JPS5882221A - Optical switching array - Google Patents

Abstract

PURPOSE:To form an optical switching array which can be driven with a low voltage and as a high contrast, by forming a common electrode or individual electrodes on a substrate as prescribed. CONSTITUTION:A pair of grooes 14 and 15 having a depth D are formed a proper length apart from each other in parallel on the surface of a substrate 10. A common electrode 12 and individual electrodes 13 are so formed that a pair of wall faces 16a and 16b facing each other of a wall part 16 between grooves 14 and 15 are partial forming faces of these electrodes. In an optical switching array formed in this manner, the effective depth of the electric field generated in the thickness direction of the substrate 10 depends upon the depth D of grooves, and the depth D is set to a proper value to set easily the effective depth of the electric field to a desired value. Thus, the optical switching array which can be driven with a low voltage and has a high contrast is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switcher array that makes full use of electro-optic effects, and more particularly to an optical switching array that can be driven at low voltage and that enhances the contrast of emitted light.

Optical switching arrays applied to spatial light modulators, optical printers, and the like are known that make full use of the electro-optic effects of various crystalline materials.

This is, for example, 1 composition # (Pb1-, Laz) (Z
r, -yTi,), -,0° (hereinafter referred to as PLZT), and its second-order electro-optic effect
(Japanese Patent Application Laid-Open No. 52-8842) uses the Kerr effect to perform the original on/off control. That is, as shown in the plan view 1 (b) K and the vertical cross-sectional view taken along the line I-I in FIG. 1 (a) K, a common electrode 2& is formed on the surface of the substrate 1 made of PLZT, A plurality of individual electrodes 3 are spaced apart by an appropriate length to face this.
When a DC voltage is selectively applied between the 1 individual electrode 3a and the common electrode 2a, the surface layer K of the substrate 1 between the two
When an iI field is generated and incident light polarized in one direction by a polarizer is incident in the thickness direction of the substrate 1 between the individual electrode 3a and the common electrode 2a where an electric field is generated, the electro-optic effect causes The plane of polarization of the light wave is polarized by 90 degrees. Therefore.

If an analyzer is installed in the direction perpendicular to the direction of polarization of the polarizer at the pass point of the emitted light, the emitted light that has propagated between the electrodes with the full voltage applied will pass through the analyzer, and the other emitted light will pass through the analyzer. An optical switch array is constructed that is shielded from light and turns on and off light waves after passing through an analyzer in response to on and off of applied voltage.

Further, the optical switching array shown in FIG. 2(a) (vertical cross-sectional view taken along line nn in FIG. 2(b)) and FIG. 2(b) (plan view) has a comb on the surface of the substrate 10. tooth-shaped common electrode 2b
"fr" is formed, and an individual electrode 3b is formed between the comb tooth portions, and similarly, the individual electrode 3b and the common IE&2
Between b! The plane of polarization of the light wave is deflected by the electric field generated in the surface layer of the substrate 1 between the two by applying pressure. However, in order to use these optical switching arrays to deflect the plane of polarization of light waves and control the light waves on and off with a practically sufficient contrast (difference in intensity between on and off light waves), a high electric field is required. The problem was that a voltage driving power source was required.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an optical switching array that can be driven with low voltage and has high contrast. The optical switching array of the present invention includes a substrate comprising one optical transmission medium and having at least one #I formed on its surface, a common electrode formed on the surface of the substrate extending in the longitudinal direction of the groove, and an appropriate distance apart from the common electrode such that the longitudinal direction thereof is perpendicular to the longitudinal direction of the groove? and a plurality of individual electrodes formed in parallel in a strip shape, and at least one of the common electrode or the individual electrodes forms at least a part of the entire wall surface of the groove. It is. In this case, the substrate #'i has a pair of grooves arranged in parallel, the common electrode has one wall surface between the pair of grooves as at least a part of its forming surface, and the common electrode The pole is preferably configured such that the other wall surface forms at least a part of the surface on which it is formed.

