SEMICONDUCTOR LIGHT-EMITTING DEVICE

Abstract: A semiconductor light-emitting device which provides optically undistorted light includes a semiconductor light-emitting element (1) and at least one optical element (8). The light emitting-element (1) and the optical element (8) are sealed and held in a resin (5) which is transparent to light emitted from the light-emitting element in such a predetermined positional relationship with each other that light emitted from the light-emitting element travels through the optical element. The entire optical path (6a) from the light-emitting element to the light entrance portion (8a) of the optical element (8) extends within the resin (5), with the light exit portion (8b) of the optical element (8) being located outside of the resin (5).

Description: This invention relates to a semiconductor light-emitting device which can be used in a light pickup of an optical disc apparatus, or as a module in an optical communications system, or the like, as ontlined in the preamble of claim 1. Generally, a conventional semiconductor light-emitting device comprises a semiconductor light-emitting element mounted on a heat sink block which, in turn, is mounted on a stem. The semiconductor light-emitting element, the heat sink block and the stem are covered by a hollow envelope joined to the stem. Light goes out through a glass window provided in the hollow envelope. With this structure, the light-emitting element can be operated in a hermetically sealed, stable environment. In view of stability against environment, easy production, and reduced manufacturing cost of such semiconductor light-emitting devices, resin-molding is considered to be more advantageous. For example, as shown in Figure 1, a semiconductor light-emitting element 1 is mounted on a base 4 with an Si submount 2 and a heat sink block 3 interposed therebetween, and the element 1, the submount 2 and the heat sink block 3 are sealed in a transparent resin on the base 4. Light 6 emitted from the semiconductor light-emitting element 1 emerges through the transparent resin 5. The emitted light 6 from the semiconductor light-emitting element 1 of the semiconductor light-emitting device shown in Figure 1 is usually made to pass through one or more of optical elements, such as a beam splitter, a lens, an optical fiber, a glass plate and the like. The emitted light 6 must have an optically undistorted light intensity distribution so that coupling of light to an optical system is not adversely affected. If the light intensity distribution is distorted, it is difficult to obtain for example, a parallel light beam. The emitted light 6 emerges from the device through a surface portion 7 of the transparent resin, and, therefore, the flatness of the surface portion 7 which interfaces with exterior is critical. If the portion 7 does not have an optically desirable surface state, the light intensity distribution of the emitted light 6 is distorted and, therefore, undesired optical coupling with a succeeding optical system may result. In order to provide an optically desirable surface for the portion 7, the portion 7 could be finished by, for example, polishing. However, it is difficult to provide such working as to give flatness of the same degree as those of optical elements to the surface portion 7, and the productivity of such finishing is low. Furthermore, since ordinary resins are easily damaged and poor in etch-resistance, a surface of such resins is not suitable for use as a light emerging surface. From Electronic Design Vol. 30, No. 10, May 1982, pages 35 - 36, and Wireless World, No. 1581, June 1984, pages 27-30, as well as from GB-A-2046472, it is known to couple an optical fiber to a semiconducter light-emitting device by enclosing one end of said fiber and the said light-emitting device by a transparent resin. According to the present invention, a semiconductor light-emitting device as outlined in claim 1 is provided. A semiconductor light-emitting device according to the present invention includes a semiconductor light-emitting element and a beam splitter or a glass plate disposed in such a predetermined position that light emitted by the semiconductor light-emitting element travels through said elements. The light-emitting element and part of said optical element are sealed in a transparent resin member comprising a resin which is transparent to the light emitted by the semiconductor light-emitting element, in such a manner that the entire optical path extruding between the semiconductor light-emitting element and the light entrance portion of said optical element is positioned within the resin member. The light exit portion of said optical element from which the light emitted by the semiconductor light-emitting element exits the device is positioned outside of the resin member. According to additional feature of the present invention, at least one additional optical element can be disposed in the optical path between the semiconductor light-emitting element and the light entrance portion of the cited optical element. Since the optical path extending between the semiconductor light-emitting element and the optical element is within the resin, output light from the semiconductor light-emitting device does not pass through an interface between the resin and the outer space surrounding the resin, the intensity distribution of the emitted light is not disturbed and, therefore, undistorted light output can be provided from the exit portion of the optical element positioned outside the resin member. The resin member isolates the semiconductor light-emitting element from the external atmosphere and also secures the light-emitting element and the optical element in a predetermined positional relationship. Figure 1 is a perspective view schematically illustrating the structure of a conventional semiconductor light-emitting device as explained in detail above; Figure 2 is a cross-sectional side view schematically illustrating the structure of a semiconductor light-emitting device according to an embodiment of the present invention; Figure 2 illustrates a semiconductor light-emitting device according to a prefered embodiment of the present invention. The semiconductor light-emitting device comprises a semiconductor light-emitting element 1 fixedly mounted on a base 4 and emitting light 6 from its light-emitting region 1a, and a beam splitter 8 also fixed to the base 4. A transparent resin 5 covers the entirety of the light-emitting element 1 on the base 4, and also a substantial portion of the beam splitter 8, including a light incident portion of a surface 8a thereof, while leaving a light exit surface 8b exposed, whereby the entirety of the optical path 6a for light from the semiconductor light-emitting element 1 extending between the element 1 and the beam splitter 8 is located in the resin 5. The resin 5 is transparent to light emitted by the semiconductor light-emitting element 1. A cyclic aliphatic epoxy resin, for example, may be used. Another resin, such as diglycidyl ester, may also be usable. The transparent resin 5 adheres to and fills the space between the light-emitting region 1a of the light-emitting element 1 and the light incident surface 8a of the beam splitter 8, leaving no gap between the resin 5 and the region 1a or between the resin and the light entrance portion of the surface 8a. The light 6 emitted by the semiconductor light-emitting element 1 passes through the transparent resin 5, enters into the beam splitter 8 where it is deflected 90°, and emerges from the device from the surface 8b of the beam splitter 8. Since the beam splitter 8 has its light-incident surface 8a well-finished so as to give no distortion to light intensity distribution and, furthermore, it is in intimately contact with the resin, the light 6 emitted from the semiconductor light-emitting element 1 can emerge from the device without being distorted. Optical elements, for example, glass plates, other than the ones used in the described embodiment may be used. The optical elements usable in the present invention are light transmissive. Types, numbers and arrangements of optical elements in the sealing resin are determined in accordance with the purpose of the light-emitting device. With the above-described arrangement of the present invention, the surface of sealing resin need not be provided with any special finishing as is provided for optical elements in order to produce undistorted, stable light output from a semiconductor light-emitting device because light emerges from the device through a well-finished surface of an optical element. Furthermore, because the light-emitting element is sealed in a resin, its stability against environment is improved, and also, the positional relationship between the light-emitting element and the associated optical element(s) can be maintained fixed.

