Quantum cascade laser device

Abstract

The quantum cascade laser device of the present invention comprises: a QCL element, a lens arranged opposite to the end face of the QCL element, and a lens holder for holding the lens. The lens holder comprises: a small diameter hole, a large diameter hole, and an annular countersunk surface connecting the small diameter hole and the large diameter hole. At least a portion of the side surface of the lens is fixed to the inner side surface of the large diameter hole via a resin adhesive in a state where the edge of the incident surface of the lens abuts against the countersunk surface. The center axis of the small diameter hole is eccentric from the center axis of the large diameter hole. Along the direction from the center axis of the large diameter hole toward the center axis of the small diameter hole, the side surface of the lens is positioned relative to the inner side surface of the large diameter hole. The center axis of the lens is arranged at a position closer to the center axis of the small diameter hole than the center axis of the large diameter hole.

Description

Technical Field

[0001] The present disclosure relates to quantum cascade laser devices. Background Art

[0002] At present, there is known a semiconductor laser device (semiconductor laser module) in which a semiconductor laser element is housed in a package (for example, Patent Document 1). Patent Document 1 discloses a structure in which a semiconductor laser element and a lens holder housing a lens for collimating laser light emitted from the semiconductor laser element are housed in the package.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-315633 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Here, the radiation angle of the laser beam emitted from the quantum cascade laser element, which is one of the semiconductor laser elements, is relatively large. In addition, in order to achieve miniaturization of the package, it is sought to miniaturize the size of the lens contained in the package. Therefore, when the quantum cascade laser element is used as a semiconductor laser element, in order to focus the laser light from the quantum cascade laser element with a large radiation angle through a small lens, it is sought to use the effective area of ​​the lens without waste.

[0008] Therefore, an object of the present disclosure is to provide a quantum cascade laser device that can efficiently utilize the effective area of ​​a lens.

[0009] Technical solutions to the problem

[0010] A quantum cascade laser device according to one aspect of the present disclosure comprises: a quantum cascade laser element; a lens arranged opposite to an emission surface of laser light of the quantum cascade laser element; and a lens holder holding the lens, the lens holder having: a first hole portion extending in an optical axis direction along an optical axis of the laser light; a second hole portion provided at a position farther from the quantum cascade laser element than the first hole portion, including the first hole portion and being larger than the first hole portion when viewed in the optical axis direction; and an annular countersunk surface connecting the first hole portion and the second hole portion, extending along a surface intersecting the optical axis direction. The lens comprises: an incident surface for incident laser light; and a side surface extending from an edge of the incident surface along the optical axis direction, at least a portion of the side surface is fixed to the inner side surface of the second hole portion via a resin adhesive when the edge of the incident surface abuts against the countersunk surface, the center axis of the first hole portion is eccentric from the center axis of the second hole portion, and the side surface of the lens is positioned relative to the inner side surface of the second hole portion along a direction from the center axis of the second hole portion toward the center axis of the first hole portion, and the center axis of the lens is arranged at a position closer to the center axis of the first hole portion than the center axis of the second hole portion.

[0011] In the above-mentioned quantum cascade laser device, the lens holder has: a first hole portion and a second hole portion whose central axes are eccentric to each other. In addition, the side surface of the lens is positioned relative to the inner side surface of the second hole portion along the direction from the central axis of the second hole portion toward the central axis of the first hole portion. As a result, it is possible to appropriately suppress the position deviation of the lens (movement of the lens relative to the lens holder) caused by the surface tension of the resin adhesive arranged around the lens if the lens is arranged in the central portion of the second hole portion. Moreover, in a state where the lens is positioned in this way, the central axis of the lens is arranged at a position close to the central axis of the first hole portion. As a result, the area of ​​the region where the effective area of ​​the lens (the area within the effective diameter centered on the central axis of the lens) interferes (overlaps) with the countersunk surface can be reduced. As a result, the effective area of ​​the lens can be efficiently utilized.

[0012] The central axis of the lens may also be substantially consistent with the central axis of the first hole, and the effective diameter of the lens may also be substantially consistent with the diameter of the first hole. According to the above structure, the entire effective area of ​​the lens (the area within the effective diameter) can be exposed through the first hole. Thus, the area of ​​the countersunk surface can be ensured by minimizing the size of the first hole, thereby appropriately supporting the edge of the incident surface of the lens and maximally utilizing the effective area of ​​the lens.

[0013] The inner side surface of the second hole portion may also be formed with a recessed portion extending along the optical axis to the counterbore surface, and the resin adhesive may enter the recessed portion. According to the above structure, the resin adhesive can be easily injected between the side surface of the lens and the inner side surface of the second hole portion through the recessed portion.

[0014] The quantum cascade laser device may further include: a heat sink equipped with a lens holder, the lens holder may also include: a first mounting surface formed with a plurality of first protrusions protruding toward the heat sink, and the plurality of first protrusions may also be bonded to the second mounting surface of the heat sink via an adhesive layer composed of a photocurable resin. According to the above structure, since the locations where the adhesive layer (photocurable resin) is provided can be dispersed on the plurality of first protrusions, the adhesive layer on each first protrusion can be easily and appropriately cured compared to the case where the adhesive layer is provided over a large area on the entire surface.

[0015] The second mounting surface may also be formed with: a plurality of second protrusions protruding toward the lens frame at positions corresponding to the plurality of first protrusions, and the plurality of first protrusions may also be joined to the plurality of second protrusions via an adhesive layer. According to the above structure, an adhesive layer is disposed in the central portion of the space formed between the first mounting surface and the second mounting surface. Thus, the light reflected by the first mounting surface and the second mounting surface in the space can be appropriately irradiated to the adhesive layer. As a result, the adhesive layer can be more appropriately cured, and the lens frame can be stably fixed to the heat sink.

[0016] The first wall portion of the lens holder having the first mounting surface may also be provided with a through hole or cutout for guiding light to the second mounting surface of the heat sink. According to the above structure, the second mounting surface of the heat sink can be irradiated with light from the side opposite to the side of the lens holder where the heat sink is arranged, through the through hole or cutout provided in the first wall portion. Thus, light irradiation for curing the adhesive layer between the first mounting surface and the second mounting surface can be easily performed.

[0017] The lens holder may also include: a second wall portion opposite to the first wall portion via a second hole portion, and the second wall portion may also be formed in a manner that does not overlap with at least a portion of a through hole or a cutout provided in the first wall portion when viewed from a direction opposite to the first wall portion and the second wall portion. According to the above structure, the lens disposed in the second hole portion can be appropriately protected from the outside by the first wall portion and the second wall portion. In addition, by forming the second wall portion in a manner that does not overlap with at least a portion of a through hole or a cutout provided in the first wall portion, it is possible to irradiate light onto the second mounting surface of the heat sink by irradiating light onto the lens holder from the outside of the lens holder (on the opposite side of the first wall portion sandwiching the second wall portion).

[0018] The quantum cascade laser element and the lens holder may also be mounted on the same heat sink. According to the above structure, by making the base (heat sink) on which the quantum cascade laser element and the lens holder are mounted common, the relative movement of the lens holder relative to the quantum cascade laser element can be suppressed when the heat sink expands or contracts due to heat. As a result, the occurrence of optical axis deviation (deviation of the center axis of the lens relative to the optical axis of the laser emitted from the quantum cascade laser element) caused by temperature changes in the package can be suppressed.

[0019] It may also include: a package that airtightly accommodates the quantum cascade laser element, the lens, and the lens holder, and the package may also include: a bottom wall; a side wall that is erected on the bottom wall and is formed in a ring shape in a manner to surround the area accommodating the quantum cascade laser element and the lens holder when viewed from a direction perpendicular to the bottom wall; and a top wall that blocks the opening of the side wall on the side opposite to the bottom wall, and the side wall may also be provided with: a light exit window that allows the laser light that has passed through the lens to pass through. According to the above structure, as described above, the effective area of ​​the lens arranged in the package can be efficiently utilized, so that the lens can be miniaturized and the package can be miniaturized.

[0020] Effects of the Invention

[0021] According to the present invention, it is possible to provide a quantum cascade laser device capable of efficiently utilizing the effective area of ​​a lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a perspective view of a quantum cascade laser device according to one embodiment.

[0023] Figure 2 yes Figure 1 A side cross-sectional view of a quantum cascade laser device is shown.

[0024] Figure 3 yes Figure 1 A top view of the quantum cascade laser device shown.

[0025] Figure 4 This is a diagram showing a typical example of the relationship between the radiation angle (horizontal axis) and the radiation intensity (vertical axis) of laser light emitted from a quantum cascade laser.

[0026] Figure 5 yes Figure 1 A partial enlarged view of the quantum cascade laser device shown.

[0027] Figure 6 It is a front view of the portion of the side wall including the small-diameter hole and the large-diameter hole.

[0028] Figure 7 In the figure, (A) is a diagram showing an incident surface of a window member, (B) is a cross-sectional view of the window member, and (C) is a diagram showing an exit surface of the window member.

[0029] Figure 8 , (A) is a top view of the Peltier module, and (B) is a side view of the Peltier module.

[0030] Fig. 9 (A) is a top view of the radiator, (B) is a side view of the radiator, and (C) is a bottom view of the radiator.

[0031] Fig.10 (A) is a top view of a heat sink on which various components are mounted, and (B) is a side view of a heat sink on which various components are mounted.

[0032] Fig.11 It is a three-dimensional diagram of the lens holder.

[0033] Fig.12 It is a front view of the lens holder.

