Jae-Hyuk Park

High-speed optical microscanner driven with resonation of Lam Waves using Pb(Zr.Ti)O3 thick films formed by aerosol deposition

A high-performance optical microscanner with a resonance frequency over 20 kHz and a scan angle (peak-to-peak value) over 30° in atmospheric ambient, was successfully fabricated by deposit piezoelectric materials at a high rate by the AD method onto a metal scanner structure, which was fabricated by mechanical machining. The scanner is applicable to SVGA high-resolution display of 800×600 or more. This method is a powerful tool for realizing ceramic integration with metal components.

Fabrication and Evaluation of Lead-Free Piezoelectric Ceramic LF4 Thick Film Deposited by Aerosol Deposition Method

(K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 (LF4) thick films were directly prepared on glass, stainless-steel and Pt/Ti/ZrO2 substrates at room temperature by the aerosol deposition method (ADM). The effects of moisture content in the starting powder and postdeposition annealing temperature on the dielectric properties of LF4 film were investigated. The LF4 film prepared using preheated powder (moisture content of 0.006%) has dielectric properties with high stability at increasing frequencies, whereas the LF4 film prepared with non-preheated powders (0.21%) has a dielectric constant that decreases abruptly at higher frequencies. When the postdeposition annealing temperature of the film was 600 °C, the dielectric constant increased from 200 to 343 at 1 MHz with increasing preheating temperature from 150 to 1100 °C. Also, the dielectric constant of the film increased from 231 to 559 with increasing annealing temperature from 400 to 1000 °C. These results strongly indicate that moisture elimination in starting powders through preheating and postdeposition annealing for ADM plays an important role in realizing good dielectric properties of LF4 film for practical application as lead-free piezoelectric ceramics. Also, the Curie temperature (Tc) of the deposited LF4 film was 250 °C.

Magnetooptic Spatial Light Modulator for Volumetric Digital Recording System

A novel reflective magnetooptic spatial light modulator has been fabricated and its dynamic switching testing was investigated. Improvements by a factor of three in pixel switching sensitivity and power consumption could be achieved by the use of a wedge-shaped drive line, compared to the use of a conventional reflective magnetooptic spatial light modulator. Simpler fabrication processes by a factor of two could also be achieved by the use of a drive line which covers most of the surface of the pixel, a non-rectangular channel and a unpatterned insulator layer.

Magneto-optic spatial light modulators driven by an electric field

A magneto-optic spatial light modulator driven by an electric field is fabricated by using the electrostrictive effect of [Pb(Zr0.52Ti0.48)O3] (PZT) thin film. As the stress field induced by the PZT thin film reduces the anisotropy energy of the structured garnet film, we find that the pixels can be easily switched in accordance with or without the small external bias field. When peak-to-peak 8 V at the X and Y conductors is applied with the external bias field of 40 Oe at the fabricated device, the selected pixel is switched independently.

Effects of groove depth and patterned permalloy film on magnetization switching of LPE-garnet pixels for use in magneto-optic spatial light modulators

Effects of pixel groove depth and patterned permalloy assist film for the magnetization switching of LPE-garnet film were studied experimentally. The results showed that the magnetization field to switch a structured pixel could be reduced by controlling the pixel groove depth. It was also found that the permalloy assist film creates a unique pair-domain pattern within a single garnet pixel, which is useful for realizing a new type of magneto-optic spatial light modulator with high resistivity to noise.

Magnetooptic spatial light modulator with one-step pattern growth on ion-milled substrates by liquid-phase epitaxy

We demonstrate a magnetooptic spatial light modulator with one-step pattern formation of iron-garnet films on ion-milled substrates by liquid-phase epitaxy (LPE). The one-step pixel growth is acquired by the combination of a single-crystal epitaxial film growth by LPE and an impeded film growth on a substrate whose surface has been locally damaged and milled by ion bombardment before film deposition. The interface between pixel (single-crystal expitaxial area) and pixel gap (perturbed epitaxial area) guides magnetic walls just like a groove. The fabricated prototype magnetooptic spatial light modulator (MOSLM) is switched by applying driving currents of 40 mA for the bottom conductor line and 80 mA for the top conductor line under external bias field of 20 Oe, which is over two times smaller than that of the conventional MOSLM. The novel MOSLM can provide higher resolution, simpler fabrication process, more compact systems, and lower driving current.

Surface Plasmon Resonance in Novel Nanocomposite Gold/Lead Zirconate Titanate Films Prepared by Aerosol Deposition Method

We prepared gold/lead zirconate titanate (PZT) nanocomposite thick films by the aerosol deposition method (ADM) for the first time and report their enhanced surface plasmon resonance (SPR) properties. ADM has been attracting much attention for its ability to deposit complex composite films at a high deposition rate and a low process temperature. Composite metal–dielectric powders are prepared from submicron particles of PZT and nano particles of gold (10–40 nm) with concentrations below 1 wt %. Nanocomposite gold/PZT 3-µm-thick film acquired enhanced SPR at approximately 640 nm as a result of annealing. The SPR position in nanocomposite films deposited by ADM can be precisely controlled by adjusting the dielectric constant of the host matrix by annealing. Moreover, nanogold particles were spatially very well distributed in the PZT matrix and showed no growth in spite of annealing at 600 °C.

Fabrication and Characterization of Optical Micro-Electro-Mechanical System Scanning Devices Using BaTiO3-Based Lead-Free Piezoelectric-Coated Substrate Sheet by Aerosol Deposition

We demonstrated high-speed metal-based Lamb-wave-resonance piezoelectric-drive optical micro-electric-mechanical system (MEMS) scanning devices using lead-free piezoelectric direct coated substrate sheets. The BaTiO3-based lead-free piezoelectric direct coated substrate sheet prepared by aerosol deposition achieved a piezoelectric d31 of approximately -138 pm/V. The metal-based optical scanning devices have a 1 mm circular mirror. Under the ambient air, the wide optical scanning angle of 58° and the high resonance frequency of 26.681 kHz were achieved at the applied voltage of less than 30 V.

Magnetooptic Spatial Light Modulator Array Fabricated by IR Annealing

We demonstrated a flat-surface magneto-optic spatial light modulator (MOSLM) without physically isolated pixels and an external bias coil. The flat-surface MOSLM, which was fabricated by a simple process, was designed as a compact system with a high resolution and very low driving current. Flat-surface pixels for the novel MOSLM were produced by the combinatory use of the local annealing effect that reduced magnetization 4πMs of pixel areas and the stress effect that produced sharp variations of magnetic anisotropy in a magnetic garnet film under the edge of a metal layer. The fabricated MOSLM was switched by applying currents of 6 mA for a bottom conductor line and 10 mA for a top conductor line.

Selective-Area Micropatterning of Liquid-Phase Epitaxy-Grown Iron Garnet Films

We investigated selective-area micropatterning of iron garnet film grown by liquid-phase epitaxy (LPE). This method of producing a flat-surface structure overcomes the disadvantages of geometrical grooves, which are formed by wet or dry etching, with a limited resolution due to underetching and nonplanar structure. Moreover, patterned iron garnet films grown by selective-area LPE have better single-crystal properties than films grown by selective-area sputter epitaxy deposition. Thus, this method offers new possibilities for the fabrication of integrated magnetooptic light switch arrays, magnetic waveguides and other magnetooptic devices.