JPH059770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical gate array using the principle of Fabry-Perot electro-optic modulator.

(Prior Art) A Fabry-Perot electro-optic modulator is known, which combines an electro-optic crystal whose refractive index changes depending on an applied electric field and a Fabry-Perot resonator. FIG. 4 is a schematic diagram showing the principle of this Fabry-Perot electro-optic modulator. Two concave mirrors 1 and 2 are arranged with an optical path length L, and an electro-optic crystal element 3 is arranged between these concave mirrors. The electro-optic crystal element is
It has electrodes 4a and 4b arranged opposite to each other on both sides in a direction perpendicular to the optical axis of this element, and a bias power supply 5 is connected between these electrodes to apply an electric field to the electro-optic crystal element 3 in a direction perpendicular to the optical axis. . When a light beam b to be frequency modulated is incident from the left side of the drawing, multiple reflections occur between concave mirrors 1 and 2,
The optical transmittance of the Fabry-Perot resonator as a whole depends on the optical frequency, that is, the wavelength, of the incident light, and the optical transmittance characteristics shown in FIG. 5 are obtained. Figure 5a shows the relationship between the optical frequency ν and the optical transmittance T when the resonator length L is constant, and Figure 5b shows the relationship between the resonator length L and the optical frequency ν when the incident light is constant. Light transmittance T
Indicates the relationship between As shown in Figure 5a, when the resonator length L is constant, the period is C/2L (C is the speed of light).
A narrow transmission band occurs. Therefore, this Fabry-Perot resonator acts as a narrow band optical band filter. On the other hand, as shown in FIG. 5b, when the optical frequency of the incident light is constant, the optical transmittance can be changed from 0 to T _nax by only slightly changing the optical length of the resonator. Therefore,
By changing the electric field intensity applied to the electro-optic crystal placed in the optical path between concave mirrors 1 and 2 and changing the optical path length of the resonator by a minute distance, the light transmittance can be controlled with high sensitivity. . in this case,
If the power source 5 has a predetermined frequency, the optical distance of the resonator will also change depending on the frequency of the power source 5, making it possible to realize a highly sensitive optical modulator.

(Problems to be Solved by the Invention) The Fabry-Perot electro-optic modulator described above has the following problems:
It has the advantage of being able to perform modulation with a relatively simple configuration compared to other frequency modulators. Furthermore, since modulation can be performed by only slightly changing the resonator length, it also has the great advantage of being able to modulate with high sensitivity. Therefore, it is possible to imagine the possibility of performing optical logic processing by utilizing such characteristics.

Therefore, an object of the present invention is to provide an optical logic gate that can perform various logic operations by utilizing the advantages of the Fabry-Perot electro-optic modulator.

(Means for Solving the Problems) An optical gate according to the present invention includes a planar electro-optic crystal whose refractive index changes depending on an applied electric field, and first and second electrodes formed on both sides of the electro-optic crystal. a reflective layer, first and second transparent electrodes respectively formed on these reflective layers, a first bias source that applies a first bias voltage to the first transparent electrode, and a second transparent electrode. a second bias source that applies a second bias voltage to the electrode; a first switching element that selectively switches the connection of the first transparent electrode between the reference potential and the first bias voltage; a second switching element that selectively switches the connection of the transparent electrode between the reference potential and the second bias voltage, the electro-optic crystal, the first and second reflective layers, and the first and a second transparent electrode constitute an optical resonator, and this optical resonator alternately occupies a narrow band light transmission peak position and a light blocking position where almost no light is transmitted, depending on the effective resonator length. The effective resonator length of the optical resonator is controlled by switching the potential applied to the first and second transparent electrodes, and the optical resonator is selectively adjusted to the light transmission peak position or the light transmission characteristic. It is characterized in that two-input optical logic processing is performed by setting it at a cut-off position and using potential signals applied to the first and second transparent electrodes as input logic signals.

