Quantum cascade laser module

Abstract

A QCL module of one embodiment of the present application includes a package that houses a QCL element and is provided with a window member that takes out laser light emitted from the QCL element to the outside, a lens holding member that holds a lens into which the laser light emitted from the window member is incident, a cooling fan that cools the package, and a base that holds the package, the lens holding member, and the cooling fan. The package and the lens holding member are fastened together with respect to the base by a common threaded member.

Description

Technical Field

[0001] This invention relates to quantum cascade laser modules. Background Technology

[0002] Currently, modules integrating a light source element, a laser holder, and a cooling fan for cooling the light source element are known (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a structure including an LED unit (LED substrate and LED package), a light-emitting section (lens assembly), and a cooling fan. In the structure described in Patent Document 1, the mounting member for the light-emitting section and the LED substrate are respectively fixed to a base. Patent Document 2 discloses a structure that fixes the light source module, the laser holder, and the cooling fan to a light source holder. In the structure described in Patent Document 2, the light source module and the laser holder are respectively fixed to the light source holder.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-188256

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-096637 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] As the light source for modules like those described above, quantum cascade lasers (hereinafter referred to as "QCLs") are sometimes used. Modules including QCLs are used, for example, for gas concentration measurement. For example, a gas chamber containing the gas to be measured is arranged between the module and a photodetector, allowing the laser emitted from the module to pass through the gas chamber. The photodetector detects the laser after it has passed through the gas chamber, thereby enabling the measurement of the gas concentration (laser absorbance) within the chamber. QCLs have excellent monochromaticity (i.e., excellent wavelength resolution), and therefore are suitable for measuring the concentration of gases as described above. On the other hand, due to their excellent monochromaticity as described above, optical noise is theoretically generated. More specifically, fringe noise (interference noise) is generated due to interference components between the radiating end face of the QCL and the interface of the lenses included in the module.

[0009] If the optical conditions between the QCL and the lens (e.g., the length of the Fabry-Perot resonator) remain constant over time, the aforementioned optical noise can be treated as an invariant, and therefore, it can be removed through background operations. However, in the case where the module includes a cooling fan as described above, a deviation may occur between the vibration of the QCL caused by the vibration of the cooling fan and the vibration of the lens. In particular, in the structure described in Patent Documents 1 and 2 above, where the light source and the lens are respectively fixed to a base member (i.e., the base in Patent Document 1 and the light source support in Patent Document 2), the vibration of the QCL and the vibration of the lens are not in phase, and the positional relationship between the QCL and the lens (i.e., the optical path length) easily changes over time. In this case, since the aforementioned optical conditions change over time, it is impossible to treat the aforementioned optical noise as an invariant. That is, it is impossible to remove the optical noise through background operations. Therefore, the sensitivity (detection limit) in the aforementioned measurement is limited.

[0010] Therefore, in order to suppress the generation of vibrations, which are the main cause of the temporal variation of the aforementioned optical conditions, it is also considered to replace the cooling fan with a water-cooled jacket or the like, which does not generate vibrations. However, in this case, a device for circulating the cooling water is required, thus increasing the overall size and complexity of the module and raising maintenance costs.

[0011] Therefore, one aspect of the present invention is to provide a quantum cascade laser module that, in a structure including a cooling fan, is able to reduce optical noise caused by temporal variations in optical conditions.

[0012] means for solving problems

[0013] One aspect of the present invention includes a quantum cascade laser module comprising: a package housing a quantum cascade laser element and having a window member for extracting laser light emitted from the quantum cascade laser element to the outside; a lens holding member holding a lens incident on the laser light emitted from the window member; a cooling fan cooling the package; and a base holding the package, the lens holding member, and the cooling fan, the package and the lens holding member being fastened together relative to the base by a common shaft member.

[0014] The aforementioned quantum cascade laser module includes a cooling fan for cooling the package. This structure allows for miniaturization and simplification of the module compared to other cooling mechanisms (e.g., water cooling). Furthermore, in the aforementioned quantum cascade laser module, the package, serving as the light source, and the lens holding member are fastened together relative to the base via a common shaft member. That is, the package and the lens holding member are integrally fixed via this common shaft member. Consequently, the vibration modes caused by the cooling fan's vibration are commonalized between the package and the lens held in the lens holding member. As a result, variations in the relative positional relationship between the package and the lens are suppressed, as are temporal variations in the optical conditions (e.g., Fabry-Perot resonator length) between the package and the lens. This reduces optical noise caused by temporal variations in optical conditions.

[0015] Alternatively, the package can be positioned between the base and the lens holding member, with the window member facing the lens. The package and the lens holding member are fastened to the base by the lens holding member, and are thus fastened together relative to the base. In this way, the lens holding member and the package can be integrally fixed relative to the base by clamping the package with the lens holding member and the base.

