JPH0459790B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION This invention relates to optical semiconductor devices. Optical semiconductor device means a semiconductor device with a single function of emitting or receiving light, or a semiconductor device with both functions of emitting and receiving light,
This concept includes a light emitting device, a light receiving device, a light emitting device, and a light receiving device.

The light emitted from light-emitting devices such as laser diodes (LDs) and light-emitting diodes (LEDs) is spread and divergent light, so in order to utilize this light, a separate A collimating lens is often provided to convert the light into parallel light. However, if a collimating lens is provided, a device using this light emitting element will inevitably become larger, and optical axis adjustment, focal length adjustment, etc. will be required. Furthermore, the light emitted from the LD has anisotropic spread angle, so it diverges into an elliptical cone shape. Therefore, it is not possible to completely collimate this light with a single normal lens, and in order to obtain sufficiently collimated light, a combination lens or an aspherical lens must be used, which is expensive.

On the other hand, in light receiving elements such as photodiodes (PD) and avalanche photodiodes (APD), it has conventionally been necessary to provide an external lens in order to efficiently focus incident light onto the light receiving surface.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems by providing a new type of compact optical system near an optical semiconductor element chip.

This invention is of a type in which an optical semiconductor chip is mounted using a cap with a window, in which a diffraction type micro Fresnel lens is placed in the above-mentioned window opened at a light passing position on the surface where the unevenness is formed. It is characterized by being provided with the inside.

When the optical semiconductor chip is a light emitting element chip,
It is preferable that the light emitted from the light emitting element be substantially collimated by the micro Fresnel lens, and when the optical semiconductor chip is a light receiving element chip, the focal point of the micro Fresnel lens should be It is preferable to position it substantially on the light-receiving surface of the light-receiving element.

When the optical semiconductor chip is a light-emitting and light-receiving element chip having both light-emitting and light-receiving functions, the micro Fresnel lens is positioned and shaped appropriately. For example, in a device with a light emitting section in the center and a light receiving section around it, the light emitted from the center becomes parallel light and is output to the outside, and much of the light incident from the outside reaches the surrounding light receiving sections. It is preferable to create a Fresnel lens with two focal points that converge.

Furthermore, if the optical semiconductor chip is an LD and the divergence angle of the emitted light differs depending on the direction, the pattern of the Fresnel lens can be made into an elliptical pattern with a focal length that differs depending on the direction. , it is also possible to obtain almost completely collimated light.

According to this invention, the light emitted from the light-emitting element chip is almost parallelized, resulting in relatively high intensity (high brightness) and good directivity, and the light incident on the light-receiving element chip is directed toward the light-receiving surface. Since the light is focused upward, the light collection efficiency is good and the sensitivity is high.

In addition, since the micro Fresnel lens can be molded in plastic immediately after the light emitting and light receiving element chips, it is highly productive and can be provided at low cost. Because of this, there is no optical axis misalignment, resulting in excellent environmental resistance, and further downsizing and weight reduction can be expected.

Furthermore, according to the present invention, the diffractive micro Fresnel lens is provided in the window opened at the light passing position, with the surface on which the unevenness is formed inside, so that the surface on which the unevenness is formed is is not exposed to the outside. This prevents dust from clogging the grooves formed by the micro-machined concavities and convexities, and prevents the concavities and convexities from being damaged by external forces, ensuring highly efficient lens action at all times.

Since the micro Fresnel lens is a diffractive lens, it has no aberration in principle and can efficiently collimate or focus light.

