JPH02226783A - Coupling method of semiconductor laser and optical waveguide, and optical device obtained by same coupling method - Google Patents

Abstract

PURPOSE:To improve coupling efficiency, and stably operate a laser without affection of reflected light by coupling the outputting surface of a semiconductor laser and the end surface of an optical waveguide, via optical adhesive agent. CONSTITUTION:By using transparent optical adhesive agent such as ultraviolet ray curing adhesive agent and epoxy adhesive agent, the following are fixed; the end surface 8 of the side, of an optical waveguide member 5, which corresponds with a semiconductor laser 3, the end surface 9 of a step part of a heat sink 1, and the outputting surface 10 of the semiconductor laser 3. The optical waveguide member 5 is constituted of a substrate 6 and an optical waveguide 7 formed thereon, and the semiconductor laser 3 is constituted of a high reflectivity coating layer 13 and an active layer 14. Since the optical adhesive agent 12 is positioned at the outputting surface 10 side of the laser 3, the reflectivity of the outputting surface 10 side is decreased, and the total reflectivity can be increased by a coating layer 13. The reflectivity of the adhesive agent 12 is smaller than that of the air, so that the laser light effectively makes an incidence into the waveguide 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of coupling a semiconductor laser and an optical waveguide.

(Prior Art) Conventionally, when obtaining an optical device that integrates a semiconductor laser and an optical waveguide that guides its emitted light, for example, each is placed on a heat sink, and the emission surface of the semiconductor laser and the end surface of the optical waveguide are in contact with each other. It is fixed in the state in which it is to be used.

(Problem to be Solved by the Invention) However, with such a configuration, an air layer with a thickness of several μm inevitably remains between the emission surface of the semiconductor laser and the end face of the optical waveguide, resulting in the following problems. there were.

First, since the refractive index of the air layer is large, the diffusion of the emitted light from the semiconductor laser is facilitated by the air layer.On the other hand, the optical waveguide to which it should enter is as small as about 3μ thick, so it enters the optical waveguide. The amount of light transmitted decreased, and the so-called coupling efficiency decreased.

Also, since there is a large difference in refractive index between the air layer and the optical waveguide,
The amount of reflection at the end face of the optical waveguide increased, which caused the above-mentioned reduction in coupling efficiency, and the operation of the semiconductor laser became unstable due to the reflected return light.

Furthermore, since the semiconductor laser and the optical waveguide are each fixed on a heat sink, as the shape of the heat sink contracts and expands due to environmental temperature changes, the positional shift between the output surface of the semiconductor laser and the end surface of the optical waveguide may occur. occurs,
There have been cases where the semiconductor laser does not enter the optical waveguide normally.

The present invention has been made in view of the above-mentioned problems, and is a semiconductor laser and an optical guide that have excellent coupling efficiency, do not have the problem of reflected light from the end face of an optical waveguide in a semiconductor laser, and can be used stably against environmental changes. The purpose is to provide a coupling structure with a wave path.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides the following:
In the invention of 1), the method of coupling the semiconductor laser and the optical waveguide is such that the emission surface of the semiconductor laser and the end face of the optical waveguide are coupled via an optical adhesive.

In the invention of claim (2), the optical device has a structure in which a semiconductor laser and an optical waveguide are coupled by the coupling method of claim (1).

(Function) According to the configuration of the present invention, since the optical adhesive is interposed between the emission surface of the semiconductor laser and the end face of the optical waveguide, the optical adhesive has a lower refractive index than air, so that light from the semiconductor laser is is efficiently incident on the optical waveguide without much promotion of diffusion, and since the difference in refractive index between the optical adhesive and the optical waveguide is not so large, the amount of reflection at the end face of the optical waveguide is reduced. The fixing function ensures that the output surface of the semiconductor laser and the end face of the optical waveguide are always correctly positioned.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of the optical device, and FIG. 2 is a sectional view thereof.

In the figure, reference numeral 1 denotes a heat sink, and one side of the heat sink is formed high in a stepped manner, and a semiconductor laser 3 is provided on the high portion 2, and an optical waveguide member 5 is provided on the low portion 4. The optical waveguide member 5 includes an optical waveguide 7 formed by diffusing a titanium layer on a substrate 6 made of, for example, lithium niobate.

The end surface 8 of the optical waveguide member 5 on the side corresponding to the semiconductor laser 3, the stepped end surface 9 of the heat sink 1, and the output surface IO of the semiconductor laser 3 are transparent when an ultraviolet curable adhesive or an epoxy adhesive is cured. In this way, the emission surface 10 of the semiconductor laser 3 and the end surface 8a of the optical waveguide 7 are bonded via the optical adhesive 12, and in the conventional method, the emission surface 10 of the semiconductor laser 3 and the end surface 8a of the optical waveguide 7 are bonded together. The air layer that existed in □ is removed.

