Semiconductor laser device

Abstract

A quantum cascade laser device of the present application has a QCL element and a package. On a side wall of the package, an optical exit window through which laser light emitted from the QCL element passes is provided. The optical exit window is composed of a small-diameter hole, a large-diameter hole larger than the small-diameter hole, an annular counterbore surface connecting the small-diameter hole and the large-diameter hole, and a window member disposed on the inner side of the large-diameter hole. An incident surface of the window member has a first region in which an antireflection film is provided, and a second region which is annularly formed so as to surround the first region with a space therebetween and is metallized. The second region is joined to the counterbore surface by a solder member.

Description

Technical Field

[0001] This disclosure relates to semiconductor laser devices. Background Technology

[0002] Currently, semiconductor laser devices (semiconductor laser modules) that house semiconductor laser elements within a package are known (e.g., Patent Document 1). In the aforementioned semiconductor laser device, a light exit window is provided on the side wall of the package for extracting the laser emitted from the semiconductor laser element and directing it to the outside of the package.

[0003] Existing technical documents

[0004] Patent documents

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

[0006] The problem that the invention aims to solve

[0007] In semiconductor laser devices like those described above, an anti-reflective coating is sometimes formed on the light exit window to improve laser extraction efficiency. If the anti-reflective coating has a relatively low heat resistance temperature, and a solder with a high melting point is used to solder the light exit window to the package, the anti-reflective coating may be damaged by the heat generated during soldering. Furthermore, in semiconductor laser devices like those described above, the interior of the package needs to be in a vacuum state or an inert gas atmosphere; therefore, the package requires hermeticity.

[0008] Therefore, the purpose of this disclosure is to provide a semiconductor laser device that can suppress damage to the anti-reflective film disposed on the light exit window and ensure high hermeticity of the package.

[0009] Technical means for solving problems

[0010] One aspect of this disclosure relates to a semiconductor laser device comprising: a semiconductor laser element; and a package that hermetically houses the semiconductor laser element, the package comprising: a bottom wall; a side wall erected on the bottom wall and, when viewed from a direction perpendicular to the bottom wall, formed in an annular shape to surround the area housing the semiconductor laser element; and a top wall that blocks the openings of the side wall opposite to the bottom wall side. The side wall is provided with a light exit window through which laser light emitted from the semiconductor laser element passes, the light exit window comprising: a first aperture opening inside the package along the optical axis direction of the laser beam; and a second aperture opening outside the package, which, when viewed from the optical axis direction... Below, there is a first hole portion and a portion larger than the first hole portion; an annular countersunk surface connecting the first hole portion and the second hole portion, extending along a surface intersecting the optical axis; and a window member disposed inside the second hole portion, the window member having: an incident surface for laser incidence; an exit surface opposite to the incident surface, which emits the laser transmitted through the window member to the outside of the package; and a side surface connecting the incident surface and the exit surface, extending along the optical axis, the incident surface having: a first region containing a central portion of the incident surface and having a first antireflective film disposed thereon; and a second region formed in an annular shape to surround the first region at intervals from the first region and being metallized, the second region being joined to the countersunk surface via a solder member.

[0011] In the aforementioned semiconductor laser device, the light exit window is bonded to the sidewall of the package via a solder component with a melting point lower than that of the solder. This suppresses heat-induced damage to the window component (especially the anti-reflective coating) compared to the use of solder, and ensures close contact between the window component and the countersunk surface. Furthermore, on the incident surface of the window component, a first region with an anti-reflective coating (first anti-reflective coating) and a second region with a solder component are spaced apart. This suppresses stress transmission from the melting or solidification of the solder component in the second region to the anti-reflective coating in the first region. Consequently, damage to the anti-reflective coating (cracks or peeling, etc.) caused by the aforementioned stress is suppressed. Therefore, according to the aforementioned semiconductor laser device, damage to the anti-reflective coating provided in the light exit window can be suppressed, and high hermeticity of the package can be ensured.

[0012] The side surface may also have a third region that is metallized in a manner continuous with the second region, and at least a portion of the side surface may be joined to at least a portion of the inner surface of the second hole via a solder member. According to the above structure, by metallizing the region continuously extending from the second region to the side surface (third region) of the window member, a portion of the solder member can be appropriately wetted and extended to the third region side during soldering. As a result, the solder member can be positioned between the side surface of the window member and the inner surface of the second hole, thereby appropriately improving the hermeticity of the package.

[0013] The length of the first aperture along the optical axis can be shorter than the length of the second aperture along the optical axis. According to the above structure, compared to the case where the length of the first aperture is greater than or equal to the length of the second aperture, the light exit window can be positioned closer to the semiconductor laser element. Therefore, even when the radiation angle of the laser beam emitted from the semiconductor laser element is large, the laser beam can still be incident on the light exit window when the laser beam spread is still small. As a result, miniaturization of the light exit window is possible, and consequently, miniaturization of the package can be achieved.

[0014] The exiting surface can also have a fourth region provided on the second antireflective film, which, when viewed from the optical axis direction, includes the first region and is larger than the first region. When a laser beam, as diverging light, is incident on the window member, the area through which the laser passes on the incident surface of the window member is smaller than the area through which the laser passes on the exiting surface of the window member. Therefore, by making the first antireflective film on the incident surface side smaller than the second antireflective film on the exiting surface side (i.e., by making the first region smaller than the fourth region) as described above, the second region can be ensured to correspond to the difference between the fourth region and the first region. In this way, by designing the dimensions of the first, second, and fourth regions taking into account the laser beam radiation angle, the window member can be miniaturized, and consequently, the package can be miniaturized.

[0015] The aforementioned semiconductor laser device may also include a lens disposed on the outside of the package to focus or collimate the laser light passing through the light exit window. According to this structure, by making the lens an external component disposed on the outside of the package, the lens can be flexibly configured and replaced.

[0016] The wavelength of the laser can also be in the range of 4μm to 12μm. Generally, the antireflective film corresponding to light of 4μm to 12μm has a low heat resistance temperature. In the above-mentioned semiconductor laser device, since a solder component with a relatively low melting point is used as the bonding material, it is possible to suppress the damage of the antireflective film caused by heat, and the window component with the antireflective film is installed on the side wall by welding.

[0017] The exit surface of the window member may also protrude further outward from the outer side of the encapsulation member than the outer side of the sidewall where the light-emitting window is located. This structure improves the operability of joining the window member to the sidewall from the outside of the encapsulation member. Furthermore, when an external lens is mounted on the exit surface of the window member, the operability of lens mounting is also improved.

[0018] The effects of the invention

[0019] According to this disclosure, a semiconductor laser device can be provided that can suppress damage to the anti-reflective film disposed on the light exit window and ensure high hermeticity of the package. Attached Figure Description

[0020] Figure 1 This is a three-dimensional view of a quantum cascade laser device according to one implementation method.

[0021] Figure 2 yes Figure 1 The diagram shows a side cross-section of a quantum cascade laser device.

[0022] Figure 3 yes Figure 1 A top view of the quantum cascade laser device shown.

[0023] Figure 4 This is a typical example of the relationship between the radiation angle (horizontal axis) and radiation intensity (vertical axis) of a laser emitted from a quantum cascade laser.

[0024] Figure 5 yes Figure 1 A partially enlarged view of the quantum cascade laser device shown.

[0025] Figure 6 This is a front view of the section of the sidewall that includes the small-diameter and large-diameter holes.

[0026] Figure 7 In the diagram, (A) is a view showing the incident surface of the window member, (B) is a cross-sectional view of the window member, and (C) is a view showing the exit surface of the window member.

[0027] Figure 8 In the diagram, (A) is a top view of the Peltier module, and (B) is a side view of the Peltier module.

[0028] Figure 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.

[0029] Figure 10 (A) is a top view of the heat sink with the components mounted, and (B) is a side view of the heat sink with the components mounted.

[0030] Figure 11 It is a three-dimensional diagram of the lens frame.

[0031] Figure 12 This is a front view of the lens holder.

[0032] Figure 13 In the diagram, (A) is a top view of the lens holder, (B) is a bottom view of the lens holder, and (C) is a side cross-sectional view of the lens holder.

[0033] Figure 14 It schematically shows along Figure 12 A diagram of the cross section of line XIV-XIV.

