JP4906545B2 - Light emitting device and optical transmission module - Google Patents

Description

  The present invention relates to a light emitting device used for wireless optical communication, and an optical transmission module.

  In wireless optical communications, light emitting diodes (LEDs) that emit infrared rays are used as the light source, but in recent years communication data has become increasingly large in volume, and there has been a demand for higher communication speeds. . For this reason, an attempt has been made to use a semiconductor laser element capable of high-speed communication as compared with an LED as a light source for optical communication. However, the semiconductor laser light source has a small spot diameter of light emitted into space and has high coherency. Therefore, if it is used as it is, there is a great risk to eyes. Therefore, it is necessary to reduce the coherency by diffusing light and widen the spot diameter. Patent Document 1 has been proposed as a technique relating to such a light source device.

JP 2005-209797 A

  Such a light-emitting device is shown in FIG. A circular counterbore hole 502 is formed in the substrate 501, and a semiconductor laser element 504 is provided at the bottom 503 of the counterbore hole 502. The inclined surface 505 of the counterbore hole 502 forms an angle of about 45 ° with the bottom 503. The counterbore hole 502 and the semiconductor laser element 504 are covered with a resin 506 including a diffusion material 509. A lens 507 is disposed above the resin 506 to form the light emitting device 500.

  The light 508 emitted from the semiconductor laser element 504 travels while being diffused inside the resin 506 by the diffusing material 509, is reflected by the inclined surface 505 of the counterbore hole 502, and travels toward the upper lens 507. The light 508 is spread by the lens 507 and emitted into the space as light that is safe for the eyes. The lens 507 is designed so that the light extraction efficiency into the space is maximized, and the lens center is designed and mounted so as to be aligned with the center of the optical axis.

  However, when the semiconductor laser element is mounted on the bottom of the counterbored hole, “shift” in the direction parallel to and perpendicular to the laser beam emission direction, or the semiconductor laser element rotates in a plane parallel to the bottom surface of the counterbored hole. A “deviation” sometimes occurred (see the dotted line in FIG. 5). When such “deviation” occurs, the central axis of the light reflected from the side surface does not pass through the center of the lens 507, and as a result, the light extraction efficiency into the space is reduced. Due to this decrease in efficiency, it may not be possible to obtain a light output for securing a communicable distance as an optical transmission module incorporating a light emitting device, which deteriorates the yield as an optical transmission module and increases the manufacturing cost. I was invited.

  SUMMARY An advantage of some aspects of the invention is to provide a light-emitting device and an optical transmission module that can improve the yield and reduce the manufacturing cost.

According to the present invention for solving the above-described problem, in the light emitting device in which the semiconductor laser element is provided at the bottom of the counterbore of the substrate having the counterbore , the shape of the bottom is rectangular, and the semiconductor laser element a resonator direction length, the length of the bottom rather equal, the counterbore is continuous in the length direction of the bottom, further comprising a pair of inclined surfaces facing each, the semiconductor laser element, the The resonator direction and the length direction of the bottom portion are arranged to coincide with each other.

With this arrangement, since the semiconductor and the resonator direction length of the laser device, the length L1 of the bottom of the countersunk hole is rather equal, and the shape of the bottom of the countersunk hole is rectangular, when mounting the semiconductor laser element, Since the position of the semiconductor laser element is regulated so as to match the length of the bottom part of the counterbore hole having the same length as the cavity direction of the semiconductor laser element, mounting displacement does not occur. Therefore, the yield can be increased.
In addition, rotational deviation of the semiconductor laser element can be prevented.

  In the above configuration, the width L2 of the bottom portion of the counterbore hole may be greater than or equal to the semiconductor laser element width and less than or equal to the cavity length.

  If the width L2 of the bottom of the counterbore is less than the width of the semiconductor laser element, the semiconductor laser element cannot be mounted on the bottom of the counterbore. On the other hand, if the width L2 at the bottom of the counterbore is greater than or equal to the resonator length, the semiconductor laser element may be mounted sideways (perpendicular to the light extraction direction). Therefore, it is preferable to regulate as described above. Here, when the width L2 of the bottom portion of the counterbore hole changes, it is necessary to satisfy this relationship at all positions.

