present invention relates to a laser device and an artificial satellite.

[0002] Conventionally, a fiber-coupled laser device is known in which excitation light obtained from a laser diode (LD) disposed separately from a laser resonator is transmitted through an optical fiber and guided to an active medium in a sealed container in which the optical resonator is disposed (see, for example, Patent Document 1). Patent Document 1: International Publication No. 2017 / 138373 General Disclosure

[0003] In a laser device, it is preferable that the optical loss in the path from the optical fiber to the optical resonator is small. In addition, the inside of the container in which the optical resonator is disposed may need to be sealed.

[0004] In order to solve the above problem, in one aspect of the present invention, a laser device is provided. The laser device may include a housing section that houses a resonator. Any of the above laser devices may include an excitation light source that is provided outside the housing section and includes a fiber cable that outputs excitation light. Any of the above laser devices may include a fixing section that fixes an emission end of the fiber cable outside the housing section, and causes the excitation light from the emission end to enter the resonator inside the housing section via spatial transmission.

[0005] In any of the above laser devices, the housing section may have an incident window that allows the excitation light to pass through while achieving sealing of the housing section.

[0006] Any of the above laser devices may include a condensing optical system that is provided between the incident window and the emission end of the fiber cable, and condenses the excitation light to make it enter the resonator.

[0007] Any of the above laser devices may include a condensing optical system that is provided between the incident window and the resonator, and condenses the excitation light to make it enter the resonator.

[0008] Any of the above laser devices may include a focusing optical system that focuses the excitation light and directs it into the resonator. In any of the above laser devices, one end of the focusing optical system may be exposed to the outside of the housing and the other end may be exposed to the inside of the housing.

[0009] In any of the laser devices described above, the housing may be sealed and filled with gas.

[0010] In any of the above-described laser devices, the inside of the housing may be at atmospheric pressure.

[0011] In any of the laser devices described above, the housing may be sealed and filled with liquid.

[0012] Any of the above laser devices may include a cooling unit for cooling at least one of the fixed unit and the excitation light source.

[0013] In any of the above laser devices, the cooling unit may have a metal mounting base on which the fixed unit and the excitation light source are placed. In any of the above laser devices, the mounting base described above may have a radiating surface that releases heat from the fixed unit and the excitation light source.

[0014] The area outside the containment may be a vacuum or a space environment.

[0015] A second embodiment of the present invention provides a satellite comprising a laser device according to the first embodiment and a housing for the laser device.

[0016] The above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention.

[0017] This is a schematic diagram showing an example configuration of a laser device 100 according to one embodiment of the present invention. This is a schematic diagram showing another example configuration of the laser device 100. This is a schematic diagram showing another example configuration of the laser device 100. This is a schematic diagram showing another example configuration of the laser device 100. This is a schematic diagram showing another example configuration of the laser device 100. This is a cross-sectional view showing an example of the fixed part 52. This is a diagram showing an example configuration of a laser device 150 according to a reference example. This is a schematic diagram illustrating an example of an artificial satellite 200.

[0018] The present invention will be described below through embodiments of the invention, but the following embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustration. In addition, in a single drawing, elements having the same function and configuration may be denoted by a representative reference numeral, while reference numerals are omitted for others.

[0019] In this specification, when terms such as "identical" or "equal" are used, it may include cases where there are errors due to manufacturing variations, etc. Such errors are, for example, within 10%. Also, in this specification, when terms such as "up" or "down" are used, it describes a relative positional relationship in any direction and is not limited to up and down in the direction of gravity.

[0020] Figure 1 is a schematic diagram showing an example configuration of a laser device 100 according to one embodiment of the present invention. The laser device 100 emits laser light 120. The laser device 100 is installed in space 110. Space 110 is, for example, a vacuum or a space environment, but is not limited thereto. The space environment may refer to outer space itself, or to the space inside a structure existing in outer space. The laser device 100 is used, for example, in artificial satellites, but the applications of the laser device 100 are not limited thereto.

[0021] The laser device 100 comprises a resonator 40, a housing 30, an excitation light source 10, and a fixing unit 52. The laser device 100 may further comprise at least one of a mounting base 50 and a focusing optical system 20.