[0034] Fig.13 In the figure, (A) is a top view of the lens frame, (B) is a bottom view of the lens frame, and (C) is a side sectional view of the lens frame.

[0035] Fig.14 is schematically shown along Fig.12 Figure 1 is a cross-section of line XIV-XIV.

[0036] Fig.15 It is a diagram schematically showing the positional relationship between the lens and the lens frame when the lens frame according to the comparative example is used.

[0037] Fig.16 It is shown Figure 1 A diagram showing a portion of the assembly steps of a quantum cascade laser device.

[0038] Fig.17 , (A) is a front view of a lens frame according to a first modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0039] Fig.18 , (A) is a front view of a lens frame according to a second modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0040] Fig.19 , (A) is a front view of a lens frame according to a third modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0041] Fig. 20 It is a side cross-sectional view of a quantum cascade laser device according to a modified example. DETAILED DESCRIPTION

[0042] Hereinafter, the embodiments of the present disclosure will be described with reference to the accompanying drawings. The same reference numerals are used for the same or corresponding parts in each figure, and repeated descriptions are omitted. In addition, in the accompanying drawings, some parts are exaggerated in order to easily understand the structures involved in the embodiments, and sometimes they are different from the actual sizes. In addition, in the following description, the words "upper" and "lower" are used for convenience based on the states shown in the drawings.

[0043] like Figure 1 to Figure 3As shown, a quantum cascade laser device 1 (semiconductor laser device) includes a quantum cascade laser element (hereinafter referred to as a “QCL ​​element”) 2 and a package 3 that hermetically houses the QCL element 2 .

[0044] The QCL element 2 is a type of semiconductor laser element. The QCL element 2 has an end face 2a (exit face) intersecting a direction (the X-axis direction in the present embodiment), and is configured to emit laser light L having a wide-band wavelength (for example, 4 μm to 12 μm) in the mid-infrared region from the end face 2a. In the present embodiment, the optical axis of the laser light L emitted from the QCL element 2 is along the X-axis direction. The QCL element 2 has, for example, a structure in which a plurality of active layers having different central wavelengths are stacked in a stack, and is capable of emitting wide-band light as described above. However, the QCL element 2 may also have a structure consisting of a single active layer, in which case it is also possible to emit wide-band light as described above. As Figure 4 As shown, the laser light L emitted from the QCL element 2 has a beam radiation angle (divergence angle) that is much larger than that of a laser diode or the like based on the principle of quantum cascade laser.

[0045] The package 3 is a so-called butterfly package. The package 3 has a bottom wall 31, side walls 32 and a top wall 33. Figure 3 In the figure, the top wall 33 of the package 3 is omitted.

[0046] The bottom wall 31 is a rectangular plate-shaped component. The bottom wall 31 is formed of a metal material such as copper tungsten. The bottom wall 31 is a base component equipped with various components such as the Peltier module 4 described later. For convenience in this specification, the long side direction of the bottom wall 31 is represented as the X-axis direction, the short side direction of the bottom wall 31 is represented as the Y-axis direction, and the direction perpendicular to the bottom wall 31 (that is, the direction orthogonal to the X-axis direction and the Y-axis direction) is represented as the Z-axis direction. As mentioned above, the X-axis direction is also the direction along the optical axis of the laser L emitted from the QCL element 2 (optical axis direction).

[0047] The side wall 32 is erected on the bottom wall 31. When viewed from the Z-axis direction, the side wall 32 is formed in a ring shape so as to surround the area (internal space S) in which the QCL element 2 and the like are accommodated. In the present embodiment, the side wall 32 is a rectangular cylindrical member that surrounds the internal space S. The side wall 32 is formed of a metal material such as kovar. The side wall 32 is, for example, a kovar frame plated with Ni / Au. In the present embodiment, the side wall 32 is arranged in the central part of the long side direction (X-axis direction) of the bottom wall 31. The width of the side wall 32 along the short side direction (Y-axis direction) is consistent with the width of the bottom wall 31 in the short side direction, and the width of the side wall 32 along the long side direction (X-axis direction) is shorter than the width of the bottom wall 31 in the long side direction. That is, on both sides of the long side direction of the bottom wall 31, there are protrusions 31a that extend more outward than the side wall 32. Screw holes 31 b for attaching the package 3 (bottom wall 31 ) to other members are provided in portions of the protruding portion 31 a corresponding to the four corners of the bottom wall 31 .

[0048] The top wall 33 is a member that blocks the opening of the side wall 32 on the side opposite to the bottom wall 31. The top wall 33 is in the shape of a rectangular plate. The outer shape (width in the long side direction and the short side direction) of the top wall 33 observed from the Z-axis direction is substantially consistent with the outer shape of the side wall 32. The top wall 33 is formed of, for example, the same metal material (such as Kovar) as the side wall 32.

[0049] In a portion 321 extending along the long side direction (X-axis direction) of the side wall 32 (i.e., a portion intersecting the short side direction (Y-axis direction)), a plurality of lead pins 10 (in the present embodiment, 7 on each side in the short side direction, for a total of 14) are inserted for allowing current to flow to components such as the QCL element 2 housed in the package 3.

[0050] In one of the portions 322 extending along the short side direction (Y-axis direction) of the side wall 32 (i.e., the portion intersecting the long side direction (X-axis direction)), a light exit window 11 is provided for allowing the laser light L emitted from one end face 2a of the QCL element 2 to pass therethrough.

[0051] like Figure 5 and Figure 6 As shown, the light exit window 11 includes: a small diameter hole 12 formed by a side wall 32 (part 322), a large diameter hole 13 and a countersunk hole surface 14 and a window member 15. In addition, the window member 15 is provided with anti-reflection films 151, 152 and a metal film 153 (see Figure 7 ). These components are very thin compared to the main body of the window component 15, so Figure 7 Illustration of these components is omitted in other figures.

[0052] The small diameter hole 12 opens on the inner side (i.e., the internal space S) of the package 3 in the optical axis direction (i.e., the X-axis direction) along the optical axis of the laser L. The large diameter hole 13 opens on the outer side of the package 3. The large diameter hole 13, when viewed from the X-axis direction, has a shape that includes the small diameter hole 12 and is larger than the small diameter hole 12. The small diameter hole 12 and the large diameter hole 13 extend in the X-axis direction, respectively. A through hole that penetrates in the X-axis direction is formed by the small diameter hole 12 and the large diameter hole 13 connected by the countersunk surface 14. In the present embodiment, each of the small diameter hole 12 and the large diameter hole 13 is formed in a circular shape, and the diameter d2 of the large diameter hole 13 is larger than the diameter d1 of the small diameter hole 12 (d2>d1). In addition, the central axis of the small diameter hole 12 and the central axis of the large diameter hole 13 may also be consistent with the optical axis of the laser L emitted from the QCL element 2. The countersink surface 14 is an annular surface that connects the small diameter hole 12 and the large diameter hole 13 and extends along a surface (YZ plane) that intersects the X-axis direction. More specifically, the countersink surface 14 connects the end of the small diameter hole 12 on the large diameter hole 13 side and the end of the large diameter hole 13 on the small diameter hole 12 side. The large diameter hole 13 and the countersink surface 14 can be formed by countersinking from the outside of the package 3. In addition, in the present embodiment, the countersink surface 14 is formed into a continuous annular shape, and the countersink surface 14 can also be formed into a discontinuous annular shape. For example, a cutout can be formed in a portion of the inner wall surface of the small diameter hole 12, and the countersink surface 14 can be divided in the portion where the cutout is formed.

[0053] In the present embodiment, the diameter d1 of the small diameter hole 12 is 3.8 mm, the diameter d2 of the large diameter hole 13 is 5.7 mm, and the radial width ((d2-d1) / 2) of the countersunk surface 14 is 0.95 mm. In addition, the length w1 of the small diameter hole 12 along the X-axis direction is shorter than the length w2 of the large diameter hole 13 along the X-axis direction. In the present embodiment, the thickness t (length along the X-axis direction) of the side wall 32 is 1 mm, the length w1 of the small diameter hole 12 is 0.23 mm, and the length w2 of the large diameter hole 13 is 0.77 mm.

[0054] The window member 15 is formed of a material (e.g., germanium, etc.) that allows the laser light L of the wavelength in the mid-infrared region to pass through. The window member 15 is formed in the shape of a disk and is arranged on the inner side of the large-diameter hole 13. The window member 15 has an incident surface 15a, an exit surface 15b, and a side surface 15c. The incident surface 15a and the exit surface 15b are surfaces intersecting the X-axis direction and formed into a circular shape. The incident surface 15a is a surface on the side of the internal space S, and is a surface on which the laser light L (in this embodiment, the laser light L collimated by the lens 8) is incident. The exit surface 15b is a surface on the opposite side of the incident surface 15a (i.e., a surface on the outside of the package 3), and is a surface that emits the laser light L passing through the window member 15 to the outside of the package 3. The side surface 15c is a surface that connects the incident surface 15a and the exit surface 15b and extends along the X-axis direction. In the present embodiment, the diameter of the window member 15 (the incident surface 15 a or the emission surface 15 b ) is 5.4 mm, and the thickness (the length in the X-axis direction) of the window member 15 is 0.7 mm.