[0034] Figure 15 This is a diagram schematically showing the positional relationship between the lens and the lens holder when using the lens holder involved in the comparative example.

[0035] Figure 16 It is shown Figure 1 A diagram showing a portion of the assembly steps for a quantum cascade laser device.

[0036] Figure 17 In the diagram, (A) is a front view of the lens frame of the first modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0037] Figure 18 In the diagram, (A) is a front view of the lens frame of the second modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0038] Figure 19 In the diagram, (A) is a front view of the lens frame of the third modified example, and (B) is a cross-sectional view of the lens frame along line BB of (A).

[0039] Figure 20 This is a side cross-sectional view of a modified quantum cascade laser device. Detailed Implementation

[0040] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Identical or equivalent parts in the drawings will be labeled with the same reference numerals, and repeated descriptions will be omitted. Furthermore, some parts in the drawings are exaggerated for ease of understanding of the structures involved in the embodiments, and sometimes differ from the actual dimensions. In addition, in the following description, terms such as "upper" and "lower" are used conveniently based on the states shown in the drawings.

[0041] like Figures 1-3 As shown, the quantum cascade laser device 1 (semiconductor laser device) includes: a quantum cascade laser element (hereinafter referred to as "QCL element") 2, and a package 3 that hermetically houses the QCL element 2.

[0042] QCL element 2 is a type of semiconductor laser element. QCL element 2 has an end face 2a (emission surface) intersecting a direction (the X-axis direction in this embodiment), and is configured to emit a broadband laser L in the mid-infrared region with a wavelength (e.g., 4 μm to 12 μm) from this end face 2a. In this embodiment, the optical axis of the laser L emitted from QCL element 2 is along the X-axis direction. QCL element 2, for example, has a structure in which multiple active layers with different center wavelengths are stacked, enabling it to emit broadband light as described above. However, QCL element 2 can also have a structure composed of a single active layer, in which case it can also emit broadband light as described above. Figure 4 As shown, the laser L emitted from QCL element 2 has a much larger beam radiation angle (divergence angle) compared to laser diodes, based on the principle of quantum cascade lasers.

[0043] Package 3 is a so-called butterfly package. Package 3 has a bottom wall 31, side walls 32, and a top wall 33. Figure 3 The top wall 33 of the package 3 is omitted from the illustration.

[0044] The base wall 31 is a rectangular plate-shaped component. The base wall 31 is formed, for example, from a metallic material such as copper-tungsten. The base wall 31 serves as the base component for mounting various components, including the Peltier module 4 described later. For convenience, in this specification, the direction of the long side of the base wall 31 is represented as the X-axis direction, the direction of the short side of the base wall 31 is represented as the Y-axis direction, and the direction perpendicular to the base wall 31 (i.e., the direction orthogonal to the X-axis and Y-axis directions) is represented as the Z-axis direction. As mentioned above, the X-axis direction is also along the optical axis (optical axis direction) of the laser L emitted from the QCL element 2.

[0045] Sidewall 32 is erected on bottom wall 31. Viewed from the Z-axis direction, sidewall 32 is formed in a ring shape to surround the area (internal space S) containing QCL element 2, etc. In this embodiment, sidewall 32 is a rectangular cylindrical member surrounding the internal space S. Sidewall 32 is formed of a metallic material such as Kovar. For example, sidewall 32 is a Kovar frame plated with Ni / Au. In this embodiment, sidewall 32 is located at the center of the long side direction (X-axis direction) of bottom wall 31. The width of sidewall 32 along the short side direction (Y-axis direction) is the same as the width of bottom wall 31 along the short side direction, but the width of sidewall 32 along the long side direction (X-axis direction) is shorter than the width of bottom wall 31 along the long side direction. That is, protrusions 31a extending outwards from both sides of bottom wall 31 along the long side direction are formed. Screw holes 31b are provided in the portions of the protrusion 31a that correspond to the four corners of the bottom wall 31 for mounting the package 3 (bottom wall 31) to other components.

[0046] The top wall 33 is a component that blocks the opening of the side wall 32, which is opposite to the side of the bottom wall 31. The top wall 33 is rectangular in shape. The shape of the top wall 33 (width in the long and short directions) viewed from the Z-axis direction is approximately the same as that of the side wall 32. The top wall 33 is formed, for example, from the same metallic material as the side wall 32 (e.g., Kovar).

[0047] In the portion 321 extending along the long side direction (X-axis direction) of the sidewall 32 (i.e., the portion intersecting the short side direction (Y-axis direction), there are inserted a plurality of lead pins 10 for allowing current to flow to components such as the QCL element 2 housed in the package 3 (in this embodiment, there are 7 on each side in the short side direction, for a total of 14).

[0048] One of the portions 322 extending along the short side direction (Y-axis direction) of the sidewall 32 (i.e., the portion intersecting the long side direction (X-axis direction)) is provided with a light exit window 11 that allows the laser L emitted from one end face 2a of the QCL element 2 to pass through.

[0049] like Figure 5 and Figure 6 As shown, the light-emitting window 11 includes: a small-diameter hole 12 (first hole portion) formed by sidewalls 32 (part 322), a large-diameter hole 13 (second hole portion), a countersunk surface 14, and a window member 15. Furthermore, the window member 15 is provided with anti-reflective films 151 and 152 and a metal film 153 (see reference 153). Figure 7 These components are very thin compared to the main body of window component 15, therefore... Figure 7 Illustrations of these components are omitted from other diagrams.

[0050] The small-diameter hole 12 opens inside the package 3 (i.e., the internal space S) along the optical axis direction (i.e., the X-axis direction) of the laser L. The large-diameter hole 13 opens outside 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 along the X-axis direction, respectively. A through hole is formed in the X-axis direction by the small-diameter hole 12 and the large-diameter hole 13 connected by the countersunk surface 14. In this 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). Furthermore, the central axis of the small-diameter hole 12 and the central axis of the large-diameter hole 13 may also be aligned with the optical axis of the laser L emitted from the QCL element 2. The countersunk surface 14 is an annular surface extending along a plane (YZ plane) intersecting the X-axis direction, connecting the small-diameter hole 12 and the large-diameter hole 13. More specifically, the countersunk 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 countersunk surface 14 can be formed by countersunk machining from the outside of the package 3. In this embodiment, the countersunk surface 14 is formed as a continuous annulus, but it can also be formed as a discontinuous annulus. For example, the countersunk surface 14 can be interrupted at the portion where a cut is formed in a part of the inner wall surface of the small-diameter hole 12.

[0051] In this 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. Furthermore, the length w1 of the small-diameter hole 12 along the X-axis is shorter than the length w2 of the large-diameter hole 13 along the X-axis. In this embodiment, the thickness t (length along the X-axis) of the sidewall 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.

[0052] The window member 15 is formed of a material (e.g., germanium) that allows laser light L of mid-infrared wavelengths to pass through. The window member 15 is formed in a circular plate shape and disposed inside the large-diameter aperture 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 are formed in a circular shape. The incident surface 15a is the surface on the side of the internal space S, and is the 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 the surface opposite to the incident surface 15a (i.e., the surface on the outside of the encapsulation 3), and is the surface that emits the laser light L passing through the window member 15 outwards from the encapsulation 3. The side surface 15c is a surface connecting the incident surface 15a and the exit surface 15b and extending along the X-axis direction. In this embodiment, the diameter of the window member 15 (incident surface 15a or exit surface 15b) is 5.4 mm, and the thickness (length along the X-axis) of the window member 15 is 0.7 mm.

[0053] like Figure 7 As shown in (A) and (B), the incident surface 15a has a first region A1 and a second region A2. The first region A1 is the region containing the central part of the incident surface 15a, where an antireflective film 151 (the first antireflective film) is provided. The antireflective film 151 is a film component that has the function of suppressing the reflection of laser light L with wavelengths in the infrared region of the incident surface 15a. The antireflective film 151 is formed, for example, from a high refractive index material such as germanium (Ge) or 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 the mid-infrared are alternately stacked. The antireflective film 151 is formed in a circular shape. The thickness (length along the X-axis) of the antireflective film 151 is determined according to the design of the transmitted wavelength (the wavelength of the transmitted laser light L) of the antireflective film 151. The thickness of the antireflective film 151 is, for example, 1.0 μm or more and 3.0 μm or less. For example, when the designed transmission wavelength is 5.2 μm, the thickness of the antireflective film 151 is set to 1.4 μm. Furthermore, in this embodiment, the diameter of the antireflective film 151 (i.e., the diameter of the first region A1) is 4.2 mm.

