Novel Solid-State Spatial Light Modulator on Integrated Circuits for High-Speed Applications with Electro-Optic Thin Film

Abstract

Novel solid-state spatial light modulator (SLM) is developed. An electro-optic spatial light modulator (EOSLM) has advantages of high-speed operation, solid-state structure and easy integration with silicon LSIs in comparison with liquid crystal displays (LCD) and micro-electro-mechanical system (MEMS) displays. We propose a kind of Fabry-Perot type planer optical pixel to achieve high optical efficiency and high aperture ratio. The use of sol-gel technique makes it possible to fabricate optically smooth 800nm-thick lead zirconate titanate (PZT) films, which results in sufficient transparency for the three primary colors of visible light. The large electro-optic effects of An=0.026 is confirmed, and the optical switching response of 7ns is fastest compared with that have ever been reported. The prototype 180x1 80 SLM chip, which includes pixel driver circuits, is fabricated and successfully demonstrated.High-speed SLM has been strongly demanded for holographic data storage, massively parallel optical processors and 3-dimmensional displays. An electro-optic spatial light modulator (EOSLM) has advantages of low drive current and high transparency at short wavelength region corresponding to blue color compared with high-speed Magneto-optic spatial light modulator (MOSLM) [1]. However, EOSLM had been problems of high drive voltage i.e. 100V and low aperture ratio. We propose a kind of Fabry-Perot type planer optical cell to solve above two problems. This paper describes the novel spatial light modulator device technology, such as an electro-optic thin film, device structure and optical switching characteristics. A key point of the proposed technique is to fabricate an optical film with large electro-optic effects on Si LSIs. The PLZT-on-LSI technology results in successful demonstration of 180x1 80 SLM chip display. Figure 1 illustrates basic structure of an optical switching cell. The PLZT thin film, which has high electro-optic effects, is fabricated on Si LSIs together with its top and bottom electrodes. The top electrode is made of transparent conductive material, such as indium tin oxide (ITO). A dielectric multi-layer mirror (DMM) is deposited on the ITO electrode, and a Fabry-Perot resonator is formed between the upper mirror and the bottom platinum electrode. It has resonant wavelengths represented by 4, . A refractive index ellipsoid of the PZT film is deformed by applied electric field and the refractive index for a normal incidence light increases by applying electric field. The refractive index change An13 affects resonant wavelength A,. Figure 2 shows simulated optical switching properties of PZT capacitors. The reported highest value of An is 0.1 for bulk PLZT (Lanthanum doped PZT). In this case, the refractive index can be controlled from 2.5 to 2.6 by applying electric field. In the case that reflectance of the DMM and the bottom Pt are same, the minimum reflectance becomes zero and the cell can switch the incident light by applying electric field.Electro-optic PLZT thin films are deposited by sol-g...

High Performance Ridge Type PLZT Optical Switch With Offset Upper Electrode

“…It was reported that the EO coefficient of PLZT(8/65/35:x=8%,y=65%,1-y=35%)ceramic is 612 pm/V [1], [2] , and the reported value for PLZT (9/65/35) thin films was 45 pm/V [2], which is larger than that of the lithium niobate (LN). The optical switches and modulators fabricated based on PLZT waveguides with nano-second speed were reported [3]- [8].To increase the modulation efficiency and decrease device size, Indium Tin Oxide (ITO) electrode fabricated on top of the ridge type waveguide directly [9] is required.…”