3(a), ■) shows the vicinity of the opposing region of the individual electrode 3a and the common electrode 2a of the conventional optical switching array of FIG. 1, and FIG. 3(b) is a plan view, and FIG. ) is its ■−
■It is a vertical cross-sectional view taken along lines. Individual electrode 3a and common electrode 2
When a DC voltage is applied between a and a, an electric field is generated as shown by the lines of electric force indicated by the arrows in the figure. Then, as shown by the white arrow in Figure 1, linearly polarized light polarized in the direction of 45 with respect to this electric field direction is transmitted to the substrate l between the individual wL pole 3a and the common pole 2a.
When incident on the substrate 1 in its thickness direction, the PLZ constituting the substrate 1
Due to the Kerr effect of T, an optical phase difference occurs in this light wave, and when this phase difference is 180° (π), the light emitted from the substrate 1 becomes linearly polarized light whose polarization plane is perpendicular to that of the incident light. ,ru.

Therefore, let the magnitude of the optical phase difference be tr.

F is expressed by the following formula (1).

r-, jn do ・・・・・・・・・−・−
...(1) -2π, -0 However, λ: jt, wave wavelength h: refractive index difference of PLZT between the electric field direction and the direction perpendicular to this do: As shown in Fig. 3 C1; JK, the electric field The effective depth refractive index difference formed by - is expressed as the following equation.

jn = ”@n511 R@E” −=−−
-・=-(2) However, the refractive index of crab PLZT R: the force-(Kerr) constant E: the applied electric field strength, and the intensity of the incident light is t-If, and the plane of polarization is changed by the field E to that of the incident light. What is the intensity of the outgoing light that is deflected at right angles and passes through the analyzer? If I, then the relationship between I and Ii will be as shown in equation (3) below.

Engineering=IIIi-Ding・・・・・・・・・・・・・
...(3) By the way, the intensity I of the emitted light after passing through the analyzer is determined by the optical phase difference r caused by the Il field Eff.
The larger the value, the higher the value, and therefore, the contrast of the emitted light becomes higher depending on whether the applied voltage is turned on or off. In other words, high intensity emitted light can be obtained with a lower value of the electric field E.

The magnitude of the optical phase difference r depends on the effective depth dof, but as shown in FIG.
If the distance from a is fd, the effective depth dO at which an effective electric field is formed within the substrate 1 is approximately equal to dK. Therefore, in order to increase r, it is necessary to increase the electrode spacing d, but there is a practical limit to increasing the length of d, especially when increasing the density of the optical switching array. Pole spacing d is 10
It becomes 0 μm or less. This situation is the same in the optical switching array shown in FIG. 2, as well as in the conventional optical switching array.

Electric field strength E? I had no choice but to set it to a high value to obtain the optical phase difference rf necessary for actual armor.

With this background in mind, the present invention has been developed based on the applied voltage (and therefore the electric field E)? In order to obtain a practically sufficient optical phase difference while setting it to a low value, K was determined from the viewpoint that it is necessary to make the effective depth at which the electric wire is formed the entire length, and the following is shown below. , the optical switching array according to the present invention will be specifically explained. Figure 4(b) is its plan view, Figure 4(a)
is a vertical cross-sectional view taken along line IV-IV in FIG. 4(b), FIG. 5 is a schematic diagram of the implementation state of light wave on/off control by the optical switching array of the present invention, and FIG. 6 is a detailed diagram of the present invention. It is an explanatory diagram. Substrate 10 (composed of PLZT as shown in No. 4. In the case of x=0°09°y=Q, 35, that is,
Composition ratio of Pb/La/Zr/Ti #91/9/65
/35-t' 6 PLZT exhibits a remarkable second-order electro-optic effect (Kerr effect).

It is preferable to use PLZT'f having this composition ratio.

A pair of grooves 14 and 15 having a depth D are formed on the surface of the substrate 100 so as to be parallel to each other and separated by an appropriate length. These grooves 14 and 15 are formed by photolithography ([by PLZT]).
k It can be easily formed by etching with a strong acid such as HCL.

