JPH1152437A - Semiconductor optical device - Google Patents

Abstract

(57) [Problem] To provide a semiconductor optical device having a small and simple structure and having no polarization dependence. SOLUTION: An output waveguide 31 is connected in cascade with interference waveguides for interfering and propagating light propagating from input waveguides 11 to 14.
To 34 are connected in tandem to form the multimode interference type waveguide 1, and the input waveguides 11 to 14 or the output waveguide 31
To 34, at least one of the gain regions 15 is formed by a pn junction having different conductivity types.
18 and 35 to 38, and electrons and holes are injected into this gain region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a semiconductor optical waveguide device, and more specifically, it distributes an optical signal propagated through an input waveguide to one or more specific output waveguides. The present invention relates to an optical multiplexing / branching element for multiplexing and a so-called optical switching element using the same.

[0002]

2. Description of the Related Art Conventionally, signal light propagating through one input waveguide is distributed to a plurality of output waveguides, or a specific light selected arbitrarily from the plurality of waveguides. As a so-called optical switch element that performs an operation of outputting to a waveguide, a device using a reflection type Y branch circuit and a device using a directional coupler circuit are known.

[0003] In these circuits, one input propagating light is divided into two output propagating lights, or two input propagating lights are multiplexed into one output propagating light. The connection relationship between the outputs is basically one-to-two or two-to-one. In any case, in order to obtain a desired optical switching function, a plurality of the above circuits are used, and these circuits are coupled by a waveguide.

For example, in order to configure a 4-input / 4-output optical switch element using a reflection type Y-branch circuit, as shown in FIG. 6, 24 multiplexing / branching circuits 70 are used. For this reason, as the number of input / output waveguides increases, the number of multiplexing / branching circuits 70 also increases, and an extremely advanced technique is required for manufacturing the optical switch element.

Further, the reflection type Y branch circuit and the directional coupler circuit are affected by the propagation characteristics of the propagation state of the propagation light. For example, in the reflection type Y branch circuit, the reflection phenomenon of light has polarization dependence, and in the directional coupler circuit, there is a problem that the propagation constant in the waveguide differs depending on the polarization state. Has also essentially affected the propagation characteristics.

[0006]

As the number of input / output waveguides increases, the number of branch circuits used for the input / output waveguides also increases. One is that the multiplexing / branching circuit used is on a one-to-two or two-to-one basis. In the case of the reflection type Y branch circuit, it is necessary to propagate approximately 800 μm in a straight line in order to realize a stable propagation state in the waveguide after the branch operation is performed. Must be kept at least 800 μm. The same applies to the case where a directional coupler is used. In order to realize a stable propagation state in the directional coupler, the element length of the directional coupler needs to be about 1000 μm. Was. Therefore, an optical switch having a large number of input / output waveguides has an extremely large area, and a high level of technology is required for fabricating the device. For this reason, the production yield of the device is reduced, and it is inevitable that the production cost of the device will inevitably increase.

Further, the waveguide of the input propagating light generally has
A TE wave and a T wave having two fundamental polarizations, ie, a magnetic field component in the traveling direction or an electric field component in the traveling direction.
M-waves are present in a mixed state. Therefore, an optical multiplexing / branching circuit element for distributing and multiplexing such propagation light needs to have characteristics independent of the polarization state. The present invention has been made in view of such a situation, and provides an optical multiplexing / branching circuit element having a small and simple structure and suitable for cost reduction, and a multiplexing / branching circuit that does not depend on the polarization state of propagating light. It is intended to provide behavior.

[0008]