In the present invention, a Fabry-Perot resonator is constructed by forming reflective layers on both sides of a foil-like or thin-film electro-optic crystal. Strip-shaped transparent electrodes are formed perpendicularly to each other on both sides of the Fabry-Perot resonator in the optical axis direction, with the electrodes on one side serving as column electrodes and the electrodes formed on the other side serving as row electrodes. The effective optical length of each area defined in a matrix by the transparent electrodes of the Fabry-Perot resonator changes depending on the voltage applied to the electrodes, so these micro areas are fabricated into a Fabry-Perot resonator with a small area. This will constitute an element. Then, set the effective optical length L of each resonator element when bias is applied to both the row and column electrodes to be L = λ/2m (m is an integer and λ is the wavelength of the incident light). For example, each resonator element is in a high light transmission state. On the other hand, if a bias state other than this is set, a light blocking state occurs in which almost no light is transmitted. Therefore, by using two bias voltages as input signals, it is possible to realize a two-input optical logic gate element that performs AND processing or E-OR processing.

(Example) FIG. 1 shows an optical logic gate according to the present invention and part 2.
1A is a perspective view, FIG. 1B is a top view, and FIG. 1C is a plan view. An electro-optic crystal 10 made of an electro-optic crystal material whose refractive index changes depending on the applied electric field strength, such as potassium dihydrogen phosphate, potassium deuterium phosphate, lithium tantalate, lithium niobate, AsGa, InP, etc. Use. The electro-optic crystal 10 can be a foil-like body or a thin film having a thickness of about 50 μm or less, for example. First and second reflective layers 11 and 12 are formed on both sides of this electro-optic crystal body 10, respectively. These reflective layers are composed of a dielectric multilayer film or a metal film. A first transparent electrode group EDY ₁ to EDY ₄ (column electrodes) and a second transparent electrode group are formed on these first and second reflective layers.
Form EDX ₁ to EDX ₄ (row electrodes), respectively. These electrodes are strip-shaped, for example, the first electrode EDY
extends in the Y direction, and the second electrode EDX extends in the X direction orthogonal to the Y direction. Although four electrodes are used to simplify the drawing, it is of course possible to use a large number of electrodes, and by using m and n electrodes, m×n matrix electrodes can be constructed.
As shown in FIG. 1C, the first electrode group EDY ₁ ~
EDY ₄ is the first switching element group.
SWY ₁ to SWY ₄ are connected to the first voltage source 13, and second electrode groups EDX ₁ to EDX ₄ are connected to the second voltage source 13 via second switching element groups SWX ₁ to SWX ₄ , respectively.
Connect to voltage source 14.

When the parallel light beam b is projected perpendicularly onto the electro-optic crystal 10, the incident light undergoes multiple reflections between the first reflective layer 11 and the second reflective layer 12, and therefore the electro-optic crystal 10 and the first and Second reflective layer 11 and 1
2 constitute a Fabry-Perot resonator.

On the other hand, the refractive index of the electro-optic crystal 10 changes depending on the applied electric field strength, and the optical length changes due to the change in the refractive index. And the first and second
The electric field intensity generated in the electro-optic crystal by the voltage source is the electric field intensity generated by the sum of the bias of the first voltage source and the bias of the second voltage source. Therefore, among the Fabry-Perot resonators as a whole array, the first electrode group EDY and the second electrode group
The minute areas defined in a matrix by the EDX are in an unbiased state controlled by the first and second switching element groups, in a state in which only the bias from the first voltage source is applied, and in a state in which only the bias from the first and second switching elements is applied. A Fabry-Perot resonator element is configured that selectively occupies three types of bias states, including a state where a bias is applied by a second voltage source.

FIG. 2 is a graph showing the relationship between the resonator length L and the optical transmittance of the Fabry-Perot resonator having the configuration shown in FIG. As described above, the Fabry-Perot resonator exhibits extremely steep narrow-band light transmission characteristics when the resonator length L satisfies the following equation.