Claims: A semiconductor light-emitting device comprising: a semiconductor light-emitting element (1); an optical element (8) disposed in a predetermined positional relationship with said light-emitting element (1) such that light (6) emitted from said light-emitting element (1) travels through said optical element (8) and a resin (5) sealing and holding said semiconductor light-emitting element (1) and said optical element (8) in said predetermined positional relationship, said resin being transparent to light (6) emitted from said light-emitting element (1), characterized in that said optical element (8) is a beam splitter or glass plate, the beam entrance surface (8a) of said optical element (8) being in contact with said resin (5), the beam exit surface (8b) of said optical element (8) being not covered by said resin, and the entire optical path for light emitted from said light-emitting element extending from said light-emitting element to the beam enhance surface (8a) of said optical element is located within said resin (5). A semiconductor light-emitting device according to claim 1, characterized in that at least one additional optical element is disposed between the beam exit surface (1a) of said semiconductor light-emitting element (1) and the beam entrance surface (8a) of said optical element (8). A semiconductor light-emitting device according to claim 1 or 2, characterized in that said resin (5) is a cyclic aliphatic epoxy resin. A semiconductor light-emitting device according to claim 1 or 2, characterized in that said resin (5) is diglycidyl ester.

Inventors: HASEGAWA, KAZUYOSHI, ISHII, MITSUO, KUBOTA, MASAYUKI, NAGAI, SEIICHI
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1990
Main classification: H01L33
IPC codes: H01S5, G02B6, H01L33