JPH0750403A - Photomatrix switch - Google Patents

Abstract

PURPOSE:To provide a photomatrix switch outputting after exchanging the propagation path and propagation wavelength of light pulse trains in time series at high extinction ratio and optical cross-talk within wide wavelength range making no loss in opticalsignal at all. CONSTITUTION:This photomatrix switch for switching the propagation path of opticalsignals is composed of n(n=integer exceeding 2) each of photooutputting bistable lasers 131, 132 respectively having at least m(m=integer exceeding 2) each of saturable absorbent regions 151-1, 152-1, 151-2. 151-2 as well as m each of optical inputting wave-guides 121, 122, intersecting m each of respective saturable absorbent regions 151-1, 152-1, 152-2. 152-2 of n each of bistable lasers 131, 132.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical matrix switch for exchanging the propagation paths or wavelengths of a plurality of inputted time-series optical pulse trains, or both of them for output.

[0002]

2. Description of the Related Art FIG. 14 shows an example of a conventional optical matrix switch. An optical waveguide having optical input ports I ₁ , I ₂ and optical output ports O ₁ , O ₂ is formed on the semiconductor substrate 11, and directional couplers 12, 13, 14, 15 are provided in the middle of these optical waveguides. Further, electrodes (not shown) for applying a control voltage V _dc to each of the directional couplers 12 to 15 are provided. More specifically, the light input from the optical input port I ₁ is transmitted to the optical output port O ₁ via the directional couplers 12 and 13,
Further, the light guided to the optical output port O ₂ through the directional couplers 12 and 15 respectively, while the light input from the optical input port I ₂ is transmitted through the directional couplers 14 and 15 to the optical output port O _2. O ₂ and via the directional couplers 14 and 13 to the optical output port O ₁ , respectively. Further, in each of the directional couplers 12 to 15, when the control voltage V _dc is low, the incident light is guided and emitted through the same waveguide, and when the control voltage V _dc is high, the incident light is adjacent to the directional coupler. The light is moved to the waveguide of and is emitted.

FIG. 15 shows an operation timing chart of such an optical matrix switch. That is, in this optical matrix switch, the input optical signal P _in1 input from the optical input port I ₁ is output to the optical output port O ₁ when the control voltage V _dc applied to the directional couplers 12 to 15 is low.
As an output optical signal P _out1 from each directional coupler 1
When the control voltage V _dc applied to 2 to 15 is high, it is output from the optical output port O _{2 as the} optical output signal P _out2 . On the other hand, the input optical signal inputted from the optical input port I ₂ P _in2, an output optical signal P _out1 from the optical output port O ₁ when the control voltage V _dc applied to each directional coupler 12 to 15 is higher Also, each directional coupler 12-1
When the control voltage V _dc applied to 5 is low, it is output as the optical output signal P _out2 from the optical output port O ₂ .

[0004]

However, since the above-mentioned conventional optical matrix switch uses the directional coupler composed of the passive waveguide, the optical loss is unavoidable. Further, the directional coupler has a problem that the extinction ratio and the crosstalk sharply deteriorate when the incident wavelength deviates from the optimum wavelength. Furthermore, the above-mentioned optical matrix switch does not have the function of controlling the wavelength on the output side.

In view of such circumstances, the present invention exchanges the propagation paths and the propagation wavelengths of a plurality of time-series input optical pulse trains without loss of optical signals and with a high extinction ratio and low crosstalk over a wide wavelength range. It is an object of the present invention to provide an optical matrix switch that outputs the light.

[0006]

SUMMARY OF THE INVENTION The present invention for achieving the above object is achieved by n (n is an integer of 2 or more) light outputs each having at least m (m is an integer of 2 or more) saturable absorption regions. Bistable lasers, and m optical input waveguides that intersect the m saturable absorption regions of each of the n bistable lasers.

In the optical matrix switch of the present invention, the bistable laser is a distributed feedback type semiconductor laser and can have a distributed feedback structure.

Further, in the optical matrix switch of the present invention, the bistable laser may be a distributed reflection type semiconductor laser and may have a distributed reflection structure and a phase adjusting region.