L=λ/2m Here, λ is the wavelength of the incident light, and m is an integer.
Therefore, the resonator length L ₀ when no bias is applied and the resonator length Lo when only one bias is applied.
The resonator length is set so that +ΔL is located midway between the resonator lengths at the light transmission peak, and the resonator length Lo+2ΔL when both the first and second biases are applied satisfies the condition Lo+2ΔL=λ/2m. In addition, by setting the bias values of the first and second voltage sources, each Fabry-Perot resonator element can be selectively switched between a high light transmission state (on state) and a low light transmission state (off state) in which almost no light is transmitted. can be occupied. As a result, the area defined in a matrix by the first and second electrode groups EDY and EDX functions as a light gate element that selectively occupies the high light transmission state and the low light transmission state, and therefore, in this example. The Fabry-Perot resonator constitutes a two-dimensional optical gate array. In other words, two bias voltages are used as input signals to perform AND processing.
An input type optical logic gate can be realized.
Furthermore, since the Fabry-Perot resonator has an extremely steep narrow band optical transmission characteristic, it is controlled with a low driving voltage by bringing the resonator length Lo in the unbiased state close to the position of the resonator length where the optical transmission peak occurs. You can also do that. With this configuration, when turning on the gate element of the address displayed in the i-th row and the j-th row, the i-th row electrode switching element is brought into a conductive state, and the j-th column electrode switching element is brought into a conductive state. It can be selectively turned on. Furthermore, when rows are selected line-sequentially, the optical gate elements can be turned on line by line by turning on all the column electrode switching elements and sequentially turning on the row electrode switching elements.

In the above embodiment, the AND gate type optical gate array is turned on when two driving voltages are applied, but it is turned on when either one of the biases is applied, and when both biases are applied. It may also be an optical gate array that operates in an exclusive-OR fashion, being in an off state when the gate is turned off.

FIGS. 3a and 3b are perspective views showing an example configuration for operating a Fabry-Perot modulator at high speed. A first reflective layer 21 is formed on a transparent substrate 20, an electro-optic crystal thin film 22 is formed on this, and a second reflective layer 23 is formed on the electro-optic crystal thin film. Further, first and second strip electrodes 24 and 25 are formed on the second reflective layer at a predetermined distance apart, and a matching load 27 is connected to one end of these electrodes. Then, a light beam to be modulated is made to enter between the first transparent electrode and the second electrode, and the first electrode 24
A driving voltage source 26 is connected between the first electrode 25 and the second electrode 25 . Generally, in an electro-optic modulator, an electro-optic interaction occurs in which the refractive index changes depending on the electrical signal at a portion where an electrical signal and an optical signal overlap, and the optical beam is modulated by this interaction. in this case,
In the low frequency region, the longer the electro-optic interaction region, the better the modulation sensitivity becomes, whereas in the high frequency region, the modulation characteristics deteriorate. The reason for this is that the electrical transmission characteristics of the electrode deteriorate at high electrical frequencies due to skin effects, etc., and the transmission speed of electrical signals is different from the transmission speed of light, so optical and electrical signals are transmitted through the interaction region. This is thought to be due to the fact that the phase of the electrical signal when viewed from the optical side is reversed, and the modulation effect is canceled out. When the interaction length is about 1 mm, the travel time of light passing through this region is at most several picoseconds, so if an electrical signal can be applied well enough, a modulator that responds in picoseconds with an interaction length of about 1 mm can be created. can be configured. However, when the electrode length is 1 mm or more, it is difficult to transmit an electrical signal of several picoseconds over this electrode, and in order to obtain an electrical band of picoseconds, the electrode length must be shorter than 1 mm, for example, 100 μm. It is necessary to do the following. However, this results in a lack of interaction length necessary to obtain sufficient modulation sensitivity. Therefore, if a Fabry-Perot resonator structure is used in which light repeatedly passes between short electrodes many times as shown in FIG. 3, a modulator that is electrically short and optically long can be constructed. The electrode length for the modulation section is several tens of micrometers, and if the light beam to be modulated is focused to a minute diameter, it can be put into practical use, and even modulation signals of several hundred GHz can be transmitted to the modulation region without distortion. On the other hand, the modulation band is determined by the transmission band of the optical resonator, and since the resonator length is short at about 10 to 20 μm, the finesse is 50 μm.
It is possible to achieve a speed of about 200 to 300 GHz.

