JPS5978589A - Photo semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the coupling efficiency of a semiconductor laser chip output to a glass fiber and thus improve the reproducibility by holding a spherical lens by means of a tapered through hole having the same axis as the center axis of a laser light flux. CONSTITUTION:A stem 2 loaded with the semiconductor laser chip 1 has the tapered through hole 9 in proximity to the chip, and the center axis of the tapered hole 9 is so processed and arranged with accuracy as to be coincident with the optical axis of the laser light passing through the chip 1 and the glass fiber 5. The distance between the laser light radiation surface of the chip 1 and the surface of the spherical lens is adjusted at an appropriate value according to the diameter and the refractive index of the spherical lens. The spherical lens can be easily arranged within the distance by suitably selecting the tapered angle and the diameter of the hole 9.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to the structure of an optical semiconductor device.

[Technical background of the invention and its problems]

In recent years, the technological progress of semiconductor lasers and light emitting diodes as light-emitting elements for optical transmission has been remarkable, and some of them have already reached the stage of practical use. With the advancement of light sources for optical transmission,
Optical transmission systems are also becoming longer-distance and more sophisticated.
This has further spurred improvements in the performance of light-emitting devices. Glass fibers with a core diameter of 50 μm and a cladding diameter of 125 μm are most commonly used as optical transmission glass fibers.

Therefore, it is advantageous in designing a transmission system to incorporate as much light emitted from the light emitting element as possible into the glass fiber f2 with a core diameter of 50 μm (hereinafter referred to as optical coupling to the glass fiber). For this reason, in the development of semiconductor devices as light sources for optical transmission, various efforts have been made to increase optical coupling to glass fibers. Figure 1 shows
This is a conventional example showing optical coupling of a laser diode to a glass fiber. A stem (2) on which a semiconductor laser chip (1) is mounted and a cap (8) disposed to house the semiconductor laser chip (1) are an O cap that is hermetically sealed at a contact surface (4). (8) The laser beam emitted from the built-in semiconductor laser chip (1) is transmitted to the outside (
A glass window (8) is provided for taking out the contents. A spherical lens (6) is disposed between the glass fiber (5) and the semiconductor laser diode consisting of the semiconductor laser chip (1), stem (2), and cap (8) to increase optical coupling. 1. The spherical lens (6) is fixed on the glass window (8) with, for example, transparent silicone resin (gamma). Also, the spherical lens (6) is not fixed on the glass window (8), but on the glass fiber (5). (not shown) In the conventional example, the laser light emitted from the semiconductor laser chip (1) passes through the glass window (8) and is focused by the spherical lens (6). , glass fiber (
5).

In this case, the semiconductor laser chip (1), 2 spherical lenses (6)
and the glass fiber (6) are on the same optical axis (A), and the distances between the semiconductor laser chip (1) and the spherical lens (6) and between the spherical lens and the glass fiber (6) are respectively adjusted appropriately. There must be.

Such conventional examples have the following drawbacks.

First, it is extremely difficult to arrange and fix the spherical lens (6) on the glass window (8) in alignment with the optical axis (A), and the spherical lens (6) is made of only silicone resin (7). Since the spherical lens is fixed at It is necessary to simultaneously adjust the lens (6) and the CF glass fiber (6) in the direction of the binary axis and in a plane perpendicular to it, which makes the adjustment jig and method complicated, resulting in poor reproducibility and the output of the semiconductor laser chip. The coupling efficiency to the glass fiber is 3o±8%.

[Purpose of the invention]

The present invention eliminates these drawbacks of the conventional example and provides an optical semiconductor device with stable optical coupling and excellent reproducibility.

