JPH01201626A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To realize high switching speed by varying a propagation constant of one waveguide of a waveguide type 2-luminous flux interferometer by a control light through a non-linear optical effect, and allowing it to have a switching action. CONSTITUTION:A signal light and a control light (a pump light for generating a non-linear optical effect) are divided, a propagation constant of a non-linear optical medium waveguide is varied by the control light, the non-linear optical effect is generated, and thereafter, the control light propagated through the same waveguide as that of the signal light is eliminated by a waveguide type band pass filter part. Since the non-linear optical effect is utilized, high speed operation of at least >=3 digits can be expected, comparing with an element which has utilized a thermo-optical effect being a similar technique.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide type optical switch essential for optical communication and optical information processing.

[Prior Art/Problems to be Solved by the Invention] There are the following five typical configuration examples of waveguide type optical switches.

■ Utilization of electro-optic effect Switching effects are avoided by using an inorganic optical crystal such as LiNbO3 and electrically controlling the degree of coupling with a directional coupler.

(2) Utilizing the thermo-optic effect Utilizing the temperature change of refraction t', a switching effect is produced by heating a portion of the waveguide of a directional coupler, Matsuhatsu-Ender interferometer, etc.

■ Utilizing the acousto-optic effect The change in refractive index caused by the propagation of surface acoustic waves (dynamic grating by SAW waves) is used to deflect light and create a switching effect.

(2) Utilizing the change in the refractive index induced by the refractive index of a semiconductor The refractive index is induced in a part of the semiconductor waveguide using electrical and optical methods, and the resulting change in the refractive index causes a switching effect.

■ Utilize nonlinear optical effects Change the refractive index of a part of the waveguide using optical Kerr effect, etc. to create a switching effect.

Among these methods, method (2) is the easiest method to use in a single boat, but it is difficult to fabricate a buried waveguide. Regarding (2), it is difficult to avoid concentrating the energy V- of the SAW wave in the waveguide, and this is not practical.

Regarding (2), in order to apply it to a single-needle optical waveguide switch, it is necessary to prevent the diffusion of the induced 'Ft = rear, and a complicated structure with the pillars of a hanging well structure is unavoidable. .

In method (2), the switching speed depends on the nonlinear response speed of the material, and operation of J3, G117 or higher can be expected. However, until now, inspections have been unsuccessful due to the lack of materials with relatively large nonlinear optical effects and fast nonlinear response speeds.

In particular, glass materials have been relatively well applied to waveguides, but their nonlinear optical effects are so low that little consideration has been given to their response to waveguide-type optical switches.

Here, method (2), which is structurally closest to the present invention, will be explained. FIG. 4 is a diagram showing the structure of the switch.

The light incident from the input boat 18 is transmitted to the optical directional coupler 21.
Therefore, the light beam enters with optical power equal to the demultiplexed beam F'L2 beam interference correction 20. In the two-beam interferometer 20, since the two waveguides have the same propagation constant and the same optical path length, the multiplexing optical directional coupler 2
The phases of the two lights incident on 2 are equal, and as a result, the same light as the incident light is emitted from the output boat 19 after multiplexing. In this state, when the glass waveguide is heated by the heater 23, the refractive index of the glass waveguide changes due to the thermo-optic effect, and as a result, the phases of the two lights incident on the multiplexing directional coupler 22 are shifted. If the heating temperature is adjusted so that the phase difference becomes 180 degrees, the output light from the output boat 19 becomes zero, and it can operate as an optical switch. The problem with this method is that the operating speed is theoretically slow (on the order of m5ec) because it uses the thermo-optic effect of glass.

The present invention aims to provide an optical switch that utilizes nonlinear optical effects using a glass waveguide that has good compatibility with a silica-based optical fiber, and that is capable of high-speed operation. .