[0016] Alternatively, it may also include a spacer disposed between the lens holding member and the base, the encapsulation having a flange that abuts against the base and extends along the base, the spacer forming a gap between the lens holding member and the window member by means of a surface disposed between the base side of the lens holding member and the lens holding member side of the flange. This prevents deformation of the window member due to contact between the lens holding member and the window member. As a result, laser degradation caused by such deformation can be suppressed.

[0017] Alternatively, the flange may have a first flange and a second flange formed on both sides of the clamping window member, and the spacer may have: a first spacer disposed between the base side surface of the lens holding member and the lens holding member side surface of the first flange; and a second spacer disposed between the base side surface of the lens holding member and the lens holding member side surface of the second flange. In this way, by arranging a pair of spacers (the first spacer and the second spacer) in a balanced manner between the encapsulation member and the lens holding member, the physical stability of the encapsulation member and the lens holding member can be improved, and changes in the relative positional relationship between the encapsulation member and the lens holding member can be effectively suppressed.

[0018] Alternatively, the lens holding member, spacer, flange, and base may each have through holes for the insertion of a shaft member. The lens holding member is then fastened relative to the base using a shaft member that passes through the respective through holes in these members, thereby securing the lens holding member, spacer, and flange together with respect to the base. In this case, by having the shaft member pass through the through holes in the lens holding member, spacer, and flange and be inserted into the base, the lens holding member, spacer, and flange can be integrally and securely fixed relative to the base. This effectively suppresses changes in the relative positional relationship between the package and the lens holding member.

[0019] Alternatively, with the lens holding member and the base each having through holes for the insertion of a shaft member, and a spacer and a flange positioned between the lens holding member and the base, the lens holding member is secured relative to the base using a shaft member inserted into the through holes of both the lens holding member and the base. This secures the lens holding member, spacer, and flange together relative to the base. In this case, by having the shaft member pass through the through holes of the lens holding member and the base, and by using the lens holding member and the base to clamp the spacer and flange positioned between them, the lens holding member, spacer, and flange can be integrally and securely fixed relative to the base. This effectively suppresses changes in the relative positional relationship between the package and the lens holding member.

[0020] Alternatively, the spacer can be formed of a material with a lower thermal conductivity than the substrate. This allows the heat generated in the encapsulation to be efficiently released to the base side instead of the spacer side.

[0021] Invention Effects

[0022] According to one aspect of the present invention, a quantum cascade laser module can be provided, which, in a structure including a cooling fan, can reduce optical noise caused by temporal variations in optical conditions. Attached Figure Description

[0023] Figure 1 This is a three-dimensional view of a quantum cascade laser module according to one implementation method.

[0024] Figure 2 yes Figure 1 An exploded 3D view of a quantum cascade laser module.

[0025] Figure 3 yes Figure 1 A top view of the quantum cascade laser module.

[0026] Figure 4 yes Figure 1 A side view of the quantum cascade laser module.

[0027] Figure 5 This is a diagram showing a portion of a modified quantum cascade laser module. Detailed Implementation

[0028] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the following description, the same or equivalent elements will be referred to by the same reference numerals, and repeated descriptions will be omitted.

[0029] [Structure of a quantum cascade laser module]

[0030] like Figures 1-4 As shown, the quantum cascaded laser module 1 (hereinafter referred to as "QCL module 1") has the following main components: a package 2 serving as a light source, a lens holding member 4 holding a lens 3 into which the laser emitted from the package 2 is incident, a cooling fan 5 for cooling the package 2, and a base 6 holding the package 2, the lens holding member 4, and the cooling fan 5. In the following description, the optical axis direction of the laser emitted from the package 2 will be referred to as the Z-axis direction, and the two directions orthogonal to the Z-axis direction and mutually orthogonal to each other will be referred to as the X-axis direction and the Y-axis direction.

[0031] Package 2 is a high heat load (HHL) packaged quantum cascade laser (QCL). Package 2, for example, houses a quantum cascade laser element (hereinafter referred to as a "QCL element") that generates light in the mid-infrared wavelength region (e.g., wavelengths of 5–30 μm). As an example, package 2 is formed in a generally cuboid shape. Package 2 has a first surface 21 on one side in the Z-axis direction and a second surface 22 opposite to the first surface 21.

[0032] The first surface 21 is the surface opposite to the lens holding member 4. A window member 23 for extracting the laser emitted from the QCL element to the outside is provided approximately at the center of the first surface 21. The material of the window member 23 is, for example, zinc selenide (ZnSe) or germanium (Ge). The second surface 22 is the surface opposite to the base 6 and abuts against the base 6. The second surface 22 is larger than the first surface 21 by the amount of flanges 24A and 24B (described later). The package 2 is disposed between the base 6 and the lens holding member 4 with the window member 23 opposite to the lens 3.

