Yi Chiu

Fabrication and nonlinear optical properties of nanoparticle silver oxide films

We report the fabrication of nanoparticle silver oxide thin films by rf magnetron sputtering and characterization of their nonlinear optical properties. The chemical decomposition and reversibility of AgOx compounds were studied by thermogravimetric analysis, differential scanning calorimetry, and x-ray diffraction. Electron spectroscopy for chemical analysis measurements revealed a 0.5 eV negative binding energy shift from AgO to Ag2O phase. The effect of particle plasmon resonance was confirmed by the absorption band shift with increased Ag2O particle size. The measured third-order nonlinear susceptibility (χ3=3.4×10−7 esu) and response time (27 ps) of the Ag2O nanoparticles makes it promising for applications in all-optical switching devices and optical data storage systems.

A capacitive vibration-to-electricity energy converter with integrated mechanical switches

Due to recent advances in low-power VLSI design technology, it has become feasible to power portable or remote electronic devices by scavenging the ambient energy. The design, fabrication and measurement of a capacitive vibration-to-electricity energy converter are presented in this paper. With a device area constraint of 1 cm2 and an auxiliary battery supply of 3.6 V, the device was designed to generate an output power of 31 µW with an output saturation voltage of 40 V. An external mass of 4 g was needed to adjust the device resonance to match the input vibration of 2.25 m s−2 at 120 Hz. Mechanical contact switches were integrated onto the device to provide accurate charge–discharge energy conversion timing. The device was fabricated in SOI (silicon-on-insulator) wafers by deep silicon etching technology. Parasitic capacitance was minimized by partial back side substrate removal. Resonant frequencies of the fabricated device with and without the external mass agreed with the expected values. Without the external mass, the measured ac output power was 1.2 µW with a load of 5 MΩ at 1870 Hz. Detailed circuit modeling and ac output power measurement of the devices with the external mass attached are in progress.

Guided-wave electro-optic beam deflector using domain reversal in LiTaO/sub 3/

We have fabricated and demonstrated the operation of electro-optic beam deflectors using domain reversal in planar waveguides fabricated on LiTaO/sub 3/ substrates. The planar waveguides were made using proton exchange on z-cut substrates, and proton exchange with subsequent rapid thermal annealing was used to form the inverted domains. The deflection sensitivity of the device was measured to be about 6.7 mrad/kV. Calculations indicate that the deflection sensitivity should be increased by a factor of 25 to 30 with improvements in device geometry. >

Flat and robust out-of-plane vibrational electret energy harvester

This paper reports the design, fabrication and testing of two types of out-of-plane electret energy harvesters. Copper plates and flexible printed circuit board (FPCB) were used to fabricate the harvesters for a lower fabrication cost and a more robust structure. Several dielectric materials were investigated and SiO2/Si3N4?double layers were found to have better charge stability. The measured surface potential and charge density of the SiO2/Si3N4?electret were??400?V and 13.5 mC m?2, respectively. It was found that charge stability could be improved by multiple corona charging cycles. Using SiO2/Si3N4?as the electret material, the measured power output was 20.7??W at 110?Hz for 2?G acceleration with a 50?M? load for the copper harvester and 0.82??W at 172?Hz for 2?G acceleration with a 30?M? load for the FPCB harvester.

Shape-optimized electrooptic beam scanners: analysis, design, and simulation

This paper presents the analysis of a general nonrectangular electrooptic (EO) scanner and compare its performance to a rectangular device. Since the scanning sensitivity of an EO scanner is inversely proportional to its width, high sensitivity requires the device contour to be close to the ray trajectory of a beam propagating through the device. Accordingly, a shaped-optimized scanner is designed so that the beam trajectory at maximum deflection is parallel to the device contour. A beam propagation method (BPM) simulation shows the performance agrees well with the analysis.

Design, Fabrication, and Control of Components in MEMS-Based Optical Pickups

Small-form-factor optical pickups and disk drives have been an area of intense research since the rise of portable consumer electronic products. In current technology, most of the devices are manufactured by the precision assembly of discrete miniaturized optomechanical components. The assembly process can be simplified and cost reduced by using the batch fabrication processes developed in microelectromechanical systems (MEMS). In this paper, the fabrication and testing of optical and actuator components for a MEMS-based optical pickup are presented. A novel design methodology is also applied to the servo control system of the pickup

Integrated optical device with second-harmonic generator, electrooptic lens, and electrooptic scanner in LiTaO/sub 3/

This paper reports the first demonstration of an integrated optical device in z-cut LiTaO/sub 3/ that contains the following three functional parts: a quasiphase-matched second-harmonic generation (SHG) grating, an electrooptic (EO) lens, and an electrooptic scanner. The SHG device consists of channel waveguides passing through periodic domain-inverted gratings. The frequency of the input infrared (IR) light at 864 nm was doubled into blue light at 432 nm. A stack of EO lenses was used to collimate the light from the channel waveguide. The measured beam size at the output facet for various applied voltages to the lenses agreed with simulation. After collimation, light passes through an EO scanner that controls the angle of the output beam. A scanning sensitivity of 17 mrad/kV was measured for the scanner, compared to the calculated value of 15 mrad/kV.

Design and simulation of waveguide electrooptic beam deflectors

Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed. >

Microlens array fabricated by excimer laser micromachining with gray-tone photolithography

We demonstrate the fabrication of a refractive microlens array by using 248 nm excimer laser micromachining with coded gray-tone mask photolithography. With pre-corrections to the nonlinear exposure process, the maximum deviation from the designed shape was below 5%. The fabricated hemispherical lens of 30 µm radius was used as a solid immersion lens (SIL) and combined with a 0.54 numerical aperture (NA) objective to achieve a 0.87 effective NA through the knife-edge scanning test. The experimental results agreed with those of the simulation. Unlike the methods such as the thermal melting process, this one-step optical exposure method with a coded mask provides a relatively fast and cost-effective way to realize a microlens array in optical data storage, information processing, and optical interconnection applications.

Electro‐optic beam scanner in KTiOPO4

We have fabricated and demonstrated both wafer and waveguide electro‐optic beam scanners in KTiOPO4 using alternating domain‐inverted triangular patterns in the substrate. This device is an extension of previous work in LiTaO3. The domain inversion was achieved by pulsed electric field poling. The deflection sensitivity was 2.1 mrad/kV, compared to the calculated value of 2.3 mrad/kV for this geometry. The bandwidth of the devices was measured to be at least 200 kHz, which was limited by the high voltage driver.