DESCRIPTION OF THE EMBODIMENTS Referring to FIGS. 1 and 2, a submount or heat sink 3 is provided on a stem or mount 1 having several terminals 2;
An element chip 4 is attached to this heat sink 3. As mentioned above, the element chip 4 includes LD,
Chips such as LED, PD, APD, etc. The element chip 4 is covered with a cap 5. cap 5
is fixed to the mount 1 by can sealing, gluing, welding or other conventional methods. A window 5a is provided at the top (upper surface) of the cap 5, that is, at the position where the light emitted from the element chip 4 passes or the light incident on the element chip 4 passes through, and a window 5a is provided in the window 5a, and a transparent resin micro-film is provided in the window 5a.
A Fresnel lens 6 is attached. This Fresnel lens 6 is fixed at its periphery to the inner peripheral surface of the window 5a by adhesive. The Fresnel lens 6 is a Fresnel lens as shown in FIG.
The lens 6 is arranged so that the finely machined surface on which the concave and convex portions are formed faces the inside of the cap 5. This protects the microfabricated surface from external forces and prevents deterioration of lens characteristics. It is even better to provide a protective glass outside the window 5a of the cap 5.

When the element chip 4 is a light emitting element (LD, LED, etc.), the position and focus of the micro Fresnel lens 6 are determined so that the light emitted from the element 4 is almost collimated by the micro Fresnel lens 6. It will be done. In addition, when the element chip 4 is a light receiving element (PD, APD, etc.), the position, focus, etc. of the micro Fresnel lens 6 are determined so that the incident light is almost focused on the light receiving surface of the element 4. Ru.

In particular, when the element chip 4 is an LD, the spread angle of the emitted light exhibits anisotropy, and as shown in FIG. 3, the divergence angles are different in the X direction and the Y direction. Therefore, the cross section of the emitted light is elliptical. In order to almost completely collimate such emitted light, a Fresnel lens having an elliptical pattern as shown in FIG. 4 is used.

In FIG. 1, it goes without saying that the electrodes of the element chip 4 are wire-bonded to the corresponding terminals 2.

Such a micro Fresnel lens 6 can be integrally molded from transparent resin by injection molding or other methods.

The female mold of the micro Fresnel lens for resin molding can be made in various ways, for example, as follows.

An electron beam resist is applied onto a predetermined substrate, a micro Fresnel lens pattern is drawn on the resist by electron beam lithography, and then this resist is developed. Then, the remaining resist pattern on the substrate is transferred to the substrate by dry etching. This board becomes the female mold (patent application 1986-
3419).

Alternatively, a female mold is formed by electroforming using the above residual film resist pattern as a male mold. In other words, the remaining resist pattern is plated with metal,
Thereafter, by dissolving the remaining film pattern and the substrate with an organic solvent or the like, only the metal-plated parts are left (see Japanese Patent Application No. 61-3420).

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, a partially cutaway perspective view, Fig. 2 is a sectional view of the cap and micro Fresnel lens shown in Fig. 1, and Fig. 3 shows the light emitted from the semiconductor laser. FIG. 4 shows a micro Fresnel lens pattern suitable for collimating light having such a divergence angle. 4... Light emitting or light receiving element chip, 5... Cap, 5a... Window, 6... Micro Fresnel.
lens.

Claims (1)

[Claims] 1. In a type of optical semiconductor chip mounted by a cap with a window, a diffraction type micro Fresnel lens is formed in the above-mentioned window opened at the light passage position, and its concavities and convexities are formed. An optical semiconductor device characterized in that the optical semiconductor device is provided with the side facing inside. 2. The optical semiconductor device according to claim 1, wherein the optical semiconductor chip is a light receiving element chip, and the light emitted from the light emitting element is substantially collimated by the micro Fresnel lens. 3. The optical semiconductor device according to claim 1, wherein the optical semiconductor chip is a light receiving element chip, and the focal point of the micro Fresnel lens is located substantially on the light receiving surface of the light receiving element. 4. The optical semiconductor device according to claim 1, wherein the optical semiconductor chip is a light emitting light receiving element. 5. A patent in which the optical semiconductor chip is a semiconductor laser chip, and the micro Fresnel lens has an elliptical pattern so as to convert light emitted from the semiconductor laser chip and diffused in different directions into parallel light. An optical semiconductor device according to claim 1.