An object of the present invention is to provide a waveguide constituted by a waveguide structure sandwiched on both sides by a material comprising a core layer and a cladding layer having a lower refractive index than the core layer, One or more input waveguides are connected in cascade with interference waveguides for interfering and propagating light propagating from the input waveguides, and one or more output waveguides for outputting propagating light from the interference waveguides By connecting the output waveguides in tandem, a multi-mode interference waveguide coupling / branching element is configured, and a part or all of the input waveguide, or a part or all of the output waveguide, at least one of On the other hand, this is achieved by a coupling / branching element comprising a gain region formed by pn junctions having different conductivity types and a means for injecting electrons and holes into the gain region.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS With the above configuration, it is possible to form a 1: n (n.gtoreq.2) multiplexing / branching circuit by one multimode interference type waveguide multiplexing / branching element. In comparison with the conventional multi-input / multi-output multi-branch circuit element, which is based on the multi-branch circuit of FIG. Further, in this multi-mode interference type waveguide coupling / branching device, the propagation light from the input waveguide is divided into higher order propagation modes such as first, second and third order in addition to the fundamental mode in the interference waveguide region. The principle is used that, at the connection point of a plurality of output waveguides that propagate and connect, these separately propagated higher-order propagation modes interfere and converge. For this reason, the coherence of the higher-order propagation modes separately propagated is determined by the refractive index difference between the higher-order propagation modes. Since the refractive index difference between the higher-order propagation modes has the same value in both the TE polarization and the TM polarization, the propagation characteristic of this element is essentially independent of the polarization state of the propagating light. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The semiconductor optical device of the present invention will be described below based on embodiments. FIG. 1 is a schematic configuration diagram showing one embodiment of the semiconductor optical device of the present invention. 11, 12, 1 in FIG.
Input waveguides 3 and 14 have four input waveguides in this embodiment. Also, reference numeral 1 in FIG. 1 denotes a multi-mode interference waveguide.
Light propagated from 3 and 14 propagates through the multi-mode interference waveguide 1 and is connected to the opposite side of the multi-mode interference waveguide 1 4
The shape of the output waveguides 31, 32, 33, and 34 is determined so that light is collected at each connection point. In this embodiment, the width is 18 μm and the length is 48 μm. Each of the input waveguides 11, 12, 13, 14 has a gain region 1
5, 16, 17, 18 and the output waveguides 31, 3
2, 33, and 34 respectively have gain regions 35, 36,
37 and 38 are provided.

FIG. 2 is a view showing a cross section of the semiconductor optical device of FIG. 1. Reference numeral 10 denotes a gain region core layer of an input / output waveguide.
19 is a cladding layer on the gain region of the input / output waveguide, made of p-type InP, 20 is a cladding layer on the gain region of the input / output waveguide, and n is a GaAsP (band gap wavelength = 1.5 μm). It is composed of a type InP.

The input / output waveguide 61 is a core layer.
62 is an upper clad layer of the input / output waveguide, made of non-doped InP, and 63 is a lower clad layer of the input / output waveguide, made of non-doped InP. Have been. 50 of the multimode interference waveguide is InGaAsP
(Band gap wavelength = 1.3 μm) core layer,
Reference numeral 56 denotes an upper cladding layer, and 57 denotes a lower cladding layer, which is made of non-doped InP. Each input waveguide and output waveguide is provided with a current injection electrode 4 as a means for injecting electrons and holes.

An example of the branching operation of the semiconductor optical device of the present invention will be described. Table 1 shows that the input waveguide 13 has wavelengths of 1..
It is a table | surface which shows the signal light of 54 micrometers and intensity -5dBm input through a fiber, and measured the output light intensity from each output waveguide. A current of 8 mA was injected into the electrodes of the input waveguide 13 and the electrodes of the output waveguides 31, 33, and 34, respectively. Output light amplified from input light was obtained from each of the waveguides into which current was injected, and a value less than the measurement limit was recorded from the output waveguide 32 without current injection.
As described above, one input light could be output from three arbitrarily set output waveguides by using this element.

Further, when the total intensity of the input light is fixed,
As a result of measuring the output light intensity while changing the ratio of the wave component and the TM wave component, the total intensity of the output light is constant for any ratio, and the operation is independent of the polarization state. It was confirmed that was achieved. According to the operation principle of the present element, it is possible to output the propagating light input to an arbitrary input waveguide to an arbitrarily selected output waveguide by injecting a current into the corresponding output waveguide through an electrode. is there. The one-to-four multiplexing / branching circuit is, in the prior art,
Although an element length of 3 mm or more was required, according to the present invention, realization became possible by using a multimode interference type waveguide coupling / branching element of only 50 μm as shown in the above embodiment.