[0022] The resonator 40 generates laser light 120 in response to the incident excitation light. The resonator 40 in this example includes a first mirror 41, a laser medium 44, a Q-switch 46, and a second mirror 42. The first mirror 41 and the second mirror 42 in this example reflect light from each other, causing the light to travel back and forth. Thus, the first mirror 41 and the second mirror 42 constitute the resonator 40. The first mirror 41 is, for example, a total reflection mirror, and the second mirror 42 is, for example, a partial reflection mirror. The second mirror 42 emits a portion of the incident light as laser light 120.

[0023] The laser medium 44 and the Q-switch 46 are arranged in a path through which light travels back and forth between the first mirror 41 and the second mirror 42. The laser medium 44 amplifies the light by stimulated emission or the like. For example, the laser medium 44 is a laser crystal containing a solid material such as YAG.

[0024] The Q-switch 46 controls the attenuation rate within the resonator 40. The Q-switch 46 may control whether or not light travels back and forth inside the resonator 40. When excitation light is introduced into the resonator 40, energy is stored in the laser medium 44 by blocking the travel of light back and forth within the resonator 40. When sufficient energy has been stored in the laser medium 44, a pulsed laser beam 120 with high intensity can be generated by starting the travel of light back and forth within the resonator 40.

[0025] The housing section 30 houses the resonator 40. The housing section 30 may seal the resonator 40. In this example, the housing section 30 may be a pressure vessel that maintains the internal pressure at a set value different from the pressure of the space 110. The housing section 30 may maintain the pressure of the internal space housing the resonator 40 at atmospheric pressure. The housing section 30 may maintain the internal space pressure at 0.5 atm or more and 3 atm or less. By using a pressure vessel as the housing section 30, the pressure around the resonator 40 can be maintained at a set value such as atmospheric pressure even if the space 110 is in an environment such as a vacuum. For this reason, a resonator 40 similar to that in the Earth environment can be used, and the design cost of the laser device 100 can be reduced.

[0026] The interior of the containment section 30 may be filled with a gas. This gas may be an inert gas such as nitrogen gas or a noble gas. The interior of the containment section 30 may be filled with a liquid. This liquid may be, for example, water.

[0027] The excitation light source 10 is provided outside the housing section 30 and outputs excitation light. The excitation light source 10 has a light-emitting element 12 and a fiber cable 14. The light-emitting element 12 generates excitation light. The light-emitting element 12 is, for example, a laser diode. The fiber cable 14 is an optical fiber cable that transmits the excitation light generated by the light-emitting element 12 and outputs it from the output end 16. The laser device 100 in this example is a device that uses fiber coupling in which the fiber cable 14 transmits excitation light and injects it into the resonator 40.

[0028] The fixing part 52 fixes the exit end 16 of the fiber cable 14 outside the housing part 30, and causes the excitation light from the exit end 16 to enter the resonator 40 inside the housing part 30 by spatial transmission through the space 110. The fixing part 52 may fix the fiber cable 14 near the exit end 16 to a member such as a mounting base 50.

[0029] The mounting base 50 supports the excitation light source 10 and the fixed part 52. The mounting base 50 may further support the housing part 30. The excitation light source 10 and the fixed part 52 may be mounted on separate mounting bases 50, or they may be mounted on the same mounting base 50 as shown in the figure. The mounting base 50 may be made of metal. The fixed part 52 may be a member fixed to the mounting base 50 and holding the fiber optic cable 14. The mounting base 50 may function as a cooling unit to cool at least one of the fixed part 52 and the excitation light source 10. The mounting base 50 may release heat from the excitation light source 10 or the fixed part 52 to the outside. The mounting base 50 may further function as a cooling unit to cool the housing part 30. The mounting base 50 may further support the focusing optical system 20, which will be described later. The mounting base 50 may further function as a cooling unit to cool the focusing optical system 20.

[0030] In this example, the fiber optic cable 14 is not inserted into the housing section 30. A space 110 exists between the exit end 16 of the fiber optic cable 14 and the housing section 30. When the fiber optic cable 14 is inserted into the housing section 30, an optical connector is provided on the wall of the housing section 30 to connect the fiber optic cable 14 to the inside of the housing section 30. This optical connector optically connects, for example, the fiber optic cable 14 of the excitation light source 10 to the fiber optic cable installed inside the housing section 30.

[0031] However, when the inside and outside of the housing 30 are optically connected using an optical connector, optical loss occurs in the optical connector. For example, optical loss occurs when some of the excitation light is not transmitted to the internal cable due to axial misalignment between the cores of the fiber cable 14 and the internal cable of the housing 30, or due to reflection of light at the end face.

