JP2001235715A - Dielectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that in an optical device of a thin film waveguide type using a bulk single crystal, it is required to make light propagate in a long waveguide because the electro-optic effect of the dielectric material is not so high, and this causes decay in the light intensity or requires high voltage to drive. SOLUTION: In the dielectric device consisting of an electrode, a dielectric thin film formed on the electrode and an electrode formed on the dielectric thin film, the dielectric film consists of a ferroelectric material film. The film has such a structure that a plurality of regions having polarization direction of the ferroelectric material perpendicular to each other are alternately arranged in the film plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in optical modulators, shutters, and the like used in optical communication equipment, display devices, and the like.

[0002]

2. Description of the Related Art In an era where an optical fiber is connected to each home and a large amount of information can be freely accessed, a small and highly efficient optical device, particularly an optical modulator and an optical shutter are required. Until now, in an optical device using a dielectric, a dielectric waveguide was formed on a substrate, and a voltage was applied to an electrode formed on the waveguide to modulate light by an electro-optic effect of the dielectric. . Alternatively, the surface of the bulk electro-optic crystal is treated to partially increase the refractive index (eg, LiNbO
_In the case of forming an optical waveguide by performing Ti diffusion or proton exchange with respect to _3, for example, studies are being made. According to these methods, since the electro-optic effect of the dielectric is not so large, a large driving voltage is required or a long waveguide is required. In addition, poor crystallinity occurs during the initial stage of crystal growth at the interface between the thin film and the waveguide, and unevenness at the substrate interface causes light scattering and causes light attenuation in the waveguide. ing.

[0003]

In an optical element using a thin film waveguide type bulk single crystal, as described in the prior art, an effective effect is produced since the electro-optic effect of the dielectric is not so large. To achieve this, it was necessary to obtain a great effect by propagating light through a long waveguide. Therefore, there has been a problem that the light intensity is attenuated or a high voltage is required for driving.

[0004]

In a dielectric element comprising an electrode, a dielectric thin film formed on the electrode, and an electrode formed on the dielectric thin film, the dielectric film is a ferroelectric film,
A dielectric element has a structure in which a plurality of regions in which the polarization directions of the ferroelectrics are orthogonal to each other are alternately arranged in the film plane. At that time, in the dielectric element, the direction of one polarization of the ferroelectric is parallel to the film surface,
The dielectric element is characterized in that the other is perpendicular to the film surface. Furthermore, a dielectric element characterized by being formed of a material that transmits visible light is used as the electrode. At this time, as a ferroelectric thin film, Pb, La, Ti,
The use of an oxide ferroelectric containing Zr as a main component can provide a still greater effect. Alternatively, a similar result can be obtained by forming a dielectric element using an oxide ferroelectric thin film mainly containing Ba and Ti as the ferroelectric thin film. It is also effective to use an oxide ferroelectric thin film containing Li, Ta, and Nb as main components as the ferroelectric thin film.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

(Example 1) A p-type having a resistance of 0.01 Ω · cm
(100) 10 nm thick TiO on Si substrate 1 _TwoMembrane 2
Is formed by sputtering, and
100 width by technology and reactive ion etching
It was processed into a stripe shape of nm. After that, Y_TwoO_Three
After the thin film 3 is similarly formed by the sputtering method, the CMP
Polished surface by TiO_TwoAnd Y_TwoO_Three100 thin films
Substrates alternately arranged in stripes of nm were prepared.
Then, (PbLa) (ZrTi) O_Three(PLZT) thin
The films (4 and 5) are
Growing by the talling method. Substrate temperature is 600 ℃, gas pressure
Is 10 mTorr (1 Torr = 133.322P)
a), Ar / O_TwoThe ratio is 9/1. Growth rate at this time
The degree was 6 nm per minute. PL produced by this method
ZT thin film is made of TiO_TwoAbove, the (111) orientation 4, Y_TwoO_Three
Above, the (001) orientation was 5. After that, PLZT
Form tin-added indium oxide (ITO) electrode 6 on the film
Then, the substrate is removed by etching to form an opening 8.
Then, an ITO electrode 7 was formed from the back surface by sputtering, and FIG.
The dielectric element shown in FIG.

The manufactured dielectric element is inserted between the polarizer and the analyzer, and a voltage of about 600 is applied while applying a voltage between the electrodes.
nm monochromatic light was incident, and the light intensity was measured. FIG. 2 shows the relationship between the transmitted light intensity and the voltage. As is apparent from the figure, the amount of transmitted light sharply decreased when a voltage of 5 V was applied. This indicates that the dielectric element of the present invention functions as an optical switch.

[0008] The dynamic characteristics were examined by applying an AC voltage to the device. The frequency response of the device was flat up to 2 GHz. Further, at high frequencies, a phenomenon was observed in which the ON / OFF of light was reduced. This is due to defects, grain boundaries, etc.
It is considered to be caused by the crystallinity of ZT, and it is clear that higher crystallization of PLZT also enables response at higher frequencies. From this, it became clear that the dielectric element of the present invention can be applied as a high-frequency optical modulator.

In this embodiment, PLZT is used as the ferroelectric film.
In addition, similar experiments were performed using BaTiO ₃ , LiNbO ₃ , and LiTaO _{3. In} each case, similar results were obtained, and it was demonstrated that the dielectric element according to the present invention can be manufactured with good reproducibility. Was.

[0010]

As described above, by implementing the present invention, it is possible to easily provide an optical switch and an optical modulator operating at high speed, and it is expected that the economic effect on the industry will be remarkable. Is done.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a dielectric element manufactured in an example according to the present invention.

FIG. 2 is a diagram showing a relationship between a voltage and a light transmittance of a dielectric element.

[Explanation of symbols]

Reference Signs List 1 Si substrate 2 TiO ₂ thin film 3 Y ₂ O ₃ thin film 4 (111) -oriented PLZT 5 (001) -oriented PLZT 6 Upper electrode 7 Lower electrode 8 Opening

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takashi Nishikawa 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H079 AA02 AA13 BA01 CA05 DA03 DA04 DA22 EA02 EB04

Claims (6)

[Claims] 1. A dielectric device comprising an electrode, a dielectric thin film formed on the electrode, and an electrode formed on the dielectric thin film, wherein the dielectric film is a ferroelectric film, and the polarization of the ferroelectric is A dielectric element having a structure in which a plurality of regions whose directions are orthogonal to each other are alternately arranged in a film plane. 2. The dielectric element according to claim 1, wherein the direction of polarization of one of the ferroelectrics is parallel to the film surface and the other is perpendicular to the film surface. 3. The dielectric element according to claim 1, wherein the electrode is formed of a material that transmits visible light. 4. A ferroelectric thin film comprising Pb, La, Ti,
A dielectric element comprising an oxide ferroelectric containing Zr as a main component. 5. A dielectric element according to claim 1, wherein said ferroelectric thin film is an oxide ferroelectric thin film containing Ba and Ti as main components. 6. A dielectric element characterized in that the ferroelectric thin film is an oxide ferroelectric thin film containing Li, Ta, and Nb as main components.