[0033] A pair of flanges 24 (flanges 24A and 24B) are provided on the edge of the second surface 22 side of the package 2. Flanges 24A (first flange) and 24B (second flange) are provided at both ends of the package 2 in the X-axis direction. More specifically, in the X-axis direction, flanges 24A and 24B are located on opposite sides. That is, flanges 24A and 24B are formed on both sides of the window member 23 in the X-axis direction. Flanges 24A and 24B are formed as rectangular plates extending along the Y-axis direction, protruding from the side surface 25 of the package 2 that intersects the X-axis direction in the X-axis direction. The second surface 22 of flanges 24A and 24B is continuous with the second surface 22 of the portion other than flanges 24A and 24B, abuts against the base 6 (specifically, the bottom wall 61 described later) and extends along the base 6.

[0034] On one side 26 of the package 2, which intersects the Y-axis direction, a plurality of (nine in this embodiment) lead pins 27 are inserted for supplying power from the outside to components such as QCL elements housed in the package 2.

[0035] The lens holding member 4 is positioned opposite to the first surface 21 of the package 2. The lens holding member 4 may be composed of multiple components. In this embodiment, the lens holding member 4 mainly includes: a sub-base 41, a lens support 42, a lens barrel 43, a lens retaining ring 44, and a lens protection ring 45.

[0036] The lens holder 42 is a cross-shaped movable support that is movable in both the X-axis and Y-axis directions. An opening 42a extending through the lens holder 42 in the Z-axis direction is provided in the center of the lens holder 42. A lens tube 43 is inserted into this opening 42a.

[0037] The lens barrel 43 is a cylindrical member that houses the lens 3. A male thread is formed on the outer peripheral surface of the lens barrel 43. On the other hand, a female thread corresponding to the male thread (i.e., threaded into the male thread) is formed on the inner surface of the opening 42a of the lens holder 42. Thus, the lens barrel 43 can be inserted into the opening 42a of the lens holder 42 while rotating. In addition, by adjusting the amount of rotation of the lens barrel 43 relative to the lens holder 42, the position (i.e., insertion amount) of the lens barrel 43 relative to the lens holder 42 in the Z-axis direction can be adjusted. Thus, the position of the lens 3 in the Z-axis direction can be adjusted (i.e., the focusing adjustment of the laser (beam) after passing through the lens 3). In addition, an O-ring can be provided at the fitting portion of the lens barrel 43 to apply resistance (i.e., prevent loosening) when the lens barrel 43 slides relative to the lens holder 42.

[0038] Lens 3, lens retaining ring 44, and lens protective ring 45 are sequentially housed within lens barrel 43. Lens retaining ring 44 is a component used to fix lens 3 to the inner side of lens barrel 43 via lens protective ring 45. Lens protective ring 45 is a component disposed between lens 3 and lens retaining ring 44 to prevent damage to the surface of lens 3 caused by contact between lens retaining ring 44 and the surface of lens 3. Lens protective ring 45 is formed, for example, from a resin material such as Teflon (registered trademark).

[0039] The sub-base 41 is a plate-shaped member disposed between the lens holder 42 and the package 2. The sub-base 41 has a first surface 411 opposite to the lens holder 42 and a second surface 412 opposite to the first surface 411 and opposite to the package 2. The material of the sub-base 41 is, for example, aluminum.

[0040] The aforementioned lens holder 42 is mounted on the first surface 411 of the sub-base 41. More specifically, at the four corners of the lens holder 42, viewed from the Z-axis direction, there are insertion holes 42b for inserting support rods 46 that are used to fix the lens holder 42 to the sub-base 41. Each insertion hole 42b extends in the Z-axis direction. A portion of the wall forming each insertion hole 42b has a hole communicating with the insertion hole 42b, into which a fastening screw 47 for fixing the support rod 46 to the lens holder 42 is inserted. The front end of the support rod 46 (the end on the sub-base 41 side) is fixed to the first surface 411 of the sub-base 41. As an example, a threaded groove is formed at the front end of each support rod 46, and four threaded holes 411a are formed on the first surface 411 of the sub-base 41 at positions corresponding to each support rod 46. The lens holder 42 is fixed to the sub-base 41 via the support rod 46 by screwing the front end of the support rod 46 into the threaded hole 411a. In this way, the sub-base 41 and the lens holder 42 are integrally combined to form the lens holding member 4.

[0041] A circular through hole 413 is formed in the center of the sub-base 41 when viewed from the Z-axis direction, extending from the first surface 411 to the second surface 412. The front end of the lens tube 43 is inserted into the through hole 413 and protrudes further toward the package 2 than the second surface 412 (see reference). Figure 3 ).

