Semiconductor laser device and semiconductor laser module

Abstract

In the present invention, a metal block (2) is formed on the main surface of a disc-shaped metal stem (1). The block (2) has a mounting surface (2a) and a heat-dissipating surface (2b) on the opposite side from the mounting surface (2a). A semiconductor laser chip (6) is mounted on the mounting surface of the block (2). A cap (9) has a lens (10) that condenses laser light emitted from the semiconductor laser chip (6), and a lens barrel (11) that holds the lens (10) and is fixed to the metal stem (1) or the block (2). The heat-dissipating surface of the block (2) is not covered by the lens barrel (11), and is flush with the side surface of the metal stem (1).

Description

Semiconductor laser device and semiconductor laser module

[0001] The present disclosure relates to a TO-CAN type semiconductor laser device and a semiconductor laser module.

[0002] In a TO-CAN type semiconductor laser device, a semiconductor laser chip is mounted on a block formed on the main surface of a disk-shaped metal stem (see, for example, Patent Document 1). Heat generated when the semiconductor laser chip is driven is dissipated via the block and the metal stem.

[0003] Japanese Patent Application Publication No. 2007-027375

[0004] In the past, to achieve compactness, the semiconductor laser chip, block, and other components were all housed inside the lens barrel. Because the space inside the lens barrel was limited, it was difficult to ensure sufficient volume for the block, which served as a heat dissipation path. Furthermore, the only path for dissipating heat propagating radially from the semiconductor laser chip was from the block toward the metal stem, limiting the amount of heat dissipation. Therefore, conventional semiconductor laser devices had poor heat dissipation capabilities, resulting in problems such as reduced optical output, element failure, and degradation of semiconductor laser characteristics.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its object is to provide a semiconductor laser device and a semiconductor laser module that can improve heat dissipation.

[0006] The semiconductor laser device according to the present disclosure is a TO-CAN type semiconductor laser device comprising: a disk-shaped metal stem; a metal block formed on a main surface of the metal stem and having a mounting surface and a heat dissipation surface opposite the mounting surface; a semiconductor laser chip mounted on the mounting surface of the block; a lens that focuses laser light emitted from the semiconductor laser chip; and a cap having a lens barrel that holds the lens and is fixed to the metal stem or the block, wherein the heat dissipation surface of the block is not covered by the lens barrel and is flush with the side surface of the metal stem.

[0007] In this disclosure, the heat dissipation surface of the block is not covered by the lens barrel and is flush with the side surface of the metal stem. This allows heat from the semiconductor laser chip to be dissipated not only laterally from the block toward the metal stem, but also vertically from the heat dissipation surface of the block toward the outside. This allows heat propagating radially from the semiconductor laser chip to be efficiently dissipated, improving heat dissipation.

[0008] 1 is a side view showing a semiconductor laser device according to a first embodiment; a front view showing the interior of the semiconductor laser device according to the first embodiment; a perspective view showing a stem, a block, and a cap of the semiconductor laser device according to the first embodiment; a side view showing a semiconductor laser device according to a comparative example; a front view showing the interior of the semiconductor laser device according to the comparative example; a side view showing a semiconductor laser device according to a second embodiment; a side view showing a semiconductor laser device according to a third embodiment; a front view showing the interior of the semiconductor laser device according to the third embodiment; a perspective view showing the stem, a block, and a cap of the semiconductor laser device according to the third embodiment; a side view showing a semiconductor laser device according to a fourth embodiment; a front view showing the interior of the semiconductor laser device according to the fourth embodiment; a perspective view showing the stem, a block, and a cap of the semiconductor laser device according to the fourth embodiment; a side view showing a semiconductor laser device according to a fifth embodiment; a top view showing a semiconductor laser device according to the fifth embodiment; a front view showing the interior of the semiconductor laser device according to the fifth embodiment; a perspective view showing the stem, a block, and a cap of the semiconductor laser device according to the fifth embodiment; a side view showing a semiconductor laser device according to a sixth embodiment; a front view showing the interior of the semiconductor laser device according to the sixth embodiment; a perspective view showing the stem, a block, and a cap of the semiconductor laser device according to the sixth embodiment. FIG. 13 is a cross-sectional view showing a semiconductor laser module according to a seventh embodiment.