[0054] The second region A2 is formed as an annular region that surrounds the first region A1 at intervals. The second region A2 is metallized by a metal film 153. The metal film 153 is formed of a material suitable for soldering (i.e., a material with good affinity to the solder component 16 described later). The metal film 153 is formed, for example, by Cr / Ni / Au (0.2μm / 0.5μm / 0.5μm). In this 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 this embodiment, an annular region with a width of 0.15mm is formed between the outer edge of the first region A1 and the inner edge of the second region A2, exposing the incident surface 15a (germanium substrate).

[0055] like Figure 7 As shown in (B), the side surface 15c has a third region A3 that is metallized in a manner continuous with the second region A2. That is, the metal film 153 is continuously disposed from the second region A2 to the side surface 15c.

[0056] like Figure 7 As shown in (B) and (C), the emission surface 15b has a fourth region A4 on which an antireflective film 152 (the second antireflective film) is provided. The antireflective film 152 is a film member that has the function of suppressing the reflection of laser light L with wavelengths in the infrared region in the emission surface 15b. The antireflective film 152 is formed into a circular shape from the same material as the antireflective film 151. In this embodiment, the diameter of the antireflective film 152 (i.e., the diameter of the fourth region A4) is 4.6 mm. That is, when viewed 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.

[0057] Window member 15 is directly joined to sidewall 32 (part 322). Specifically, the second region A2 of incident surface 15a (i.e., the region metallized by metal film 153) is joined to countersunk surface 14 via an annular solder member 16. The solder member refers to a bonding material having a melting point below 450°C. Solder member 16 is, for example, formed from a SnAgCu-based solder member with a melting point of 220°C. Solder member 16 is originally a sheet-like member formed in an annular shape (see reference). Figure 16 ).

[0058] In this embodiment, the solder member 16 in its pre-soldering state (i.e., in the state of a ring-shaped sheet) has a thickness of 0.1 mm, an outer diameter of 5.5 mm, and an inner diameter of 4.2 mm. That is, in this embodiment, the inner diameter (4.2 mm) of the solder member 16 matches the diameter (4.2 mm) of the first region A1, and the first region A1 and the solder member 16 do not overlap. Furthermore, the first region A1, to which the anti-reflective film 151 is formed, is spaced apart from the second region A2, to which the metal film 153 is formed. By completely separating the first region A1 and the second region A2, an area of ​​the substrate of the window member 15 (a germanium substrate in this embodiment) is exposed between the first region A1 and the second region A2, thereby preventing the solder member 16 from easily flowing onto the first region A1 (the anti-reflective film 151) during soldering. On the other hand, the solder member 16 easily wets and extends onto the metal film 153, which has a high affinity with the solder member 16. Therefore, the stress caused by the melting or solidification of the solder component 16 during welding is not easily transmitted to the anti-reflective film 151 on the first region A1.

[0059] Furthermore, as described above, the solder component 16 extends to the metal film 153 through wetting, and a portion of the solder component 16 also extends to the third region A3 (see reference). 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. In other words, at least a portion of the side surface 15c of the window member 15 is engaged with at least a portion of the inner side surface of the large-diameter hole 13 via the solder member 16. Thus, the hermeticity of the package 3 is effectively improved at the mounting portion of the window member 15.

[0060] In this embodiment, the exit surface 15b of the window member 15 and the outer surface 32a (the outer side surface of the encapsulation member 3) of the side wall 32 on which the light exit window 11 is provided are substantially coplanar. That is, the length w2 of the large-diameter hole 13 (i.e., the depth of the countersunk hole) is adjusted so that the exit surface 15b and the outer surface 32a of the side wall 32 are substantially coplanar.

[0061] Next, the components housed in package 3 will be described. Within the internal space S formed by package 3, besides the QCL element 2, the following are mainly housed: Peltier module 4, heat spreader 5, heat sink 6, submount 7, lens 8, lens holder 9, and temperature sensor T (see reference). Figure 10 ).

[0062] The Peltier module 4 is a temperature control element used to regulate the temperature of the QCL element 2. Specifically, the Peltier module 4 has a cooling / heating function to maintain 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 a temperature sensor T (reference) mounted on the heat sink 6. Figure 10 The temperature of QCL element 2 is measured.

[0063] like Figure 8 As shown, the Peltier module 4 includes: a plurality of Peltier elements 41 serving as thermoelectric semiconductor elements, and a pair of ceramic substrates 42 and 43 sandwiching the plurality of Peltier elements 41 from above and below. The ceramic substrate 42 is disposed on the top wall 33 side relative to the Peltier elements 41, and the ceramic substrate 43 is disposed on the bottom wall 31 side relative to the Peltier elements 41. Each ceramic substrate 42 and 43 is formed, for example, of alumina. The outer surface of each ceramic substrate 42 and 43 (the side opposite to the Peltier element 41 side) is a metallized surface formed by plating a metal film 44 of Cu / Ni / Au, etc. Furthermore, an In foil 45 serving as a solder component is disposed on the outer surface of the ceramic substrates 42 and 43, separated by 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 side opposite to the top wall 33) of the bottom wall 31 of the package 3 via the In foil 45. On a ceramic substrate (ceramic substrate 43 in this embodiment), two wires 20 are electrically connected to allow direct current to flow to the Peltier module 4. The two wires 20 are respectively connected to different pins 10.

[0064] Heatsink 5 is a component mounted on the Peltier module 4, which dissipates heat generated by the QCL element 2 to the Peltier module 4. Heatsink 5 is formed, for example, of a material with excellent thermal conductivity such as copper. Figure 9 As shown, the heat sink 5 has: via an In foil 45 disposed on a ceramic substrate 42 (see reference) Figure 8 The bottom surface 51, which is welded to the Peltier module 4, the first upper surface 52, which is equipped with the heat sink 6 and the sub-base 7, and the second upper surface 53 (second mounting surface), which is equipped with the lens holder 9.

[0065] Here, the coefficient of thermal expansion of copper is approximately 17 × 10⁻⁶. -6 The coefficient of thermal expansion ( / K) is greater than that of alumina (approximately 7 × 10� -6 / K). Therefore, if the ceramic substrate 42 of the Peltier module 4 is formed of alumina and the heat sink 5 is formed of copper, and 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 the large temperature difference between the upper and lower surfaces of the Peltier element 41.

[0066] Therefore, in this embodiment, a groove 51a is formed on the bottom surface 51 of the heat sink 5 to divide the mating surface with the Peltier module 4 into multiple parts. In this embodiment, as an example, two grooves 51a divide the bottom surface 51 into three parts along the long side direction (X-axis direction) and extend along the short side direction (Y-axis direction). Through these two grooves 51a, the mating surface with the Peltier module 4 is divided into approximately three equal parts. By dividing the mating surface with the Peltier module 4 into multiple parts (here, three), the stress caused by the difference in thermal expansion coefficients between the ceramic substrate 42 material (alumina) and the heat sink 5 material (copper) is reduced, and the generation of cracks in the aforementioned Peltier element 41 is suppressed.

[0067] Furthermore, the four corners (corners) of the Peltier module 4 are particularly weak in mechanical strength. Therefore, in this embodiment, notches 51b are formed at the four corners of the bottom surface 51 of the heat sink 5. As a result, the bonding between the ceramic substrate 42 and the bottom surface 51 of the heat sink 5 can be avoided 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 thermal expansion coefficients can be effectively reduced.

[0068] Furthermore, the aforementioned groove 51a and notch 51b also function as escape channels for air layers (voids) mixed in during the welding of the ceramic substrate 42 and the bottom surface 51 via the In foil 45. This improves the bonding quality and thermal conductivity between the Peltier module 4 (ceramic substrate 42) and the heat sink 5.

[0069] Furthermore, by using soft solders such as In and InSn (In in this embodiment) as solder components for bonding the Peltier module 4 (ceramic substrate 42) and the heat sink 5, the stress caused by thermal expansion or contraction can be appropriately absorbed, thereby improving the reliability of the quantum cascade laser device 1.