Further, in the optical matrix switch of the present invention, the optical input waveguide has a total reflection mirror,
Incident light can be reflected by the total reflection mirror to enter the bistable laser.

Further, in the optical matrix switch of the present invention, the optical input waveguide and the bistable laser may be constituted by a curved waveguide. Further, in the present invention, the optical matrix switches can be connected in multiple stages.

[0011]

A bistable laser having a saturable absorption region is provided only when light is injected into the saturable absorption region by controlling a reverse applied voltage to the saturable absorption region and an injection current into the gain region. Can be set to oscillate. If control is performed so that laser oscillation occurs only when light is injected into one of the saturable absorption regions of a plurality of bistable lasers that intersects each optical input waveguide, When light is input from the optical waveguide, it is output from the bistable laser including any of the saturable absorption regions. By controlling the reverse application voltage to each saturable absorption region in this manner, the output port of the light input from each optical input waveguide can be controlled.

The oscillation wavelength of the bistable laser is set independently of the wavelength of incident light. Therefore, it is possible to control the output port and the output wavelength at the same time. Of course, it is also possible to exchange only the wavelengths.

[0013]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 shows an optical matrix system according to one embodiment.
It is a top view of an switch. As shown in FIG. 1, the semiconductor substrate
Reference numeral 101 denotes an optical input waveguide 121a, 121b, 12
1c (sometimes referred to as 121) and optical input waveguide
122a, 122b, 122c (may be referred to as 122
Is formed, and these optical input waveguides 121a, 12a are formed.
The end of 2a is the optical input port I₁ , I₂ Has become. Well
Further, the semiconductor substrate 101 includes the optical input waveguides 121, 1
First and second distributed feedback bistable ray orthogonal to 22
The first distributed feedback type in which the 131 and 132 are formed
The bistable laser 131 includes gain regions 141a to 141c,
And due to the saturable absorption regions 151-1 and 152-1,
In addition, the second distributed feedback bistable laser has a gain region 14
2a to 142c, and saturable absorption regions 151-2, 1
52-2, respectively. And profit
The ends of the gain regions 141c and 142c are the optical output port O.₁ ，
O ₂ Has become.

FIG. 2 is a sectional view taken along the line AA of FIG. Figure 2
As shown in, the InP (n ⁺ ) substrate 102 is
P (n) clad layer 103, InGaAsP lower guide layer 104, quantum well (hereinafter referred to as MQW) active layer 1
05, InGaAsP upper guide layer 106, InP
(P) The cladding layer 107, the InGaAsP contact layer 108, and the electrode 109 are formed,
A lower surface electrode 110 is formed below the (n ⁺ ) layer 102. In addition, the InGaAsP upper guide layer 106 and I
A distributed feedback diffraction grating 111 is formed between the nP (p) clad layer 107. Further, the electrode 109 includes the gain regions 141a to 141c (142a to 142c) and the saturable absorption regions 151-1 and 152-1 (151-).
2, 152-2) and the electrode separation groove 112 provided between
Are electrically separated by. The electrode separation groove 112 is
It is formed by etching up to the upper part of the InP (p) cladding layer 107, and is ion-implanted so as to have a high resistance. Thereby, each gain region 141a
To 141c (142a to 142c), the current I _L1 is commonly used.
(I _L2 ) is injected and saturable absorption region 151-1 (15
1-2) voltage V _c11 is (V _c12) is applied to the voltage V _c21 (V is the saturable absorption region 152-1 (152-2)
_c22 ) is applied. Instead of the electrode separation groove 112, the active layer 105 may be etched and then filled with high resistance InP to obtain the same electrode separation effect. In addition, the optical input waveguides 121, 1
A low reflection coating 113 is formed on both end faces of 22.

FIG. 3 is a sectional view taken along line BB of FIG. Figure 3
As shown in FIG.
a-121c (122a-122c) and each saturable absorption area 151-1, 151-2 (152-1, 152-2)
Are electrically separated by an electrode separation groove 112 provided between Thereby, each optical input waveguide 121
a, 121b (122a, 122b) have a common current I
_w1 (I _w2 ) is injected. At this time,
Optical input waveguides 121a and 121b (122a and 122)
b) has an optical amplification function. The low-reflection coating 1 is provided on both end faces of the distributed feedback bistable lasers 131 and 132.
13 is formed.

