JPS606922A - Thin-film optical control element - Google Patents

Abstract

PURPOSE:To obtain an optical control element which has superior reproducibility and high-speed operability by arranging >=1 couples of electrodes on the surface of a thin dielectric film grown on a transparent substrate, and applying voltages to the electrode couples. CONSTITUTION:The thin dielectric film 32 which is, specially, a thin film of a PLZT compound is grown on the transparent substrate 31 of sapphire, etc., to an about 30mum thickness so that 0.14< La and La+Pb<0.4 with regard to the content mol ratio of Pb and La in the film. Then, Comb-shaped type counter electrodes 33 and 33' are fitted onto the film 32 at a narrow interval of about 20mum to form an optical modulating element. Coherent light having an optional image pattern 34 is made incident at right angles to the surface of the film 32 and a voltage is applied between the electrodes 33 and 33' to modulate an output pattern 35 according to the level of the applied voltage. In this example, such fast modulation that a response speed is several n seconds with a 180 deg. modulating voltage 100V is realized. Thus, the thin dielectric film 32 is used to manufacture a high-speed optical shutter, ligical arithmetic element, etc., to small size faster than before.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a light control element that controls light by applying an electric field. In particular, it relates to a light control element capable of high-speed operation.

2. Description of the Related Art Structures of Conventional Examples and Their Problems With the recent development of the field of optical information processing, various demands on optical elements are increasing. In particular, it is desired to develop devices that can be controlled at high speed in response to human input signals. For example, when considering an optical shutter that turns light on and off in response to an input signal, there are conventional shutters that use mechanical power, and those that use electro-optic PLC: Old A. Turn on the light to the mechanical structure.

The device to be turned off inevitably requires a large device, and the response speed is fast, on the order of m, sec, so it is considered difficult to use in the recent field of high-speed optical information processing. An example of a light control element using the spun electro-optic PARCUIA material is shown in FIG. 1. An electric field is applied to the electro-optic bulk material 11 to change its optical characteristics, and the light 15 passing through that part is controlled, and electrodes 12 are provided on both end surfaces of the bulk 11 as shown in FIG. 1a. Alternatively, as shown in FIG. 1, 016 is an outgoing light having a structure in which a parallel counter electrode 12 is provided on one surface of the bulk.

In the element having the structure shown in FIG. 1A, only one light beam is controlled, but the optical characteristics of the bulk can be uniformly changed, so that light can be controlled efficiently.

Although the element having the structure shown in FIG. 1 does not efficiently change its optical characteristics due to an electric field, it is possible to construct a pair of electrodes on the surface of the bulk 11, so that a large area image can be controlled.

In order to operate at high speed in an optical element having the structure described above, it is necessary to reduce the capacitance between the electrode pair. Incidentally, the electro-optic bulk material usually has a high dielectric constant, and in order to reduce the capacitance between the electrode pairs, the electrode pair spacing 13 must be widened considerably, but the width 14 must be shortened. Increasing the electrode pair spacing 13 increases the operating voltage,
This poses a practical obstacle. The width 14 can be narrowed by polishing, but the limit is about 50 .mu.m.Thicknesses of this order are difficult to handle, but since they have a thickness distribution of at least 30 .mu.m, it is difficult to construct a stable element. Usually the thickness is several hundred μm
The above are used. Therefore, the operating speed of an element using this type of bulk is on the order of 11SeC, which still does not meet the requirements of the field of high-speed information processing. Furthermore, since the light control element using the electro-optic bulk has a certain thickness (width 14), it absorbs a large amount of heat from the transmitted light beam, and has problems such as the life span of the element and reproducibility.

The present inventors invented a thin film light control element based on the discovery that by constructing a light control element having the above structure with a thin film grown on a transparent substrate, it can perform well even in a tone sequence.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a light control element that is stable and capable of high-speed operation by improving the light control element in which reproducibility and high speed have been problems in the past.

Structure of the Invention The thin film light control device according to the present invention has at least one pair of electrodes arranged on the surface of a dielectric thin film grown on a transparent substrate, and by applying a voltage between the electrode pairs, the thin film light control element can be applied across the thin film surface. It controls the light that passes through it. In conventionally used light control elements using electro-optic bulk, as the optical path width 14 is shortened, the capacitance between the electrode pairs becomes smaller, but conversely, the optical path width for changing the light becomes shorter, and sufficient operation is not achieved. It has been said that it cannot be done. In the case of the thin film light control element of the present invention, the thickness of the thin film can be made uniform to several tens of micrometers or less.
Even if the distance between the electrode pairs is made extremely short, the capacitance between the electrode pairs can be kept small, and because the distance between the electrode pairs is short, the electric field strength will be strong even for the same applied voltage. Therefore, the lack of optical path length due to the thinness of the thin film is compensated for by the strong electric field strength, and a configuration that was previously thought to be impossible to control light passing across thin materials such as thin films is now possible. , it was found that other things were also good. Since the thin film optical control element having the above structure has a small interelectrode capacitance, a response speed of less than n5lIC can be achieved, making it suitable for application to high-speed optical information processing.

Further, in the thin film light control element according to the present invention, the dielectric thin film is made of, for example, a PLZT thin film. The dielectric thin film needs to have a large electro-optic effect.