The common electrodes 12 and 12 are etched so that a pair of opposing wall surfaces 16a and 16b of the wall portion 16 remaining without being etched between the grooves 14 and 15 become at least a part of the forming surface thereof. Individual electrode 13? Form. These are all thin layers of Au or the like, and include the wall surface 16a of the common electrode 12, the bottom surface of the groove 14, and the groove 1.
4 are formed along the longitudinal direction of the groove 14 on the opposing wall surface and a part of the surface of the substrate 10. On the other hand, 13 individual electrodes are not completely band-shaped when viewed from above, and a plurality of individual electrodes are formed in parallel at appropriate length intervals in the longitudinal direction of the groove 5.
Each individual [t#i13 is the wall surface 16b, the bottom surface of the groove 15, the groove 1
The wall surface 16b of the groove 150 is formed on a portion of the opposing wall surface and the surface of the substrate 100, with its elongated direction perpendicular to the longitudinal direction of the groove 150.

In the optical switching array constructed as described above, the common electrode 12 and the individual l! VC between Kiwami 13! When the total pressure is applied, as shown in FIG.
An electric field (or an electric field in the opposite direction) is generated toward the individual electrode 13 formed with K. Therefore, as shown by the white arrow in Figure 1, the common electrode 12 and the individual electrodes 13
When all of the light waves are made incident so as to pass between them, the light waves are subjected to the electro-optic effect and their plane of polarization is deflected. Therefore, when controlling the light waves on and off using this optical switching array, as shown in FIG. Then, the -jQ switching array is installed so that the light waves propagate from the surface of the wall portion 16 in the thickness direction of the substrate 10.

That is, the light wave from the lamp light source 21 is condensed by the slit 23 and becomes a thin parallel beam extending in the longitudinal direction of the wall 16 of the substrate 10, and is incident on the surface of the wall 16, and the lamp light source A polarizer 22 is provided on the optical path between the lamp light source 21 and the slit 23 to direct the light waves from the lamp light source 21 in the direction of the electric field to be formed in the all-optical switching array, that is, from the groove 14 of the substrate 10 to the groove 15. The light is polarized by 45 degrees with respect to the direction and is made to be incident on the wall 16 of the substrate 10. An analyzer 24 is provided in the passband of the light emitted from the original switching array, and the analyzer 24 passes through the polarization direction perpendicular to the polarization direction of the polarizer 22.
The light waves that have passed through the optical fiber array 25 are irradiated onto an irradiation surface 26 by a focusing optical fiber array 25.

By the way, among the several individual electrodes 13, the wall 16ff between the individual electrode 13 to which a voltage is applied and the common pole 12
Since a Kt field is generated between both electrodes as shown in FIG. 6, the incident light that is narrowed by the polarizer 22 so as to be inclined at 45 degrees with respect to the electric field direction passes through this electric field generation region. An optical phase difference occurs due to the electro-optic effect, and the polarizer 22
The light passes through an analyzer 24 whose polarization direction is perpendicular to the direction of polarization, and is irradiated by an optical fiber array 25 onto an irradiation surface 26 at a position corresponding to the electric field generation area.

On the other hand, the light waves incident on the wall 16 between the individual electrodes 13 and the common electrode 12 to which no pressure is applied contain the polarization direction in the same direction as the incident light without causing an optical phase difference. Since the light waves are emitted from the substrate 10, they do not pass through the analyzer 24, and therefore, the light waves are not irradiated onto the irradiation surface 26 at the position corresponding to this non-electric field generation area. In this way, one individual electrode 13
By applying a selective KIl pressure to the irradiation surface 26, the light waves irradiated onto the irradiation surface 26 can be turned on and off.