FIG. 4 is a sectional view taken along the line CC of FIG. Figure 4
As shown in FIG. 3, the waveguide region has a high resistance I doped with iron.
It is embedded with nP114, and an insulating film 115 is formed on the high resistance InP114.

Here, a method for manufacturing the optical matrix switch of this embodiment will be briefly described. First, on the InP (n ⁺ ) substrate 102, the InP (n) clad layer 103, InG
aAsP lower guide layer 104, active layer 105 of MQW,
The InGaAsP upper guide layer 106 is formed by MO-VPE (Me
tal Organic Vapor Phase Epitaxy (Epitaxial growth). Next, In
The distributed feedback diffraction grating 1 is formed on the GaAsP upper guide layer 106.
11 is formed by forming a resist pattern of a diffraction grating by EB (Electron Beam) exposure or holographic exposure and etching with saturated bromine water. Then, an In-layer is formed on the distributed feedback diffraction grating 111 by an MO-VPE device.
A P (p) clad layer 107 and an InGaAsP contact layer 108 are grown. Here, ECR (Electron C
A waveguide core is formed by an etching device. Next, the waveguide is filled with high-resistance InP 114 by the MO-VPE apparatus, and then the insulating film 115 is formed.
To form. Then, the electrodes 109, 1 are formed by a vapor deposition device.
10 is vapor-deposited. Then, the p-side electrode 109 is patterned by an ion milling etching device. Here, hydrogen ions or Be ions are injected into the electrode separation groove 112 by an ion implantation device to increase the separation resistance. Finally, the chip is cleaved to form a low reflection coating 113 on each end face.

Next, the operation of the optical matrix switch of this embodiment will be described.

The bistable lasers 131 and 132 composed of the saturable absorption region and the gain region apply the reverse voltage by controlling the reverse applied voltage to the saturable absorption region and the injection current to the gain region. The laser oscillation can be set only when light is injected into the saturable absorption region.
FIG. 5 shows the optical output of the bistable laser with respect to the intensity of light injected into the saturable absorption region of the bistable laser. The oscillation wavelength of the bistable laser is determined by the pitch of the distributed feedback diffraction grating 111 and is set independently of the wavelength of incident light.
That is, the bistable laser can convert and output the wavelength of the intensity-modulated optical signal. However, when a forward voltage is applied to the saturable absorption region and a forward current is injected, the saturable absorption region to which this forward voltage is applied functions as a normal gain region, and most of the injected light is absorbed. Without passing through.

[0021] In the bistable laser 131, each forward current I _L1 and I _L2 are injected into the gain region 141a~141c and 142 a to 142 c, a forward current in the saturable absorption region 151-1 and 152-2 Functions as a gain region when injected (voltages V _c11 and V
_c22 is a positive voltage higher than the built-in voltage),
Other saturable absorption regions 152-1 and 151-2 function as saturable absorption regions (voltages V _c21 and V
_c12 is less than or equal to the built-in voltage). In this case, the wavelength λ incident from the optical input port I ₁
Incident signal light P _in1 of _1, the optical input waveguide 121a guided, forward current saturable absorber are implanted region 15
In 1-1, it is transmitted without being absorbed, and the optical input waveguide 121
It is guided in b and is absorbed in the saturable absorption region 151-2.
Here, the distributed feedback bistable laser 132 is set to oscillate at a wavelength λ ₂ ′ only when light is incident on the saturable absorption region 151-2. Therefore, when the incident signal light P _in1 is input from the optical input port I ₁ as described above, the output light P _{out2 of the} wavelength λ ₂ ′ is output from the optical output port O _2.
Is output. On the other hand, the incident signal light P _in2 of wavelength lambda ₂ incident from the optical input port I ₂ has optical input waveguide 122
The light is guided in a and is absorbed in the saturable absorption region 152-1.
Here, the distributed feedback bistable laser 131 is set to oscillate at the wavelength λ ₁ ′ only when light is incident on the saturable absorption region 152-1. Therefore, when the incident signal light P _in2 is incident from the optical input port I ₂ , the output light P _out1 having the wavelength λ ₁ ′ is output from the optical output port O ₁ .

