JPH02199886A - Optical hybrid integrated circuit - Google Patents

Abstract

PURPOSE:To reduce the degree of freedoms of aligning and to facilitate it by forming a diffraction grating in which a period is specified in a semiconductor light source or an optical waveguide, and so adhering the surfaces of the semiconductor light source and the optical waveguide that the propagating directions of both the lights substantially coincide. CONSTITUTION:A diffraction grating 200 is provided on a P-type InGaAsP contact layer 5 in a window 9a formed at the electrode 9 of a semiconductor light source 100, adhered to an optical waveguide, and the part of the light is thereby introduced into the optical waveguide via the diffraction grating. When the equivalent refractive index of the light source 100 is n1 and the equivalent refractive index of the optical waveguide is n2, the period A of the diffraction grating 200 satisfies ALPHA=Nlambda/¦n1+ or -n2¦. In order to adhere the light source 100 to the waveguide, the light source 100 is inverted upside down, so placed on a board 11 that the propagating directions of both the lights coincide, so ally adjusted that the emitting light from the waveguide becomes maximum, and the electrode 9 is adhered to an electrode 13 by heating. Thus, the coupling is performed only by aligning in a plane.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Minute Hand> The present invention relates to an optical hybrid integrated circuit formed by coupling a semiconductor light source and an optical waveguide.

<Prior Art> Conventionally, a semiconductor light source and an optical waveguide have been coupled by a method shown in FIG. That is, light 52 emitted from a semiconductor laser 51 as a semiconductor light source is focused using a lens 53, and is made incident on the end face of an optical waveguide 55 on a substrate 54.

<Problems to be Solved by the Invention> According to the above-described combining method, since the focal length of the lens 53 is constant, the position and angle of each component must be adjusted with high precision, and therefore, a high level of alignment is required. Fixation technology is essential and costs are high.

As described above, the conventional technology for coupling a semiconductor light source and an optical waveguide requires alignment with multiple degrees of freedom and high precision.

SUMMARY OF THE INVENTION In view of these circumstances, it is an object of the present invention to provide an optical hybrid integrated circuit which is inexpensive by reducing the degree of freedom in positioning and facilitating the positioning technique.

Means for Solving the Problems> The optical hybrid integrated circuit according to the present invention that achieves the above objects has the following features:
In an optical hybrid integrated circuit that couples light from a semiconductor light source with a multilayer structure including an active layer to a guiding waveguide formed on a substrate, the optical wavelength is λ, the equipolarization index of the semiconductor light source is n8, and the equipolarization index of the optical waveguide is λ. When the polarization index is n2 and the diffraction order is N, the semiconductor light source is a diffraction grating that is parallel to the traveling direction of light and whose period A approximately satisfies the following relational expression. Alternatively, it is formed inside or on the surface of an optical waveguide, and the surfaces of the semiconductor light source and the optical waveguide are bonded together so that the traveling directions of the light from both are substantially the same, so that the light from the semiconductor light source is guided to the optical waveguide. Features.

Effect> With the above configuration, mode coupling of light between the semiconductor light source and the optical waveguide occurs, and the light from the semiconductor light source is guided to the optical waveguide via the diffraction grating, but the periodic expression of the diffraction grating satisfies the above-mentioned expression. By almost satisfying the condition, the phase matching condition between both modes will be almost satisfied, and coupling with a large coupling coefficient will be realized.

Kujo Example Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a sectional view of an optical hybrid integrated circuit according to an embodiment, and FIGS. 2 and 3 are perspective views showing a semiconductor light source and an optical waveguide formed on a substrate, respectively.

First, the configuration of the semiconductor light source 100 will be explained with reference to FIG. In the figure, l is n-1nP substrate) 2 is n-1n
P cladding layer, 3 is InGaAgP active layer, 4 is p-
1nP cladding layer, 5 a p-InGaAsP contact layer, 6 a p-1nP buried layer, 7 an n-1nP buried layer, 8 and 9 electrodes, and a window 9a formed in the electrode 9.
A diffraction grating 200 is provided on the inner p-1nGaAsP:2 contact 45.