[Summary of the invention]

The present invention provides an optical semiconductor device comprising a semiconductor laser chip and a spherical lens for converging laser light from the semiconductor laser chip and guiding it to an optical fiber. A tapered through hole located in the middle and having the same axis as the central axis of the laser beam! - An optical semiconductor device characterized in that it is held by:

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic cross-sectional view showing an embodiment of the optical semiconductor device of the present invention. The stem (2) on which the semiconductor laser chip (1) is mounted has a tapered through hole (9) close to the semiconductor chip, and the central axis of the tapered hole is located between the semiconductor laser chip (1) and the glass. It is precisely machined and placed so that it coincides with the optical axis (A) of the laser beam tracing the fiber (5).The distance between the laser beam emission surface of the semiconductor laser chip and the spherical lens surface is determined by the diameter of the spherical lens, the refraction For example, in the case of a spherical lens with a diameter of 2 and a refractive index of 1.7, the distance should be adjusted to an appropriate value depending on the index.
6±0. It needs to be adjusted to about IN. According to the present invention, by appropriately selecting the taper angle and hole diameter of the tapered through hole (9), it is possible to easily arrange the two-sphere lens within the above distance.
(Fig. 3) is preferably 20 to 300. Furthermore, according to the structure of the present invention, the tapered surface of the through hole and the surface of the spherical lens are always in contact with each other, so that the center line of the spherical lens may shift from the optical axis (A) due to temperature changes as described in the conventional example. can be prevented. In Figure 2, the cap (8) has a built-in semiconductor laser chip (1) and a spherical lens (6) disposed in the tapered through hole (9), and is connected to the stem (2) and the contact surface (4). Hermetically sealed.

Therefore, light is coupled to the glass fiber (6) by combining the laser light that is focused by the spherical lens (6) and transmitted through the light extraction window (8) with the glass fiber (5) in the optical axis direction and in the direction perpendicular to it. [This can be achieved by adjusting the semiconductor laser tip, spherical lens, and glass fiber at the same time as in the past, the adjustment method and jig are simple, and the reproducibility is good. The invention also increases the coupling efficiency of the semiconductor laser chip output to the glass fiber, making it possible to obtain stable optical output.

[Embodiments of the invention]

Next, the present invention will be explained in detail. A semiconductor laser tip with a wavelength of 13 microns was mounted on a stem made of Kovar using the usual method, and the protrusion was mounted so that the distance between the laser beam emitting surface of the semiconductor chip and the surface of the spherical lens was 06 ± 0.1 m. A tapered through hole with an angle of θ=28.8° was formed, and a spherical lens with a diameter of 2 iu+ and a refractive index of 17 was disposed within the tapered through hole.

By adjusting the light transmitted through the light extraction window of the cap (81) and the glass fiber in the optical axis direction and in the plane perpendicular to it, a coupling efficiency of 40 ± 2% is achieved for the glass fiber with a core diameter of 50 μm NA O and 21. you can get
We were able to obtain extremely good results compared to the conventional coupling efficiency of 30±8%. In addition, this semiconductor laser was
Even after repeated heating to ℃, no fluctuation in optical output due to positional deviation of the spherical lens was observed.

If the lower surface of the spherical lens protrudes further toward the semiconductor laser chip than the lower surface of the tapered through hole as in this embodiment, the laser beam receiving surface becomes wider and efficiency is improved.

〔Effect of the invention〕

The present invention has the following effects.

(1) The coupling efficiency of the semiconductor laser chip output to the glass fiber is high, and the reproducibility is good.

(2) No fluctuation in optical output due to positional shift of the spherical lens due to temperature change is observed.

(8) The optical coupling method and jig are simple, making work more efficient.

As described above, the present invention can provide high optical coupling efficiency and safe optical output. Although the gist of the present invention has been explained using a semiconductor laser as an example, it goes without saying that the present invention is also applicable to edge-emitting light emitting diodes.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a conventional optical coupling, FIG. 2 is a schematic sectional view showing an optical coupling according to the present invention, and FIG. 3 is an enlarged sectional view of a tapered through hole. (1)...Semiconductor laser chip (2)...Stem (5)...Glass fiber (6)...Spherical lens (9)...Thematic through hole

Claims (1)

[Claims] In an optical semiconductor device including a semiconductor laser chip and a spherical lens for focusing laser light from the semiconductor laser chip and guiding it to an optical fiber, the spherical lens includes:
An optical semiconductor device, characterized in that the tapered through hole is located between the semiconductor laser chip and the optical fiber and has the same axis as the central axis of the laser beam.