On the contrary, in the bistable lasers 131 and 132, a forward current is injected into the saturable absorption regions 152-1 and 151-2 to function as a gain region (voltage V _c21
And V _c12 are positive voltages equal to or higher than the built-in voltage), saturable absorption regions 151-1 and 152-2 function as saturable absorption regions (voltages V _c11 and V _c22 are equal to or lower than the built-in voltage). Voltage), when the incident signal light P _in1 is input from the optical input port I ₁ , the output light P of the wavelength λ ₁ ′ is output from the optical output port O _1.
out1 is output, and the incident signal light P is output from the optical input port I _{2.
When in2} is incident, the wavelength λ ₂ ′ from the optical output port O ₂
Output light P _out2 is output.

FIG. 6 shows a timing chart of the above-mentioned operation of the optical matrix switch of this embodiment. In this way, the optical matrix switch of the present embodiment converts the wavelength of the incident signal light and outputs this light by exchanging the output port, and thus functions as an optical matrix switch having a wavelength conversion function. Of course, the wavelength conversion may not be performed, or the wavelength conversion may be performed only.

FIG. 7 is a plan view of an optical matrix switch according to the second embodiment. Here, members having the same functions as those in FIG. 1 are designated by the same reference numerals, and duplicated description will be omitted. In this embodiment, the bistable laser intersecting the optical input waveguides 121 and 122 is a distributed reflection type bistable laser 21.
1, 212. First distributed reflection bistable laser 21
1 is the first distributed reflector 221 and the gain regions 231a to 231a-2.
31c, a phase adjustment area 241, a second distributed reflector 251
And saturable absorption regions 151-1 and 152-1. The second distributed reflection bistable laser 212 has a first
The distributed reflector 222, the gain regions 232a to 232c, the phase adjustment region 242, the second distributed reflector 252, and the saturable absorption regions 151-2 and 152-2.

FIG. 8 is a sectional view taken along line DD of FIG. As shown in FIG. 8, the electrode 109 includes the first distributed Bragg reflector 22.
1 (222), gain region 231a (232a), saturable absorption region 151-1 (151-2), gain region 231b.
(232b), saturable absorption region 152-1 (152-)
2), gain region 231c (232c), phase adjustment region 2
41 (242), and the second distributed reflector 251 (25
The electrodes are electrically separated by the electrode separation groove 112 provided between the regions 2). As a result, the gain region 2
Forward current I _L1 (I _L2 ) is injected into 31a to 231c (232a to 232c), and saturable absorption region 151-1 and
152-1 (151-2, 152-2) has a voltage V
_c11, it has become _{V c21 (V c12, V c22} ) can be applied to. In addition, the first distributed reflection region 221 (222)
A current I _K1 (I _K2 ) is applied to the phase adjustment region 241 (24
The current I _M1 (I _M2 ) is supplied to the second distributed reflection region 25 in 2).
A current I _N1 (I _N2 ) can be injected into each 1 (252). In addition, the first distributed reflection region 22
1 (222) and the second distributed reflection region 251 (25
2) is an InGaAsP layer 2 having a composition transparent at the oscillation wavelength.
61 (262) are embedded in each of the first
The distributed reflection structure 271 (272) and the second distributed reflection structure 281 (282) are formed.

The optical matrix switch of the present embodiment converts the wavelength of the incident signal light and outputs this light by exchanging the output port, as in the case of the first embodiment described above. However, since the distributed reflection laser structure is used, the output wavelength of each bistable laser structure can be controlled. FIG. 9 shows the oscillation wavelength of the distributed Bragg reflector laser 211 (212) and the second distributed reflector 251.
The relationship with the injection current I _N1 (I _N2 ) into (252) is shown.
In FIG. 9, the solid line shows the case where the current is injected only into the second distributed reflector 251 (252) without injecting the current into the first distributed reflector 221 (222) and the phase adjustment region 241 (242). In some cases, there are wavelengths that cannot be oscillated. And the current I _K1 in the first distributed reflector 221 (222) and the phase adjustment region 241 (242), respectively.
When (I _K2 ) and I _M1 (I _M2 ) are injected and adjusted, it becomes possible to oscillate at all wavelengths within the variable range as shown by the broken line in FIG. That is, in this embodiment, in addition to the operation of the first embodiment, the output wavelength from each output port can be set freely. For example, if there are n output ports, the output wavelengths λ ₁ ′ to λ _n ′ (n is an integer of 2 or more) from each output port can be freely set, and the output wavelengths function as an optical matrix switch.