In order to realize such an element, first, n-I n P
After sequentially growing an n-I nP cladding layer 2, an InGaAsP monolayer 3, a p-1nP cladding layer 4, and a p-1nGaAsP contact layer 5 on a substrate 1 by a liquid phase growth method or the like, photoetching is performed. Using a technique, a stripe is formed on each grown film using the sputtered S i 0gl film as a mask, and then a p-1nP buried layer 6 and an n-1nP buried layer N7 are successively grown on the side surfaces of the stripe by a liquid phase growth method or the like. Next, after removing the 5in2 film, an Au-Ge-Ni alloy is placed on the substrate 1 side as an n-type electrode 8, and a p-type electrode is placed on the crystal growth phase side.
An Au-Zn alloy is deposited as a shaped electrode 9. Then, a part of this electrode 8119 is removed by photoetching, and a diffraction grating is formed on the p-1nGaAsP contact layer 5 within the window 9a by etching using photolithography such as two-beam interference method or electron beam exposure method. Form 200. Note that this diffraction grating 200 may be formed in advance, and the electrochaos 9 may be formed so as to partially overlap thereon.

A semiconductor light source having such a structure operates as a semiconductor laser with its end face as a reflector, but by connecting it to an optical waveguide, which will be described later, via the diffraction grating 200, a part of the light is guided to the optical waveguide by the diffraction grating. It will be destroyed. In this example, in order to increase the coupling coefficient with the optical waveguide, I) I
The thickness of the nPn cladding layer 4 is approximately 2.5 mm, which is the thickness of a normal cladding layer.
Compared to the voice, it is about 1 voice thinner.

Next, the configuration of the optical waveguide will be explained with reference to FIG.

In the figure, 11 is a L i N b 03 substrate, 12 is a core of an optical waveguide, 13 is an electrode for connecting the semiconductor light source, the core 12 is formed by thermally diffusing Ti, and the electrode 13 is formed by successive vapor deposition of Cr and Au-Sn alloy.

In order to join the semiconductor light source 100 and the optical waveguide described above, as shown in FIG. After adjusting the axis so that the light emitted from the wave path is maximized, the electric fM9 and the electrode 13 are bonded together by heating. Thereby, the semiconductor light source 100 and the optical waveguide are mode-coupled via the diffraction grating 200, and the semiconductor light source 100 and the optical waveguide are mode-coupled.
A part of the forward wave 14 and the backward wave 15 in 00 are emitted as the forward wave 16 and the backward wave 17 in the optical waveguide.

Here, if the equiambipolar refractive index of the semiconductor light 111100 is n8 and the equiambipolar refractive index of the optical waveguide is n2, then the diffraction grating 2000
The period A almost satisfies the following equation.

Therefore, the phase matching condition between the modes of the semiconductor light source 100 and the optical waveguide is almost satisfied, and coupling with a large coupling coefficient can be realized.

Generally, the transmission vectors of the semiconductor light source and the optical waveguide are respectively β5. Assuming that β, in order for these two waves to combine, the following equation (2) %Formula %(2) K must satisfy the lattice vector, βb = nt 2 x /λ, β, = n 22 r
/λ, to=2yr/λ.

Substituting q=N into equation (2), A=Nλ/ (n - n ) Also, β, = n, 2+r/λ, β, = n 22 x /
λ, =2π/λp Substituting q=N into equation (2) yields A=Nλ/(n+n).

Therefore, the phase matching condition between the modes of the semiconductor light source and the guiding waveguide is almost satisfied, and coupling with a large coupling coefficient is realized.

Note that even if the period A of the diffraction grating 200 deviates somewhat from the condition of equation (1), the coupling coefficient will only become smaller, and the coupling of the two is possible.

Thus, according to the present invention, the in-plane alignment t! This allows coupling of the semiconductor light source and the optical waveguide.

That is, compared to the conventional coupling method which has many degrees of freedom, the present invention has two degrees of freedom, which is significantly smaller, and alignment becomes very simple.