  In the above configuration, the angle formed by the inclined surface of the counterbore hole facing the light emitting surface of the semiconductor laser element and the substrate may be 45 °.

When an inclined surface with an inclination angle of 45 ° is employed, excellent light extraction efficiency can be obtained .

  In the above configuration, the semiconductor laser element and the counterbored hole may be covered with a resin containing a diffusing material.

  With this configuration, since the laser light is scattered by the diffusing material, an eye-safe light-emitting device with low coherency and a wide spot diameter can be realized.

  When an optical transmission module is manufactured using any of the light-emitting devices described above, an optical transmission module with high light extraction efficiency without misalignment of the semiconductor can be realized.

  In the light emitting device of the present invention, the positional deviation of the semiconductor laser element mounted in the counterbore hole on the substrate is induced and corrected by the shape of the bottom part of the counterbore hole, so that the positional deviation during mounting does not occur. Therefore, according to the present invention, the laser light emitted in the direction perpendicular to the substrate after being reflected by the inclined surface of the counterbore hole can be taken out with good reproducibility, so that the light emitting device excellent in directivity and safety Can be provided with good yield. Also, by using this, it is possible to realize a low-cost and highly reliable optical transmission module.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic perspective view of the light emitting device according to the first embodiment of the present invention, and FIG. 2 is a schematic side view thereof.

  In the light emitting device 100, a counterbore hole 102 having a rectangular bottom is formed in a circuit board 101, and a semiconductor laser element 104 as a light source is mounted on the bottom 103 of the counterbore 102. The counterbore hole 102 and the semiconductor laser element 104 are covered with a silicon resin 105 containing a diffusing material (not shown), and a lens 106 is provided above the silicon resin 105.

  The circuit board 101 is an example of a board, and the silicon resin 105 is an example of a resin, and other than these may be used.

Hereinafter, a method for manufacturing the light-emitting device 100 will be described.
First, a counterbore hole 102 in which the shape of the bottom portion 103 is rectangular and the bottom portion and the inclined surface 107 form 45 ° is formed on the circuit board 101. Next, a small amount of silver paste (not shown) is applied on the bottom portion 103, the semiconductor laser element 104 is mounted thereon, and baked using an oven, thereby fixing the semiconductor laser element to the bottom portion of the counterbored hole. .

  The counterbore 102 has a depth that does not hinder the emission of laser light from the semiconductor laser element 104. Further, the roughness of the surface of the counterbore hole 102 is adjusted so as not to adversely affect the radiation angle of the laser beam. In the light emitting device of this embodiment, the depth of the counterbore hole 102 is set to about 300 μm, for example, and the length of the bottom 103 (L1 in FIGS. 1 and 2) is the resonance of the semiconductor laser element 104. The length is set equal to the length in the vessel direction (for example, about 500 μm). The width L2 of the bottom 103 is set to be shorter than the length in the resonator direction and equal to or larger than the semiconductor laser element width.

  Further, an end face protective film (not shown) is applied to the resonator mirror (surface perpendicular to the direction in which the laser beam 110 is emitted from the semiconductor laser device 104) of the semiconductor laser device 104. An end face protective film having a low reflectance is mainly provided on the surface from which the laser light 110 is extracted, and an end face protective film having a high reflectance is provided on the opposite surface, so that the laser light 110 can be efficiently extracted from one surface. It is made as follows.

  Subsequently, a wire 108 for injecting current is bonded to the semiconductor laser element 104, and the entire counterbore hole 102 including the semiconductor laser element 104 is filled with a liquid silicon resin 105 mixed with a diffusion material 109 that diffuses light. Add a suitable amount. As a result, the silicon resin 105 stays in the counterbore hole 102 due to surface tension, and covers the semiconductor laser element 104 and the counterbore hole 102.