[0032] Optical loss is converted into heat. When heat is generated, it can damage individual components or affect the operation of the resonator 40. The heat problem becomes more pronounced, especially when the space 110 is a vacuum, as it is difficult to dissipate the heat generated inside the optical connector or housing 30 to the outside. For example, even small amounts of heat, if generated continuously, can cause individual components to become overheated.

[0033] In this example, the laser device 100 introduces excitation light into the resonator 40 without using connecting components such as optical connectors. This suppresses optical loss and heat generation. Furthermore, by placing the excitation light source 10 outside the housing 30, cooling of the excitation light source 10 by the mounting base 50 or the like becomes easier.

[0034] The housing section 30 in this example has an incident window 32 that allows excitation light to pass through. The incident window 32 is made of a material that has low absorption of excitation light. For example, the incident window 32 is a quartz substrate. The incident window 32 transmits excitation light while maintaining the airtightness of the housing section 30.

[0035] The housing section 30 may further have an exit window 34 for passing the laser beam 120 through. The exit window 34 and the entrance window 32 may be made of the same material or different materials. The material of the exit window 34 or the entrance window 32 may be BK7 (boron silicate crown glass), quartz, or CaF ２ , ZnSe, etc. The material of the exit window 34 or the incident window 32 is selected according to the wavelength or intensity of the laser light 120. The incident window 32 may be formed of a material that absorbs excitation light less than the exit window 34. The exit window 34 may be formed of a material that absorbs laser light 120 less than the incident window 32.

[0036] Light emitted from the exit end 16 of the fiber optic cable 14 enters the entrance window 32. For example, the exit end 16 of the fiber optic cable 14 is positioned opposite the entrance window 32. In other examples, the light from the exit end 16 of the fiber optic cable 14 may be reflected by a mirror, deflected by a wedge, or its direction of travel may be controlled by other means. In this case, the exit end 16 does not have to be positioned opposite the entrance window 32. The excitation light emitted from the exit end 16 enters the resonator 40 through the space 110 and the entrance window 32.

[0037] In the laser device 100 of this example, a focusing optical system 20 is provided between the entrance window 32 and the exit end 16 of the fiber cable 14. The focusing optical system 20 focuses the excitation light and directs it into the resonator 40.

[0038] The focusing optical system 20 may have one or more lenses. In this example, the focusing optical system 20 has a first lens 21 and a second lens 22. The first lens 21 focuses the excitation light emitted from the exit end 16 of the fiber cable 14 into parallel light. The second lens 22 focuses the parallel light from the first lens 21 and directs it into the resonator 40 through the entrance window 32. By providing the focusing optical system 20, the relationship between the mode of the optical resonator and the size of the excitation light can be optimized, achieving high efficiency. Furthermore, it is possible to select a lower-order optical resonator mode. The lens configuration of the focusing optical system 20 is not limited to this example.

[0039] Figure 2 is a schematic diagram showing another configuration example of the laser device 100. In this example, the arrangement of the focusing optical system 20 differs from that of the example in Figure 1. Also, in this example, the incident window 32 is omitted in the housing section 30. The other structures are the same as those of the example in Figure 1.

[0040] In this example, the focusing optical system 20 has one end exposed to the outside of the housing 30 and the other end exposed to the inside of the housing 30. In this example, the first lens 21 and the second lens 22 function as the two ends of the focusing optical system 20. In the example of Figure 2, the first lens 21 also serves as the entrance window 32, and the second lens 22 is housed inside the housing 30. In this example, the first lens 21 is embedded in the wall of the housing 30.

[0041] With this configuration, excitation light can be introduced into the housing section 30 without using connecting components such as optical connectors. This reduces optical loss. In this example, the incident window 32 can be omitted, so no optical loss occurs in the incident window 32. This further reduces optical loss. Also, since the second lens 22 can be housed in the housing section 30, the second lens 22 can be protected.

[0042] Figure 3 is a schematic diagram showing another configuration example of the laser device 100. In this example, the arrangement of the focusing optical system 20 differs from that of the example in Figure 1 or Figure 2. Also, in this example, the incident window 32 is omitted in the housing section 30. The other structures are the same as those of the example in Figure 1 or Figure 2.

[0043] The condensing optical system 20 of the present example also has one end exposed to the outside of the housing portion 30 and the other end exposed to the inside of the housing portion 30. In the example of Figure 3, the first lens 21 is disposed outside the housing portion 30, and the second lens 22 also serves as the incident window 32. The second lens 22 of the present example is embedded in the wall of the housing portion 30.