FIG. 10 is a plan view of an optical matrix switch according to the third embodiment, and FIG. 11 is an E of FIG.
It is a -E line sectional view. Here, members having the same functions as those in FIGS. 1 to 4 are designated by the same reference numerals, and duplicate description will be omitted.
The optical matrix switch of this embodiment is a bistable laser 1
Optical input waveguides 121 and 122 intersecting with 31 and 132
Is formed by two straight waveguides that are orthogonal to each other and is bent at a right angle, and the optical input ports I ₁ and I ₂ are arranged on the opposite side of the optical output ports O ₁ and O ₂ . That is, each of the optical input waveguides 121a and 122a is formed by two linear waveguides and is bent at a right angle, and a hole 116 perpendicular to the substrate is formed outside the intersecting portion. It functions as the reflection mirror 117. Hole 116
Can be formed by a chlorine-based ECR etching device or an ethane or methane-based ECR etching device. The optical matrix switch of this embodiment operates in the same manner as the above-mentioned embodiment, but the feature of this embodiment is that the optical input ports I ₁ and I ₂ and the optical output ports O ₁ and O ₂ are relative to the semiconductor substrate 101. Since it is arranged on the facing surface, it is easy to modularize the element.

FIG. 12 is a plan view of an optical matrix switch according to the fourth embodiment. Here, members having the same functions as those in FIG. 7 are designated by the same reference numerals, and duplicated description will be omitted. In the optical matrix switch of this embodiment, the bistable lasers 211 and 212 and the optical input waveguides 121 and 122 are formed by curved waveguides, and the optical input port I is provided on the opposite side of the optical output ports O ₁ and O _{2. 1} and I ₂ are arranged. The optical matrix switch of this embodiment operates in the same manner as the above-mentioned embodiment, but the feature of this embodiment is that the optical input ports I ₁ and I ₂ and the optical output ports O ₁ and O ₂ are relative to the semiconductor substrate 101. Since it is arranged on the facing surface, it is easy to modularize the element.

FIG. 13 is a plan view of an optical matrix switch according to the fifth embodiment. 311, 31 in the figure
Reference numerals 2, 321 and 322 denote optical matrix switches according to the third or fourth embodiment, respectively.
11 optical output port O ₁ and switch 321 optical input port I ₂ ; switch 311 optical output port O ₂ and switch 322 optical input port I ₂ ; switch 312 optical output port O ₁ and switch 321 optical input port I ₁ , the optical output port O ₂ of the switch 312 and the optical input port I ₁ of the switch 322 are coupled by the transparent waveguide 331, respectively. The feature of this embodiment is that a large-scale optical matrix switch of the present invention is configured by integrating optical matrix switches in multiple stages through the transparent waveguide 331 on the same substrate. There is a lower limit to the length of the saturable absorption region with respect to the cavity length of the bistable laser, which is required to function as a bistable laser. Therefore, when the optical matrix switch becomes large-scale and the resonator length becomes long, saturable absorption becomes insufficient if only the intersecting portion with the optical waveguide is set as the saturable absorption region. Then 4
It is considered that the number of elements with four inputs and four outputs is the limit. However, by combining the optical matrix switches of the present invention in multiple stages as in this embodiment, a larger-scale optical matrix switch can be easily constructed.

In the above embodiment, for convenience of explanation, 2 inputs and 2 inputs are used.
Although the description has been centered on the output device, it goes without saying that the number of input ports and output ports may be further increased. A bulk active layer or a strained quantum well active layer can be used instead of the MQW active layer. Further, the semiconductor material can be similarly composed of, for example, a GaAs-based semiconductor material and is not particularly limited. Further, the waveguide structure is not particularly limited, and a waveguide structure such as a ridge type waveguide or a pn buried type waveguide can be applied. Furthermore, in the above-mentioned embodiment, the optical input waveguide is an active waveguide having an optical amplification function, but it goes without saying that it may be an optical waveguide which is transparent in the operating wavelength range.