In the semiconductor laser 3, 13 is a high reflectance coating layer and 14 is an active layer, and the coating layer 13 is not one in which the optical adhesive I2 is located on the emission surface 10 side of the semiconductor laser 3 as in the present invention. This is provided to improve the total reflectance of the semiconductor laser 3, since the reflectance on the output surface lO side, which is necessary for resonance operation in the semiconductor laser 3, decreases.

With the above configuration, since the optical adhesive 12 has a smaller refractive index than air, the light from the semiconductor laser 3 is efficiently incident on the optical waveguide 7 without much promotion of diffusion. Furthermore, since the difference in refractive index between the optical adhesive lO and the optical waveguide 7 is not so large, the amount of reflection at the optical waveguide end face 8a is reduced.

Further, due to the fixing function of the optical adhesive 12, the output surface IO of the semiconductor laser 3 and the end surface 8a of the optical waveguide 7 are always positioned so as to correctly face each other.

FIG. 3 shows a second embodiment, in which a heat sink 1 having a protrusion 20 at one corner is used, a semiconductor laser 3 is disposed horizontally on the front side of the heat sink 1, and an optical waveguide member is provided. An optical adhesive 12 is interposed between the end surface of the heat sink 1 on the side corresponding to the semiconductor laser 3, the end surface of the protrusion 20 of the heat sink 1, and the emission surface of the semiconductor laser 3. In this second embodiment, the semiconductor laser 3 is arranged so that the active layer 14 is in the vertical direction, whereas in the first embodiment, the semiconductor laser 3 is arranged so that the active layer 14 is in the horizontal direction. The structure is such that higher coupling efficiency can be obtained.

That is, the emitted light from the semiconductor laser 3 is an elliptical diffused light, and its spread angle is small in the direction coinciding with the surface direction of the active layer 14 (approximately to') and large in the direction orthogonal to it (approximately 35 degrees). Therefore, as shown in this embodiment, by aligning the direction in which the divergence angle is small with the thickness direction of the optical waveguide 7, the light emitted into the substrate and the air can be reduced, and the loss of light can be further reduced. be.

4 and 5 show a third embodiment, in which a part of the optical waveguide 7 and the substrate 6 of the optical waveguide member 5 are cut out integrally, and a semiconductor is placed above the cutout position. A laser 3 is provided, a heat sink 30 is provided on the semiconductor laser 3, and an optical adhesive 12 is interposed between the cutout end surface 8 of the optical waveguide member 5 and the emission surface 10 of the semiconductor laser 3. 31 is an electrode.

Since the optical waveguide member 5 is formed by cutting out the substrate 6 by vertical etching, the dimension a due to the notch can be obtained with high precision.
This makes it possible to easily align the semiconductor laser 3 with respect to the optical waveguide 7 when it is installed in the height direction. Further, since the semiconductor laser 3 and the optical waveguide member 5 are not provided on a heat sink, the semiconductor laser 3 is affected by contraction and expansion corresponding to temperature changes of the heat sink.
The positional relationship between the output surface lO and the optical waveguide 7 is always maintained at the correct position.

Further, as shown in the third embodiment above, the optical waveguide member 5
If the semiconductor laser 3 is provided with a notch, by selecting the direction of the notch in the horizontal direction, the direction of incidence from the semiconductor laser 3 to the optical waveguide 7 can be adjusted appropriately as shown in the plan view of FIG. You will be able to set it.

In FIGS. 3 to 6, parts corresponding to those in FIGS. 1 and 2 are given the same numbers.

(Effects of the Invention) Therefore, according to the present invention, since the optical adhesive is interposed between the emission surface of the semiconductor laser and the end face of the optical waveguide, the optical adhesive has a lower refractive index than air, so that the optical adhesive is free from the semiconductor laser. Light is efficiently incident on the optical waveguide without much promotion of diffusion, thereby improving the coupling efficiency between the semiconductor laser and the optical waveguide.

In addition, since the difference in refractive index between the optical adhesive and the optical waveguide is not that large, the amount of reflection at the end face of the optical waveguide is reduced, which allows the semiconductor laser to operate stably without being affected by reflected light. Ru.

Further, due to the fixing function of the optical adhesive, the emission surface of the semiconductor laser and the end face of the optical waveguide are always correctly positioned, and the incidence from the semiconductor laser to the optical waveguide is always performed stably.

[Brief explanation of the drawing]

1 to 5 relate to embodiments of the present invention, in which FIG. 1 is a perspective view of an optical device, FIG. 2 is a sectional view thereof, FIG. 3 is a perspective view of the second embodiment, and FIG. 4 is a perspective view of the optical device. Perspective view of 3rd embodiment, 5th
The figure is a sectional view of the same, and FIG. 6 is a plan view showing a modification of the third embodiment. 3... Reflection surface, 7... Optical waveguide, 8a... Optical waveguide end surface, 10... Output surface, 12... Optical adhesive.

Claims (2)

[Claims] (1) A method for coupling a semiconductor laser and an optical waveguide, characterized by coupling the emission surface of the semiconductor laser and the end face of the optical waveguide via an optical adhesive. (2) An optical device in which a semiconductor laser and an optical waveguide are coupled by the coupling method according to claim (1).