KR20020026646A - Optical device - Google Patents

Abstract

PURPOSE: An optical device is provided to accumulate a dielectric film having a specific refractive index and an electro-optical thin film having a refraction index varied by an applied electric field, and to transmit light in a specific wavelength of a photonic band gap formed in the dielectric film and change a wavelength of the transmitted light by applying an electric field, so that the light wavelength is changed without using a polarizer. CONSTITUTION: An electro-optical thin film(1) acts as a defect layer. A dielectric film(2) is accumulated in an upper and a lower parts of the electro-optical thin film. The dielectric film(1) and the electro-optical thin film(1) are alternatively and sequentially accumulated, centered on the electro-optical thin film(1). When an electric field is not applied in an optical device, only a specific wavelength of light is transmitted. When an electric field is applied, a refraction index of the electro-optical thin film(1) is varied and a light transmitting wavelength is moved. Accordingly, incident light is switched, modulated and filtered without using a polarizer. When light is irradiated to optical materials, a photonic band gap preventing the transmission of light is formed due to the periodicity of the electro-optical thin film(1) and the dielectric film(2). The specific light transmitting wavelength exists in the photonic band gap, by the electro-optical thin film inserted in a center of the optical materials.

Description

Optical device {OPTICAL DEVICE}

TECHNICAL FIELD The present invention relates to an optical device, and more particularly, to an optical device that enables the wavelength of light to be transmitted to be transmitted by application of an electric field.

Generally, optical devices are used in the fields of optical information processing, optical computing, optical information storage using holography, micro displays, and the like, and conventional optical devices use electro-optic crystals and magneto-optical crystals. Both methods using optical and magneto-optic crystals use a method of rotating the polarization plane of incident light and then modulating the intensity of incident light using a polarizer.

As such, when a separate polarizer is used, its structure is complicated, and the extinction ratio is reduced due to the loss of light by the polarizer itself.

As described above, the conventional optical device uses a polarizer to modulate incident light, so that the structure thereof is complicated, and thus manufacturing is not easy, and the extinction ratio is relatively small due to light loss of the polarizer itself.

It is an object of the present invention to provide an optical device capable of modulating incident light without using a polarizer.

1 is a cross-sectional view of an embodiment of the optical device of the present invention.

FIG. 2 is a graph showing changes in wavelength of transmitted light according to application of an electric field in FIG. 1; FIG.

Fig. 3 is another embodiment of the present invention optical device.

Fig. 4 is a cross-sectional view of the electrode provided on the upper and lower front surfaces of the optical device in Fig. 1;

Fig. 5 is a cross-sectional view of the electrode provided on the upper and lower front surfaces of the optical device in Fig. 3;

FIG. 6 is a cross-sectional view of FIG. 1 in which a plurality of electrodes are spaced apart from each other by a predetermined distance on the upper and lower portions of the optical device.

FIG. 7 is a cross-sectional view of FIG. 3 in which a plurality of electrodes are spaced apart from each other by a predetermined distance on the upper and lower portions of the optical device.

* Description of the symbols for the main parts of the drawings *

1: electro-optic thin film 2, 6: dielectric film

3: photonic band gap 4: localized light transmission wavelength

7: electrode

The above object is an electro-optic thin film which acts as a defect layer; This is achieved by constructing a dielectric film and an electro-optical thin film which are alternately stacked on the upper and lower surfaces of the electro-optical thin film, and described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of an optical device of the present invention, in which a dielectric film 2 and an electro-optical thin film 1 are alternately stacked on both sides with respect to an electro-optic thin film 1 acting as a defect layer as shown therein. Has a structure.