[0009] A semiconductor laser device and a semiconductor laser module according to an embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

[0010] First Embodiment Fig. 1 is a side view showing a semiconductor laser device according to a first embodiment. Fig. 2 is a front view showing the interior of the semiconductor laser device according to the first embodiment. Fig. 3 is a perspective view showing the stem, block, and cap of the semiconductor laser device according to the first embodiment. The semiconductor laser device according to this embodiment is a TO-CAN type semiconductor laser device.

[0011] A metal block 2 is formed on the main surface 1a of a disk-shaped metal stem 1. The metal stem 1 and block 2 are made of the same material and are integrally formed. The block 2 has a flat mounting surface 2a and a heat dissipation surface 2b opposite the mounting surface 2a. The mounting surface 2a is perpendicular to the main surface 1a of the metal stem 1. The heat dissipation surface 2b is a curved surface at the bottom end of the block 2, and is flush with the side surface of the metal stem 1. When viewed perpendicularly to the main surface 1a of the metal stem 1, the block 2 is semicircular.

[0012] A lead 3 for current flow passes through a through hole 1b in the metal stem 1. Sealing glass 4 is filled in the through hole 1b to insulate the lead 3 from the metal stem 1. The lead 3 is placed above the metal stem 1 so as not to interfere with the block 2 below the metal stem 1.

[0013] A submount 5 is die-bonded near the center of the mounting surface 2a of the block 2. A semiconductor laser chip 6 is die-bonded to a metallized portion of the submount 5. A photodiode 7 is mounted on the main surface 1a of the metal stem 1 via a submount 8, and monitors the light extracted from the rear end face of the semiconductor laser chip 6. The lead 3 is wire-bonded to the surface electrode of the semiconductor laser chip 6. Another lead 3 is wire-bonded to the metallized portion of the submount 5. This forms a path for current injection.

[0014] The cap 9 has a lens 10 that focuses the laser light emitted from the semiconductor laser chip 6, and a lens barrel 11 that holds the lens 10. The lens barrel 11 is fixed by projection welding to three surfaces, namely the main surface 1a of the metal stem 1, the mounting surface 2a of the block 2, and the tip surface of the block 2, so as to cover the semiconductor laser chip 6 and the like (hermetic sealing). In this case, it is necessary to perform positioning with high precision so that the laser light emitted from the semiconductor laser chip 6 is efficiently coupled to the lens 10. These techniques are among the most basic in optical communication technology.

[0015] Specifically, first, the position of the cap 9 is adjusted in the Y direction so that the center lines of the lens 10 and the semiconductor laser chip 6 are aligned. Next, the cap 9 is lowered in the -X direction until it contacts the mounting surface 2a of the block 2. Next, the cap 9 is slid in the -Z direction, and the cap 9 is welded and fixed to the metal stem 1 and the block 2. With this method, the positioning of the block 2 can be completed mainly by adjusting the position in the Y direction alone, eliminating the need for axial adjustment in two or more dimensions as in the past.

[0016] A notch 11a is formed on the side of the lens barrel 11 to match the shape of the heat dissipation surface 2b of the block 2. The notch 11a of the lens barrel 11 is fitted into the block 2. The heat dissipation surface 2b of the block 2 is exposed to the outside of the lens barrel 11 through the notch 11a and is not covered by the lens barrel 11.

[0017] The lens barrel 11 may be fixed by adhesive or other welding methods, and the fixing location is not limited to the above example, as long as it does not interfere with heat dissipation from the heat dissipation surface of the block 2. The presence or absence of airtight sealing can also be selected depending on the intended use or environment. The mounted chip is not limited to the semiconductor laser chip 6, and any heat-generating chip can enjoy the advantages unique to the structure. The semiconductor laser chip 6 may be mounted on the block 2 without using the submount 5.

[0018] Next, the effects of this embodiment will be explained in comparison with a comparative example. Fig. 4 is a side view showing a semiconductor laser device according to the comparative example. Fig. 5 is a front view showing the interior of the semiconductor laser device according to the comparative example. In the comparative example, the semiconductor laser chip 6, submount, block 2, etc. are all housed within the lens barrel 11. Because the space within the lens barrel 11 is limited, it is not possible to ensure a sufficient volume for the block 2, which serves as a heat dissipation path. Furthermore, the only path for dissipating heat from the semiconductor laser chip 6 is from the block 2 toward the metal stem 1, so the amount of heat dissipation is limited. Therefore, the semiconductor laser device according to the comparative example has poor heat dissipation properties.