[0042] The base 6 is a plate-shaped member formed in an L-shape. The base 6 has: a bottom wall 61, which faces the second surface 22 of the encapsulation member 2; and a side wall 62, which is erected along the Z-axis direction from one end of the bottom wall 61 in the Y-axis direction. The material of the base 6 is, for example, aluminum, copper, etc.

[0043] The bottom wall 61 is a rectangular plate-shaped portion extending parallel to the XY plane. The bottom wall 61 has a first surface 611 opposite to the package 2 and a second surface 612 opposite to the first surface 611 and opposite to the cooling fan 5. That is, the package 2 and the lens holding member 4 are disposed on the first surface 611 side of the bottom wall 61, and the cooling fan 5 is disposed on the second surface 612 side of the bottom wall 61.

[0044] The sidewall 62 is a rectangular plate-shaped portion extending parallel to the XZ plane. The sidewall 62 extends relative to the bottom wall 61 towards the side where the encapsulation member 2 is disposed, covering the side of the heat sink 7 (described later). In this embodiment, as an example, the sidewall 62 has: an insertion hole 621 for inserting a rod member for fixing the QCL module 1 to an experimental table or the like (for fixing the QCL module to a fixed object), and a countersunk hole 622 communicating with the insertion hole 621.

[0045] The cooling fan 5 is a mechanism for forced air cooling of the heat generated in the package 2 (mainly from the QCL elements inside the package 2). The cooling fan 5 is fixed to the second surface 612 of the bottom wall 61 via the heat sink 7. The heat sink 7 has: a flat plate portion 71 that abuts against the second surface 612; and a plurality of heat sink fins 72 (in this embodiment, a plurality of rod-shaped members arranged in a grid pattern) formed on the surface of the flat plate portion 71 opposite to the bottom wall 61. On the side opposite to the heat sink 7, where the cooling fan 5 is sandwiched, a finger guard 8 is provided for safety (i.e., to prevent human fingers or the like from entering the cooling fan 5). That is, the heat sink 7, the cooling fan 5, and the finger guard 8 are arranged sequentially from the side closest to the second surface 612 of the bottom wall 61.

[0046] The radiator 7, cooling fan 5, and finger guard 8 are fastened together relative to the bottom wall 61 by a plurality of screws 9 (four in this embodiment). More specifically, the radiator 7 (flat plate 71), cooling fan 5, and finger guard 8, when viewed from the Z-axis direction, each have through holes 71a, 5a, and 8a for inserting the screws 9, and a threaded hole 612a is formed on the second surface 612 of the bottom wall 61 (see reference). Figure 3 and Figure 4Each screw 9 is inserted into the through hole 71a of the radiator 7, the through hole 5a of the cooling fan 5, and the through hole 8a of the finger guard 8, and is screwed into the threaded hole 612a of the bottom wall 61, thereby fixing the radiator 7, the cooling fan 5, and the finger guard 8 integrally with respect to the bottom wall 61. Furthermore, in order to efficiently dissipate heat transferred from the encapsulation 2 to the bottom wall 61, thermal grease can be applied between the second surface 22 of the encapsulation 2 and the first surface 611 of the bottom wall 61. Similarly, thermal grease can be applied between the second surface 612 of the bottom wall 61 and the flat plate portion 71 of the radiator 7.

[0047] The encapsulation member 2 and the sub-base 41 (lens holding member 4) are fastened together relative to the base 6. In this embodiment, a spacer 10 is disposed between the sub-base 41 and the base 6. The spacer 10 is disposed between the second surface 412 (the surface on the side of the base 6) of the sub-base 41 and the upper surface 24a (the surface on the side of the sub-base 41) of the flange 24. More specifically, the spacer 10 has: a spacer 10A (first spacer) corresponding to the flange 24A; and a spacer 10B (second spacer) corresponding to the flange 24B. That is, the spacer 10A is disposed between the second surface 412 of the sub-base 41 and the upper surface 24a of the flange 24A, and the spacer 10B is disposed between the second surface 412 of the sub-base 41 and the upper surface 24a of the flange 24B. That is, the spacers 10A and 10B are disposed on both sides of the window member 23 in the X-axis direction. Spacers 10A and 10B are each formed into a rectangular plate shape. More specifically, each spacer 10A and 10B is an elongated member extending in the Y-axis direction (i.e., the direction opposite to the direction in which the window member 23 is sandwiched between spacers 10A and 10B, i.e., the direction intersecting the Z-axis direction). By forming spacers 10A and 10B into elongated shapes, the lens holding member 4 and the encapsulation member 2 can be more stably secured together with respect to the base 6 via spacers 10A and 10B. Spacer 10 is formed of a material with a lower thermal conductivity than the base 6. The material of spacer 10 is, for example, stainless steel or nickel. As a result, the heat generated in the encapsulation member 2 can be efficiently dissipated to the base wall 61 side rather than the spacer 10 side.