At this time, the electro-optical thin film 1 is a thin film in which the refractive index of the light is changed by the application of an electric field. For example, K (TaNb) O ₃ (KTN), BaTiO ₃ , KNbO ₃ , PLZT, LiNbO ₃ , (SrBa) Nb ₂ O ₆ , Ba ₂ NaNb ₅ O ₁₅ , K ₃ Li ₂ Nb ₅ O ₁₅ , KSr ₂ Nb ₅ O ₆ , KNSBN, KH ₂ PO ₄ (KDP), KD ₂ PO ₄ (KD ^* P), NH ₄ H One or multiple thin films selected from ₂ PO ₄ (ADP), KH ₂ AsO ₄ , RbH ₂ PO ₄ (RDA), Pb ₅ Ge ₃ O ₁₁ , KTiOPO ₄ (KTP), liquid crystals are used.

In addition, the dielectric film 2 uses, for example, one or a plurality of thin films selected from Ta ₂ O ₅ , SiO ₂ , TiO ₂ , SiN, and AlN.

Such an optical device transmits only light having a specific wavelength when no electric field is applied. When the electric field is applied, the refractive index of the electro-optic thin film 1 is changed, and the light transmission wavelength is shifted. Without this, incident light can be switched, modulated, and filtered.

FIG. 2 is a graph showing wavelengths of incident light modulated by the present invention. As shown in FIG. 1, when the light is irradiated to the optical material of the present invention shown in FIG. 1, the electro-optic thin film 1 and the dielectric film 2 Due to the periodicity of), a photonic band gap 3 is formed in which light transmission is not allowed.

However, the localized light transmission wavelength 4, which is a specific wavelength region in which incident light is transmitted in the photonic band gap 3 by the electro-optic thin film 1 inserted in the center of the optical material as a defect layer, It exists.

The transmittance of the localized light transmission wavelength 4 located in the photonic band gap 3 at this time exhibits a value close to one.

As described above, the optical device according to the present invention selectively transmits only light having a specific wavelength in a wavelength region that does not transmit light, and when the electric field is applied to the optical material, the localized light transmission wavelength 4 As shown in FIG. 2, the localized light transmission wavelength 4 is shifted by the change of the wavelength according to the change of the refractive index of the electro-optic thin film 1 by the change of the refractive index of the optical thin film 1 Light is transmitted at the wavelength (5).

By changing the wavelength of the transmitted light without using a polarizer as described above, it is possible to improve the sensitivity by preventing the loss of the transmitted light, and the application field of such an optical device is that the incident light of a specific wavelength without the application of the electric field Since the light is transmitted, it is possible to easily use the optical switch in the off state when the electric field is applied and the incident light of the specific wavelength is not transmitted.

In addition, since the degree of movement of the first localized light transmission wavelength 4 is determined according to the first or second function in the intensity of the applied electric field, it can be used as an analog light modulator using an electric field, and the movement rate is determined. Therefore, application to a tunable optical filter is also possible.

The thickness of the electro-optical thin film 1 and the dielectric film 2 is set to λ / (4n) when the wavelength order of the light source to be used, that is, the refractive index of the dielectric thin film is n, and the wavelength of the light source is λ. do.

As described above, the optical device of the present invention shifts the localized light transmission wavelength 4 according to the presence or absence of an electric field to block or transmit the light of the light source, and does not use a polarizer for blocking and transmitting the light. Small extinction ratio can be obtained. In the region of the localized light transmission wavelength 4, the light transmittance of almost 1 is shown. After shifting the wavelength, the transmittance at the localized light transmission wavelength 4 is reduced to 0 so that a large extinction ratio can be obtained. Thus, when applied to each application field, the sensitivity can be improved.

FIG. 3 is another embodiment of the optical device of the present invention, in which an electro-optic thin film 1, which is a defect body, is placed at the center, and has a refractive index different from that of the first dielectric film 2 and the first dielectric film 2. As shown in FIG. The second dielectric films 6 are stacked in this order.

In the above example, the electro-optic thin film 1 is positioned only at the center of the optical device, and when the electric field is applied, the refractive index of the electro-optic thin film 1 located at the center is changed so that the localized light transmission wavelength 4 is moved. Done.