[0019] In contrast, in this embodiment, the heat dissipation surface of the block 2 is not covered by the lens barrel 11, and is flush with the side surface of the metal stem 1. By bringing the flush side surface of the metal stem 1 and the heat dissipation surface of the block 2 into contact with an external heat sink (not shown), heat can be dissipated from both the metal stem 1 and the block 2. As a result, heat from the semiconductor laser chip 6 is not only dissipated laterally from the block 2 toward the metal stem 1, but also vertically from the heat dissipation surface 2b of the block 2 toward the outside. Therefore, heat propagating radially from the semiconductor laser chip 6 can be efficiently dissipated, improving heat dissipation performance.

[0020] The block 2 is also extended in the -X direction until the heat dissipation surface 2b at the bottom end of the block 2 is flush with the side surface of the metal stem 1. Furthermore, the block 2 is also extended in the Z direction, which is the laser light emission direction, within a range where the tip of the block 2 does not interfere with the cap 9. This increases the volume of the block 2, expanding the path for diffusing heat from the semiconductor laser chip 6 and improving heat dissipation. The improved heat dissipation improves the semiconductor laser characteristics, especially during high temperature operation.

[0021] Since the laser light emitted from the semiconductor laser chip 6 and the lens 10 are perpendicular to each other, the shape of the lens barrel 11 that holds the lens 10 is simple. Also, since there is no interfering portion above the mounting surface 2a of the block 2, the mounting of the semiconductor laser chip 6 and the submount 5 is easy.

[0022] In the comparative example, the lens barrel 11 is positioned so that the center of the cap 9 is aligned with the center of the metal stem 1, which takes time to adjust the optical axis. On the other hand, in this embodiment, the optical axis can be adjusted in a short time by fitting the notch 11a of the lens barrel 11 into the block 2. By ensuring the accuracy of the shapes of the fitting notch 11a of the lens barrel 11 and the block 2, it is possible to suppress variations in positioning. Furthermore, the shape of the lens barrel 11 is simple, as only a portion of the cylindrical lens barrel 11 is cut out to expose the block 2.

[0023] When a highly light-concentrating ball lens or the like is used as the lens 10, it is necessary to increase the height of the lens barrel 11 in order to ensure a sufficient distance between the semiconductor laser chip 6 and the lens 10. In this embodiment, the lens 10 of the cap 9 is disposed in the direction of emission of the laser light, so there are no restrictions on the type of lens 10, the height of the lens barrel 11, etc. Therefore, even if the height of the lens barrel 11 is increased, the laser light can pass through the lens 10. This allows for a high degree of freedom in optical design, and high coupling efficiency with the lens 10.

[0024] If a cap is formed by combining a rectangular lens barrel with a circular spherical lens, stress will concentrate at the four corners of the lens barrel window, causing concerns about the cap characteristics. On the other hand, the cap 9 of this embodiment uses a cylindrical lens barrel 11, which prevents stress concentration, has isotropy, and can achieve stable cap characteristics.

[0025] Second Embodiment Fig. 6 is a side view showing a semiconductor laser device according to a second embodiment. The block 2 extends in the z direction in which the laser light 12 is emitted from the semiconductor laser chip 6. The length of the block 2 in the Z direction is limited to prevent the tip of the block 2 from interfering with the laser light 12 between the semiconductor laser chip 6 and the lens 10. This makes it possible to improve the optical coupling of the laser light 12 to the lens 10. The other configurations and effects are the same as those of the first embodiment.

[0026] The laser beam 12 is emitted from the semiconductor laser chip 6 in an elliptical shape, with the output power decreasing from the center to the periphery. Therefore, even if part of the laser beam 12 interferes with the tip of the block 2 and is not coupled to the lens 10, this does not pose a problem as long as the required optical output power is satisfied.

[0027] Embodiment 3 Fig. 7 is a side view showing a semiconductor laser device according to embodiment 3. Fig. 8 is a front view showing the inside of the semiconductor laser device according to embodiment 3. Fig. 9 is a perspective view showing a stem, a block, and a cap of the semiconductor laser device according to embodiment 3.