[0048] The height (length in the Z-axis direction) of the spacer 10 is greater than the difference between the height (length in the Z-axis direction) of the encapsulation member 2 and the height (length in the Z-axis direction) of the flange 24. That is, when the spacer 10 abuts against the upper surface 24a of the flange 24, the end 10a of the spacer 10 on the sub-base 41 side protrudes further towards the sub-base 41 side than the first surface 21 of the encapsulation member 2. By setting the height of the spacer 10 in this way, a gap S is formed between the sub-base 41, the first surface 21 of the encapsulation member 2, and the window member 23 (see reference). Figure 3Therefore, deformation of the window member 23 due to contact between the lens holding member 4 and the window member 23 (i.e., the lens holding member 4 being pressed against the window member 23) can be prevented. As a result, the degradation of the laser (laser emitted from the window member 23) caused by such deformation can be suppressed. Furthermore, as in this embodiment, even if the through hole 413 (see reference) is present at the front end of the lens barrel 43... Figure 2 When the lens tube 43 protrudes slightly to the side of the encapsulation component 2, the size of the gap S can be adjusted by adjusting the height of the spacer 10 to prevent the front end of the lens tube 43 from contacting the window component 23.

[0049] The sub-base 41, spacer 10, and flange 24 are fastened together relative to the bottom wall 61 by a plurality of (four in this embodiment) threaded members 11 (shaft members). The threaded members 11 are, for example, hexagonal bolts. More specifically, at each of the four corners of the sub-base 41, spacer 10, flange 24, and bottom wall 61 viewed from the Z-axis direction, insertion holes 41a, 10b, 24b, and 61a are formed for the threaded members 11 to pass through. Two insertion holes 10b are provided on the two side edges of each spacer 10A and 10B in the Y-axis direction. Two insertion holes 24b are provided on the two side edges of each flange 24A and 24B in the Y-axis direction. The insertion hole 61a of the bottom wall 61 opens on the first surface 611 and is a threaded hole with a threaded groove. Furthermore, a countersunk groove 41b for accommodating the head 11a of the threaded member 11 is provided on the first surface 411 of the sub-base 41, communicating with the through hole 41a. Moreover, each threaded member 11 is inserted from the first surface 411 side of the sub-base 41 into the through hole 41a of the sub-base 41, the through hole 10b of the spacer 10, and the through hole 24b of the flange 24, and is screwed into the through hole 61a of the bottom wall 61. Thus, the lens holding member 4 (sub-base 41) is fastened relative to the base 6 (bottom wall 61) via the spacer 10 and the flange 24.

[0050] [Functions and Effects]

[0051] The QCL module 1 described above includes a cooling fan 5 for cooling the package 2. This structure allows for miniaturization and simplification of the module compared to other cooling mechanisms (e.g., water cooling). Furthermore, in the QCL module 1, the package 2, serving as the light source, and the lens holding member 4 (sub-base 41) are fastened together relative to the base 6 (bottom wall 61) by shared threaded members 11 (four threaded members 11 in this embodiment). That is, the package 2 and the lens holding member 4 are integrally fixed by the common threaded members 11. As a result, the vibration mode caused by the vibration of the cooling fan 5 is common between the package 2 and the lens 3 held in the lens holding member 4. Consequently, variations in the relative positional relationship between the package 2 and the lens 3 are suppressed, as are temporal variations in the optical conditions (e.g., Fabry-Perot resonator length) between the package 2 and the lens 3. This reduces optical noise caused by temporal variations in optical conditions.

[0052] Regarding the aforementioned effects, a specific example will be given of a gas concentration measurement using QCL module 1. In such a gas concentration measurement, for example, QCL module 1 and a photodetector such as a photodetector are prepared, and a gas chamber containing the gas to be measured is placed between QCL module 1 and the photodetector. Furthermore, the laser emitted from QCL module 1 (i.e., the laser emitted from the window member 23 of package 2 and passing through lens 3) passes through the gas chamber, and the laser after passing through the gas chamber is detected by the photodetector. Thus, the concentration of the gas in the gas chamber (the absorbance of the laser) can be measured. QCL has excellent monochromaticity (i.e., excellent wavelength resolution), and therefore is suitable for the aforementioned gas concentration measurement, etc. However, since QCL has excellent monochromaticity, in principle, fringe noise caused by the etalon effect is generated. This fringe noise is caused by the limited reflectivity of the optical elements such as lens 3 and window member 23 between the QCL element and the photodetector disposed in package 2, i.e., the existence of an optical reflection interface in the laser's optical path. A Fabry-Perot resonator is formed by such a reflective interface and the radiating end face of the QCL element, generating fringe noise due to light interference. If the length of the Fabry-Perot resonator remains constant, this fringe noise (i.e., the Fabry-Perot interference condition) is constant, and therefore, it can be treated as an invariant. That is, the fringe noise can be removed by background operations (differential operations). On the other hand, if the length of the Fabry-Perot resonator varies with time, the Fabry-Perot interference condition also varies with time, and therefore, the fringe noise cannot be treated as an invariant. As a result, the fringe noise cannot be removed by the background operations described above. Furthermore, in gas concentration measurements using QCL module 1, wavelength-variable semiconductor laser absorption spectroscopy (TDLAS) is widely used, where the oscillation wavelength of the laser changes with time. When using such a measurement method, the variation in the Fabry-Perot interference condition caused by the change in the oscillation wavelength of the laser also overlaps with the fringe noise, thus generating extremely complex optical noise. Such optical noise is the main reason that limits the detection limit of the gas concentration measurement described above.