[Means to solve and overcome problems]

The present invention provides a configuration of a waveguide type optical switch in which signal light is controlled by control lights of different wavelengths, in which all the optical waveguides constituting the optical circuit are single mode optical waveguides, and a pair of optical directional couplers are used. The two main components are a two-beam interferometer and a bandpass filter, and their mutual positional relationship is such that the output end of the two-beam interferometer is optically connected to the input end of the bandpass filter. The bandpass filter has a characteristic that the signal light wavelength is within the transmission wavelength band and the control light wavelength is outside the transmission wavelength band,
In addition, the two-beam interferometer has a control light input boat that is multiplexed to one of the two waveguides, and is further connected to at least a boat for controlling light multiplexing among the two waveguides. A waveguide in which a nonlinear optical material having an optical Kerr effect is used in a part of the waveguide or a part of each of the two waveguides, and a boat for controlling light multiplexing of the two waveguides is connected. It is characterized in that the position of the nonlinear optical material provided in the control light beam is located on the output side of the merging portion for multiplexing the control beam.

As the nonlinear optical material r1, etc., glass doped with semiconductor microcrystals, a semiconductor waveguide, etc. can be used.

A feature of the present invention is that the propagation constant of one waveguide of a waveguide-type two-beam interferometer is changed by control light through a nonlinear optical effect (optical Kerr effect), thereby achieving a switching effect. . However, in order to directly perform a switching operation using the optical nonlinear optical effect using the optical intensity of the signal light as in the conventional method, a high-intensity signal light is required, and it is difficult to obtain a clear switching operation. .

The features of the optical circuit configuration of the present invention are: ■ Signal light and control light (pump light (control light) that causes nonlinear optical effects)
(1) The point where the propagation constant of the nonlinear optical medium waveguide is changed by the control light; (2) The control light that propagates through the same waveguide as the signal light after producing the nonlinear optical effect is transferred to the waveguide by one band pass. The purpose is to remove it with the mold filter section. The method of configuring the optical circuit is significantly different from the conventional method. 7 In the present invention,
Because it utilizes nonlinear optical effects, it can be expected to operate at n-speed at least three orders of magnitude faster than a similar technology, an element that utilizes thermo-optic effects.

〔Example〕

(Example 1) FIG. 1 is a diagram showing the configuration of an optical switch according to an example of the present invention. FIG. 2 is a diagram showing an example of the operation of the optical switch shown in the embodiment. FIG. 3 is a diagram schematically showing the method for manufacturing the waveguide of this example.

First, the manufacturing method will be briefly explained. The waveguide film was fabricated on a silicon substrate by flame deposition. Here, the single flame selvage method means that raw materials such as chlorides (S
j(!,+,GeCl4.PC3,8C13'8)
Glass particles generated by a thermal hydrolysis reaction in a flame are deposited on a substrate heated and maintained at an appropriate temperature (deposited as a porous film), and then heated in an atmosphere such as helium and treated to make it transparent. This is used to form a waveguide film. The manufacturing order will be explained according to FIG. 3. FIG. 3 shows the manufacturing process, and each figure (a) to (e) is a cross-sectional view and a plan view, respectively. First, as a first step, a porous film that will become the lower cladding glass film 14 is deposited on the silicon substrate 13, as shown in FIG. 3(a). The composition of the film is 5j02
-GeO28203-P2O5, and its refractive index is 0.25% lower than that of pure silica glass. Next, J1 layers of porous films to be the core glass film 15 were stacked. The composition of the film is 5LO2'-Ge02-B283P2O
5, and compared to the glass film for the lower cladding, Ge0
The number of two components is increased to make the refractive index the same as that of pure silica glass. After depositing two types of porous 'RwA, heat treatment was performed at 1390° C. in helium gas to vitrify the entire structure. As a second step, as shown in FIG. 3(b), only the portion of the core glass film 15 on which semiconductor microcrystalline glass was to be deposited was removed by reactive etching. A glass film 16 having the same composition as the core glass film 15 and containing microcrystals of S (crystal grain size approximately 200Δ) is deposited on the removed portion, as shown in FIG. 3(C), and vitrified in the same manner. did. After vitrification, an optical circuit pattern shown in FIG. 1 as shown later was formed by photolithography. (See Figure 3(d).In addition, this Figure 3(
In d), the plan view shows a state rotated by 90 degrees from FIG. 3(C). ) Finally, as shown in FIG. 3(e), an upper cladding glass film 17 was deposited. The composition of the film is Si02ceo2-B2o3-p2o5, and the refractive index is 0.25 compared to pure silica glass.
% is low.