[0028] A recess 2c is partially formed in the center of the tip of the block 2 in the passage path of the laser light emitted from the semiconductor laser chip 6. Because the laser light passes through the recess 2c, the tip of the block 2 does not interfere with the laser light between the semiconductor laser chip 6 and the lens 10. This makes it possible to improve the optical coupling of the laser light to the lens 10. The other configurations and effects are the same as those of the first embodiment.

[0029] Fourth Embodiment Fig. 10 is a side view showing a semiconductor laser device according to a fourth embodiment. Fig. 11 is a front view showing the inside of the semiconductor laser device according to the fourth embodiment. Fig. 12 is a perspective view showing a stem, a block, and a cap of the semiconductor laser device according to the fourth embodiment.

[0030] A semicircular recess 2d is formed at the tip of mounting surface 2a of block 2 to match the curvature of disk-shaped lens barrel 11. The outer periphery of lens barrel 11, which has been machined to be shorter than in embodiment 1, is fitted into recess 2d. This secures lens barrel 11 to block 2. Note that the securing method may be, for example, welding or adhesive, but is not limited to these.

[0031] The block 2 extends in the Z direction and also serves to fix the lens barrel 11. As a result, the area of ​​the mounting surface 2a of the block 2 can be increased, improving the mountability and assembly of the semiconductor laser chip 6 and submount 5. The fixing work of the lens barrel 11 can also be made more efficient. The fitting structure reduces positioning variations, improving optical coupling to the lens 10. Furthermore, the use of a short lens barrel 11 is expected to reduce component prices, simplify the manufacturing method, and reduce costs. The other configurations and effects are the same as those of the first embodiment.

[0032] The semiconductor laser chip 6 and submount 5 are mounted near the center of the mounting surface 2a of the block 2 and are not covered by the lens barrel 11 (non-hermetic sealing). Depending on the usage environment, such as installation in an indoor facility, the lens barrel 11 does not necessarily need to protect the semiconductor laser chip 6. Furthermore, since the semiconductor laser device is covered by hardware such as a holder when being made into a TOSA or mounted in a module, there are also specifications in which the lens barrel 11 does not protect the semiconductor laser chip.

[0033] Fifth embodiment Fig. 13 is a side view showing a semiconductor laser device according to a fifth embodiment. Fig. 14 is a top view showing a semiconductor laser device according to the fifth embodiment. Fig. 15 is a front view showing the inside of the semiconductor laser device according to the fifth embodiment. Fig. 16 is a perspective view showing a stem, a block, and a cap of the semiconductor laser device according to the fifth embodiment.

[0034] The block 2 has a two-tier structure including a lower block 21 and an upper block 22 formed on the upper surface of the lower block 21 and narrower than the lower block 21. The lower surface of the lower block 21 is the heat dissipation surface 2b. The semiconductor laser chip 6 and the submount 5 are fixed near the center of the mounting surface 2a of the upper block 22. By making the block 2 have a two-tier structure, heat diffused radially from the semiconductor laser chip 6 can be efficiently dissipated.

[0035] The lens barrel 11 is fixed by projection welding to two surfaces, the main surface 1a of the metal stem 1 and the upper surface of the lower block 21, and is hermetically sealed (hermetically sealed). The two-stage structure of the block 2 provides excellent assembly and expandability.

[0036] Lower block 21 extends in the Z direction to a position immediately below lens 10. The width of upper block 22 in the X direction is expanded to a range that can be accommodated within lens barrel 11, taking into consideration factors such as ease of mounting submount 5. Upper block 22 extends in the Z direction to a position that does not interfere with lens barrel 11 and lens 10. However, it is preferable to limit the length of upper block 22 in the Z direction as in embodiment 2, or to form recess 2c as in embodiment 3, so that the tip of upper block 22 does not interfere with the laser light.

[0037] Sixth Embodiment Fig. 17 is a side view showing a semiconductor laser device according to a sixth embodiment. Fig. 18 is a front view showing the inside of the semiconductor laser device according to the sixth embodiment. Fig. 19 is a perspective view showing a stem, a block, and a cap of the semiconductor laser device according to the sixth embodiment.

[0038] The outer diameter of the block 2 is the same as that of the metal stem 1, and the side surface of the block 2, including the heat dissipation surface 2b, is flush with the side surface of the metal stem 1. The block 2 has an inclined surface 2e inclined at an angle θ with respect to the main surface 1a of the metal stem 1. A mounting surface 2a perpendicular to the main surface 1a of the metal stem 1 is formed in the center of the inclined surface 2e. The semiconductor laser chip 6 and the submount 5 are mounted on the mounting surface 2a. A recess 2f is formed on the outer periphery of the inclined surface 2e.