In the optical switching array according to the present invention, as shown in FIG.
The effective depth Do#t of the electric field ' formed in the thickness direction of the groove 14.15 depends on the depth D of the groove 14.15 (see FIG. 4 (IL)),
By appropriately setting the groove depth D, the effective depth l of the electric field can be increased.
)o? It can be easily set to a desired value. Therefore, even if the distance between one individual electrode 13 and the common W11 pole 12 is small in a high-density optical switching array, 1) o can be set to a long dimension, so (1), (2)
As is clear from the equation, an extremely strong optical phase difference r? at low power (i.e., low electric field) As shown in (3) above, the intensity I#i of the emitted light after passing through the analyzer is extremely high. Therefore, the contrast when the light waves are turned on and off is high, and it can be driven with low voltage. By the way, 1
Linear polarization with a plane of polarization perpendicular to the incident light, giving rise to a maximum phase difference of 80° (r=π)? In conventional optical switching arrays (see Figures 1 and 2), the applied voltage V required to obtain
is 0.55μ, R=3− for PLZTK.
8 X 10-” (m”/V”) s n =2-
3, so these numbers, r-π and E=v/d
(1), (Substituting the relationship t into equation 21, teV=98(
i lt) is required. On the other hand, in the optical switching array according to the present invention (see FIGS. 4 and 6), assuming that the depth field of the groove is Dt-250μ and the effective depth Do of the electric field is equal to D, ()≧D ).

It is determined that V=55 (/lt), and the same - phase difference can be obtained with an extremely low voltage compared to the conventional method. In other words, in the present invention, with the same applied voltage as in the past, an extremely large phase difference can be obtained compared to the conventional one, and the contrast during one-element switching is high.1 The optical switching array of the present invention is extremely efficient. As described in detail, according to the present invention, an optical switching array that can be driven at low voltage and has high contrast is realized. Note that the present invention is not limited to the above-described specific embodiments, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the depth of the grooves 14 and 15 and the height of the wall portion 16 do not necessarily have to match vr1 as in the above embodiment.

Further, the cross-sectional shape of the grooves 14 and 15 may not be rectangular as in the above embodiment, but may be curved. Furthermore, the number of grooves in one groove is not two (one pair) as in the above embodiment (although even one groove can have a sufficient effect. In this case, electrode formation is performed using common 11E electrodes as shown in FIG. Alternatively, at least one of the individual electrodes may be formed on the wall surface 18#c of the groove 17.

[Brief explanation of the drawing]

FIG. 1 (m: J and A) and FIG. 2 (A) and A) are a longitudinal sectional view and a plan view, respectively, of a conventional optical switching array. Figures 3 (a) and (b) are explanatory diagrams of the electro-optic effect;
Figures (a) and (6) are a vertical cross-sectional view and a plan view, respectively, of the optical switching array according to the invention, Figure 5 is a schematic diagram of the state in which light wave on-off control is implemented by the original switching array, and Figure 6- Detailed explanatory diagram of Morimoto's invention. FIG. 7 is a schematic diagram showing another embodiment of the present invention.〇(Explanation of symbols) 1, 10-・Substrate 21L, 2b, 12
""Common electrodes 3a, 3b, 13-individual electrodes 14
．． 15.17-...Groove 16...Wall part 1
6a, 16b, 18 = wall patent applicant Rico Co., Ltd. - Figure 1 Figure 2

Claims (1)

[Claims] 1. A substrate made of an optical transmission medium and having at least one groove formed on its surface, a common electrode formed on the surface of the substrate extending in the longitudinal direction of the groove, and the common electrode [ # has a plurality of individual electrodes formed in parallel in a strip shape at appropriate length intervals so that the longitudinal direction thereof is perpendicular to the longitudinal direction of the groove, and at least one of the common electrodes or the individual electrodes is provided. One side shall be at least a part of the wall surface t of the groove where it is formed.
2. In the above item 1, the substrate has a pair of grooves in parallel, and the common electrode is connected to one of the wall tubes of the wall between the pair of grooves. An optical switching array characterized in that the individual electrodes have the other wall surface as at least a part of the forming surface.