Next, the optical circuit shown in FIG. 1 will be explained. In this figure, 1 is a signal light input boat, 2 is a control light input boat, 3 is an output boat, 4, 5, 6, and 10 are optical directional couplers, 7 is a semiconductor microcrystal doped glass waveguide, and 8 is a bandpass. type filters, B r , 8n are each the first . The second filter part 9 is a two-beam interferometer.

In the above configuration, the relative refractive index difference between the core and cladding is 0.
．． 25% and 1.06I1m, making it a single mode optical waveguide. The core shape is a square with a negative side of 12.3μ7n. The optical directional coupler 4 (for demultiplexing), the optical directional coupler 5 (for multiplexing), the optical directional coupler 6 (for multiplexing), and the optical directional coupler 10 have a 3 dB coupler characteristic. , 2 cores (same shape) are 3.27m with a core spacing of 3.1μTn.
They are located in parallel with a length of m(1). The cross-sectional shape of the glass waveguide 7 doped with semiconductor microcrystals is the same as that of the other waveguide sections, and the length is 10 m. Bandpass filter 8
The difference in length between the inner and outer waveguides of the 8' and 8'' sections is 2 ctn and 4 as.The characteristic of this section as a bandpass filter is that the center wavelength is 1.6
It has a bandwidth of 20 G11z at 6 μm.

Figure 2 shows the measurement results of the characteristics of the fabricated optical circuit. Second
In the figure, 11 is the signal light intensity, and 12 is the control light intensity.

As the signal light, we used monochromatic light with a wavelength of 1.066 μm, which was obtained by dividing white light from a halogen lamp into 1':1 ratio.
As control light for switching, light (peak intensity IW) obtained by intensity modulating (100% modulation) Nd:YAG laser light with a wavelength of 1°064 μm using an acousto-optic modulator was used. As shown in FIG. 2, it can be seen that the signal light is modulated depending on the intensity of the control light. This is because the control light incident on the semiconductor microcrystal-doped glass waveguide 7 in FIG. ) The phase of the two signal lights incident on the optical directional coupler 5 is 180d(!(1,
This is a result of the deviation. In order to obtain the required phase difference in the 7 portions of the semiconductor microcrystal-doped glass waveguide with a length of 1 cm, the refractive index only needs to change by 104 degrees, and therefore the nonlinear refractive index of the SL microcrystal-doped glass and Considering the mode field of the guided light, the required control light intensity is estimated to be about 1W. The experimental results shown in FIG. 2 show the characteristics as designed and confirm the effectiveness of this device structure.

(Example 2) A second example of the present invention will be described. Is it bigger than Example 1? , is that a monolithic semiconductor waveguide is used as the nonlinear optical material.

A GaAS/Ga^IAs waveguide was used as the semiconductor waveguide. The configuration of the optical fiber circuit was similar to that shown in FIG. 1, but the dimensions of the circuit were slightly different because the wavelength used was 0.85μ7n. In the circuit fabrication process, the semiconductor microcrystal-doped glass layer stacking is omitted from the steps shown in FIG. 3 (steps (b) and (C) in FIG. 3), and the glass film 17 for the upper cladding is
After formation, the portion into which the semiconductor was to be inserted was removed by etching, and a separately manufactured semiconductor waveguide was inserted.

The dimensions of the optical circuit will be explained. The relative refractive index difference between the core and cladding is 0.25% and is 0.85 μm, forming a medium-mode optical waveguide. The core shape is 1. -Side 4.12μ
It is a square of m. Optical directional coupler 4 (for demultiplexing), optical directional couplers 5 and 6 (for multiplexing), and optical directional coupler '10
has a 3 dB coupler characteristic, and two cores (of the same shape) are located in parallel with a core spacing of 6° and 2 μm and a length of 4.05 m.