  Then, it is heated at 80 ° C. for about 5 minutes to be cured until the silicon resin 105 becomes jelly. Thereafter, the silicon resin 105 is covered with a transparent epoxy resin mold including a lens 106 for controlling the laser beam radiation angle. The lens 106 is integrally formed with the epoxy mold above the semiconductor laser element 104.

  The semiconductor laser element 104 is fixed to a laser driving negative electrode portion (not shown) on the circuit board 101. The other end of the wire 108 bonded to the semiconductor laser element 104 is connected to a laser driving positive electrode portion (not shown) on the circuit board 101. With this electrical wiring, a current is injected into the semiconductor laser element 104, and the light emitting device 100 capable of emitting the laser light 110 is completed.

  According to the light emitting device having the above configuration, when the semiconductor laser element 104 is mounted on the bottom portion of the counterbore hole 102, the inclined surface 107 causes the semiconductor laser element 104 to be guided to the inclined surface 107 by the inclined surface 107. Get closer to. Further, the length L1 of the bottom 103 is the same as the resonator length of the semiconductor laser element 104, and the position of the semiconductor laser element 104 is regulated by this length, so the resonator direction of the semiconductor laser element 104 is the light extraction direction. Will not be mounted.

  Further, since the shape of the bottom portion of the counterbore hole 102 is rectangular, there is no room for the semiconductor laser element to rotate within the counterbore hole. For this reason, even when baking is performed to fix the semiconductor laser element 104, the semiconductor laser element 104 is not rotationally displaced. Therefore, according to the light emitting device having this structure, the laser light emitted from the semiconductor laser element 104 and reflected by the inclined surface 107 and then emitted in a direction perpendicular to the circuit board 101 can be extracted with good reproducibility. . Therefore, a light-emitting device that can improve the yield and reduce the manufacturing cost can be obtained.

  Further, according to the light emitting device of the first embodiment, since the laser light 110 emitted from the semiconductor laser element is diffused by the diffusing material 109, the light becomes safe even if it enters the eye. Therefore, it is not necessary to design the margin of the lens 106 in consideration of the positional deviation, and the output of the laser beam 110 can be used more effectively. As a result, the light output amount of the light emitting device necessary for performing desired optical transmission, that is, the light output amount of the semiconductor laser element can be lowered, so that power consumption can be reduced and reliability can be improved.

  In the light emitting device of the first embodiment, the lens 106 is circular. However, in consideration of mounting displacement in a direction perpendicular to the resonator length direction of the semiconductor laser element 104, the direction in which the mounting displacement can occur is determined. An elliptical lens having a long axis may be used. Accordingly, it is possible to prevent a decrease in light extraction efficiency due to mounting displacement, and thus a light emitting device that can further improve the yield and reduce the manufacturing cost can be obtained.

  Further, by making the shape of the bottom portion of the counterbore 102 the same as the planar shape of the semiconductor laser element 104, it is possible to prevent a mounting shift in a direction perpendicular to the direction of the resonator length.

  In the light emitting device of the first embodiment, the inclined surface 107 of the counterbore hole 102 forms 45 ° with the circuit board 101 in all directions, but faces the light emitting surface of the semiconductor laser element 104. It is sufficient if the inclined surface forms an angle of 45 ° with the circuit board 101, and the same effect can be obtained if the angle between the inclined surface on the opposite side and the circuit board 101 is less than 90 °. In particular, if the angle is close to 90 °, the area when viewed from above the counterbore can be made smaller, so that the area of the circuit board 101 can be effectively utilized (for example, the degree of freedom in designing other circuits and electrodes is increased). A light-emitting device capable of being obtained).

  Here, if the countersunk hole is circular as in the conventional light emitting device, at least the substrate needs to have a bottom part of the countersunk hole having a diameter equal to or longer than the length of the diagonal line of the planar shape of the semiconductor laser element. Further, since it is necessary to have an inclined surface that forms an angle of 45 ° with the substrate, the entire counterbore hole needs to have a size including the inclined surface. That is, a useless space increases in the counterbore. However, in the light emitting device of the first embodiment, since the planar shape of the counterbore hole is rectangular, the necessary counterbore hole size can be made smaller than that of the conventional light emitting device. This means that a light emitting device can be manufactured with a smaller substrate even if semiconductor laser elements having the same size are used. Therefore, a light-emitting device that can further reduce the manufacturing cost can be obtained, and by using this light-emitting device, an optical transmission module that can be incorporated into a more downsized optical transmission system can be provided.