[0070] The first upper surface 52 is located higher than the second upper surface 53 (on the side of the top wall 33). In this embodiment, as an example, the first upper surface 52 is provided with two screw holes 52a for screwing the heat sink 6, and a protrusion 52b protruding upwards (on the side of the top wall 33). The protrusion 52b extends along the short side (Y-axis direction) from its end in the long side direction (X-axis direction) of the first upper surface 52 (the end opposite to the side of the second upper surface 53). The protrusion 52b is used to position the end of the heat sink 6 against the ground.

[0071] The second upper surface 53 is provided with a plurality of protrusions 53a (four in this embodiment) formed in the shape of islands. The four protrusions 53a are the parts that engage with the lens holder 9 described later.

[0072] The heat sink 6 is a component mounted on the first upper surface 52 of the heat sink 5. Like the heat sink 5, the heat sink 6 is formed of a material with excellent thermal conductivity, such as copper. The heat sink 6 is formed in a generally cuboid shape. For example, its width along the X-axis is 5 mm, and its width along the Y-axis is 6 mm. Figure 10 As shown, on the upper surface 6a (the surface on the side of the top wall 33) of the heat sink 6, there is a sub-base 7 for mounting the QCL element 2, 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 in case of malfunction, the heat sink 6 is fixed to the heat sink 5 by screws. In the heat sink 6, for such screw fixing, there is a screw hole 6c extending in the Z-axis direction and a countersunk groove 6d formed around the screw hole 6c. The screw hole 6c is provided with the screw hole 52a of the heat sink 5 (see reference). Figure 9 The corresponding positions are as follows. For example, a screw component (not shown) with screw fastener (an adhesive for screw fastening) applied to its tip is inserted into screw holes 6c and 52a, and the heat sink 6 is fixed to the heat sink 5. The countersunk groove 6d is a groove provided to accommodate the head of the screw component. In addition, as the screw fastener, a thermosetting resin adhesive (such as epoxy resin) that does not produce outgassing is appropriately used.

[0073] Temperature sensor T and ceramic pattern SP are electrically connected to designated pin 10 via wires (not shown). Furthermore, QCL element 2 is electrically connected to designated pin 10 via ceramic pattern SP and wires (not shown). Thus, power is supplied from an external power supply to QCL element 2 and temperature sensor T via pin 10.

[0074] The sub-base 7 is a rectangular plate-shaped component on which the QCL element 2 is mounted. The QCL element 2 is mounted on the sub-base 7 such that the optical axis of the laser L emitted from the end face 2a is aligned 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 sub-base 7 is formed of a material (e.g., aluminum nitride) having a coefficient of thermal expansion close to that of the QCL element 2. The QCL element 2 is bonded to the sub-base 7, for example, via an AnSn-based solder material. Furthermore, the sub-base 7 is bonded to the heat sink 6, for example, via a SnAgCuNiGe-based solder material.

[0075] Next, refer to Figures 11-15 This describes lens 8 and lens holder 9. As mentioned above, laser L, based on the principle of quantum cascade lasers, has a relatively large beam radiation angle (refer to...). Figure 4 Therefore, in order to effectively utilize laser L, optical elements such as lenses are needed to shape the laser L's beam (focusing, collimation, etc.). On the other hand, since laser L, with its oscillation wavelength in the mid-infrared region, is invisible, a high-cost beam monitor or detector with sensitivity in the mid-infrared region is required for aligning (aligning) the lens used for beam shaping. Therefore, in this embodiment, a lens 8 for beam shaping is pre-installed inside the package 3. This structure has the advantage of eliminating the need for lens alignment (external lens) on the user side.

[0076] Lens 8 is a component used to focus or collimate the laser L emitted from QCL element 2. Lens holder 9 is a component that holds lens 8. Lens 8 is configured opposite to the exit surface, i.e., end face 2a, of laser L from QCL element 2.

[0077] Lens 8 is, for example, an aspherical lens formed of ZnSe. Figure 11 and Figure 14 As shown, 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 L is incident. In this 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 (i.e., the X-axis direction) of the laser L. The exit surface 8c is the surface from which the laser L passing through the lens 8 exits. In this embodiment, the exit surface 8c is formed as an aspherical curved surface. In this embodiment, the diameter of lens 8 (the diameter of the incident surface 8a) is 5 mm, and the effective diameter of lens 8 is 4.5 mm. The effective diameter of lens 8 refers to the diameter of the incident beam that satisfies the optical characteristics of the lens on the surface (incident surface 8a) orthogonal to the optical axis direction (X-axis direction) of the laser L (in the case of lens 8 being a collimating lens, as a lens specification, the diameter of the incident light that can be transmitted and collimated). Furthermore, the area within the effective diameter of lens 8 is called the effective region.

[0078] like Figure 11 As shown, the lens holder 9 is a component with a generally rectangular parallelepiped shape. The lens holder 9 is formed, for example, of aluminum treated with alumite. A through-hole extending along the X-axis is provided in the central portion of the lens holder 9 when viewed from the X-axis direction. The lens holder 9 has a small-diameter hole 9a and a large-diameter hole 9b constituting this through-hole. The small-diameter hole 9a and the large-diameter hole 9b extend along the X-axis direction. The large-diameter hole 9b is located further away from the QCL element 2 than the small-diameter hole 9a. That is, the small-diameter hole 9a is located closer to the QCL element 2 than the large-diameter hole 9b. When viewed from the X-axis direction, the large-diameter hole 9b has a shape that includes the small-diameter hole 9a and is larger than the small-diameter hole 9a. The large-diameter hole 9b is formed with a size larger than the outer dimensions of the lens 8 so that the lens 8 can be accommodated inside it. In this 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 surface (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 to the end of the large-diameter hole 9b on the small-diameter hole 9a side. Furthermore, in this embodiment, the countersunk surface 9c is formed as a continuous ring, but it can also be formed as a discontinuous ring. For example, the countersunk surface 9c can be interrupted at the portion where a cut is formed in a part of the inner wall surface of the small-diameter hole 9a.

[0079] like Figure 11 and Figure 12 As shown, a groove 9d (recess) is formed on the inner surface of the large-diameter hole 9b, extending from the end of the lens holder 9 opposite to the QCL element 2 side along the X-axis direction to the countersunk surface 9c. In this embodiment, viewed from the X-axis direction, a pair of grooves 9d are formed that face each other along one diagonal of the rectangular lens holder 9.

[0080] like Figure 12 and Figure 14 As shown, the central axis AX1 of the small-diameter hole 9a is not aligned with the central axis AX2 of the large-diameter hole 9b. That is, the central axis AX1 of the small-diameter hole 9a is eccentric to the central axis AX2 of the large-diameter hole 9b. Furthermore, in Figure 14 In the text, for ease of explanation, a pair of grooves 9d are omitted. That is, Figure 14 As a structure in which a pair of slots 9d are not provided in the large diameter hole 9b, it is schematically shown along... Figure 12 The cross-sectional structure of the XIV-XIV line.

[0081] In this embodiment, the central axis AX1 of the small-diameter hole 9a is offset in direction D relative to the central axis AX2 of the large-diameter hole 9b. Direction D is the direction from one groove 9d to another groove 9d when viewed from the X-axis direction. Furthermore, 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. Moreover, as described above, by offsetting the central axis AX1 relative to the central axis AX2, thus... Figure 12 and 14 As shown, the width of the countersunk surface 9c (excluding the groove 9d) on the straight line passing through central axes AX1 and AX2 is the minimum width wmin of the countersunk surface 9c. Furthermore, the width of the countersunk surface 9c (excluding the groove 9d) on the straight line passing through central axes AX1 and AX2 is 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 central axes AX1 and AX2 is 0.075 mm.

[0082] The edge of the incident surface 8a of lens 8 abuts against the countersunk surface 9c. Furthermore, in lens 8, along direction D from the central axis AX2 of the large-diameter aperture 9b towards the central axis AX1 of the small-diameter aperture 9a, the side surface 8b of lens 8 is positioned relative to the inner surface of the large-diameter aperture 9b. Specifically, the side surface 8b of lens 8 touches the inner surface of the large-diameter aperture 9b along direction D. Therefore, the central axis AX3 of lens 8 is positioned closer to the central axis AX1 of the small-diameter aperture 9a than the central axis AX2 of the large-diameter aperture 9b. In this embodiment, as described above, the following are set: the diameter (5 mm) and effective diameter (4.5 mm) of lens 8, the diameter d3 (4.5 mm) of the small-diameter aperture 9a, the diameter d4 (5.15 mm) of the large-diameter aperture 9b, and the distance d (0.075 mm) between the central axes AX1 and AX2. Thus, the central axis AX3 of lens 8 is approximately aligned with the central axis AX1 of the small-diameter aperture 9a. That is, when viewed from the X-axis direction, the entire effective area of ​​lens 8 overlaps with the small-diameter aperture 9a. In other words, the entire effective area of ​​lens 8 is exposed to the QCL element 2 side through the small-diameter aperture 9a. Thus, the effective area of ​​lens 8 can be utilized to the maximum extent.

