Patent Application
20050147149
This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-433275, filed Dec. 26, 2003, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a semiconductor laser device, and in particular, to a semiconductor laser device comprising a rod lens or cylindrical les that collimates laser light emitted by a semiconductor laser.
2. Description of the Related Art
Laser light emitted by a semiconductor laser (laser diode: hereinafter referred to as an LD), particularly a high-power LD, has a large spread angle in a direction perpendicular to an active layer. Accordingly, a rod lens or a cylindrical lens is placed near a light exit facet of the LD to collimate the light emitted by the LD. The light is thus efficiently coupled to the succeeding optical element.
Jpn. Pat. Appln. KOKAI Publication No. 2000-98190 discloses an example of such a technique. This document describes a technique for using a base on which an LD and rod lenses are mounted and bonding the rod lenses to the respective exit facets of two convex portions provided on the respective sides of the LD to collimate light emitted by the LD. The rod lenses are provided in proximity to the LD and on a side of the LD from which light is emitted. A light exit facet of the LD is parallel to the central axis of the rod lenses. An adhesive is applied to the cylindrical surfaces of opposite ends of each rod lens. The rod lenses are thus bonded to the respective end surfaces of the base which are located on the corresponding sides of the LD.
According to Jpn. Appln. KOKAI Publication No. 2000-98190, if the thickness of the adhesive, which fixes the rod lenses, is changed by a change in ambient temperature, the rod lenses move in the direction of the optical axis of laser light. This changes the distance between each rod lens and the light exit facet of the LD. The change in distance may significantly degrade collimate performance. Further, the light exit facet and the surface to which each rod lens is fixed are located on the same side of the rod lens. Moreover, the gap between the end surface of the base, including the surface to which each rod lens is fixed, and the rod lens is narrow over the length of the rod lens. The gap is located in proximity to the gap between the rod lens and the light exit facet of the LD. Consequently, when the rod lens is fixed using the adhesive, a capillary phenomenon may cause the adhesive to enter the gap between the light exit facet and the rod lens via the fine gap between the end surface of the base and the rod lens. When the adhesive thus infiltrates between the LD and the rod lens to close the light exit facet of the LD, the collimate performance of the rod lens is significantly degraded.
A semiconductor laser device according to the present invention comprises a semiconductor laser, a collimate lens placed opposite a light exit facet of the semiconductor laser, and a base on which the semiconductor laser is mounted, from which sleeve portions projects in a direction in which laser light is emitted, the sleeve portions being formed at respective ends of the base to hold the collimate lens, at least two notches being formed in a side surface of the base which is closer to the collimate lens, and located between the two sleeve portions.
When the collimate lens is fixed to the base, the adhesive is prevented from infiltrating between the LD and the collimate lens, thus enabling the semiconductor laser device to be manufactured with a high yield. It is further possible to suppress a variation in the position of the collimate lens and thus the degradation of collimate performance.
The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
A first embodiment of the preset invention will be described below with reference to the drawings.
A nonconductive insulating block 15 formed of ceramics or the like is mounted on one end of a surface 11a of the base 11 on which the LD 12 is mounted. A terminal 16 is placed on a top surface of the insulating block 15 so as to be connected to an external power source (not shown). An electrode (not shown) provided on a top surface of the LD is connected to the terminal 16 via a wire 17 consisting of gold. The LD 12 is connected to the external power source via the terminal 16. Further, an electrode 12b (see
The LD 12 is thus mounted on the base 11 in a junction down manner. An active layer 12a from which laser light is emitted is located in proximity to the base 11 via the solder layer. A rod lens 14 is placed opposite a light exit facet 12c of the LD 12. The rod lens 14 collimates laser light emitted in a Z direction while spreading in a Y direction. Further, the rod lens 14 is placed in proximity to the active layer 12a of the LD 12 so that the optical axis of the LD 12 passes through the center of the rod lens 14 in the direction of the Y axis.
Sleeve portions 13 are formed at the respective ends of the base 11 in the X direction. The sleeve portions 13 project in the direction in which laser light is emitted (Z direction). The sleeve portions 13 sandwich the rod lens 14 between them via an adhesive 19. The adhesive 19 is, for example, of an ultraviolet curing type. The gap between the rod lens 14 and the base 11 is very small. Accordingly, if the adhesive 19 is applied to a facet 13a of the rod lens 14 which is further from the LD 12, the capillary phenomenon may cause the adhesive, which has not been cured yet, to reach the LD 12. Thus, in the present embodiment, a notch 18 is formed in each of the opposite surfaces of the sleeve portions 13. Accordingly, the adhesive, which otherwise reaches the LD 12, is collected in the notches 18.
The ultraviolet curing adhesive 19 is applied to ends 14a of the rod lens 14 before the rod lens 14 is inserted between the sleeve portions 13. Alternatively, the rod lens 14 may be inserted between the sleeve portions 13 before the ultraviolet curing adhesive 19 is applied to between each of the ends 14a and the corresponding sleeve portion 13. Subsequently, the position of the rod lens 14 is finely adjusted. The adhesive 19 is then irradiated with ultraviolet rays to fix the rod lens 14 to the base 11.
In this embodiment, the cylindrical rod lens is described as an example of a collimate lens. However, the lens provided opposite the light exit facet 12c of the LD is not limited to the cylindrical rod lens. Another collimate lens such as a cylindrical lens 20 shown in
The second embodiment has basically the same configuration as the first embodiment except for the positions of the notches provided to prevent the entry of the adhesive. At least two notches 21 are formed on a side 11b of the base 11 which is closer to the collimate lens, and located between the two sleeve portions. In the present embodiment, the two notches 21 are formed in a ridge 22 formed by the side 11b of the base 11 located between the two sleeve portions 13 and located closer to the rod lens 14, and the surface 11a of the base 11 on which the LD 12 is mounted. Accordingly, as in the case of the first embodiment, the adhesive, which has not been cured yet and which otherwise reaches the LD 12, is collected in the notches 21.
Alternatively, as shown in
In the fourth embodiment, the sleeve portions 13, formed integrally with the base 11 according to the second embodiment, are provided separately from the base 11 as holding members 51. At least two notches 21 are formed in the side 11b of the base 11 located between the holding members 51 and located closer to the rod lens. In the present embodiment, the two notches 21 are formed in the ridge 22, formed by the side 11b of the base 11 which is located closer to the rod lens and the surface 11a of the base 11 on which the LD 12 is mounted. Since the notches for preventing the entry of the adhesive are formed in the base 11, the holding members 51 need not be provided with any notches for preventing the entry of the adhesive.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-433275 | Dec 2003 | JP | national |