[0031]

As described above, the optical matrix switch of the present invention includes a bistable laser for optical output having a saturable absorption region and an optical input waveguide intersecting the saturable absorption region of the bistable laser. Which functions as an optical switching node that wavelength-converts a set of optical signals from an arbitrary wavelength to another wavelength and outputs by exchanging propagation paths, and a high extinction ratio,
It has the advantage that it can operate with low crosstalk and has gain and waveform shaping functions in the switch. Further, since the optical matrix switch of the present invention can be modularized in a small size, it has an advantage that it is easy to handle and can be incorporated into other devices, such as a high-speed optical signal processing device and a wavelength division multiplexing transmission device. Can be used for

[Brief description of drawings]

FIG. 1 is a plan view of an optical matrix switch according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

4 is a cross-sectional view taken along the line CC of FIG.

FIG. 5 is a light input / output characteristic diagram of a bistable laser.

FIG. 6 is a timing chart of the operation of the optical matrix switch of the first embodiment.

FIG. 7 is a plan view of an optical matrix switch according to a second embodiment of the present invention.

8 is a cross-sectional view taken along the line DD of FIG.

FIG. 9 is an emission wavelength control characteristic diagram of the second embodiment.

FIG. 10 is a plan view of an optical matrix switch according to a third embodiment of the present invention.

11 is a cross-sectional view taken along the line EE of FIG.

FIG. 12 is a plan view of an optical matrix switch according to a fourth embodiment of the present invention.

FIG. 13 is a plan view of an optical matrix switch according to a fifth embodiment of the present invention.

FIG. 14 is a plan view of a conventional optical matrix switch.

FIG. 15 is a timing chart of the operation of the conventional optical matrix switch.

[Description of Reference Signs] 101 semiconductor substrate 102 InP (n ⁺ ) substrate 103 InP (n) cladding layer 104 InGaAsP lower guide layer 105 MQW active layer 106 InGaAsP upper guide layer 107 InP (p) cladding layer 108 InGaAsP contact layer 109 electrode 110 Lower surface electrode 111 Distributed feedback diffraction grating 112 Electrode separation groove 113 Low reflection coating 114 High resistance InP 115 Insulating film 116 Total reflection mirror 117 Holes 121a to 121c, 122a to 122c Optical input waveguide 131, 132 Distributed feedback bistable Lasers 141a to 141c, 142a to 142c Gain region 151-1, 152-1, 152-1, 152-2 Supersaturated absorption region 211, 212 Distributed reflection type bistable laser 221, 222 First distributed reflection part 231 -231c, 232a-232c Gain area 241,242 Phase adjustment area 251,252 2nd distributed reflection part 261,262 InGaAsP layer 271,272 1st distributed reflection structure 281,282 Distributed distribution structure 311,312 321 and 322 Optical Matrix Switch 331 Transparent Waveguide

Claims (6)

[Claims] 1. N (n is an integer of 2 or more) bistable lasers for optical output, each having at least m (m is an integer of 2 or more) saturable absorption regions, and these n bistable lasers. 2. An optical matrix switch comprising: m optical input waveguides that intersect with the m saturable absorption regions. 2. The optical matrix switch according to claim 1, wherein the bistable laser is a distributed feedback semiconductor laser and has a distributed feedback structure. 3. The optical matrix switch according to claim 1, wherein the bistable laser is a distributed Bragg reflector semiconductor laser, and has a distributed Bragg reflector structure and a phase adjusting region. 4. The optical matrix switch according to claim 1, wherein the optical input waveguide has a total reflection mirror, and the total reflection mirror reflects incident light to reflect the bistable laser. An optical matrix switch characterized by being incident on. 5. The optical matrix switch according to claim 1, wherein the optical input waveguide and the bistable laser are curved waveguides. 6. An optical matrix switch, wherein the optical matrix switches according to claim 1 are connected in multiple stages.