[0055] like Figure 7 As shown in (A) and (B), the incident surface 15a has a first area A1 and a second area A2. The first area A1 is an area including the central part of the incident surface 15a, and is provided with an anti-reflection film 151 (first anti-reflection film). The anti-reflection film 151 is a film component having the function of suppressing the reflection of the laser light L of the wavelength in the mid-infrared region at the incident surface 15a. The anti-reflection film 151 is formed, for example, of a high refractive index material such as germanium (Ge) and silicon (Si), an intermediate refractive index material such as zinc sulfide (ZnS) and zinc selenide (ZnSe), a low refractive index material such as yttrium fluoride (YF3), or a dielectric multilayer film in which multiple materials with different refractive indices that transmit mid-infrared are alternately stacked. The anti-reflection film 151 is formed in a circular shape. The thickness (length along the X-axis direction) of the anti-reflection film 151 is determined according to the design of the transmission wavelength (wavelength of the transmitted laser light L) of the anti-reflection film 151. The thickness of the anti-reflection film 151 is, for example, not less than 1.0 μm and not more than 3.0 μm. For example, when the design value of the transmission wavelength is 5.2 μm, the thickness of the anti-reflection film 151 is, for example, set to 1.4 μm. In addition, in this embodiment, the diameter of the anti-reflection film 151 (i.e., the diameter of the first area A1) is 4.2 mm.

[0056] The second region A2 is an annular region that surrounds the first region A1 at a distance from the first region A1. The second region A2 is metallized by a metal film 153. The metal film 153 is formed by a material suitable for welding (i.e., a material having good affinity with the solder member 16 described later). The metal film 153 is formed, for example, of Cr / Ni / Au (0.2μm / 0.5μm / 0.5μm). In the present embodiment, the inner diameter of the metal film 153 formed on the incident surface 15a (i.e., the inner diameter of the second region A2) is 4.5mm. That is, in the present embodiment, between the outer edge of the first region A1 and the inner edge of the second region A2, a 0.15mm wide annular region is formed in which the incident surface 15a (germanium substrate) is exposed.

[0057] like Figure 7 As shown in (B), the side surface 15c has a third region A3 that is metalized so as to be continuous with the second region A2. That is, the metal film 153 is provided continuously from the second region A2 to the side surface 15c.

[0058] like Figure 7 As shown in (B) and (C), the exit surface 15b has a fourth region A4 provided with an anti-reflection film 152 (second anti-reflection film). The anti-reflection film 152 is a film member having a function of suppressing the reflection of the laser light L of a wavelength in the infrared region in the exit surface 15b. The anti-reflection film 152 is formed into a circular shape by the same material as the anti-reflection film 151. In the present embodiment, the diameter of the anti-reflection film 152 (i.e., the diameter of the fourth region A4) is 4.6 mm. That is, when observed from the X-axis direction, the fourth region A4 is a region that includes the first region A1 and is larger than the first region A1.

[0059] The window member 15 is directly bonded to the side wall 32 (portion 322). Specifically, the second region A2 of the incident surface 15a (i.e., the region metallized by the metal film 153) is bonded to the countersunk surface 14 via a solder member 16 formed in an annular shape. The solder member refers to a bonding material having a melting point of 450°C or less. The solder member 16 is formed, for example, of a SnAgCu-based solder member having a melting point of 220°C. The solder member 16 is a sheet-like member originally formed in an annular shape (see Fig.16 ).

[0060] In the present embodiment, the thickness of the solder member 16 in the state before welding (i.e., the state of the annular sheet) is 0.1 mm, the outer diameter is 5.5 mm, and the inner diameter is 4.2 mm. That is, in the present embodiment, the inner diameter (4.2 mm) of the solder member 16 is consistent with the diameter (4.2 mm) of the first region A1, and the first region A1 and the solder member 16 do not overlap each other. In addition, the first region A1 formed with the anti-reflection film 151 is separated from the second region A2 formed with the metal film 153. By completely separating the first region A1 from the second region A2 in this way, there is an area where the base (germanium base in the present embodiment) of the window member 15 is exposed between the first region A1 and the second region A2, so that during welding, the solder member 16 is not easy to flow onto the first region A1 (on the anti-reflection film 151). On the other hand, the solder member 16 easily infiltrates and spreads onto the metal film 153 with high affinity to the solder member 16. Thus, stress generated when the solder member 16 melts or solidifies during soldering is less likely to be transmitted to the anti-reflection film 151 on the first area A1 .

[0061] Furthermore, as described above, the solder member 16 wets and spreads onto the metal film 153, and a portion of the solder member 16 also climbs onto the third region A3 (see Figure 5 ). That is, a portion of the solder member 16 enters between the side surface 15c and the inner side surface of the large diameter hole 13. That is, at least a portion of the side surface 15c of the window member 15 is bonded to at least a portion of the inner side surface of the large diameter hole 13 via the solder member 16. Thus, the airtightness of the package 3 is effectively improved at the mounting portion of the window member 15.

[0062] In this embodiment, the light exit surface 15b of the window member 15 is substantially flush with the outer surface 32a of the side wall 32 (the outer surface of the package 3) provided with the light exit window 11. That is, the length w2 of the large diameter hole 13 (that is, the depth of the countersinking process) is adjusted so that the light exit surface 15b and the outer surface 32a of the side wall 32 are substantially flush with each other.

[0063] Next, the components contained in the package 3 are described. In the internal space S formed by the package 3, in addition to the QCL element 2, the Peltier module 4, the heat spreader 5, the heat sink 6, the sub mount 7, the lens 8, the lens holder 9, and the temperature sensor T (see Fig.10 ).

[0064] The Peltier module 4 is a temperature control element for adjusting the temperature of the QCL element 2. Specifically, the Peltier module 4 has a cooling / heating function for maintaining the temperature of the QCL element 2 at a temperature corresponding to the oscillation wavelength of the QCL element 2. The temperature control by the Peltier module 4 is based on the temperature sensor T (see Fig.10 ) is performed based on the temperature of the QCL element 2 measured.

[0065] like Figure 8 As shown, the Peltier module 4 includes: a plurality of Peltier elements 41 as thermoelectric semiconductor elements, and a pair of ceramic substrates 42 and 43 that sandwich the plurality of Peltier elements 41 from above and below. The ceramic substrate 42 is provided on the top wall 33 side relative to the Peltier elements 41, and the ceramic substrate 43 is provided on the bottom wall 31 side relative to the Peltier elements 41. Each of the ceramic substrates 42 and 43 is formed of, for example, alumina. The outer surface (the surface opposite to the Peltier element 41 side) of each of the ceramic substrates 42 and 43 is a metallized surface on which a metal film 44 of Cu / Ni / Au or the like is formed by plating. In addition, an In foil 45 as a solder member is provided on the outer surface of the ceramic substrates 42 and 43 via the metal film 44. The ceramic substrate 42 is soldered to the heat sink 5 via the In foil 45. On the other hand, the ceramic substrate 43 is soldered to the upper surface 31c (the surface opposite to the top wall 33) of the bottom wall 31 of the package 3 via the In foil 45. Two lead wires 20 for allowing a direct current to flow to the Peltier module 4 are electrically connected to one ceramic substrate (the ceramic substrate 43 in the present embodiment). The two lead wires 20 are connected to different pins 10 , respectively.

[0066] The heat sink 5 is a member mounted on the Peltier module 4, and dissipates the heat generated by the QCL element 2 toward the Peltier module 4. The heat sink 5 is formed of a material having excellent thermal conductivity, such as copper. Fig. 9 As shown, the heat sink 5 has: an In foil 45 (see Figure 8 ) and a bottom surface 51 welded to the Peltier module 4, a first upper surface 52 on which the heat sink 6 and the sub-base 7 are mounted, and a second upper surface 53 (second mounting surface) on which the lens holder 9 is mounted.

[0067] Here, the thermal expansion coefficient of copper (about 17×10 -6 / K) is larger than the thermal expansion coefficient of aluminum oxide (about 7×10 -6Therefore, when the ceramic substrate 42 of the Peltier module 4 is formed of alumina and the heat sink 5 is formed of copper, if the entire bottom surface 51 of the heat sink 5 is bonded to the ceramic substrate 42 via the In foil 45, during long-term use and temperature control of the quantum cascade laser device 1, cracks may occur in the Peltier element 41 due to a large temperature difference between the upper surface and the lower surface of the Peltier element 41.

[0068] Therefore, in the present embodiment, a groove 51a is formed on the bottom surface 51 of the heat sink 5, which is used to divide the bonding surface with the Peltier module 4 into multiple parts. In the present embodiment, as an example, two grooves 51a extend in the short side direction (Y axis direction) at the position where the bottom surface 51 is divided into three parts in the long side direction (X axis direction). The bonding surface with the Peltier module 4 is roughly equally divided into three parts by the two grooves 51a. By dividing the bonding surface with the Peltier module 4 into multiple parts (here 3), the stress generated by the difference in thermal expansion coefficient between the material (alumina) of the ceramic substrate 42 and the material (copper) of the heat sink 5 is reduced, and the generation of cracks in the above-mentioned Peltier element 41 is suppressed.

[0069] In addition, the mechanical strength of the four corners (corners) of the Peltier module 4 is particularly weak. Therefore, in the present embodiment, cutout grooves 51b are formed at the four corners of the bottom surface 51 of the heat sink 5. Thus, the ceramic substrate 42 and the bottom surface 51 of the heat sink 5 can be prevented from being joined at the portions corresponding to the four corners of the Peltier module 4, and the stress on the four corners of the Peltier module 4 caused by the difference in the above-mentioned thermal expansion coefficient can be effectively reduced.