In addition, instead of current injection, a YAG laser (yttrium, aluminum, garnet type crystal structure laser) is irradiated to the gain region of the corresponding waveguide,
It was confirmed that similar results were obtained even when electrons and holes were generated. The multimode interference waveguide described in the present invention can be configured by adjusting its dimensions according to the required number of input waveguides and the required number of output waveguides. It is possible to configure a semiconductor optical device according to the scale, such as 2-input, 2-output, 8-input, 8-output.

FIG. 3 is a schematic structural view showing another embodiment of the semiconductor optical device of the present invention, and FIG. 4 is a view showing a cross section of the semiconductor optical device of FIG. In the present invention, the configuration as shown in FIGS. 3 and 4 is also possible. That is, the multimode interference waveguide region has a pn junction gain structure, a current injection electrode is provided in this region, and the input / output waveguide portion has a core layer and a cladding made of a material having a smaller refractive index than the core layer. When the waveguide structure is sandwiched on both sides by the layer, it is possible to simultaneously distribute one input to a plurality of outputs simply by injecting current into one electrode of the multimode interference waveguide region. As shown in each of the above embodiments, an extremely small 4-input / 4-output optical switch element can be obtained, and since this element can inject current, the transmission characteristics between fibers are degraded. There is no.

[0017]

The semiconductor optical device of the present invention has a small and simple structure as compared with the prior art, so that an optical coupling / branching circuit device suitable for cost reduction can be provided, and the semiconductor optical device depends on the polarization state of propagating light. This has a remarkable effect that a non-combined branching operation can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a semiconductor optical device of the present invention.

FIG. 2 is a diagram showing a cross section of the semiconductor optical device of FIG. 1;

FIG. 3 is a schematic configuration diagram showing another embodiment of the semiconductor optical device of the present invention.

FIG. 4 is a view showing a cross section of the semiconductor optical device of FIG. 3;

FIG. 5 is a table showing measurement results of the output light intensity from each output waveguide with respect to the input light intensity of −5 dBm in the example according to the present invention.

FIG. 6 is a schematic configuration diagram of a conventional 4-input / 4-output optical switch element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Multimode interference waveguide 4 ... Electrode 10 ... Gain area core layer 11, 12, 13, 14 ... Input waveguide 15, 16, 17, 18 ... Gain area 19 ... Gain area upper cladding layer 20 ... Gain area lower cladding Layer 30 Gain region core layer 31, 32, 33, 34 Output waveguide 35, 36, 37, 38 Gain region 39 Gain region upper cladding layer 40 Gain region lower cladding layer 50 Multimode interference waveguide core Layer 56: Multi-mode interference waveguide upper cladding layer 57: Multi-mode interference waveguide lower cladding layer 61: Input / output waveguide core layer 62: Input / output waveguide upper cladding layer 63: Input / output waveguide lower cladding layer 64: Many Mode interference waveguide p-type upper cladding layer 65 ... Multi-mode interference waveguide gain region core layer 66 ... Multi-mode interference waveguide n-type lower cladding layer 70 ... Conventional combining / branching circuit

Claims (4)

[Claims] 1. An at least one input waveguide constituted by a core layer and a waveguide structure sandwiched on both sides by a cladding layer made of a material having a lower refractive index than the core layer. A multiplexing / branching device in which multi-mode interference type waveguide regions are formed by cascade-connecting interference waveguides for transmitting propagating light and cascading at least one output waveguide for outputting propagating light from the interference waveguide. A gain region formed of a pn junction having a different conductivity type from at least one of a part or the whole of the input waveguide and a part or the whole of the output waveguide; A semiconductor optical device comprising means for injecting electrons and holes into a region. 2. An at least one input waveguide constituted by a core layer and a waveguide structure sandwiched on both sides by a cladding layer made of a material having a lower refractive index than the core layer. A multiplexing / branching device in which multi-mode interference type waveguide regions are formed by cascade-connecting interference waveguides for causing propagating light to interfere with each other, and cascading at least one output waveguide for outputting propagating light from the interference waveguide. Wherein at least a part of the multi-mode interference type waveguide region includes a gain region formed of a pn junction having different conductivity types, and means for injecting electrons and holes into the gain region. Characteristic semiconductor optical device. 3. The semiconductor optical device according to claim 1, wherein said means for injecting electrons and holes is current injection means. 4. The apparatus according to claim 1, wherein said means for injecting electrons and holes is light irradiation means.
3. The semiconductor optical device according to item 1.