[0083] Next, the method of fixing lens 8 to lens holder 9 will be explained. For example... Figure 14As shown, at least a portion of the side surface 8b of the lens 8, while the lens 8 is positioned relative to the lens holder 9 as described above, is fixed to the inner surface of the large-diameter hole 9b by a resin adhesive B1. The resin adhesive B1 is, for example, formed of a thermosetting resin such as epoxy resin. For example, by allowing the resin adhesive B1 to flow into the groove 9d, the resin adhesive B1 entering the groove 9d also flows into the area between the side surface 8b of the lens 8 and the inner surface of the large-diameter hole 9b around the periphery of the groove 9d due to capillary action. Furthermore, resin adhesive B1 also flows into the area between the incident surface 8a and the countersunk surface 9c of the lens 8 due to capillary action. By performing a baking treatment on the lens holder 9 in this state, the resin adhesive B1 cures, and the lens 8 is fixed to the lens holder 9. The process of allowing the resin adhesive B1 to flow into the groove 9d can be performed, for example, by inserting a needle member for applying the resin adhesive B1 into the groove 9d, and injecting the resin adhesive B1 from the front end of the needle member toward the countersunk surface 9c inside the groove 9d. In this case, the groove 9d can be formed to a size that allows the needle member to be inserted.

[0084] Reference Figure 15 The effect obtained by offsetting the central axis AX1 of the small diameter hole 9a relative to the central axis AX2 of the large diameter hole 9b in direction D as described above, and positioning the lens 8 in direction D (hereinafter referred to as the "eccentric structure"), will be explained in detail. Figure 15 This diagram schematically illustrates the positional relationship between lens 8 and lens holder 900 when using the lens holder 900 involved in the comparative example. In lens holder 900, the central axis AX1 of the small-diameter aperture 9a is not eccentric relative to the central axis AX2 of the large-diameter aperture 9b. That is, the central axis AX1 is aligned with the central axis AX2. In this case, in order to maximize the effective utilization of the effective diameter of lens 8, it is necessary to... Figure 15 As shown on the left, the central axis AX3 of the lens 8 is aligned with the central axis (i.e., central axes AX1 and AX2) of the lens holder 900. Maintaining this positional relationship between the lens 8 and the lens holder 900 will not cause any problems. However, in practice, when the lens 8 is positioned at the center of the lens holder 900, and the side surface 8b of the lens 8 is joined to the inner surface of the large-diameter aperture 9b via resin adhesive B1, as... Figure 15 As shown on the right, during the baking process, due to the surface tension of the resin adhesive B1, the central axis AX3 of the lens 8 may deviate from the central axis (central axes AX1, AX2) of the lens holder 9. Specifically, since the amount of resin adhesive B1 filling the space 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 strongest. In the event of such movement (positional deviation) of the lens 8, a portion of the effective area of ​​the lens 8 overlaps with the countersunk surface 9c, and the effective area cannot be utilized to the maximum extent. That is, as... Figure 15As shown on the right, 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 laser beam L cannot be captured in the portion of the effective area of ​​the lens 8 that overlaps with the countersunk surface 9c.

[0085] On the other hand, according to Figure 12 and Figure 14 The eccentric structure shown allows the side surface 8b of the lens 8 to be pre-fitted against the inner surface of the large-diameter aperture 9b, which forms the mounting end of the lens 8, along direction D. Furthermore, the closer the side surface 8b of the lens 8 is to the inner surface of the large-diameter aperture 9b (i.e., the fitted portion and its surrounding area), the stronger the surface tension of the resin adhesive B1. Therefore, even after baking, the lens 8 will not be pulled back relative to the lens holder 9 in the opposite direction to D. That is, before and after baking, the side surface 8b of the lens 8 is maintained in a state where it contacts the inner surface of the large-diameter aperture 9b along direction D (see reference). Figure 12 and Figure 14 Therefore, based on the above-described eccentric structure, the effective area of ​​the lens 8 can be adjusted so that its size coincides with the small-diameter aperture 9a when the lens 8 is positioned as described above, thereby maximizing the effective utilization of the effective area of ​​the lens 8.

[0086] Furthermore, the portion of the side surface 8b of lens 8 that touches the inner surface of the large-diameter aperture 9b is not necessarily in direct contact with the inner surface of the large-diameter aperture 9b. That is, it is also possible... Figure 14 As shown, a small amount of resin adhesive B1 may enter between the portion of the side surface 8b of the lens 8 that touches the inner surface of the large-diameter hole 9b and the inner surface of the large-diameter hole 9b due to capillary action.

[0087] like Figure 11 , Figure 12 and Figure 13 As shown in (B), the wall portion 90 (i.e., the cylindrical portion extending along the X-axis) 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 with respect to the four protrusions 53a provided on the second upper surface 53 of the heat sink 5 (see reference). Figure 9 The position corresponding to (A). Each protrusion 92b is bonded by an adhesive layer B2 (refer to) made of UV-curable resin (light-curing resin). Figure 2 It engages with each of the protrusions 53a.

[0088] In this embodiment, the four protrusions 92b are evenly arranged at the four corners of the bottom wall portion 92. That is, the four protrusions 92b are arranged such that the center of the four protrusions 92b is approximately aligned with the center of the bottom wall portion 92 when viewed from the Z-axis direction. As a result, the lens holder 9 can be stably fixed on the second upper surface 53 of the heat sink 5, and a structure that can withstand strong impacts and vibrations can be achieved.

[0089] like Figure 11 and Figure 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 across the large-diameter hole 9b. A cutout 91a is formed at the end of the top wall portion 91 opposite to the side of the small-diameter hole 9a. In addition, a cutout 92c is also formed at the end of the bottom wall portion 92 opposite to the side of the small-diameter hole 9a. When viewed from the Z-axis direction, the cutouts 91a and 92c have overlapping portions. That is, the top wall portion 91 is formed in such a way that at least a portion of the cutout 92c of the bottom wall portion 92 does not overlap with the top wall portion 91 when viewed from the direction opposite to the bottom wall portion 92 (Z-axis direction). Moreover, through the overlapping portion of the cutouts 91a and 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, through the aforementioned portion, light can be irradiated from above the top wall portion 91 onto the second upper surface 53 of the heat sink 5. With this structure, after the lens holder 9 is placed on the second upper surface 53 of the heat sink 5 in such a way that the positions of the four protrusions 53a are aligned with the positions of the four protrusions 92b, UV light can be irradiated from above the lens holder 9, thereby appropriately guiding the UV light into the space between the lower surface 92a of the lens holder 9 and the second upper surface 53 of the heat sink 5. This allows the adhesive layer B2 disposed between each protrusion 92b and each protrusion 53a to be properly cured.

[0090] Furthermore, by defining the areas where the adhesive layer B2 is coated by the island-shaped protrusions 92b and 53a, the locations and amount of adhesive layer B2 coated can be uniformly applied across multiple products (quantum cascade laser device 1). Additionally, there is a limit to the depth to which UV light can penetrate the interior of the UV-curable resin. Therefore, if the protrusions 92b and 53a are not provided, and the UV-curable resin is coated entirely on the lower surface 92a, the UV light may not reach the interior (center side) of the UV-curable resin, potentially resulting in incomplete curing. By defining the areas where the adhesive layer B2 is coated as islands as described above, this problem can be avoided. Furthermore, by providing island-shaped protrusions 92b and 53a, sufficient space for UV light to pass through is formed between the lower surface 92a and the second upper surface 53 at positions where the protrusions 92b and 53a do not overlap. Thus, UV light entering the space can be reflected at the valleys (the portions where the protrusions 92b and 53a are not formed) of the lower surface 92a and the second upper surface 53, irradiating the adhesive layer B2 on each protrusion 53a with UV light.

