JPS63155009A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To finely adjust optical coupling by injecting carrier to an input end and/or an output end of an optical waveguide. CONSTITUTION:After the input end part or the output end part of an optical waveguide 1 made from a semiconductor is formed into a lens shape or a diffraction grating shape to improve coupling between an external optical element and an optical waveguide 1, the refractive index of a lens 9 or a diffraction grating area 8 is changed by injection of carrier. Since the refractive index of the semiconductor is changed about 10% by injection of carrier, the shape of an optical part is properly selected to vary the focal length of an optical system. Thus, the coupling efficiency is adjusted without moving an optical integrated circuit 7 and an optical element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical integrated circuit suitable for single-source communication or optical information processing.

[Conventional technology]

Conventional coupling between an optical integrated circuit and an optical fiber, a light source, and a photoreceiver can be achieved by 1.
Coupling is performed using a lens or the like, and once the two are fixed, it is difficult to optimize coupling by readjustment. This means, for example, W, A,
Report by 5tallards (integrated
Qptics, pp. 164-168), the input end of a waveguide in an optical integrated circuit is a passive optical waveguide, which is electrically or electrically connected.

This is due to the fact that it is not possible to optically change the waveguide characteristics to oT& from the outside.

[Problem that the invention seeks to solve]

The above conventional technology changes the optical characteristics of the waveguide when coupling light, that is, when making light enter the waveguide from the outside, or when making light emitted from the waveguide enter an external optical component. Therefore, systems in which the relative positions between elements cannot be adjusted on a case-by-case basis have to be used with reduced coupling characteristics due to changes in temperature or optical systems that are misaligned during assembly of the elements.

An object of the present invention is to provide a system that allows fine adjustment of the optical integrated circuit and external optical system after assembly, and to provide an optical integrated circuit that is not affected by temperature changes, mechanical deviations, etc. It is.

[Means to resolve the issue]

The above object can be achieved by externally controlling the optical characteristics of the input and output ends of the optical integrated circuit.

That is, the input end or the output end of the optical waveguide made of semiconductor is made into a lens shape or a diffraction grating shape to improve the coupling between the external optical element and the optical waveguide.
The refractive index of the lens or diffraction grating region is changed by injection of carriers.

Due to the injection of carriers, the refractive index of the semiconductor changes.

Since the focal length can vary by about 10%, by appropriately selecting the shape of the optical components, the focal length of the optical system can be varied by 1lliT.

[Effect]

Such a function corresponds to changing the position of the optical system by ±10 degrees, and is sufficient as a position fine adjustment mechanism after one assembly.

〔Example〕

Examples will now be described.

Embodiment 1 FIG. 1 is a top view conceptually showing how a semiconductor laser 4 and an optical integrated circuit 5 are coupled. In the figure, 1 is InUaASP optical waveguide, 2 is InG
aAsPj! il- shows the embedded 1nP cladding. The optical waveguide also has In in the thickness direction of the crystal (perpendicular to the plane of the paper).
It is embedded in P. The input end of the optical integrated circuit has a radius of 20
It is etched in the shape of a μm arc. Furthermore, in the shaded area indicated by 3, p-1nP and n-, Inp face each other with undoped In()aAsP in between, and p, Zn
Electrodes are attached via diffusion, and the structure allows for current to be press-fitted. This structure is shown in FIG. 3 as a cross-sectional view taken along line AA' in FIG. Twelve n-InPll and 111GaASP optical waveguide layers each having a thickness of 17 zm are grown on the n-InP substrate 10 by the MOCvD method. The layer 12 is then etched to a width of 2 μm and filled with undoped InP.

, Diffusion mask 1 with holes in the shape shown in J 1tA3
After creating P0 region 15, diffuse Zn to the vicinity of P0 region 12.
shall be. p-side polarization 16 and n011] electrode 17 is formed,
pn to both! By flowing a current in the direction of the bias bias, the carrier concentration in the region 30 is set to 3×102°/cm.
3, and the refractive index of the optical waveguide below 3 can be decreased by 10%.

In this case, this corresponds to changing the distance between the laser and the optical waveguide by about 20 degrees.

We investigated the coupling efficiency of the assembled light emitting device and optical integrated circuit module by changing the refractive index of the incident part. Out of the 20 modules measured, an improvement in coupling efficiency of up to 15 modules was observed.

Embodiment 2 An optical integrated circuit shown at 7 in FIG. 2 is different from the optical integrated circuit shown in Embodiment 1 only in the shape of the input end. The input end has a radius of 20
It is a depression in the shape of a μm arc.

The light from the semiconductor laser 4 is focused by a lens 9 and guided to the optical waveguide 1 in 7.
It can be adjusted by changing the refractive index of

Embodiment 3 Optimal coupling can be automatically performed by applying appropriate feedback to the device that changes the refractive index of the incident portion. In FIG. 4, 18 is a GaAS optical waveguide, 19 is a semiconductor laser, 20 is a coupling lens,
21 is a carrier injection region, 22 is an optical coupler for optical monitoring, 23 is a light receiver, and 24 is an amplifier.

The partial structure of 21 is similar to that in FIG.

10 is n-GaAS substrate, 11 is n-GaAtAs, 1
The difference is that 2 is G a A S and 13 is daAtAs.

Feedback If you do not spend money, ± for one machine stock motility
Oscillations in the coupling efficiency of 8% were observed, but by applying feedback, it was possible to stabilize the efficiency within a range of ±0.1%.

As described above using the embodiments, by using the present invention, the coupling efficiency can be adjusted without moving the optical product circuit and the optical system.

That is, readjustment is possible even if one assembly is not performed optimally or if a positional shift occurs during use. More feedback mechanism? By providing this, the coupling efficiency can be kept constant even if the coupling efficiency changes due to mechanical vibration or temperature change.

These advantages are even greater when considering the loss due to absorption of free carriers.

[Brief explanation of the drawing]

1, 2, and 4 are top views showing a coupling state between a light source and a light source circuit having a refractive index 0T variant according to the present invention, and FIG. 3 is a refractive index FIG. 3 is a cross-sectional view showing the structure of the oJ bend. 1.12.18... Optical waveguide, 3, 8.21... Variable refractive index region, 4.19... Light source, 22... Coupler for optical monitor, 23... Light receiver, 24...
amplifier.

Claims (1)

[Claims] 1. In a system optically coupled to an optical waveguide A in an optical integrated circuit and an internal AND/OR external optical waveguide AND/OR optical element, the input end of the optical waveguide A is AND/OR. /O
An optical integrated circuit characterized in that it is possible to change the refractive index and adjust the optical coupling state by injecting carriers into the R output terminal. 2. The optical integrated circuit according to claim 1, wherein the input end AND/OR output end of the optical waveguide A has a function of bending an optical path, such as a lens AND/OR diffraction grating. . 3. The amount of the carrier to be press-fitted is determined by monitoring the amount of light in the optical waveguide A or by feeding back the output of a light receiver coupled to A. The optical integrated circuit according to item 2.