In this case, the modulation sensitivity is on the same level as a modulator with a length of mm, and the band is on the same level as a modulator with a length of several tens of μm. In addition, since the actual electrode length can be made to the order of mm or cm (however, only the first few tens of μm portion is capable of high-speed response and broadband operation), as shown in Figure 3b, It is also possible to move the light irradiation location along the electrode and to modulate multiple light beams at the same time, so each light beam incidence part corresponds to a modulator. Therefore, a modulator array can be constructed using a common electrode. As a result, it can be used for waveform probes of electrical signals in the relatively low-speed gigahertz frequency range, and can also be used for testing electrical signal transmission characteristics of electrode lines in the hundreds of gigahertz range.

The present invention is not limited to the embodiments described above, and various modifications and changes are possible. For example, although only two biases were used in the embodiment described above, a base bias is applied to the entire resonator, and the first and second biases are further superimposed on this base bias to determine the light transmission state of each resonator element. can also be selectively controlled.

(Effects of the Invention) As explained above, according to the present invention, reflective layers are formed on both sides of an electro-optic crystal to constitute a Fabry-Perot resonator, and transparent strips are formed on the reflective layer at right angles to each other. Since the electrodes are respectively formed, micro areas defined in a matrix by the transparent electrodes in the overall Fabry-Perot resonator constitute a light gate element that is selectively controlled by the applied bias. . As a result, a two-input optical logic gate that can be controlled by electrical signals and two
A dimensional optical gate array can be realized. Furthermore, since each gate element of the optical gate array according to the present invention is composed of a Fabry-Perot resonator element, the steep narrow band light transmission and light reflection characteristics of the Fabry-Perot resonator can be effectively utilized. Therefore, high sensitivity and low driving voltages can be operated.
In particular, while conventional electro-optic modulators need to provide a phase difference equivalent to λ/2, the present invention achieves the great advantage of being able to be driven by only providing a minute phase difference of λ/2 or less.

Furthermore, since reflective layers are directly formed on both sides of the foil-like or thin-film electro-optic crystal, and strip-like transparent electrodes are directly formed on these reflective layers, a thin and compact optical gate array can be achieved. realizable.

[Brief explanation of the drawing]

1a to 1c are a perspective view, a top view, a plan view, and a second
The figure is a graph showing the relationship between the resonator length L and the optical transmittance, Figures 3a and b are perspective views showing a configuration for operating a Fabry-Perot modulator at high speed, and Figure 4 is a conventional Fabry-Perot electro-optical device. Diagrams showing the structure of the modulator, and FIGS. 5a and 5b are graphs showing the light transmission characteristics of the Fabry-Perot modulator. 10... Electro-optic crystal, 11, 12... Reflective layer, 13, 14... Voltage source, EDY ₁ to EDY ₄ ...
1st electrode, EDX ₁ ~ EDX ₂ ... 2nd electrode, SWY ₁
~SWY ₄ ...First switching element, SWX ₁ ~
SWX ₄ ...Second switching element.

Claims (1)