[0070] In addition, the groove 51a and the notch groove 51b function as escape paths for air layers (voids) mixed in when the ceramic substrate 42 and the bottom surface 51 are welded via the In foil 45. This can improve the bonding quality and thermal conductivity between the Peltier module 4 (ceramic substrate 42) and the heat sink 5.

[0071] Furthermore, by using soft solder such as In or InSn (In in the present embodiment), as a solder member for joining the Peltier module 4 (ceramic substrate 42) and the heat sink 5, the stress of expansion or contraction caused by heat can be appropriately absorbed, thereby improving the reliability of the quantum cascade laser device 1.

[0072] The first upper surface 52 is located at a higher position (top wall 33 side) than the second upper surface 53. In the present embodiment, as an example, two screw holes 52a for screwing the heat sink 6 and a protrusion 52b protruding upward (top wall 33 side) are provided on the first upper surface 52. The protrusion 52b extends along the short side direction (Y axis direction) at the end portion (the end portion opposite to the second upper surface 53 side) in the long side direction (X axis direction) of the first upper surface 52. The protrusion 52b is a portion for positioning the end portion of the heat sink 6 by contacting with the ground.

[0073] A plurality of (four in this embodiment) convex portions 53a (second convex portions) formed in an island shape are provided on the second upper surface 53. The four convex portions 53a are portions to be joined to the lens frame 9 described later.

[0074] The heat sink 6 is a member mounted on the first upper surface 52 of the heat sink 5. The heat sink 6 is formed of a material with excellent thermal conductivity, such as copper, similar to the heat sink 5. The heat sink 6 is formed in a substantially rectangular parallelepiped shape. For example, the width of the heat sink 6 along the X-axis direction is 5 mm, and the width of the heat sink 6 along the Y-axis direction is 6 mm. Fig.10 As shown, on the upper surface 6a of the heat sink 6 (the surface on the side of the top wall 33), there are mounted: a sub-base 7 on which the QCL element 2 is mounted, a temperature sensor T for measuring the temperature of the QCL element 2, and a ceramic pattern SP for wire wiring. The lower surface 6b of the heat sink 6 abuts against the first upper surface 52 of the heat sink 5. In order to easily replace the QCL element 2 when a defect occurs in the QCL element 2, the heat sink 6 is fixed to the heat sink 5 by screws. In order to fix with such screws, the heat sink 6 is provided with: a screw hole 6c that passes through in the Z-axis direction and a countersunk groove 6d formed around the screw hole 6c. The screw hole 6c is provided so as to be aligned with the screw hole 52a of the heat sink 5 mentioned above (see Fig. 9 ) corresponding to the position. For example, a screw member (not shown) coated with a screw locking agent (adhesive for screw locking) at the front end of the screw is inserted into the screw hole 6c and the screw hole 52a, and the heat sink 6 is fixed to the heat sink 5. The counterbore groove 6d is a groove portion provided for accommodating the head of the above-mentioned screw member. In addition, as the above-mentioned screw locking agent, a thermosetting resin adhesive (such as epoxy resin, etc.) that does not generate outgas is appropriately used.

[0075] The temperature sensor T and the ceramic pattern SP are electrically connected to a predetermined pin 10 via a wire (not shown). In addition, the QCL element 2 is electrically connected to a predetermined pin 10 via the ceramic pattern SP and a wire (not shown). Thus, power is supplied to the QCL element 2 and the temperature sensor T via the pin 10 from an external power supply device.

[0076] The submount 7 is a rectangular plate-shaped member on which the QCL element 2 is mounted. The QCL element 2 is mounted on the submount 7 in such a manner that the optical axis of the laser light L emitted from the end face 2a coincides with the center of the light exit window 11 (i.e., the central axis of the small-diameter hole 12 and the large-diameter hole 13). The submount 7 is formed of a material having a thermal expansion coefficient close to that of the QCL element 2 (e.g., aluminum nitride, etc.). The QCL element 2 is bonded to the submount 7 via, for example, a solder material of the AnSn series. In addition, the submount 7 is bonded to the heat sink 6 via, for example, a solder material of the SnAgCuNiGe series.

[0077] Next, refer to Figure 11 to Figure 15 , explaining the lens 8 and the lens holder 9. As mentioned above, the laser L has a relatively large beam radiation angle (refer to Figure 4 ). Therefore, in order to effectively utilize the laser L, it is necessary to use optical elements such as lenses to perform beam shaping (focusing, collimation, etc.) of the laser L. On the other hand, since the laser L with an oscillation wavelength in the mid-infrared region is invisible, in order to align (position) the lens used for the above-mentioned beam shaping, an expensive beam monitor (beam monitor) or detector (dector) with sensitivity in the mid-infrared region is required. Therefore, in this embodiment, a lens 8 for performing the above-mentioned beam shaping is pre-built inside the package 3. In this structure, there is an advantage that there is no need to align the lens (external lens) on the user side.

[0078] The lens 8 is a member for collecting or collimating the laser light L emitted from the QCL element 2. The lens holder 9 is a member for holding the lens 8. The lens 8 is arranged to face the end face 2a of the QCL element 2, which is the emission face of the laser light L.

[0079] The lens 8 is, for example, an aspherical lens formed of ZnSe. Fig.11 and Fig.14 As shown, the lens 8 has an incident surface 8a, a side surface 8b and an exit surface 8c. The incident surface 8a is the surface on which the laser light L is incident. In the present embodiment, the incident surface 8a is a flat surface. The side surface 8b is a surface extending from the edge of the incident surface 8a along the optical axis direction of the laser light L (i.e., the X-axis direction). The exit surface 8c is the surface from which the laser light L passing through the lens 8 is emitted. In the present embodiment, the exit surface 8c is formed into an aspherical curved surface. In the present embodiment, the diameter of the lens 8 (the diameter of the incident surface 8a) is 5 mm, and the effective diameter of the lens 8 is 4.5 mm. The effective diameter of the lens 8 refers to the diameter of the incident light beam that can satisfy the optical characteristics of the lens on the surface (incident surface 8a) orthogonal to the optical axis direction (X-axis direction) of the laser light L (when the lens 8 is a collimating lens, as a specification of the lens, the diameter of the incident light that can be transmitted and collimated). In addition, the area within the effective diameter of the lens 8 is referred to as the effective area.

[0080] like Fig.11 As shown, the lens holder 9 is a member having a substantially rectangular parallelepiped shape. The lens holder 9 is formed, for example, of aluminum subjected to a surface treatment of alumite. A through hole penetrating in the X-axis direction is provided in the central portion of the lens holder 9 as viewed from the X-axis direction. The lens holder 9 has: a small-diameter hole 9a (first hole portion) and a large-diameter hole 9b (second hole portion) constituting the through hole. The small-diameter hole 9a and the large-diameter hole 9b extend in the X-axis direction, respectively. The large-diameter hole 9b is provided at a position farther from the QCL element 2 than the small-diameter hole 9a. That is, the small-diameter hole 9a is provided on the side closer to the QCL element 2 than the large-diameter hole 9b. The large-diameter hole 9b has a shape including the small-diameter hole 9a and larger than the small-diameter hole 9a when viewed from the X-axis direction. The large-diameter hole 9b is formed in a size larger than the outer shape of the lens 8 in such a manner that the lens 8 can be accommodated inside it. In the present embodiment, each of the small-diameter hole 9a and the large-diameter hole 9b is formed in a circular shape. The small diameter hole 9a and the large diameter hole 9b are connected by an annular countersunk surface 9c extending along a plane (YZ plane) intersecting the X-axis direction. More specifically, the countersunk surface 9c connects the end of the small diameter hole 9a on the large diameter hole 9b side and the end of the large diameter hole 9b on the small diameter hole 9a side. In addition, in the present embodiment, the countersunk surface 9c is formed in a continuous annular shape, but the countersunk surface 9c may be formed in a discontinuous annular shape. For example, a notch may be formed in a part of the inner wall surface of the small diameter hole 9a, and the countersunk surface 9c may be divided in the part where the notch is formed.

[0081] like Fig.11 and Fig.12 As shown, a groove 9d (recessed portion) is formed on the inner side surface of the large diameter hole 9b, extending from the end of the lens holder 9 on the side opposite to the QCL element 2 side to the counterbore surface 9c along the X-axis direction. In this embodiment, a pair of grooves 9d are formed along one diagonal line of the rectangular lens holder 9 when viewed from the X-axis direction.

[0082] like Fig.12 and Fig.14 As shown in FIG. 1 , the center axis AX1 of the small diameter hole 9a is not consistent with the center axis AX2 of the large diameter hole 9b. That is, the center axis AX1 of the small diameter hole 9a is eccentric from the center axis AX2 of the large diameter hole 9b. Fig.14 In order to make the description easier to understand, a pair of grooves 9d are ignored. That is, Fig.14 As a structure in which a pair of grooves 9d are not provided in the large diameter hole 9b, the Fig.12 Cross-sectional structure of line XIV-XIV.