[0053] Here, we consider a comparative example with a structure in which the lens holding member is not fastened to the base together with the package, but is fixed to the base separately from the package. For example, consider a structure in which a plate-like portion extending toward the lens holding member is provided on the bottom wall of the base, and the lens holding member is fixed independently to the package relative to this plate-like portion. In this comparative example with such a structure, the transmission mode of vibration from the cooling fan differs between the package and the lens holding member. More specifically, in the above comparative example, the package is fixed relative to the bottom wall of the base to which the cooling fan is fixed, while the lens holding member is fixed to a plate-like portion different from the bottom wall. Therefore, the vibration frequency of the lens held by the lens holding member is affected by the mechanical vibration resonance of the plate-like portion, and thus is not in phase with the vibration of the QCL (i.e., the package). As a result, the distance between the QCL and the lens (optical path length) varies with time, and the Fabry-Perot resonance condition between the QCL and the lens (i.e., the Fabry-Perot resonator length) also varies with time. As a result, as mentioned above, the stripe noise cannot be treated as an invariant, and therefore, the stripe noise is detected as a complex optical noise structure in the photodetector.

[0054] Furthermore, when the vibrations of the QCL and the lens are not in phase and the positional relationship (optical path length) between the QCL and the lens changes over time, the deflection of the laser light passing through the lens in the XY plane (a plane orthogonal to the Z-axis, which is the optical axis) is amplified. Therefore, in the photodetector (light-receiving part), the position of the laser spot changes over time. Thus, in the comparative example described above, the variation in the photodetector's output value caused by this change in spot position may also be generated as optical noise.

[0055] On the other hand, in the QCL module 1 described in the above embodiment, the lens holding member 4 and the package 2 are integrally and firmly fixed (tightly fastened together) relative to the base 6 (bottom wall 61). Therefore, the vibration of the QCL (package 2) and the vibration of the lens 3 held in the lens holding member 4 are in phase, and thus the Fabry-Perot resonance condition described above does not change over time. As a result, the above-mentioned stripe noise can be treated as an invariant and removed through background calculations, etc., thus reducing optical noise. In addition, the positional relationship (optical path length) between the QCL (package 2) and the lens 3 does not change over time (constant), so the deflection of the laser light after passing through the lens 3 in the XY plane is not amplified. Thus, the generation of optical noise caused by the variation of the photodetector spot position that may occur in the above comparative example can also be suppressed.

[0056] Furthermore, the encapsulation member 2 is disposed between the base 6 (bottom wall 61) and the lens holding member 4 (sub-base 41) with the window member 23 facing the lens 3. The encapsulation member 2 and the lens holding member 4 are fastened together relative to the base 6 by the lens holding member 4. Thus, the lens holding member 4 and the encapsulation member 2 can be integrally fixed relative to the base 6 by clamping the encapsulation member 2 with the base 6.

[0057] Furthermore, the QCL module 1 includes a spacer 10 disposed between the lens holding member 4 and the base 6. The encapsulation member 2 has a flange 24 that abuts against the base 6 and extends along the base 6. Moreover, the spacer 10 is disposed between the base 6 side surface of the lens holding member 4 (in this embodiment, the second surface 412 of the sub-base 41) and the upper surface 24a of the flange 24 on the lens holding member 4 side, thereby forming a gap S between the lens holding member 4 and the window member 23. As a result, deformation of the window member 23 due to contact between the lens holding member 4 and the window member 23 can be prevented. Consequently, laser degradation caused by such deformation can be suppressed.

[0058] Furthermore, the flange 24 has flanges 24A and flanges 24B formed on both sides of the clamping window member 23. The spacer 10 has: a spacer 10A disposed between the second surface 412 of the sub-base 41 and the upper surface 24a of the flange 24A; and a spacer 10B disposed between the second surface 412 of the sub-base 41 and the upper surface 24a of the flange 24B. In this way, by arranging a pair of spacers 10A and 10B in a balanced and good manner between the encapsulation member 2 and the lens holding member 4, the physical stability of the encapsulation member 2 and the lens holding member 4 can be improved, and the variation of the relative positional relationship between the encapsulation member 2 and the lens holding member 4 (i.e., the positional relationship between QCL and lens 3) can be effectively suppressed. In addition, in this embodiment, a plurality of threaded members 11 (two in this embodiment) are inserted through one spacer 10 (spacer 10A or spacer 10B). In this way, by inserting multiple threaded members 11 into a common spacer 10, the lens retaining member 4 and the encapsulation member 2 can be more stably fastened together relative to the base 6 via the spacer 10.