[Scope of Claims] 1. A planar electro-optic crystal whose refractive index changes depending on an applied electric field, first and second reflective layers formed on both sides of the electro-optic crystal, and these reflective layers. a first bias source that applies a first bias voltage to the first transparent electrode, a first bias source that applies a first bias voltage to the first transparent electrode, and a second bias voltage that applies a second bias voltage to the second transparent electrode. A first switching element selectively switches the connection between the second bias source to be applied and the first transparent electrode between the reference potential and the first bias voltage, and the connection between the second transparent electrode and the first transparent electrode at the reference potential. and a second switching element that selectively switches between the first and second bias voltages, and the electro-optic crystal, the first and second reflective layers, and the first and second transparent electrodes. This constitutes an optical resonator, and this optical resonator has a transmission characteristic that alternately occupies a narrow band light transmission peak position and a light blocking position where almost no light is transmitted, depending on the effective resonator length, and The effective resonator length of the optical resonator is controlled by switching the potentials applied to the first and second transparent electrodes to selectively set the optical resonator to a light transmission peak position or a light blocking position; An optical logic gate that performs two-input optical logic processing by using potential signals applied to first and second transparent electrodes as input logic signals. 2. A planar electro-optic crystal whose refractive index changes according to an applied electric field, first and second reflective layers formed on both sides of the electro-optic crystal, and second reflective layers formed on each of these reflective layers. a first bias source that applies a first bias voltage to the first transparent electrode, and a second bias source that applies a second bias voltage to the second transparent electrode. a first switching element that selectively switches the connection between the source and the first transparent electrode between the reference potential and the first bias voltage; and a first switching element that selectively switches the connection between the first transparent electrode and the second transparent electrode between the reference potential and the second bias voltage and a second switching element that selectively switches between the electro-optic crystal, the first and second reflective layers, and the first and second transparent electrodes to form an optical resonator. the optical resonator has a transmission characteristic that alternately occupies a narrow band light transmission peak position and a light blocking position where almost no light is transmitted according to the effective resonator length; The effective resonator length of the optical resonator is controlled by switching the potential applied to the electrode, and the optical resonator has a light transmission peak when at least first and second bias voltages are applied to the transparent electrode. 1. An optical logic gate configured to perform two-input optical logic processing by using a potential signal applied to the transparent electrode as an input logic signal. 3. A planar electro-optic crystal whose refractive index changes depending on an applied electric field, first and second reflective layers formed on both sides of the electro-optic crystal, and a first
A first electrode group consisting of a plurality of strip-shaped transparent electrodes formed on a reflective layer and extending parallel to each other, and a first electrode group formed on a second reflective layer and consisting of a plurality of strip-shaped transparent electrodes extending parallel to each other and mutually extending in a direction perpendicular to the extending direction of the first electrodes. a second electrode group consisting of a plurality of strip-shaped transparent electrodes extending in parallel; a first bias source that applies a first bias voltage to each electrode of the first electrode group; and each electrode group of the second electrode group. a second bias source that applies a second bias voltage to the electrode; a first switching element group that selectively switches the connection of each electrode of the first electrode group between a reference potential and the first bias source; a second switching element group for selectively switching each electrode of the two electrode groups between a reference potential and a second bias source; The first and second electrode groups constitute an optical resonator array consisting of a plurality of optical resonators arranged in a matrix, and these optical resonators transmit narrow band light according to the effective resonator length. It has a transmission characteristic that alternately occupies a peak position and a light blocking position where almost no light is transmitted, and the effective resonator length of each optical resonance can be adjusted by switching the potential applied to the first and second transparent electrodes. to selectively set each optical resonator to a light transmission peak position or a light blocking position, respectively, and perform two-input optical logic processing by using the potential signal applied to the transparent electrode as an input logic signal. An optical logic gate array featuring: 4. A planar electro-optic crystal whose refractive index changes depending on an applied electric field, first and second reflective layers formed on both sides of the electro-optic crystal, and a first
A first electrode group consisting of a plurality of strip-shaped transparent electrodes formed on a reflective layer and extending parallel to each other, and a first electrode group formed on a second reflective layer and consisting of a plurality of strip-shaped transparent electrodes extending parallel to each other and mutually extending in a direction perpendicular to the extending direction of the first electrodes. a second electrode group consisting of a plurality of strip-shaped transparent electrodes extending in parallel; a first bias source that applies a first bias voltage to each electrode of the first electrode group; and each electrode group of the second electrode group. a second bias source that applies a second bias voltage to the electrode; a first switching element group that selectively switches the connection of each electrode of the first electrode group between a reference potential and the first bias source; Connect each electrode of the two electrode groups to the reference potential and the second electrode group.
a second switching element group selectively switching between the bias source and the electro-optic crystal, the first and second reflective layers, and the first and second switching elements;
An optical resonator array consisting of a plurality of optical resonators having narrow band light transmission characteristics arranged in a matrix is formed by the electrode group, and the effective resonator length of each optical resonator is When both the first and second bias voltages are applied, the effective cavity length is set to the light transmission peak position, and in other bias states, the incident light is is set to a light-blocking state where almost no light is transmitted, or the effective resonator length is set to the light transmission peak position when only the first bias voltage or the second bias voltage is applied, and in other bias states. The optical logic is characterized in that the optical logic is set to a light shielding state that hardly transmits incident light, and performs two-input optical logic processing by using potential signals applied to the first and second transparent potentials as input logic signals. gate array.