  Next, a light emitting device according to a modification of the first embodiment is shown in FIGS. FIG. 3A shows a plan view of the light emitting device, and FIG. 3B shows a side view of the light emitting device.

  A feature of the light emitting device 300 of this modification is that there are two waveguides 301 and a semiconductor laser element 304 manufactured so that light can be extracted from two resonator mirrors is used. Further, the reflectances of the end face protective films (not shown) applied to the two resonator mirrors are equal so that the output characteristics of the two laser beams 305 emitted from one waveguide are the same. Designed to be That is, the four laser beams 305 emitted from the semiconductor laser element 304 all have the same output characteristics. In addition, the angle between the inclined surface 307 of the counterbore hole 302 and the bottom surface 303 and the resin / diffusing material disposed above the semiconductor laser element 304 are the same as those of the light emitting device of the first embodiment, and the lens is the position of the light source.・ It is optimally designed according to the number.

More specifically, between the length (L3) of the bottom 303 of the counterbored hole, the distance (D) between the two waveguides, and the height (H) from the bottom 303 of the counterbored hole to the laser beam emitting part,
L3 + H × 2 = D
The semiconductor laser element 304 and the counterbore hole 302 are designed so that the following relational expression holds.

  When satisfying the above relationship, the four laser beams 305 that are reflected by the inclined surface 307 and travel upward are arranged so as to be located at the apexes of a square whose side is D when viewed from above. All have the same light output.

  According to the configuration of the light emitting device of this modification, four light emitting points can be provided for one semiconductor laser element, and the light source diameter can be further increased in addition to diffusing light by the diffusing material. . Therefore, a light-emitting device suitable for light transmission over a longer distance can be manufactured.

  Further, according to the above configuration, the four laser beams having the same output are always extracted at the top while being located at the apex of the square, so that the symmetry is excellent. Therefore, the lens design is simple and light can be extracted efficiently, so that a low-cost light-emitting device can be manufactured.

  In the first embodiment, the wavelength of the semiconductor laser element is 890 nm. However, other wavelength bands such as a 780 nm band, a 650 nm band, a 400 nm band, a 1.3 μm band, a 1.55 μm band, and the like may be used.

(Second Embodiment)
FIG. 4 is a schematic cross-sectional view of the optical transmission module 200 of the optical transmission system according to the second embodiment of the present invention. As will be described in detail later, by providing the same optical transmission module 200 on both sides (for example, a terminal and a server) that perform communication, an optical transmission system that transmits and receives optical signals between the two optical transmission modules 200 is configured. The

  As shown in FIG. 4, the optical transmission module 200 includes the InGaAs semiconductor laser element 201 having the oscillation wavelength of 890 nm described in the first embodiment as an example of a light source in the light emitting device 202, and Si (silicon). A light receiving device 204 having a light receiving element 203 which is a pin photodiode, and the light emitting device 202 and the light receiving device 204 are formed on one substrate.

  The semiconductor laser element 201 is mounted on the circuit board 206. On the surface of the circuit board 206, a pattern (not shown) of both positive and negative electrodes for driving the semiconductor laser element and a counterbore hole 205 for mounting the semiconductor laser element 201 are formed. The light receiving element 203 is also mounted on the circuit board 206 and an electric signal is taken out by the wire 207. Further, a laser driving / reception signal processing IC (integrated circuit) 208 is mounted on the circuit board 206.

  The portion of the light emitting device 202 is manufactured in the same manner as in the first embodiment. The silicon resin 210 including the diffusing material 209 is covered with a transparent epoxy resin mold 211. In the epoxy resin mold 211, a lens portion 212 for controlling the radiation angle of the laser light and a lens portion 213 for condensing the signal light are integrally formed as a mold lens. The lens part 212 is located above the semiconductor laser element 201, while the lens part 213 is located above the light receiving element 203.