[0059] Furthermore, through holes 41a, 10b, 24b, and 61a for threaded members 11 are formed in the lens holding member 4 (sub-base 41 in this embodiment), the spacer 10, the flange 24, and the base 6 (bottom wall 61 in this embodiment), respectively. The lens holding member 4 is fastened relative to the base 6 by the threaded members 11 inserted into the through holes 41a, 10b, 24b, and 61a of the lens holding member 4, the spacer 10, the flange 24, and the base 6, thereby fastening the lens holding member 4, the spacer 10, and the flange 24 together with respect to the base 6. In this case, by having a common threaded member 11 pass through the lens holding member 4, the spacer 10, and the flange 24 and be inserted into the through hole 61a of the base 6, the lens holding member 4, the spacer 10, and the flange 24 can be integrally and firmly fixed relative to the base 6. This effectively suppresses changes in the relative positional relationship between the package 2 and the lens holding member 4.

[0060] [Variation Example]

[0061] The present invention has been described above as one embodiment, but the present invention is not limited to the above embodiment. The materials and shapes of the various structures are not limited to those described above, and various materials and shapes can be used. For example, in the above embodiment, as a method of fastening together, the threaded member 11 is exemplified by being threadedly fastened to an insertion hole 61a (threaded hole) provided in the bottom wall 61 of the base 6, but the threaded member 11 can also be engaged with a nut. For example, a through hole extending from the first surface 611 to the second surface 612 can be provided in the bottom wall 61, and the threaded member 11 (bolt) can be inserted through this through hole, so that a nut disposed on the second surface 612 side engages with the front end of the threaded member 11, thereby fastening the encapsulation member 2 and the lens retaining member 4 together relative to the base 6. The same applies to the screw 9 used to fix the cooling fan 5 to the bottom wall 61.

[0062] In addition, in the above embodiment, the lens holding member 4 is formed by combining the sub-base 41 and the lens bracket 42, but the sub-base 41 may be omitted. For example, the lens bracket 42 itself may be provided with an insertion hole for the threaded member 11 to be inserted, and the lens bracket 42, the spacer 10 and the flange 24 are fastened together relative to the base 6.

[0063] Alternatively, the base 6 may not have a side wall 62. In this case, a fixing part for fixing the QCL module to a fixing object (e.g., an insertion hole for inserting the aforementioned rod member) may also be provided on the bottom wall 61. Furthermore, in this case, to ensure the area for providing the fixing part, the base 6 may also include a bottom wall larger than the bottom wall 61 shown in the above embodiment (e.g., a bottom wall wider than the width of the bottom wall 61 described above).

[0064] In addition, such as Figure 5 As shown in the modified QCL module 1A, the common threaded member 11 may not penetrate the spacer and flange. The difference between QCL module 1A and QCL module 1 is that QCL module 1A has a package 2A instead of package 2, a lens holding member 4A instead of lens holding member 4, a base 6A instead of base 6, and a spacer 110 instead of spacer 10. Figure 5 In the diagram, the cooling fan 5 and the radiator 7 are simplified, and the elements other than the sub-base 141 of the lens holding member 4A (the element corresponding to the sub-base 41) (i.e., the lens bracket 42, the lens barrel 43, etc.) are omitted.

[0065] Package 2A differs from package 2 in that it has flange 124 (flange 124A, 124B) instead of flange 24 (flange 24A, 24B). Flange 124 differs from flange 24 in that it does not have through hole 24b.

[0066] The lens holding member 4A differs from the lens holding member 4 in that it has a secondary base 141 instead of the secondary base 41. Like the secondary base 41, the secondary base 141 has a through hole 141a and a countersunk groove 141b for inserting the threaded member 11. However, it differs from the secondary base 41 in that the width of the secondary base 141 in the X-axis direction is slightly larger than that of the secondary base 41. Furthermore, the positions of the through hole 141a and the countersunk groove 141b in the X-axis direction are located further outward than those of the through hole 41a and the countersunk groove 41b in the X-axis direction of the secondary base 41.