[0083] In this embodiment, the center axis AX1 of the small diameter hole 9a deviates from the center axis AX2 of the large diameter hole 9b in the direction D. The direction D is the direction from one groove portion 9d toward the other groove portion 9d when viewed from the X-axis direction. In addition, the diameter d3 of the small diameter hole 9a is the same as the effective diameter of the lens 8, which is 4.5 mm, and the diameter d4 of the large diameter hole 9b is 5.15 mm. In addition, as described above, by eccentricity of the center axis AX1 with respect to the center axis AX2, Fig.12 and 14 As shown, the width of the countersunk surface 9c (here, the portion excluding the groove 9d) on the side of the central axis AX1 on the straight line passing through the central axis AX1 and the central axis AX2 becomes the minimum width wmin of the countersunk surface 9c. In addition, the width of the countersunk surface 9c (here, the portion excluding the groove 9d) on the side of the central axis AX2 on the straight line passing through the central axis AX1 and the central axis AX2 becomes the maximum width wmax of the countersunk surface 9c. In this embodiment, the minimum width wmin is 0.25 mm, the maximum width wmax is 0.4 mm, and the distance d between the central axis AX1 and the central axis AX2 is 0.075 mm.

[0084] The edge of the incident surface 8a of the lens 8 abuts against the countersunk surface 9c. In addition, in the lens 8, along the direction D from the central axis AX2 of the large diameter hole 9b toward the central axis AX1 of the small diameter hole 9a, the side surface 8b of the lens 8 is positioned relative to the inner side surface of the large diameter hole 9b. Specifically, the side surface 8b of the lens 8 hits the inner side surface of the large diameter hole 9b along the direction D. As a result, the central axis AX3 of the lens 8 is arranged at a position closer to the central axis AX1 of the small diameter hole 9a than the central axis AX2 of the large diameter hole 9b. In this embodiment, as described above, the diameter (5mm) and effective diameter (4.5mm) of the lens 8, the diameter d3 (4.5mm) of the small diameter hole 9a, the diameter d4 (5.15mm) of the large diameter hole 9b, and the distance d (0.075mm) between the central axis AX1 and the central axis AX2 are set. As a result, the central axis AX3 of the lens 8 is substantially consistent with the central axis AX1 of the small diameter hole 9a. That is, when viewed from the X-axis direction, the entire effective area of ​​the lens 8 overlaps with the small-diameter hole 9a. In other words, the entire effective area of ​​the lens 8 is exposed to the QCL element 2 through the small-diameter hole 9a. Thus, the effective area of ​​the lens 8 can be effectively utilized to the maximum extent.

[0085] Next, the method of fixing the lens 8 to the lens holder 9 is described. Fig.14As shown, at least a portion of the side surface 8b of the lens 8 is fixed to the inner surface of the large-diameter hole 9b via the resin adhesive B1 in a state where the lens 8 is positioned relative to the lens frame 9 as described above. The resin adhesive B1 is formed of, for example, a thermosetting resin such as an epoxy resin. For example, by allowing the resin adhesive B1 to flow into the groove portion 9d, the resin adhesive B1 that has entered the groove portion 9d also flows into the space between the side surface 8b of the lens 8 and the inner surface of the large-diameter hole 9b around the groove portion 9d due to the capillary phenomenon. In addition, the resin adhesive B1 also flows into the space between the incident surface 8a of the lens 8 and the counterbore surface 9c due to the capillary phenomenon. By performing a baking process on the lens frame 9 in this state, the resin adhesive B1 is cured, and the lens 8 is fixed to the lens frame 9. The resin adhesive B1 is flowed into the groove 9d by, for example, inserting a needle member for applying the resin adhesive B1 into the groove 9d and injecting the resin adhesive B1 from the tip of the needle member toward the counterbore surface 9c in the groove 9d. In this case, the groove 9d may be formed to a size that allows the needle member to be inserted.

[0086] Reference Fig.15 , the effect obtained by eccentrically positioning the lens 8 along the direction D by eccentrically positioning the center axis AX1 of the small-diameter hole 9a relative to the center axis AX2 of the large-diameter hole 9b as described above (hereinafter referred to as the "eccentric structure") will be described in detail. Fig.15 1 is a diagram schematically showing the positional relationship between the lens 8 and the lens frame 900 when the lens frame 900 according to the comparative example is used. In the lens frame 900, the center axis AX1 of the small diameter hole 9a is not eccentric with respect to the center axis AX2 of the large diameter hole 9b. That is, the center axis AX1 coincides with the center axis AX2. In this case, in order to maximize the effective use of the effective diameter of the lens 8, it is necessary to Fig.15 As shown in the left part of the figure, the center axis AX3 of the lens 8 is aligned with the center axis (i.e., the center axes AX1 and AX2) of the lens frame 900. If the positional relationship between the lens 8 and the lens frame 900 is maintained in this way, no problem will occur. However, in reality, when the lens 8 is set at the center of the lens frame 900 in this way and the side surface 8b of the lens 8 is bonded to the inner surface of the large-diameter hole 9b via the resin adhesive B1, as shown in the figure, the lens 8 is not fixed to the inner surface of the large-diameter hole 9b. Fig.15 As shown in the right part of , during the baking process, due to the surface tension of the resin adhesive B1, the center axis AX3 of the lens 8 may deviate from the center axis (center axis AX1, AX2) of the lens frame 9. Specifically, since the amount of resin adhesive B1 filled between the side surface 8b of the lens 8 and the large diameter hole 9b is not necessarily uniform, the lens 8 may move in the direction where the surface tension of the resin adhesive B1 is strongly acted. In the event of such movement (position deviation) of the lens 8, a portion of the effective area of ​​the lens 8 overlaps with the countersunk hole surface 9c, and the effective area cannot be effectively utilized to the maximum extent. That is, as Fig.15As shown in the right part of , when the central axis AX3 of the lens 8 is aligned with the optical axis of the laser L emitted from the QCL element 2, the beam of the laser L cannot be captured in the portion of the effective area of ​​the lens 8 that overlaps with the countersunk surface 9c.

[0087] On the other hand, according to Fig.12 and Fig.14 The eccentric structure shown can make the side surface 8b of the lens 8 close to the inner surface of the large diameter hole 9b at the setting end of the lens 8 in the direction D in advance. Moreover, the closer the distance between the side surface 8b of the lens 8 and the inner surface of the large diameter hole 9b is (that is, the close contact part and its surroundings), the stronger the surface tension of the resin adhesive B1 acts. Therefore, even if the baking treatment is performed, the lens 8 will not be pulled back to the side opposite to the direction D relative to the lens frame 9. That is, before and after the baking treatment, the side surface 8b of the lens 8 is maintained in a state of contacting the inner surface of the large diameter hole 9b along the direction D (refer to Fig.12 and Fig.14 ). Therefore, according to the above-mentioned eccentric structure, the effective area of ​​the lens 8 can be effectively utilized to the maximum extent by adjusting the size in a manner such that the effective area of ​​the lens 8 coincides with the small-diameter hole 9a while the lens 8 is positioned as described above.

[0088] In addition, the portion of the side surface 8b of the lens 8 that contacts the inner surface of the large-diameter hole 9b does not necessarily have to be in direct contact with the inner surface of the large-diameter hole 9b. Fig.14 As shown, a small amount of resin adhesive B1 may be interposed between the portion of the side surface 8b of the lens 8 that contacts the inner surface of the large-diameter hole 9b and the inner surface of the large-diameter hole 9b due to the capillary phenomenon.

[0089] like Fig.11 , Fig.12 and Fig.13 As shown in (B), the wall portion 90 (i.e., the cylindrical portion extending in the X-axis direction) constituting the large diameter hole 9b of the lens holder 9 has a bottom wall portion 92 (first wall portion) opposite to the second upper surface 53 of the heat sink 5. The bottom wall portion 92 has a lower surface 92a (first mounting surface) opposite to the second upper surface 53. A plurality of (four in this embodiment) protrusions 92b (first protrusions) protruding toward the heat sink 5 are formed on the lower surface 92a. The four protrusions 92b are provided on the same side as the four protrusions 53a provided on the second upper surface 53 of the heat sink 5 (see FIG. 2 ). Fig. 9 Each convex portion 92b is bonded to a position corresponding to (A) of FIG. 1 . Each convex portion 92b is bonded to a position corresponding to (A) of FIG. 1 . Figure 2 ) are engaged with each protrusion 53a.

[0090] In this embodiment, the four protrusions 92b are evenly arranged at the four corners of the bottom wall 92. That is, the four protrusions 92b are arranged so that the centers of the four protrusions 92b are roughly aligned with the center of the bottom wall 92 when viewed from the Z-axis direction. Thus, the lens holder 9 can be stably fixed to the second upper surface 53 of the heat sink 5, and a structure strong against impact, vibration, etc. can be realized.

[0091] like Fig.11 and Fig.13 As shown in (A), the wall portion 90 has a top wall portion 91 (second wall portion) opposite to the top wall 33 of the package 3. The top wall portion 91 is opposite to the bottom wall portion 92 via the large diameter hole 9b. A cutout 91a is formed at the end of the top wall portion 91 on the opposite side to the small diameter hole 9a. In addition, a cutout 92c is also formed at the end of the bottom wall portion 92 on the opposite side to the small diameter hole 9a. When viewed from the Z-axis direction, the cutout 91a and the cutout 92c have overlapping portions. That is, the top wall portion 91 is formed in a manner that does not overlap with at least a portion of the cutout 92c of the bottom wall portion 92 when viewed from the direction (Z-axis direction) in which the bottom wall portion 92 and the top wall portion 91 are opposite to each other. Moreover, through the overlapping portion of the cutout 91a and the cutout 92c, a portion of the second upper surface 53 of the heat sink 5 can be identified from above the top wall portion 91. That is, light can be irradiated from above the top wall portion 91 to the second upper surface 53 of the heat sink 5 via the above portion. According to such a structure, after the lens holder 9 is placed on the second upper surface 53 of the heat sink 5 in such a manner that the positions of the four convex portions 53a and the positions of the four convex portions 92b are aligned, UV light can be irradiated from above the lens holder 9, thereby appropriately guiding the UV light to the space between the lower surface 92a of the lens holder 9 and the second upper surface 53 of the heat sink 5. As a result, the adhesive layer B2 provided between each convex portion 92b and each convex portion 53a can be appropriately cured.