FIG. 4 shows an optical hybrid integrated circuit according to another embodiment.

As shown in the figure, the semiconductor light source 110 of this embodiment is almost the same as the semiconductor circuit 100 of the above embodiment, and similar members are given the same reference numerals and redundant explanations will be omitted. is formed by photoetching or lifting off a portion of the electrode 9. By forming the diffraction grating on a metal such as an electrode in this way, manufacturing costs can be reduced.

On the other hand, the leading waveguide is formed using Corning 7059 on the quartz substrate 18.
Core layer 19 made of glass and cladding layer 20 made of SiO
In order to increase the coupling coefficient with the semiconductor light source 110, the cladding layer 20 is thinned at the portion where the semiconductor light source 110 is bonded.

Further, a high reflection film 21 made of a Ws electric multilayer film, metal, or the like is formed on one end face of the semiconductor light source 110 to substantially eliminate optical loss at this end face. Note that such high reflection films may be provided on both end faces of the semiconductor light source.

Generally, semiconductor light sources are designed to oscillate only in the TE mode due to the effect of the reflective films on both end faces.1 However, when a high reflective film is provided as described above, For example, unnecessary modes such as the 7M mode may be attenuated and removed by loading metal. In the embodiment, the electrode 9 other than the portion where the diffraction grating 210 is formed operates as a TE mode transmission filter.

Furthermore, in this embodiment, the coupling efficiency can be increased by forming a high reflectance film on one end surface 22 of the leading waveguide 210.

The present invention has been described above based on examples, but it goes without saying that T
By similarly coupling a JS laser, DBR laser, DFB laser, etc. and an optical waveguide via a diffraction grating, an optical hybrid integrated circuit can be obtained.

<Effects of the Invention> As explained above, the optical hybrid integrated circuit according to the present invention can achieve a high coupling coefficient with very simple alignment by directly coupling a semiconductor light source and an optical waveguide through a diffraction grating. This has the effect that it is possible to obtain a bond.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical fart synthesis integrated circuit according to an embodiment of the present invention, FIG. 2 is a perspective view of its semiconductor light source, FIG. 3 is a perspective view of an optical waveguide, and FIG. 4 is another embodiment. Light hybrid #S applied to
FIG. 5, which is a cross-sectional view of the integrated circuit, is an explanatory diagram showing a method of coupling a semiconductor light source and an optical waveguide according to the prior art. In the drawing, 100.110 is a semiconductor light source, 200.210 is a diffraction grating, 1 is a B-1nP substrate, 2 is an n-nP cladding layer, 3 is an InGaASP active layer, 4 is a p-1nP cladding layer, 5 is p-[nGaAsP co-tact layer, 6 is p-1n
P buried layer, 7 is n-1nP buried layer, 8.9 is electrode, 11 is substrate, 12 is core of optical waveguide, 13 is electrode, 14 is forward wave in semiconductor light source, 15 is backward wave in semiconductor light source , 16 is a forward wave in the optical waveguide, 17 is a backward wave in the optical waveguide, 18 is a substrate, 19 is a core layer, 20 is a cladding layer, 21 is a high reflection film, and 22 is an end face.

Claims (1)

[Claims] In an optical hybrid integrated circuit that couples light from a semiconductor light source having a multilayer structure including an active layer to an optical waveguide formed on a substrate, the light wavelength is λ, the equivalent refractive index of the semiconductor light source is n_1, and the light guide When the equivalent refractive index of the wave path is n_2 and the diffraction order is N,
A diffraction grating that is parallel to the direction of light propagation and whose period Λ approximately satisfies the following relational expression, Λ=Nλ/|n_1±n_2|, is installed inside the semiconductor light source or optical waveguide or inside the semiconductor light source or optical waveguide. An optical hybrid integration characterized in that the semiconductor light source and the optical waveguide are formed on a surface, and the surfaces of the semiconductor light source and the optical waveguide are joined together so that the traveling directions of the light from both are substantially the same, so that the light from the semiconductor light source is guided to the optical waveguide. circuit.