It is known that PLZT compounds exhibit this type of effect, but the ones that have been used as optical elements so far have been in the form of ceramics, and it has been difficult to obtain large electro-optic effects by making them into thin films. It wasn't. The present inventors have conducted research on thinning PLZT compounds and have discovered that by selecting certain optimal growth conditions, an epitaxial thin film with a large electro-optic effect can be obtained. By using a thin film with such a large electro-optic effect, it is very possible to construct the above-mentioned thin film light control element.

The composition of the Ushita PLZT compound thin film is that lead (
If the molar ratio of pb) and lanthanum (La) is ○-14<
It was confirmed that it is particularly effective when LaAa is in the range of 10 pb < 0.4.

That is, in FIG. 2, a total change curve 21 according to the composition of the electro-optic effect is shown. It can be seen from the figure that a large electro-optical effect can be obtained in the composition range shown in region 22, and that an excellent element can be constructed with a thin film in the above composition range. Note that PLZT has ceramic 4J materials as a bulk material, but these ceramics are not expected to have this type of large electro-optic effect with the composition according to the present invention. The reason why the thin film having the composition of the present invention has a large electro-optic effect is not clear, but it is thought that the material synthesis process during thin film formation is probably involved.

DESCRIPTION OF EMBODIMENTS The thin film light control device according to the present invention will be explained below with reference to Examples.

Embodiment 1 FIG. 3 shows an image modulator using a thin film light control element according to an embodiment of the present invention. A 30 μm thick PLZT thin film 32 grown on the sapphire substrate 31 has a thickness of 20 μm.
A device is formed by attaching comb-shaped counter electrodes 33 and 33' spaced apart. The composition of PLZT has a strong electro-optic effect (La,
/La0Pb)-0,28f is used. When coherent light having an arbitrary image pattern 34 is incident perpendicularly to the thin film surface and a full voltage is applied between the opposing electrodes 33 and 33', the output pattern 35' (i-modulation can be modulated) depending on the magnitude of the voltage. It is possible.

According to the above configuration, +, 1 '8 QO modulation voltage is 10
0V.

A high-speed image modulator with a response speed of several n5cC was constructed.

Embodiment 2 FIG. 4 shows an optical shutter entirely constructed using the thin film light control element of the present invention. A polarizer 34 and an analyzer 35 are arranged in crossed nicols on the incident side and the output side of the element having the configuration of Example 1, respectively. The random light beam 41 passes through the polarizer 34 and is linearly polarized, and depending on the electric field application state of the control element, the random light beam 41 becomes 0.
It is set to take the state of ° modulation or 18♂ modulation.

Therefore, the state of the output light 42 passing through the analyzer is dark when the modulation is d and bright when the modulation is 1800. In other words, a high-speed optical shutter that turns on and off by applying a voltage of 100 μm was constructed.

Embodiment 3 By using the characteristics of the high-speed optical shutter shown in Embodiment 2, a logic operation element can be manufactured. FIG. 5a shows a configuration of an OR operation element. As can be seen from the cross-sectional view shown in FIG. 5, this element has PLZ on both sides of the sapphire substrate 31.
By growing a T thin film 32 and attaching electrode pairs 33, 33', it is possible to operate with the above-mentioned simple and compact structure.

The modulation degree of one element is set to 900 by applying an electric field. That is, the input light 42 becomes brighter by performing 900 modulation for the voltage input on one side.

For voltage inputs on both sides, it is still bright due to 1800 modulation, and there is no output light only when there are no voltage inputs on both sides.

Therefore, an OR operation is performed in which light is output when a signal is input to at least one of the two power sources. AND in addition to this
,NAND.

A NOR circuit or the like can also be constructed by combining a polarized 5Th board and an element.

Effects of the Invention As described above, the present invention realizes a light control element that is faster and smaller than conventional ones by controlling the light transmitted across a dielectric thin film using the electric field from the electrode on the thin film. Therefore, the industrial value of the present invention is high.

[Brief explanation of drawings]

Figures 1a and b are schematic diagrams of a conventional light control element, Figure 2 is a graph showing the relationship between the electro-optic effect and the composition of a PLZT thin film, and Figure 3 is a thin film image modulator according to an embodiment of the present invention. 4 is a schematic diagram of a thin film optical shutter according to another embodiment of the present invention, FIG. 5a is a diagram showing a thin film optical operation element according to another embodiment of the present invention, and FIG. It is a sectional view of the element substrate of a. 21... Curve showing the relationship between thin film composition and electro-optic effect, 22... Composition region with large electro-optic effect,
31...Sapphire substrate, 32...PLZT
Thin film, 33.33'...Parallel electrode, 34...
...Incidence light pattern, 35...Transmitted light pattern, 41...Input source, 42...Output light. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (θ,) Figure 2 16 XIO (nt7v) 2 0 0, IO, 20, 30, 40, 5
Ratio Lo-shi Pb Fig. 3 2 Fig. 5 (α)

Claims (1)

[Claims] (1) One or more pairs of electrodes are arranged on the surface of a dielectric thin film grown on a transparent substrate, and a voltage is applied between the electrode pairs to transmit light across the surface of the thin film. A thin film light control element characterized by controlling light. 3. The thin film light control element according to claim 1, wherein the dielectric thin film is made of a PLZT compound thin film. (3) In the PLZT compound thin film, lead (pb
) and lanthanum (La ) content molar ratio is 0.14 <
3. The thin film light control element according to claim 2, characterized in that ``'/La+Pb (in the range of 0.4).