[0092] In addition, by defining the place where the adhesive layer B2 is applied by each convex portion 92b and each convex portion 53a formed in an island shape, the place where the adhesive layer B2 is applied and the amount of the adhesive layer B2 applied can be unified among multiple products (quantum cascade laser devices 1). In addition, there is a limit to the depth of UV light penetrating into the interior of the UV curable resin. Therefore, if the convex portion 92b and the convex portion 53a are not provided, and the UV curable resin is applied to the entire lower surface 92a, the UV light does not reach the interior (center side) of the UV curable resin, and the problem of not being able to completely cure the UV curable resin may arise. By defining the place where the adhesive layer B2 is applied as an island shape as described above, such a problem can be avoided. In addition, by providing the island-shaped convex portion 92b and the convex portion 53a, a sufficient space for UV light to pass through is formed between the lower surface 92a and the second upper surface 53 at a position where the convex portion 92b and the convex portion 53a do not overlap. Thus, UV light entering the space can be reflected at the valleys (portions where the convex portions 92b and 53a are not formed) of the lower surface 92a and the second upper surface 53, and the adhesive layer B2 on each convex portion 53a can be irradiated with UV light.

[0093] Next, a method for manufacturing (assembling) the quantum cascade laser device 1 will be described. Fig.16 As shown in the figure, first, the package 3 is prepared before the top wall 33 and the side wall 32 are joined. Then, the window member 15 (the window member 15 (see FIG. 1 ) having the anti-reflection films 151, 152 and the metal film 153 preliminarily provided thereon) is joined to the side wall 32. Figure 7 )). Specifically, a ring-shaped sheet member, i.e., a solder member 16, which is formed in a washer shape, is sandwiched between the countersunk surface 14 and the window member 15. Then, a load is applied to the window member 15 from the outside of the package 3 in such a manner that the window member 15 is pressed relative to the countersunk surface 14. In this state, the window member 15 and the countersunk surface 14 are joined via the solder member 16, for example, by using a vacuum welding device (vacuum welding furnace). At this time, a jig for aligning the center of the window member 15 with the center axis of the countersunk opening (small diameter hole 12 and large diameter hole 13) may also be used.

[0094] Next, the heat sink 5 is placed on the Peltier module 4 with the In foil 45 as the solder member attached to the upper and lower parts, and these members are arranged at the predetermined positions on the bottom wall 31 using a jig. Then, a load is applied from above the heat sink 5 so as to press these members into the bottom wall 31. In this state, the bottom wall 31, the Peltier module 4, and the heat sink 5 are bonded via the In foil 45 arranged between the members by using, for example, a vacuum welding device. Next, as shown in FIG. Figure 2 As shown, the lead wire 20 of the Peltier module 4 is soldered to the pin 10 .

[0095] Next, the heat sink 6 on which the QCL element 2, the submount 7, the temperature sensor T, the ceramic pattern SP and other elements are pre-mounted is fixed to the first upper surface 52 of the heat sink 5. Specifically, a screw member (not shown) is inserted into the screw hole 6c of the heat sink 6 (see Fig.10 ) and the screw hole 52a of the heat sink 5, and the heat sink 6 is screwed to the heat sink 5. In addition, the temperature sensor T and the ceramic pattern SP are electrically connected to the prescribed pin 10 through a wire not shown.

[0096] Next, the lens holder 9 carrying the lens 8 is fixed to the second upper surface 53 of the heat sink 5 as described above. Specifically, a UV curable resin (adhesive layer B2) is pre-coated on each convex portion 53a formed on the second upper surface 53 of the heat sink 5. Then, the lens holder 9 is vacuum-adsorbed by, for example, a vacuum accessory (vacuum generator) and moved in the package 3. Then, the QCL element 2 is driven to emit laser light L, and active alignment is performed to align the optical axis of the laser light L with the central axis of the lens 8 while observing the laser light L through a beam monitor.

[0097] Next, the lens holder 9 is fixed to the heat sink 5 in a state where the optical axis of the laser light L is aligned with the central axis of the lens 8. Specifically, in a state where the optical axis of the laser light L is aligned with the central axis of the lens 8, UV light is irradiated from above the lens holder 9 through the cutouts 91a and 92c of the lens holder 9 toward the second upper surface 53 of the heat sink 5. Thus, the convex portions 92b of the lens holder 9 and the convex portions 53a of the heat sink 5 are bonded via the adhesive layer B2.

[0098] Here, the position of each convex portion 92b is designed so as to overlap with each convex portion 53a of the heat sink 5 when the optical axis of the laser light L is aligned with the central axis of the lens 8. Furthermore, when the optical axis of the laser light L is aligned with the central axis of the lens 8, the height dimensions (lengths in the Z-axis direction) of each convex portion 53a and each convex portion 92b are designed so as to form a gap of about several hundred μm smaller than the thickness of the UV curing resin (adhesive layer B2) pre-coated on each convex portion 53a between each convex portion 53a of the heat sink 5 and each convex portion 92b of the lens holder 9. Thus, when the lens holder 9 is moved relative to the heat sink 5 so as to align the optical axis of the laser light L with the central axis of the lens 8, each convex portion 92b of the lens holder 9 is adjusted to contact with the adhesive layer B2 on each convex portion 53a of the heat sink 5. In other words, in a state where the lens frame 9 is pressed into the UV curing resin (adhesive layer B2) pre-coated on the heat sink 5, the height dimensions of each protrusion 53a and each protrusion 92b and the thickness of the adhesive layer B2 are designed in such a way that the optical axis of the laser L is aligned with the central axis of the lens 8.

[0099] Next, the top wall 33 is joined to the upper end portion (the end portion on the opposite side to the bottom wall 31 side) of the side wall 32 of the package 3. Figure 1 The quantum cascade laser device 1 is shown.

[0100] In the quantum cascade laser device 1 described above, the light exit window 11 is bonded to the side wall 32 of the package 3 by a solder member 16 (in the present embodiment, a solder material of SnAgCu system having a melting point of 220°C) having a lower melting point than the solder (melting point of 450°C or more). As a result, compared with the case where solder is used, damage to the window member 15 and the like (especially the anti-reflection films 151 and 152) caused by heat can be suppressed, and the window member 15 can be closely attached to the counterbore surface 14. In addition, on the incident surface 15a of the window member 15, the first area A1 provided with the anti-reflection film 151 and the second area A2 to which the solder member 16 is bonded are spaced apart from each other (see FIG. 1 ). Figure 7 ). Thus, it is possible to suppress the stress of the solder member 16 in the second area A2 during melting or solidification from being transmitted to the anti-reflection film 151 in the first area A1. As a result, damage (cracks or peeling, etc.) of the anti-reflection film 151 caused by the above stress is suppressed. As described above, according to the quantum cascade laser device 1, it is possible to suppress damage to the anti-reflection film 151 provided on the light exit window 11 and ensure high airtightness of the package 3.

[0101] In addition, the side surface 15c of the window member 15 has a third area A3 that is metallized in a manner continuous with the second area A2, and at least a portion of the side surface 15c is bonded to at least a portion of the inner side surface of the large-diameter hole 13 via the solder member 16 (see Figure 5 According to the above structure, by metalizing the continuous area from the second area A2 to the side surface 15c (third area A3) of the window member 15, a part of the solder member 16 can be appropriately wetted and extended to the third area A3 side during soldering. As a result, the solder member 16 can be interposed between the side surface 15c of the window member 15 and the inner surface of the large-diameter hole 13, and the airtightness of the package 3 can be appropriately improved.

[0102] In addition, the wavelength of the laser light L emitted from the QCL element 2 is within the range of 4 μm to 12 μm. As an example, the heat-resistant temperature of the anti-reflection films 151 and 152 is about 260° C. On the other hand, in the quantum cascade laser device 1, since the solder member 16 with a relatively low melting point is used as a bonding material, it is possible to suppress the damage of the anti-reflection films 151 and 152 caused by heat, and the window member 15 provided with the anti-reflection films 151 and 152 is mounted on the side wall 32 by soldering.

[0103] In the quantum cascade laser device 1, the lens holder 9 has a small diameter hole 9a and a large diameter hole 9b whose central axes AX1 and AX2 are eccentric to each other. In addition, the side surface 8b of the lens 8 is positioned relative to the inner side surface of the large diameter hole 9b along the direction D from the central axis AX2 of the large diameter hole 9b toward the central axis AX1 of the small diameter hole 9a. As a result, it is appropriately suppressed that: if the lens 8 is arranged in the center of the large diameter hole 9b (for example, refer to Fig.15 The left part of the lens 8 is caused by the surface tension of the resin adhesive B1 arranged around the lens 8, which causes the position deviation of the lens 8 (the movement of the lens 8 relative to the lens frame 9). Furthermore, in the state where the lens 8 is positioned in this way, the center axis AX3 of the lens 8 is arranged at a position close to the center axis AX1 of the small-diameter hole 9a (in the present embodiment, the center axis AX3 coincides with the center axis AX1). As a result, the area of ​​the region where the effective area of ​​the lens 8 (the region within the effective diameter centered on the center axis AX3 of the lens) interferes (overlaps) with the countersunk surface 9c can be reduced. As a result, the effective area of ​​the lens 8 can be efficiently utilized. In addition, by efficiently utilizing the effective area of ​​the lens 8, the miniaturization of the lens 8 can be achieved, and the miniaturization of the package 3 can be achieved.