[0091] Next, the manufacturing method (assembly method) of the quantum cascade laser device 1 will be explained. For example... Figure 16 As shown, first, the encapsulation 3 is prepared before the top wall 33 and side wall 32 are joined. Then, the window member 15 (a window member 15 pre-installed with anti-reflective films 151, 152 and a metal film 153) is joined to the side wall 32. Figure 7 Specifically, a ring-shaped sheet member, i.e., a solder member 16, formed in the shape of a washer, is clamped 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 by pressing the window member 15 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 apparatus (vacuum welding furnace). At this time, a jig for aligning the center of the window member 15 with the central axis of the countersunk opening (small diameter hole 12 and large diameter hole 13) can also be used.

[0092] Next, a heat sink 5 is placed on the Peltier module 4, on which In foil 45, serving as solder components, is adhered both top and bottom. A clamp is used to position these components at predetermined locations on the bottom wall 31. Then, a load is applied from above the heat sink 5 by pressing these components relative to the bottom wall 31. In this state, the bottom wall 31, the Peltier module 4, and the heat sink 5 are joined, for example, using a vacuum welding apparatus, via the In foil 45 disposed between the individual components. Then, as... Figure 2 As shown, solder the wires 20 of the Peltier module 4 to pin 10.

[0093] Next, the heat sink 6, pre-mounted with components such as the QCL element 2, sub-base 7, temperature sensor T, and ceramic pattern SP, is fixed to the first upper surface 52 of the heat sink 5. Specifically, this is achieved by inserting a screw component (not shown) into the screw hole 6c of the heat sink 6 (see reference). Figure 10 The heat sink 6 is screwed to the heat sink 5 through screw holes 52a and screw holes 52a. Additionally, the temperature sensor T and the ceramic pattern SP are electrically connected to the designated pin 10 via wires (not shown).

[0094] Next, the lens holder 9, which houses 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 onto each of the protrusions 53a formed on the second upper surface 53 of the heat sink 5. Then, the lens holder 9 is vacuum-adsorbed using, for example, a vacuum accessory (vacuum generator), and moved within the package 3. Then, the QCL element 2 is driven to emit laser L, and active alignment is performed by aligning the optical axis of laser L with the central axis of the lens 8 while observing laser L through a beam monitor.

[0095] Next, with the optical axis of laser L aligned with the central axis of lens 8, the lens holder 9 is fixed to the heat sink 5. Specifically, with the optical axis of laser L aligned with the central axis of 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. As a result, each protrusion 92b of the lens holder 9 and each protrusion 53a of the heat sink 5 are joined via the adhesive layer B2.

[0096] Here, the positions of each protrusion 92b are designed to overlap with each protrusion 53a of the heat sink 5, with the optical axis of the laser L aligned with the central axis of the lens 8. Furthermore, with the optical axis of the laser L aligned with the central axis of the lens 8, the height dimensions (length along the Z-axis) of each protrusion 53a and each protrusion 92b of the lens holder 9 are designed such that a gap of several hundred μm, smaller than the thickness of the UV-cured resin (adhesive layer B2) pre-coated on each protrusion 53a, is formed between each protrusion 53a of the heat sink 5 and each protrusion 92b of the lens holder 9. Thus, when the lens holder 9 is moved relative to the heat sink 5 with the optical axis of the laser L aligned with the central axis of the lens 8, the protrusions 92b of the lens holder 9 are adjusted to contact the adhesive layer B2 on each protrusion 53a of the heat sink 5. In other words, with the UV-cured resin (adhesive layer B2) pre-coated on the heat sink 5 pressed into the lens holder 9, 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.

[0097] Next, the top wall 33 is joined at the upper end of the side wall 32 of the package 3 (the end opposite to the bottom wall 31). Based on the above, the following is obtained: Figure 1 The quantum cascade laser device 1 is shown.

[0098] In the quantum cascade laser device 1 described above, the light exit window 11 is bonded to the sidewall 32 of the package 3 via a solder member 16 (in this embodiment, a SnAgCu-based solder material with a melting point of 220°C) whose melting point is lower than that of the solder (melting point of 450°C or higher). Therefore, compared to the case where solder is used, damage to the window member 15 and the like (especially the anti-reflective films 151 and 152) caused by heat can be suppressed, and the window member 15 is brought into close contact with the countersunk hole surface 14. Furthermore, on the incident surface 15a of the window member 15, the first region A1 where the anti-reflective film 151 is provided and the second region A2 where the solder member 16 is bonded are spaced apart from each other (see reference 15a). Figure 7 Therefore, the stress transmitted from the melting or solidification of the solder component 16 in region 2 A2 to the antireflective film 151 in region 1 A1 can be suppressed. As a result, damage (cracks or peeling, etc.) to the antireflective film 151 caused by the aforementioned stress is suppressed. In this way, according to the quantum cascade laser device 1, damage to the antireflective film 151 provided on the light exit window 11 can be suppressed and the high hermeticity of the package 3 can be ensured.

[0099] Furthermore, the side surface 15c of the window member 15 has a third region A3 that is metallized in a manner continuous with the second region A2, and at least a portion of the side surface 15c is joined to at least a portion of the inner side surface of the large-diameter hole 13 via the solder member 16 (see reference). Figure 5 According to the above structure, by continuously metallizing the area from the second region A2 to the side surface 15c of the window member 15 (the third region A3), a portion of the solder member 16 can be appropriately wetted and extended to the third region A3 side during soldering. As a result, the solder member 16 can be positioned between the side surface 15c of the window member 15 and the inner side surface of the large-diameter hole 13, thereby appropriately improving the hermeticity of the package 3.

[0100] Furthermore, the wavelength of the laser L emitted from the QCL element 2 is within the range of 4μm to 12μm. As an example, the heat resistance temperature of the antireflective films 151 and 152 is around 260°C. On the other hand, in the quantum cascade laser device 1, since the solder component 16 with a relatively low melting point is used as the bonding material, it is possible to suppress the damage of the antireflective films 151 and 152 caused by heat, and the window component 15 on which the antireflective films 151 and 152 are provided is installed on the sidewall 32 by welding.

[0101] Furthermore, in the quantum cascade laser device 1, the lens holder 9 has a small-diameter aperture 9a and a large-diameter aperture 9b that are mutually eccentric along their central axes AX1 and AX2. Additionally, the side surface 8b of the lens 8 is positioned relative to the inner surface of the large-diameter aperture 9b along a direction D from the central axis AX2 of the large-diameter aperture 9b toward the central axis AX1 of the small-diameter aperture 9a. This appropriately suppresses the situation where, if the lens 8 is positioned at the center of the large-diameter aperture 9b (for example, referring to…),… Figure 15 The lens 8 is deviated from its position (movement of the lens 8 relative to the lens holder 9) due to the surface tension of the resin adhesive B1 disposed around the lens 8 (left side). Furthermore, with the lens 8 positioned in this way, the central axis AX3 of the lens 8 is positioned close to the central axis AX1 of the small-diameter hole 9a (in this embodiment, the central axis AX3 coincides with the central axis AX1). This reduces the area of ​​interference (overlap) between the effective area of ​​the lens 8 (the area within the effective diameter centered on the central axis AX3 of the lens) and the countersunk surface 9c. As a result, the effective area of ​​the lens 8 can be utilized efficiently. Furthermore, by efficiently utilizing the effective area of ​​the lens 8, miniaturization of the lens 8 can be achieved, thereby enabling miniaturization of the package 3.

[0102] Furthermore, in this embodiment, the central axis AX3 of the lens 8 is approximately aligned with the central axis AX1 of the small-diameter aperture 9a, and the effective diameter of the lens 8 is approximately aligned with the diameter d3 of the small-diameter aperture 9a. According to this structure, the entire effective area (the area within the effective diameter) of the lens 8 can be exposed through the small-diameter aperture 9a. Thus, by minimizing the size of the small-diameter aperture 9a, the area of ​​the countersunk surface 9c can be ensured, thereby appropriately supporting the edge of the incident surface 8a of the lens 8 and maximizing the effective utilization of the lens 8's effective area.

[0103] Furthermore, a groove 9d is formed on the inner surface of the large-diameter hole 9b, extending along the X-axis to the countersunk surface 9c, into which the resin adhesive B1 enters. According to this structure, the resin adhesive B1 can be easily injected between the side surface 8b of the lens 8 and the inner surface of the large-diameter hole 9b via the groove 9d.