The thicknesses of the two dielectric films 2 and 6 are set to a value of λ / (4n) when the refractive index of the dielectric thin film is n and the wavelength of the light source is λ. The thickness of the electro-optic thin film 1 is set to λ / (2m) when the refractive index of the electro-optic thin film 1 is m and the wavelength of the light source is λ, and is transmitted by application of an electric field as described above. It is possible to perform the operation of changing the wavelength of the light.

4 and 5 have electrodes 7 formed on the front surfaces of the top and bottom surfaces of the optical device shown in FIGS. 1 and 3, respectively, and the voltage is applied to the electrodes 7 at this time. An electric field is applied to the optical thin film 1.

6 and 7 are schematic diagrams illustrating spatial light modulators using the optical devices shown in FIGS. 1 and 3, respectively. As shown in FIG. 6, the upper surface of the optical device shown in FIGS. And a driving unit 9 disposed on the bottom surface and spaced apart from each other by a predetermined interval, and having a predetermined area, and applying a voltage to each of the plurality of electrodes 7 under the control of the controller 8. do.

By controlling each of the electrodes 7 in the above-described configuration, it is possible to use a predetermined area of the optical device located between the electrodes 7 facing the upper and lower sides as a pixel.

In this way, by controlling the application of an electric field to a specific portion of the optical device it is possible to spatially modulate the incident light, it is possible to use the binary spatial light modulator by the same voltage value applied to the electrode (7), The voltage applied to the electrode 7 can be continuously changed to be used as an analog spatial light modulator.

As described above, the optical device of the present invention stacks a dielectric film having a specific refractive index and an electro-optic thin film whose refractive index changes according to the application of an electric field, and transmits light at a specific wavelength within a photonic band gap formed by the dielectric film. By changing the wavelength of the transmitted light according to the application, it is possible to change the transmission wavelength of the light without using the polarizer, thereby simplifying the optical device and increasing the extinction ratio by preventing the loss of light by the polarizer. .

Claims (7)

An electro-optic thin film acting as a defect layer; An optical device comprising a dielectric film and an electro-optical thin film which are laminated alternately on the upper and lower surfaces of the electro-optical thin film in sequence. The method of claim 1, wherein the electro-optical thin film is a thin film (K (TaNb) O ₃ (KTN), BaTiO ₃ , KNbO ₃ , PLZT, LiNbO ₃ , (SrBa) Nb ₂ O _{6 The} refractive index changes with the application of an electric field , Ba ₂ NaNb ₅ O ₁₅ , K ₃ Li ₂ Nb ₅ O ₁₅ , KSr ₂ Nb ₅ O ₆ , KNSBN, KH ₂ PO ₄ (KDP), KD ₂ PO ₄ (KD ^* P), NH ₄ H ₂ PO ₄ (ADP), KH ₂ AsO ₄ , RbH ₂ PO ₄ (RDA), Pb ₅ Ge ₃ O ₁₁ , KTiOPO ₄ (KTP), liquid crystal). The optical device of claim 1, wherein the dielectric film is one or a plurality of thin films selected from Ta ₂ O ₅ , SiO ₂ , TiO ₂ , SiN, and AlN. The semiconductor device of claim 1, further comprising electrodes disposed on upper and lower surfaces of the stacked dielectric film and the electro-optical thin film, or a plurality of electrodes having a predetermined area spaced apart from each other by a predetermined distance and an electrode disposed on the lower front surface. Optical device characterized in that it became. An electro-optic thin film acting as a defect layer; An optical device comprising a dielectric film having different refractive indices sequentially stacked on the upper and lower surfaces of the electro-optical thin film. The optical device of claim 5, wherein each of the dielectric films having different refractive indices is one or a plurality of thin films selected from Ta ₂ O ₅ , SiO ₂ , TiO ₂ , SiN, and AlN. The electrode of claim 5, wherein the electrodes are positioned on the front and bottom surfaces of the stacked dielectric films having different refractive indices, or the plurality of electrodes having a predetermined area and a predetermined area spaced apart from each other at an upper side of the stacked dielectric films. Optical device, characterized in that it further comprises.