[0104] In addition, in the present embodiment, the central axis AX3 of the lens 8 is substantially consistent with the central axis AX1 of the small-diameter hole 9a, and the effective diameter of the lens 8 is substantially consistent with the diameter d3 of the small-diameter hole 9a. According to the above structure, the entire effective area (area within the effective diameter) of the lens 8 can be exposed through the small-diameter hole 9a. Thus, the area of ​​the countersunk surface 9c can be ensured by minimizing the size of the small-diameter hole 9a, thereby appropriately supporting the edge of the incident surface 8a of the lens 8 and effectively utilizing the effective area of ​​the lens 8 to the maximum extent.

[0105] In addition, a groove 9d is formed on the inner side surface of the large diameter hole 9b and reaches the counterbore surface 9c along the X-axis direction, and the resin adhesive B1 enters the groove 9d. According to the above structure, the resin adhesive B1 can be easily injected between the side surface 8b of the lens 8 and the inner side surface of the large diameter hole 9b through the groove 9d.

[0106] In addition, the lens holder 9 has a lower surface 92a formed with a plurality of (four in this embodiment) convex portions 92b protruding toward the heat sink 5 side, and the plurality of convex portions 92b are bonded to the second upper surface 53 of the heat sink 5 via an adhesive layer B2 composed of a UV curable resin. In this embodiment, a plurality of convex portions 53a protruding toward the lens holder 9 side are formed at positions corresponding to the plurality of convex portions 92b on the second upper surface 53, and the plurality of convex portions 92b are bonded to the plurality of convex portions 53a via the adhesive layer B2. According to the above structure, the places where the adhesive layer B2 is provided can be dispersed on the plurality of convex portions 92b, so that the adhesive layer B2 on each convex portion 92b can be easily and appropriately cured compared to the case where the adhesive layer B2 is provided over a large area on the entire surface. Further, in this embodiment, the adhesive layer B2 is arranged in the central portion (between the convex portion 92b and the convex portion 53a) of the space formed between the lower surface 92a and the second upper surface 53. Thus, the adhesive layer B2 can be appropriately irradiated with UV light reflected by the lower surface 92a and the second upper surface 53 in the space. As a result, the adhesive layer B2 can be cured more appropriately, and the lens holder 9 can be stably fixed to the heat sink 5.

[0107] In addition, the bottom wall portion 92 of the lens frame 9 is provided with a cutout 92c for guiding light to the second upper surface 53 of the heat sink 5. According to the above structure, the second upper surface 53 of the heat sink 5 can be irradiated with UV light from the opposite side of the lens frame 9 to the side where the heat sink 5 is arranged (that is, above the lens frame 9) through the cutout 92c provided in the bottom wall portion 92. Thus, light irradiation for curing the adhesive layer B2 between the lower surface 92a and the second upper surface 53 can be easily performed.

[0108] In addition, the lens holder 9 has a top wall portion 91 that is opposite to the bottom wall portion 92 across the large-diameter hole 9b. Moreover, the top wall portion 91 is formed in a manner that does not overlap with at least a portion of the cutout 92c provided in the bottom wall portion 92 when viewed from the direction in which the bottom wall portion 92 and the top wall portion 91 are opposite to each other (Z-axis direction). According to the above structure, the lens 8 arranged in the large-diameter hole 9b can be appropriately protected from the outside by the bottom wall portion 92 and the top wall portion 91. In addition, by forming the top wall portion 91 in a manner that does not overlap with at least a portion of the cutout 92c provided in the bottom wall portion 92, the second upper surface 53 of the heat sink 5 can be irradiated with light by irradiating the lens holder 9 from the outside of the lens holder 9 (the opposite side of the top wall portion 91 and the bottom wall portion 92).

[0109] In addition, a through hole penetrating in the Z-axis direction may be formed in the bottom wall portion 92 instead of the cutout 92c. Similarly, a through hole penetrating in the Z-axis direction and having a portion overlapping with the cutout 92c or the through hole provided in the bottom wall portion 92 may be formed in the top wall portion 91 instead of the cutout 91a. According to such a structure, light can be irradiated from above the lens holder 9 and the light can be guided to the second upper surface 53 of the heat sink 5.

[0110] In addition, the QCL element 2 and the lens holder 9 are mounted on the same heat sink 5. In addition, the QCL element 2 is mounted on the heat sink 5 via the sub-mount 7 and the heat sink 6. According to the above structure, by making the base (heat sink 5) on which the QCL element 2 and the lens holder 9 are mounted common, when the heat sink 5 expands or contracts due to heat, the relative movement of the lens holder 9 with respect to the QCL element 2 can be suppressed. As a result, the occurrence of optical axis deviation (deviation of the central axis AX3 of the lens 8 with respect to the optical axis of the laser L) due to temperature changes in the package 3 can be suppressed.

[0111] The package 3 airtightly accommodates the QCL element 2, lens 8, and lens holder 9. With the above configuration, the effective area of ​​the lens 8 disposed in the package 3 can be efficiently utilized, so that the lens 8 and the package 3 can be miniaturized.

[0112] [Modifications]

[0113] An embodiment of the present disclosure is described above, but the present disclosure is not limited to the above-mentioned embodiment. For example, the material and shape of each structure are not limited to the above-mentioned materials and shapes, and various materials and shapes can be used. In addition, some structures included in the above-mentioned embodiment can also be appropriately changed or omitted.

[0114] The shape of the lens holder is not limited to the shape of the above-mentioned lens holder 9. For example, instead of the above-mentioned lens holder 9, a Figure 17 to Figure 19 The lens holders 9A to 9C are shown.

[0115] like Fig.17As shown, the lens frame 9A of the first modified example is different from the lens frame 9 in that a quadrilateral large-diameter hole 9Ab is formed instead of the circular large-diameter hole 9b, and the groove portion 9d is not formed (the large-diameter hole 9Ab is formed to include a portion corresponding to the groove portion 9d). In this way, the large-diameter hole 9Ab can be formed to a size that accommodates the lens 8, and does not necessarily need to be formed in a circular shape. According to such a large-diameter hole 9Ab, it is possible to ensure sufficient space for filling the resin adhesive B1 at the four corners of the large-diameter hole 9Ab without providing the groove portion 9d. When the viewing angle is changed, the portions corresponding to the four corners of the large-diameter hole 9Ab in the lens frame 9A respectively function as recesses corresponding to the groove portion 9d of the lens frame 9. In addition, the small-diameter hole 9a can also be formed in a shape other than a circle (for example, a quadrilateral that is one size smaller than the large-diameter hole 9Ab and is the same as the large-diameter hole 9Ab, etc.).

[0116] like Fig.18 As shown, the lens frame 9B of the second modified example is different from the lens frame 9 in that the lens frame 9 has a top wall portion 91B whose upper surface is formed in a circular shape (curved surface shape) instead of the top wall portion 91. In addition, since the top wall portion 91B is adopted in the lens frame 9B, there is no space for forming the groove portion 9d provided on the side of the top wall portion 91 in the lens frame 9. Therefore, in the lens frame 9B, a pair of groove portions 9d are formed on both sides of the Y-axis direction on the side of the bottom wall portion 92. In this way, the position where the groove portion 9d is formed in the lens frame is not particularly limited. In addition, the number of the groove portions 9d is not particularly limited. In addition, in the lens frame 9B, the length of the portion of the wall portion forming the large-diameter hole 9b, excluding the bottom wall portion 92, along the X-axis direction is shorter than that of the wall portion 90 of the lens frame 9. Specifically, the length of the above portion along the X-axis direction is slightly shorter than the length of the lens 8 along the X-axis direction. According to such a configuration, since the portion that blocks the UV light from above the lens holder 9B can be reduced, the UV light for curing the adhesive layer B2 can be guided to the heat sink 5 side more appropriately.

[0117] like Fig.19As shown in FIG. 1 , the lens holder 9C of the third modified example is different from the lens holder 9 in that a top wall portion 91C having a shorter length in the X-axis direction than the top wall portion 91 is provided instead of the top wall portion 91. The length in the X-axis direction of the top wall portion 91C is about half of the length in the X-axis direction of the lens 8. In addition, in the lens holder 9C, the length in the X-axis direction of the portion of the wall portion forming the large-diameter hole 9b, excluding the bottom wall portion 92, is the same as that of the top wall portion 91C. That is, the lens holder 9C is formed in a substantially L-shape when viewed from the Y-axis direction. In the lens holder 9C, the portion that blocks the UV light from above the lens holder 9C is smaller than that of the lens holder 9B, so that the UV light for curing the adhesive layer B2 can be more appropriately guided to the heat sink 5 side. In addition, as shown in the lens holder 9C, the wall portion constituting the large-diameter hole 9b of the lens holder does not need to surround the entire side surface 8b of the lens 8, and may be configured to surround only a portion of the side surface 8a side of the side surface 8b of the lens 8.