The cross-sectional shape of the glass waveguide 7 doped with semiconductor microcrystals is the same as that of the other waveguide sections, and the length is 5.0 seconds. In the bandpass filter 8 section, the difference in length between the inner and outer waveguides of 8' and 8'' is 2 cm and 4 cm.The characteristics of this section as a bandpass filter are as follows: The wavelength is 0.85 μm and the bandwidth is 20 Gllz.

We will describe the results of measuring the characteristics of the fabricated optical circuit. As the signal light, a semiconductor laser beam with an oscillation wavelength of 0.85 μm is used, and as the control light for switching, the wavelength is 0.83 μm.
Light (peak intensity: 2 W) obtained by directly modulating (100% modulation) 7n high-power semiconductor laser light was used. The experimental results confirmed that the signal light was switched by the control light. The optical power required for switching was approximately 2.0W.

In the above examples, examples using SL microcrystal doped glass as a nonlinear medium and those using a GaAs semiconductor waveguide have been described, but CdSe, CdS,
CdTe, GaAs, GaSb, InP 1G
It goes without saying that an optical switching element can also be realized with a similar configuration for an element fabricated using glass doped with a wide range of compound 21' compound microcrystals such as alnAsP.

Furthermore, when configuring a two-beam interference beam, it is also effective to design the splitting ratio of the optical directional coupler on the splitting side by considering the propagation loss of the two waveguide sections. It goes without saying that there is.

〔Effect of the invention〕

As described above, according to the present invention, switching is performed using the nonlinear optical effect, and therefore a very high switching speed can be achieved. Furthermore, optical switching at low optical power is expected by using semiconductor microcrystal-doped glass, which has a nonlinear optical constant three orders of magnitude larger than that of conventional quartz glass. Furthermore, since the optical power density of the control light can be increased due to the use of a waveguide, there is an advantage that 1. the element can effectively operate at low power.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical switch according to an embodiment of the present invention. FIG. 2 is a polygraph showing an example of the operation of the optical switch shown in the embodiment. FIG. 3 is a process diagram showing an outline of the method for manufacturing the waveguide of the example. FIG. 4 is a schematic configuration diagram of an optical switch using the thermo-optic effect, which has been described as a conventional technique. DESCRIPTION OF SYMBOLS 1... Signal light input boat, 2... Control light input boat, 3... Output light boat 1-14... (for demultiplexing) optical directional coupler, 5... (for multiplexing) ) Optical directional coupler, 6...
・(For multiplexing) Optical directional coupler, 7...Semiconductor microcrystal doped glass waveguide, 8...(Band pass filter (8)
'. 8'' are the first and second filters respectively), 9...2-beam interferometer, 10... Optical directional coupler, 11... Signal light intensity, 12... Control light intensity, 13 ... Board, 14.
...Glass film for lower cladding, 15... Glass film for core, 16... Glass film added with semiconductor microcrystals, 17...
Glass membrane for upper cladding. Figure 1 8'8" oro 20 30 40 hours (nsec)

Claims (1)

[Claims] In the configuration of a waveguide optical switch in which signal light is controlled by control lights of different wavelengths, all the optical waveguides constituting the optical circuit are single-mode optical waveguides, and a single two-mode optical waveguide consisting of a pair of optical directional couplers is used. The two main components are a beam interferometer and a bandpass filter, and their mutual positional relationship is such that the output end of the two-beam interferometer is optically connected to the input end of the bandpass filter. Band-pass filters have the characteristics of having a signal light wavelength within the transmission wavelength band and a control light wavelength outside the transmission wavelength band, and a two-beam interferometer uses one of the two waveguides. It has a control light input port that is multiplexed into a control light input port, and also has a control light input port that is connected to at least a control light multiplexing port among the two waveguides, or a portion of each of the two waveguides. A nonlinear optical material having a Kerr effect is used, and the position of the nonlinear optical material provided in the waveguide to which the port for control light multiplexing is connected among the two waveguides is the confluence part for the control light multiplexing. A waveguide type optical switch characterized by being located closer to the output side.