  As described above, in this optical transmission system, it is assumed that the other party holds another optical transmission module and transmits and receives an optical signal. Therefore, the optical signal taken out from the semiconductor laser element 201 is received by the light receiving element 203 of the counterpart optical transmission module. In addition, an optical signal having information from the semiconductor laser element 201 of the counterpart optical transmission module is received by the light receiving element 203.

  A negative electrode portion (not shown) of the semiconductor laser element 201 is fixed to a laser driving negative electrode portion (not shown) on the circuit board 206 by silver paste. In addition, a positive electrode portion (not shown) of the semiconductor laser element 201 is electrically connected to a laser driving positive electrode portion (not shown) on the circuit board 206 via a wire 214. By forming this wiring, the optical transmission module 200 that can obtain the laser beam 215 by oscillation is completed.

  The light transmission module 200 uses the light emitting device 202 that has the above-described yield and can be manufactured at low cost, and has improved reliability. Reliability can also be improved.

  Note that the light-emitting device of the present invention is not limited to the above-described embodiment. For example, various types of light-emitting devices such as the oscillation wavelength of the semiconductor laser element and the polarity of the electrodes in the light-emitting device can be used without departing from the spirit of the present invention. Of course, changes can be made.

  As described above, according to the present invention, a light emitting device with high light extraction efficiency can be obtained with high yield. This light emitting device is useful as an optical transmission module, for example, and has great industrial significance.

FIG. 1 is a schematic perspective view of a light emitting device according to a first embodiment of the present invention. FIG. 2 is a schematic side view of the light emitting device of the first embodiment. FIG. 3 is a schematic view showing a modification of the light emitting device of the first embodiment. FIG. 4 is a schematic cross-sectional view of an optical transmission module of an optical transmission system according to the second embodiment of the present invention. FIG. 5 is a schematic perspective view of a conventional light emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Light-emitting device 101 Circuit board 102 Counterbore 103 Bottom 104 Semiconductor laser element 105 Silicon resin 106 Lens 107 Inclined surface 108 Wire 109 Diffusing material 110 Laser light 200 Light transmission module 201 Semiconductor laser element 202 Light-emitting device 203 Light-receiving element 204 Light-receiving device 205 Counterbore Hole 206 Circuit board 207 Wire 208 Laser driving / received signal processing IC (integrated circuit)
209 Diffuser 210 Silicon resin 211 Epoxy resin mold 212 Lens portion 213 Lens portion 214 Wire 215 Laser light 300 Light emitting device 301 Waveguide 302 Counterbore hole 303 Bottom portion 304 Semiconductor laser element 305 Laser light 307 Inclined surface 500 Light emitting device 501 Substrate 502 Counterbore hole 503 Bottom 504 Semiconductor laser element 505 Inclined surface 506 Resin 507 Lens 508 Light 509 Diffuser

Claims (5)

In the light emitting device in which the semiconductor laser element is provided at the bottom of the counterbored hole of the substrate in which the counterbored hole is formed,
The shape of the bottom is rectangular;
The cavity length of the semiconductor laser element is equal to the length of the bottom,
The counterbore hole further includes a pair of opposed inclined surfaces that are continuous in the length direction of the bottom portion,
The semiconductor laser element is arranged so that the resonator direction and the length direction of the bottom coincide with each other.
A light emitting device characterized by that. The light-emitting device according to claim 1.
The width of the bottom is not less than the semiconductor laser element width and not more than the length in the resonator direction.
A light emitting device characterized by that. The light-emitting device according to claim 1 or 2,
The angle formed between the inclined surface of the counterbore hole facing the light emitting surface of the semiconductor laser element and the substrate is 45 °.
A light emitting device characterized by that. The light emitting device according to any one of claims 1 to 3,
The semiconductor laser element and the counterbore hole are covered with a resin containing a diffusion material,
A light emitting device characterized by that. The optical transmission module using the light emitting device according to any one of claims 1 to 4.