[0039] The end of the cylindrical lens barrel 11 is cut off at an angle θ corresponding to the inclined surface 2e of the block 2. That is, the end of the lens barrel 11 is also inclined at an angle θ with respect to the bottom surface of the lens barrel 11 to which the lens 10 is fixed. The end of the lens barrel 11 is fitted into a recess 2f in the inclined surface 2e of the block 2. This makes it easy to position the lens barrel 11 during assembly. Furthermore, by making the bottom surface of the recess 2f slightly larger than the outer shape of the lens barrel 11, it is possible to finely adjust the position of the lens barrel 11 in the X and Y directions during assembly.

[0040] Seventh Embodiment. Figure 20 is a cross-sectional view showing a semiconductor laser module according to a seventh embodiment. The semiconductor laser device 100 shown in this figure is a semiconductor laser device according to the first embodiment, but it may also be a semiconductor laser device according to any of the second to sixth embodiments. A cylindrical holder 101 holds the semiconductor laser device 100 and optically couples it to an optical fiber in a receptacle 102. An opening 101a is formed in a portion of the curved surface at the bottom end of the holder 101, matching the shape of the block 2 of the semiconductor laser device 100. The heat dissipation surface 2b of the block 2 is exposed through the opening 101a without being covered by the holder 101. This allows heat from the semiconductor laser chip 6 to be efficiently dissipated. Furthermore, since the shape of a semiconductor laser module combining the semiconductor laser device 100 and the holder 101 is substantially the same as that of a conventional module, optical axis alignment is easy when mounting the module in an optical transceiver.

[0041] REFERENCE SIGNS LIST 1 metal stem, 1a main surface, 2 block, 2a mounting surface, 2b heat dissipation surface, 2c recess, 2d carving, 2e inclined surface, 2f recess, 6 semiconductor laser chip, 9 cap, 10 lens, 11 lens barrel, 11a notch, 21 lower block, 22 upper block, 100 semiconductor laser device, 101 holder, 101a opening

Claims

1. A TO-CAN type semiconductor laser device, comprising: a disc-shaped metal stem; a metal block formed on a main surface of the metal stem and having a mounting surface and a heat dissipation surface opposite to the mounting surface; a semiconductor laser chip mounted on the mounting surface of the block; a lens that condenses laser light emitted from the semiconductor laser chip; and a cap that holds the lens and is fixed to the metal stem or the block, wherein the heat dissipation surface of the block is not covered by the lens barrel and is flush with a side surface of the metal stem.

2. The semiconductor laser device according to claim 1, wherein a notch is formed in the lens barrel according to the shape of the heat dissipation surface of the block, the notch of the lens barrel is fitted to the block, and the heat dissipation surface of the block is exposed from the notch.

3. The semiconductor laser device according to claim 1 or 2, wherein a tip portion of the block does not interfere with the laser light between the semiconductor laser chip and the lens.

4. The semiconductor laser device according to claim 3, wherein a recess is formed in the tip portion of the block in a passing path of the laser light.

5. The semiconductor laser device according to claim 1, wherein a semi-circular indentation is formed in the mounting surface of the block, and an outer peripheral portion of the disc-shaped lens barrel is fitted into the indentation.

6. The semiconductor laser device according to any one of claims 1 to 4, wherein the block has a lower block and an upper block formed on an upper surface of the lower block and having a width narrower than that of the lower block, and the lens barrel is fixed to the main surface of the metal stem and the upper surface of the lower block.

7. The semiconductor laser device according to claim 1, wherein the block has an inclined surface inclined with respect to the main surface of the metal stem, a recess is formed in an outer peripheral portion of the inclined surface, an end portion of the cylindrical lens barrel is cut at an angle corresponding to the inclined surface, and the end portion of the lens barrel is fitted into the recess of the inclined surface.

8. A semiconductor laser module comprising: the semiconductor laser device according to any one of claims 1 to 7; and a holder that holds the semiconductor laser device and is optically coupled to an optical fiber, wherein an opening is formed in a part of the holder, and the heat radiating surface of the block is exposed from the opening.

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