[0067] The base 6A differs from the base 6 in that it has a base wall 161 instead of a base wall 61. Like the base wall 61, the base wall 161 has a first surface 161a, a second surface 161b, and a through hole 161c. However, it differs from the base wall 61 in that the width of the base wall 161 in the X-axis direction is slightly larger than that of the base wall 61. Furthermore, the position of the through hole 161c in the X-axis direction is further outward than the position of the through hole 61a in the X-axis direction of the base wall 61. Specifically, the through hole 161c is located further outward in the X-axis direction than the spacer 110 and the flange 124.

[0068] Spacer 110 (spacer 110A, 110B) differs from spacer 10 (spacer 10A, 10B) in that it does not have a through hole 10b.

[0069] In QCL module 1A, through holes 141a and 161c for threaded members 11 are formed in the sub-base 141 (lens holding member 4A) and the bottom wall 161 (base 6A), respectively. With the spacer 110 and flange 124 arranged between the sub-base 141 and the bottom wall 161, the sub-base 141 is fastened to the bottom wall 161 by using the threaded members 11 that are inserted into the through holes 141a and 161c of the sub-base 141 and the bottom wall 161, thereby fastening the lens holding member 4A, the spacer 110 and the flange 124 together with respect to the base 6A. In this case, the threaded member 11 passes through the lens holding member 4A and is inserted into the insertion hole 161c of the base 6A. The lens holding member 4A and the base 6A clamp the spacer 110 and flange 124 disposed between them (in other words, the spacer 110 and flange 124 are pressed from both sides in the Z-axis direction like a vise), thereby making it possible to integrally and firmly fix the lens holding member 4A, the spacer 110, and the flange 124 to the base 6A. As a result, changes in the relative positional relationship between the package 2A and the lens holding member 4A can be effectively suppressed. In addition, according to the QCL module 1A, it is not necessary to provide insertion holes in the spacer 110 and flange 124. On the other hand, in the QCL module 1A, the position of the threaded member 11 in the X-axis direction is further outward than in the QCL module 1. Therefore, from the viewpoint of miniaturizing the width dimension of the module in the X-axis direction, the QCL module 1 is more advantageous than the QCL module 1A.

[0070] Explanation of reference numerals in the attached figures

[0071] 1, 1A…Quantum cascade laser module; 2, 2A…Packaging component; 3…Lens; 4, 4A…Lens holding component; 5…Cooling fan; 6, 6A…Base; 10, 110A…Spacers; 10A, 110A…Spacers (first spacer); 10B, 110B…Spacers (second spacer); 11…Threaded component (shaft component); 23…Window component; 24, 124…Flanges; 24A, 124A…Flanges (first flange); 24B, 124B…Flanges (second flange); S…Gap.

Claims

1. A quantum cascade laser module, in, include: The package contains a quantum cascade laser element and is provided with a window component for extracting the laser emitted from the quantum cascade laser element to the outside. A lens holding member that holds a lens to which the laser light emitted from the window member is incident; A cooling fan that cools the package; and The base holds the package, the lens holding member, and the cooling fan. The base has a first surface and a second surface that are located on opposite sides of each other. The encapsulation member and the lens holding member, when disposed on the first surface side of the base, are fastened together relative to the base by a common shaft member. The cooling fan is fixed to the base when it is disposed on the second side of the base.

2. The quantum cascade laser module according to claim 1, wherein, The encapsulation component is disposed between the base and the lens holding component, with the window component facing the lens. The package and the lens holding member are fastened together relative to the base by means of the lens holding member.

3. The quantum cascade laser module according to claim 2, wherein, It also includes: a spacer disposed between the lens holding member and the base. The package has a flange that abuts against the base and extends along the base. The spacer is disposed between the base side surface of the lens holding member and the lens holding member side surface of the flange, thereby forming a gap between the lens holding member and the window member.

4. The quantum cascade laser module according to claim 3, wherein, The flange has: a first flange and a second flange formed on both sides of the window member. The spacer has: a first spacer disposed between the base side surface of the lens holding member and the lens holding member side surface of the first flange; and a second spacer disposed between the base side surface of the lens holding member and the lens holding member side surface of the second flange.

5. The quantum cascade laser module according to claim 3 or 4, wherein, The lens holding member, the spacer, the flange, and the base are each provided with an insertion hole for the shaft member to pass through. The lens holding member is secured relative to the base by means of a shaft member that passes through the through holes of the lens holding member, the spacer, the flange, and the base, thereby securing the lens holding member, the spacer, and the flange together relative to the base.

6. The quantum cascade laser module according to claim 3 or 4, wherein, The lens holding member and the base are respectively provided with insertion holes for the shaft member to be inserted. With the spacer and the flange disposed between the lens holding member and the base, the lens holding member is fastened relative to the base by means of the shaft member that is inserted into the insertion hole of the lens holding member and the base respectively, thereby fastening the lens holding member, the spacer and the flange together relative to the base.

7. The quantum cascade laser module according to any one of claims 3 to 6, wherein, The spacer is formed of a material with a lower thermal conductivity than the base.

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