[0118] In addition, if Fig. 20 As shown in the quantum cascade laser device 1A involved in the variation shown, the lens may not be contained in the package 3. The difference between the quantum cascade laser device 1A and the quantum cascade laser device 1 is that the lens 8 and the lens holder 9 are not provided in the package 3, but a lens 8A is provided outside the package 3 instead. That is, the quantum cascade laser device 1A includes: a lens 8A arranged outside the package 3 to focus or collimate the laser light L passing through the light exit window 11. In addition, due to this difference, the quantum cascade laser device 1A is different from the quantum cascade laser device 1 in that a heat sink 5A is provided instead of the heat sink 5, and the heat sink 5A is configured to enable the QCL element 2 to be arranged at a position close to the light exit window 11. As described above, the radiation angle of the light beam of the laser light L is very large. Therefore, in order to make the entire light beam of the laser light L pass to the outside of the package 3 through the light exit window 11 and to minimize the light exit window 11 as much as possible, it is preferred to make the light exit window 11 as close as possible to the exit surface (end surface 2a) of the laser light L of the QCL element 2. Therefore, the quantum cascade laser device 1A that does not include a lens inside the package 3 includes the heat sink 5A described above.

[0119] According to the quantum cascade laser device 1A, the lens 8A can be flexibly arranged and replaced by providing an external component disposed outside the package 3. Furthermore, as described above, the length w1 of the small diameter hole 12 along the optical axis direction (X axis direction) of the laser light L is shorter than the length w2 of the large diameter hole 13 (see Figure 5). According to the above structure, compared with the case where the length w1 of the small diameter hole 12 is greater than the length w2 of the large diameter hole 13, the light exit window 11 can be brought closer to the QCL element 2. Thus, even when the radiation angle of the laser light L emitted from the QCL element 2 is large, the laser light L can be incident on the light exit window 11 when the expansion of the laser light L is still small. As a result, the light exit window 11 can be miniaturized, and the package 3 can be miniaturized.

[0120] Furthermore, as described above, the exit surface 15b of the window member 15 has the fourth region A4 provided with the anti-reflection film 152, and the fourth region A4 includes the first region A1 and is larger than the first region A1 when viewed from the X-axis direction. When no lens is provided in the package 3 as in the quantum cascade laser device 1A, and when the laser light L as divergent light is incident on the window member 15, the region through which the laser light L passes at the incident surface 15a of the window member 15 is smaller than the region through which the laser light L passes at the exit surface 15b of the window member 15. Therefore, by making the anti-reflection film 151 on the incident surface 15a side smaller than the anti-reflection film 152 on the exit surface 15b side (that is, by making the first region A1 smaller than the fourth region A4) as in the above-mentioned structure, it is possible to ensure a region corresponding to the difference between the fourth region A4 and the first region A1 as the second region A2. In this way, by designing the sizes of the first area A1 , the second area A2 , and the fourth area A4 in consideration of the beam radiation angle of the laser light L, the window member 15 can be miniaturized, and thus the package 3 can be miniaturized.

[0121] In addition, in the above-mentioned embodiment, the exit surface 15b of the window member 15 is set to be substantially the same plane as the outer surface of the side wall 32, and the exit surface 15b of the window member 15 can also protrude further to the outside of the package 3 than the outer surface of the side wall 32. That is, the thickness of the window member 15 can also be greater than the length w2 of the large-diameter hole 13. In this case, the operability when the window member 15 is joined to the side wall 32 from the outside of the package 3 can be improved. In addition, in the case where the external lens 8A is mounted on the exit surface 15b of the window member 15 as in the quantum cascade laser device 1A, the operability of the lens installation can also be improved. In addition, the miniaturization of the package 3 can be achieved by thinning the side wall 32, or the lens 8A can be reliably arranged close to the window member 15.

[0122] In addition, in the above embodiment, a quantum cascade laser element (QCL element 2) is illustrated as an example of a semiconductor laser element, and laser elements other than quantum cascade laser elements may be used as semiconductor laser elements accommodated in the package 3. In addition, the semiconductor laser element may be a distributed feedback (DFB) semiconductor laser element having a diffraction lattice structure provided on the upper part of the active layer.

[0123] In addition, in the above embodiment, the package 3 is exemplified as a butterfly package, but the form of the package is not limited to this. For example, the package may be a can package.

[0124] Description of Reference Numerals

[0125] 1, 1A…quantum cascade laser device (semiconductor laser device); 2…quantum cascade laser element (semiconductor laser element); 2a…end face (exit face); 3…package; 5, 5A…heat sink; 8, 8A…lens; 8a…incident face; 8b…side face; 8c…exit face; 9, 9A, 9B, 9C…lens holder; 9a…small-diameter hole (first hole portion); 9b…large-diameter hole (second hole portion); 9c…counter-sinking face; 9d…groove portion (recess); 11…light exit window; 12…small-diameter hole; 13…large-diameter hole; 14…counter-sinking face; 15…window member; 15a…incident face; 15b…exit face; 15c…side face; 16…tin member; 3 1…bottom wall; 32…side wall; 33…top wall; 53…second upper surface (second mounting surface); 53a…convex portion (second convex portion); 91…top wall portion (second wall portion); 92…bottom wall portion (first wall portion); 92a…lower surface (first mounting surface); 92b…convex portion (first convex portion); 92c…cutout; 151…anti-reflection film (first anti-reflection film); 152…anti-reflection film (second anti-reflection film); 153…metal film; A1…first region; A2…second region; A3…third region; A4…fourth region; AX1, AX2, AX3…center axis; B1…resin adhesive; B2…adhesive layer; D…direction; L…laser.

Claims

1. A quantum cascade laser device, wherein: have: Quantum cascade laser components; a lens disposed opposite to an emission surface of laser light of the quantum cascade laser element; and a lens holder which holds the lens, The lens holder has: a first hole portion extending in an optical axis direction along the optical axis of the laser light; a second hole portion, which is provided at a position farther from the quantum cascade laser element than the first hole portion, includes the first hole portion and is larger than the first hole portion when viewed in the optical axis direction; and an annular countersunk surface connecting the first hole portion and the second hole portion and extending along a surface intersecting the optical axis direction, The lens has: An incident surface on which the laser is incident; and a side surface extending from an edge of the incident surface along the optical axis direction, At least a portion of the side surface is fixed to the inner side surface of the second hole portion via a resin adhesive in a state where the edge of the incident surface is in contact with the countersunk surface. The central axis of the first hole portion is eccentric to the central axis of the second hole portion, The side surface of the lens is positioned relative to the inner side surface of the second hole portion along a direction from the central axis of the second hole portion toward the central axis of the first hole portion, The central axis of the lens is arranged at a position closer to the central axis of the first hole than the central axis of the second hole.

2. The quantum cascade laser device according to claim 1, wherein: The central axis of the lens coincides with the central axis of the first hole. The effective diameter of the lens coincides with the diameter of the first hole.

3. The quantum cascade laser device according to claim 1, wherein: A recessed portion extending along the optical axis direction to the counterbore surface is formed on the inner side surface of the second hole portion. The resin adhesive enters the recessed portion.

4. The quantum cascade laser device according to claim 2, wherein: A recessed portion extending along the optical axis direction to the counterbore surface is formed on the inner side surface of the second hole portion. The resin adhesive enters the recessed portion.

5. The quantum cascade laser device according to any one of claims 1 to 4, wherein: It also includes: a heat sink equipped with the lens holder, The lens holder has a first mounting surface formed with a plurality of first protrusions protruding toward the heat sink. The plurality of first protrusions are bonded to the second mounting surface of the heat sink via an adhesive layer made of a photocurable resin.

6. The quantum cascade laser device according to claim 5, wherein: The second mounting surface is provided with a plurality of second protrusions protruding toward the lens frame at positions corresponding to the plurality of first protrusions. The plurality of first protrusions are bonded to the plurality of second protrusions via the adhesive layer.

7. The quantum cascade laser device according to claim 5, wherein: A through hole or a cutout for guiding light to the second mounting surface of the heat sink is provided on the first wall portion of the lens holder having the first mounting surface.

8. The quantum cascade laser device according to claim 6, wherein: A through hole or a cutout for guiding light to the second mounting surface of the heat sink is provided on the first wall portion of the lens holder having the first mounting surface.

9. The quantum cascade laser device according to claim 7, wherein: The lens holder includes: a second wall portion facing the first wall portion via the second hole portion; The second wall portion is formed so as not to overlap with at least a part of the through hole or the cutout provided in the first wall portion when viewed from a direction in which the first wall portion and the second wall portion oppose each other.

10. The quantum cascade laser device according to claim 8, wherein: The lens holder includes: a second wall portion facing the first wall portion via the second hole portion; The second wall portion is formed so as not to overlap with at least a part of the through hole or the cutout provided in the first wall portion when viewed from a direction in which the first wall portion and the second wall portion oppose each other.

11. The quantum cascade laser device according to any one of claims 1 to 4, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

12. The quantum cascade laser device according to claim 5, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

13. The quantum cascade laser device according to claim 6, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

14. The quantum cascade laser device according to claim 7, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

15. The quantum cascade laser device according to claim 8, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

16. The quantum cascade laser device according to claim 9, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

17. The quantum cascade laser device according to claim 10, wherein: The quantum cascade laser element and the lens holder are mounted on the same heat sink.

18. The quantum cascade laser device according to claim 1, wherein: The invention further comprises: a package for airtightly accommodating the quantum cascade laser element, the lens, and the lens holder; The package has: bottom wall; a side wall erected on the bottom wall and formed in a ring shape so as to surround a region accommodating the quantum cascade laser element and the lens holder when viewed from a direction perpendicular to the bottom wall; and a top wall that blocks the opening of the side wall on the side opposite to the bottom wall, The side wall is provided with a light exit window through which the laser light passing through the lens passes.

Images