[0044] Even with such a configuration, excitation light can be introduced into the interior of the housing portion 30 without using connection components such as an optical connector. Therefore, optical loss can be reduced. Further, in the present example, since the incident window 32 can be omitted, no optical loss occurs at the incident window 32. For this reason, optical loss can be further reduced. In addition, since the first lens 21 is disposed on the outer side of the housing portion 30, adjustment of the arrangement, orientation, or the like of the first lens 21 is facilitated. The first lens 21 may be fixed to the mounting table 50. The first lens 21 may be cooled by the mounting table 50.

[0045] In the examples of Figure 2 and Figure 3, the example in which the condensing optical system 20 has two lenses has been described. When the condensing optical system 20 has only one lens, the corresponding lens may function as the incident window 32. When the condensing optical system 20 has three or more lenses, any one of the lenses may function as the incident window 32.

[0046] Figure 4 is a schematic diagram showing another configuration example of the laser device 100. The laser device 100 of the present example differs from the examples of Figure 1 to Figure 3 in the structure and arrangement of the condensing optical system 20. Further, in the housing portion 30 of the present example, the incident window 32 is omitted. The other structures are the same as those of any of the examples from Figure 1 to Figure 3.

[0047] The condensing optical system 20 of the present example also has one end portion exposed to the outside of the housing portion 30 and the other end portion exposed to the inside of the housing portion 30. Also in this example, the first lens 21 and the second lens 22 function as the two end portions of the condensing optical system 20. However, the condensing optical system 20 of this example further includes a housing portion 24. The housing portion 24 seals the space between the first lens 21 and the second lens 22. The housing portion 24 may be, for example, a metal cylinder. The first lens 21 and the second lens 22 may be arranged at both ends of the housing portion 24. In the example of FIG. 4, the first lens 21 is arranged outside the housing portion 30, and the second lens 22 is arranged inside the housing portion 30. The housing portion 24 is provided to penetrate through the wall of the housing portion 30 so as to maintain the hermeticity of the housing portion 30.

[0048] Even with such a configuration, the excitation light can be introduced into the interior of the housing portion 30 without using connection components such as an optical connector. Therefore, optical loss can be reduced. Further, in this example, since the incident window 32 can be omitted, no optical loss occurs at the incident window 32. For this reason, the optical loss can be further reduced. In addition, since the second lens 22 can be housed in the housing portion 30, the second lens 22 can be protected.

[0049] FIG. 5 is a schematic diagram showing another configuration example of the laser device 100. The laser device 100 of this example differs from the examples of FIGS. 1 to 3 in the arrangement of the condensing optical system 20. Other structures are the same as those of any of the examples in FIGS. 1 to 3.

[0050] The condensing optical system 20 of this example is provided between the incident window 32 and the resonator 40, and condenses the excitation light to make it enter the resonator 40. The entire condensing optical system 20 of this example is housed in the housing portion 30.

[0051] Even with such a configuration, the excitation light can be introduced into the interior of the housing portion 30 without using connection components such as an optical connector. Therefore, optical loss can be reduced. In addition, since the entire condensing optical system 20 can be housed in the housing portion 30, the condensing optical system 20 can be protected.

[0052] Figure 6 is a cross-sectional view showing an example of a fixing part 52. In this example, the fixing part 52 has a main body 53 and an insertion part 54. The main body 53 is fixed to the mounting base 50. The main body 53 may be made of metal or resin. The main body 53 is provided with an insertion part 54 into which the fiber cable 14 is inserted. The insertion part 54 is a through hole that penetrates the main body 53.

[0053] The exit end 16 of the fiber optic cable 14 is exposed to the space 110. The main body 53 may be provided with a recess 56 into which the exit end 16 is exposed. In this example, the recess 56 is a portion that is recessed toward the side opposite to the housing 30. The recess 56 is provided so that the excitation light emitted from the exit end 16 does not come into contact with the main body 53. By providing the recess 56, optical loss can be reduced while protecting the exit end 16.

[0054] Figure 7 shows an example configuration of a laser device 150 according to a reference example. The laser device 150 differs from the laser device 100 in that it has an optical connector 152. Also, the housing section 30 does not have an incident window 32. The other structures are the same as those of the laser device 100. The laser device 150 does not necessarily have a mounting base 50.