[0104] Furthermore, the lens holder 9 has a lower surface 92a with a plurality of (four in this embodiment) protrusions 92b protruding toward the heat sink 5. The plurality of protrusions 92b are bonded to the second upper surface 53 of the heat sink 5 by an adhesive layer B2 made of a UV-curable resin. In this embodiment, on the second upper surface 53, a plurality of protrusions 53a protruding toward the lens holder 9 are formed at positions corresponding to the plurality of protrusions 92b, and the plurality of protrusions 92b are bonded to the plurality of protrusions 53a via the adhesive layer B2. According to the above structure, the locations where the adhesive layer B2 is provided can be distributed on the plurality of protrusions 92b. Therefore, compared with the case where the adhesive layer B2 is provided over a large area of ​​the entire surface, the adhesive layer B2 on each protrusion 92b can be cured easily and appropriately. Furthermore, in this embodiment, the adhesive layer B2 is disposed in the central portion (between the protrusions 92b and 53a) of the space formed between the lower surface 92a and the second upper surface 53. Therefore, the UV light reflected by the lower surface 92a and the second upper surface 53 within this space can be properly irradiated onto the adhesive layer B2. As a result, the adhesive layer B2 can be cured more properly, and the lens holder 9 can be stably fixed to the heat sink 5.

[0105] Furthermore, a cutout 92c for guiding light to the second upper surface 53 of the heat sink 5 is provided on the bottom wall portion 92 of the lens holder 9. According to this structure, UV light can be irradiated onto the second upper surface 53 of the heat sink 5 from the side opposite to where the heat sink 5 is located on the lens holder 9 (i.e., above the lens holder 9) via the cutout 92c in the bottom wall portion 92. This allows for easy light irradiation to cure the adhesive layer B2 between the lower surface 92a and the second upper surface 53.

[0106] Furthermore, the lens holder 9 has a top wall portion 91 that faces the bottom wall portion 92 across the large-diameter aperture 9b. Moreover, the top wall portion 91 is formed such that, when viewed from the direction opposite to the bottom wall portion 92 (Z-axis direction), at least a portion of the cutout 92c provided in the bottom wall portion 92 does not overlap with it. According to the above structure, the lens 8 disposed within the large-diameter aperture 9b can be appropriately protected from the outside by the bottom wall portion 92 and the top wall portion 91. Furthermore, because the top wall portion 91 is formed such that at least a portion of it does not overlap with the cutout 92c provided in the bottom wall portion 92, light can be irradiated onto the second upper surface 53 of the heat sink 5 by irradiating the lens holder 9 from the outside of the lens holder 9 (the side sandwiching the top wall portion 91 and the bottom wall portion 92).

[0107] Alternatively, a through hole extending in the Z-axis direction can be formed in the bottom wall portion 92 instead of the cutout 92c. Similarly, a through hole can be formed in the top wall portion 91 instead of the cutout 91a, which also extends in the Z-axis direction and has a portion overlapping with the cutout 92c or the through hole provided in the bottom wall portion 92. With such a structure, light can be directed to the second upper surface 53 of the heat sink 5 by irradiating light from above the lens holder 9.

[0108] Furthermore, the QCL element 2 and the lens holder 9 are mounted on the same heat sink 5. Additionally, the QCL element 2 is mounted on the heat sink 5 via a sub-base 7 and a heat sink 6. According to this structure, by making the base (heat sink 5) on which the QCL element 2 and the lens holder 9 are mounted common, relative movement of the lens holder 9 relative to the QCL element 2 can be suppressed when the heat sink 5 expands or contracts due to heat. As a result, optical axis deviation (deviation of the central axis AX3 of the lens 8 relative to the optical axis of the laser L) caused by temperature changes within the package 3 can be suppressed.

[0109] Furthermore, the package 3 hermetically houses the QCL element 2, lens 8, and lens holder 9. Based on this structure, since the effective area of ​​the lens 8 disposed within the package 3 can be efficiently utilized, miniaturization of both the lens 8 and the package 3 can be achieved.

[0110] [Variation Example]

[0111] The above describes one embodiment of the present disclosure; however, the present disclosure is not limited to the embodiment described above. For example, the materials and shapes of the various structures are not limited to those described above, and a wide variety of materials and shapes can be used. Furthermore, some structures included in the above embodiment may be appropriately modified or omitted.

[0112] The shape of the lens holder is not limited to the shape of the lens holder 9 described above. For example, a different lens holder 9 may be used instead. Figures 17-19 The lens holders shown are 9A to 9C.

[0113] like Figure 17As shown, the lens holder 9A in the first modified example differs from the lens holder 9 in that a quadrilateral large-diameter aperture 9Ab is formed instead of a circular large-diameter aperture 9b, and no groove 9d is formed (the large-diameter aperture 9Ab is formed to include the size corresponding to the groove 9d). Thus, the large-diameter aperture 9Ab is formed to accommodate the lens 8, and does not necessarily have to be circular. With this large-diameter aperture 9Ab, the groove 9d can be omitted, and sufficient space for filling the resin adhesive B1 is ensured at the four corners of the large-diameter aperture 9Ab. Changing the viewing angle, in the lens holder 9A, the portions corresponding to the four corners of the large-diameter aperture 9Ab function as recesses corresponding to the groove 9d of the lens holder 9. Furthermore, the small-diameter aperture 9a, like the large-diameter aperture 9Ab, can also be formed in a shape other than a circle (for example, a quadrilateral similar to the large-diameter aperture 9Ab, but slightly smaller).

[0114] like Figure 18 As shown, the difference between the lens holder 9B and the lens holder 9 in the second modification is that the top wall portion 91B, instead of the top wall portion 91, has a top wall portion 91B with a circular (curved) upper surface. Furthermore, since the lens holder 9B uses the top wall portion 91B, the space for forming the groove portion 9d on the top wall portion 91 side in the lens holder 9 is lost. Therefore, in the lens holder 9B, a pair of groove portions 9d are formed on both sides in the Y-axis direction on the bottom wall portion 92 side. Thus, the position where the groove portions 9d are formed in the lens holder is not particularly limited. Furthermore, the number of groove portions 9d is not particularly limited. In addition, in the lens holder 9B, the length along the X-axis of the portion of the wall portion forming the large-diameter hole 9b, excluding the bottom wall portion 92, is shorter than that of the wall portion 90 of the lens holder 9. Specifically, the length along the X-axis of the aforementioned portion is slightly shorter than the length along the X-axis of the lens 8. With this structure, the portion of UV light blocked from above the lens holder 9B can be reduced, thus allowing the UV light used to cure the adhesive layer B2 to be more properly directed to the heat sink 5 side.

[0115] like Figure 19As shown, the lens holder 9C in the third modification differs from the lens holder 9 in that it has a shorter top wall portion 91C in the X-axis direction than the top wall portion 91. The length of the top wall portion 91C in the X-axis direction is about half the length of the lens 8 in the X-axis direction. Furthermore, in the lens holder 9C, the length of the portion of the wall forming the large-diameter aperture 9b, excluding the bottom wall portion 92, in the X-axis direction is the same as that of the top wall portion 91C. That is, the lens holder 9C is formed in a roughly L-shape when viewed from the Y-axis direction. In the lens holder 9C, compared to the lens holder 9B, less UV light from above the lens holder 9C is blocked, thus allowing the UV light used to cure the adhesive layer B2 to be more properly guided to the heat sink 5 side. Furthermore, as shown in the lens holder 9C, the wall portion constituting the large-diameter aperture 9b of the lens holder does not necessarily need to surround the entire side surface 8b of the lens 8; it can be configured to surround only a portion of the incident surface 8a side of the side surface 8b of the lens 8.

[0116] In addition, such as Figure 20 As shown in the modified example of the quantum cascade laser device 1A, the lens may not be housed within the package 3. The difference between the quantum cascade laser device 1A and the quantum cascade laser device 1 is that the package 3 does not contain the lens 8 and lens holder 9; instead, it has a lens 8A externally located on the outside of the package 3. That is, the quantum cascade laser device 1A has a lens 8A disposed on the outside of the package 3 to focus or collimate the laser L passing through the light exit window 11. Furthermore, due to this difference, the quantum cascade laser device 1A also differs from the quantum cascade laser device 1 in that it has a heat sink 5A instead of a heat sink 5, configured to allow the QCL element 2 to be positioned close to the light exit window 11. As described above, the beam radiation angle of the laser L is very large. Therefore, in order to allow the entire beam of the laser L to pass through the light exit window 11 to the outside of the package 3 and to minimize the size of the light exit window 11, it is preferable to make the light exit window 11 as close as possible to the exit surface (end face 2a) of the laser L of the QCL element 2. Therefore, the quantum cascade laser device 1A, which does not have a lens inside the package 3, has a heat sink 5A as described above.