[0055] The optical connector 152 is provided on the wall of the housing section 30 and optically connects the fiber cable 14 outside the housing section 30 to the fiber cable 15 inside the housing section 30. As described above, the provision of the optical connector 152 causes optical loss and heat generation. This heat can damage the optical connector 152 or other components such as cables, or affect the characteristics of the resonator 40. The laser device 100 described in Figures 1 to 6 does not use the optical connector 152, so optical loss can be reduced and heat generation can be suppressed.

[0056] Figure 8 is a schematic diagram illustrating an example of an artificial satellite 200. The artificial satellite 200 comprises a laser device 100 and a housing 210. The housing 210 houses the laser device 100. The artificial satellite 200 may also be equipped with a power generation device 220, such as a solar power generation device. Power may be supplied to the laser device 100 from the power generation device 220.

[0057] The laser device 100 may be provided with a mounting base 50 that functions as a cooling unit. The mounting base 50 may be part of the housing 210. The mounting base 50 may have a radiating surface 58 that emits heat from the fixing part 52 of the laser device 100 and the excitation light source 10, etc. The radiating surface 58 emits heat by radiation. The radiating surface 58 may have a higher electromagnetic wave radiation intensity (also referred to as emissivity in this specification) per unit area than the mounting surface on which the excitation light source 10 is mounted. The radiating surface 58 may be coated with a paint that has a higher emissivity than the mounting surface. The radiating surface 58 may be coated with, for example, black paint. The radiating surface 58 may have irregularities such as fin shapes formed on it.

[0058] The radiating surface 58 may be exposed to space 110 inside the housing 210, or it may be exposed to the outside of the housing 210. In the latter case, heat can be released into outer space outside the housing 210, and the temperature rise of the artificial satellite 200 can be suppressed.

[0059] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0060] 10...Excitation light source, 12...Light-emitting element, 14...Fiber cable, 15...Fiber cable, 16...Output end, 20...Focusing optical system, 21...First lens, 22...Second lens, 24...Housing section, 30...Housing section, 32...Ingress window, 34...Output window, 40...Resonator, 41...First mirror, 42...Second mirror, 44...Laser medium, 46...Q-switch, 50...Mounting platform, 52...Fixing section, 53...Main body section, 54...Insertion section, 56...Recess, 58...Radiation surface, 100...Laser device, 110...Space, 120...Laser light, 150...Laser device, 152...Optical connector, 200...Artificial satellite, 210...Housing, 220...Power generation device

Claims

1. A laser device comprising: a housing section for housing a resonator; an excitation light source provided outside the housing section and including a fiber optic cable for outputting excitation light; and a fixing section that fixes the output end of the fiber optic cable outside the housing section and causes the excitation light from the output end to be incident on the resonator inside the housing section by spatial transmission.

2. The laser apparatus according to claim 1, wherein the housing has an incident window that allows the excitation light to pass through while achieving airtight sealing of the housing.

3. The laser apparatus according to claim 2, further comprising a focusing optical system provided between the entrance window and the exit end of the fiber cable, which focuses the excitation light and directs it into the resonator.

4. The laser apparatus according to claim 2, further comprising a focusing optical system provided between the incident window and the resonator, which focuses the excitation light and causes it to be incident on the resonator.

5. The laser device according to claim 1, further comprising a focusing optical system for focusing the excitation light and directing it into the resonator, wherein one end of the focusing optical system is exposed to the outside of the housing and the other end is exposed to the inside of the housing.

6. The laser apparatus according to claim 1, wherein the housing is sealed and filled with gas.

7. The laser apparatus according to claim 6, wherein the inside of the housing is at atmospheric pressure.

8. The laser apparatus according to claim 1, wherein the housing is sealed and filled with liquid.

9. The laser apparatus according to claim 1, further comprising a cooling unit for cooling at least one of the fixed unit and the excitation light source.

10. The laser apparatus according to claim 9, wherein the cooling unit has a metal mounting base on which the fixed unit and the excitation light source are placed, and the mounting base has a radiating surface that emits heat from the fixed unit and the excitation light source.

11. The laser apparatus according to any one of claims 1 to 10, wherein the outside of the housing is a vacuum or a space environment.

12. An artificial satellite comprising a laser device and a housing for the laser device, wherein the laser device comprises a housing for housing a resonator, an excitation light source provided outside the housing for housing and including a fiber cable that outputs excitation light, and a fixing part that fixes the output end of the fiber cable outside the housing for transmitting the excitation light from the output end into the resonator inside the housing for spatial transmission.

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