[0117] According to the quantum cascade laser device 1A, the lens 8A can be flexibly configured and replaced by setting it as an external component disposed outside the package 3. Furthermore, as described above, the length w1 of the small-diameter aperture 12 along the optical axis direction (X-axis direction) of the laser L is shorter than the length w2 of the large-diameter aperture 13 (see reference). Figure 5According to the above structure, compared to the case where the length w1 of the small-diameter aperture 12 is greater than or equal to the length w2 of the large-diameter aperture 13, the light exit window 11 can be brought closer to the QCL element 2. Therefore, even when the beam radiation angle of the laser L emitted from the QCL element 2 is large, the laser L can still be incident on the light exit window 11 when its spread is still small. As a result, the light exit window 11 can be miniaturized, and consequently, the package 3 can be miniaturized.

[0118] Furthermore, as described above, the exit surface 15b of the window member 15 has a fourth region A4 on which an anti-reflective film 152 is provided. When viewed from the X-axis direction, the fourth region A4 includes the first region A1 and is larger than the first region A1. In the case where, as in the quantum cascade laser device 1A, no lens is provided within the encapsulation 3, and the laser L, as diverging light, is incident on the window member 15, the area through which the laser L passes on the incident surface 15a of the window member 15 is smaller than the area through which the laser L passes on the exit surface 15b of the window member 15. Therefore, by making the anti-reflective film 151 on the incident surface 15a side smaller than the anti-reflective film 152 on the exit surface 15b side (i.e., by making the first region A1 smaller than the fourth region A4), the second region A2 can be ensured to correspond to the difference between the fourth region A4 and the first region A1. In this way, the dimensions of the first region A1, the second region A2, and the fourth region A4 can be designed by taking into account the beam radiation angle of the laser L, thereby enabling the miniaturization of the window component 15 and, consequently, the miniaturization of the package 3.

[0119] Furthermore, in the above embodiment, the exit surface 15b of the window member 15 and the outer surface of the sidewall 32 are made to be approximately the same surface, and the exit surface 15b of the window member 15 can also protrude further outward from the outer surface of the encapsulation 3 compared to the outer surface of the sidewall 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 of joining the window member 15 to the sidewall 32 from the outside of the encapsulation 3 can be improved. In addition, when an 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 lens mounting can also be improved. Furthermore, by thinning the sidewall 32, the encapsulation 3 can be miniaturized, or the lens 8A can be reliably positioned close to the window member 15.

[0120] Furthermore, in the above embodiments, a quantum cascade laser element (QCL element 2) is illustrated as an example of a semiconductor laser element. However, laser elements other than quantum cascade laser elements can also be used as the semiconductor laser element housed in the package 3. Additionally, the semiconductor laser element can also be a distributed feedback (DFB) semiconductor laser element with a diffraction lattice structure provided on the active layer.

[0121] Furthermore, in the above embodiment, the packaging member 3 is exemplified as a butterfly-shaped packaging member, but the packaging member is not limited to this. For example, the packaging member may also be a can-shaped packaging member.

[0122] Explanation of reference numerals in the attached figures

[0123] 1, 1A… Quantum cascade laser device (semiconductor laser device); 2… Quantum cascade laser element (semiconductor laser element); 2a… End face (emission surface); 3… Package; 5, 5A… Heat sink; 8, 8A… Lens; 8a… Incident surface; 8b… Side surface; 8c… Emission surface; 9, 9A, 9B, 9C… Lens holder; 9a… Small diameter hole; 9b… Large diameter hole; 9c… Countersunk surface; 9d… Groove (recess); 11… Light exit window; 12… Small diameter hole (first hole); 13… Large diameter hole (second hole); 14… Countersunk surface; 15… Window component; 15a… Incident surface; 15b… Emission surface; 15c… Side surface; 16… Solder component; 3 1… Bottom wall; 32… Side wall; 33… Top wall; 53… Second upper surface (second mounting surface); 53a… Protrusion (second protrusion); 91… Top wall portion (second wall portion); 92… Bottom wall portion (first wall portion); 92a… Lower surface (first mounting surface); 92b… Protrusion (first protrusion); 92c… Cutout; 151… Anti-reflective film (first anti-reflective film); 152… Anti-reflective film (second anti-reflective film); 153… Metal film; A1… First region; A2… Second region; A3… Third region; A4… Fourth region; AX1, AX2, AX3… Central axis; B1… Resin adhesive; B2… Adhesive layer; D… Direction; L… Laser.

Claims

1. A semiconductor laser device, wherein, have: Semiconductor laser components; and A hermetically sealed package that houses the semiconductor laser element. The package has: bottom wall; The sidewall, which stands on the bottom wall, is formed in a ring shape to surround the area containing the semiconductor laser element when viewed from a direction perpendicular to the bottom wall; and The top wall blocks the opening in the side wall that is opposite to the bottom wall side. The sidewall is provided with a light exit window that allows laser light emitted from the semiconductor laser element to pass through. The light exit window is composed of the following: The first hole is open on the inside of the package in the direction of the optical axis along the optical axis of the laser. The second hole, which opens on the outside of the package, includes the first hole and is larger than the first hole when viewed from the optical axis direction; An annular countersunk surface, connecting the first hole portion and the second hole portion, extends along a surface intersecting the optical axis direction; and Window component, which is disposed inside the second opening, The window component has: The incident surface of the laser; The exit surface, which is the surface opposite to the incident surface, emits the laser light passing through the window member to the outside of the encapsulation; and The side surface connects the incident surface and the exit surface, and extends along the optical axis. The incident surface has: A first region, comprising the central portion of the incident surface, and provided with a first antireflective film; and The second region, which is formed in a ring shape to surround the first region at intervals and is metallized, The second region is joined to the countersunk surface via a solder component.

2. The semiconductor laser device according to claim 1, wherein, The side surface has a third region that is metallized in a manner continuous with the second region. At least a portion of the side surface is joined to at least a portion of the inner side surface of the second hole via the solder member.

3. The semiconductor laser device according to claim 1, wherein, The length of the first aperture along the optical axis is shorter than the length of the second aperture along the optical axis.

4. The semiconductor laser device according to claim 2, wherein, The length of the first aperture along the optical axis is shorter than the length of the second aperture along the optical axis.

5. The semiconductor laser device according to any one of claims 1 to 4, wherein, The emission surface has a fourth region on which a second antireflective film is provided. The fourth region, when viewed from the optical axis direction, includes the first region and is larger than the first region.

6. The semiconductor laser device according to any one of claims 1 to 4, wherein, It also includes a lens disposed on the outside of the package to focus or collimate the laser light passing through the light exit window.

7. The semiconductor laser device according to claim 5, wherein, It also includes a lens disposed on the outside of the package to focus or collimate the laser light passing through the light exit window.

8. The semiconductor laser device according to any one of claims 1 to 4, wherein, The wavelength of the laser is in the range of 4μm to 12μm.

9. The semiconductor laser device according to claim 5, wherein, The wavelength of the laser is in the range of 4μm to 12μm.

10. The semiconductor laser device according to claim 6, wherein, The wavelength of the laser is in the range of 4μm to 12μm.

11. The semiconductor laser device according to claim 7, wherein, The wavelength of the laser is in the range of 4μm to 12μm.

12. The semiconductor laser device according to any one of claims 1 to 4, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

13. The semiconductor laser device according to claim 5, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

14. The semiconductor laser device according to claim 6, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

15. The semiconductor laser device according to claim 7, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

16. The semiconductor laser device according to claim 8, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

17. The semiconductor laser device according to claim 9, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

18. The semiconductor laser device according to claim 10, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

19. The semiconductor laser device according to claim 11, wherein, The exit surface of the window member protrudes further outward from the outer side of the encapsulation member on which the light-emitting window is provided.

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