Papers by Author: Fook Siong Chau

Abstract: The impact of developing nanophotonic components have proven to be a promising research on the future optical integrated circuit complementing the current scaling of semiconductors for faster board-board, chip-chip interconnect speeds. Essentially photonic crystals (PhC) symbolize an emerging class of periodic nanomaterials that offers flexibilities in achieving novel devices. Based on the investigations of the high-Q resonance mode energy distributions, we optimized the nano­scale tip for optimal perturbative effect with low loss resonance control in the optical near field regime. In this study to achieve larger spectral resonance, we proposed using a novel doubly nano­scale perturbative tip to achieve optimal accurate photonic crystal resonance control. Such method may be driven by a nano-electromechanical (NEMS) system that may be fabricated with monolithic approaches.

Abstract: An electrothermally actuated planar micromotor has been developed for multi degree-of-freedom (DoF) motion, including rolling along the vertical or horizontal axes, spinning about the z-axis, and also the out-of-plane piston motion. In this design, a light-weight spherical solder ball rotor with plastic core is supported by electrothermal actuator array (EAA). Each bimorph actuator consists of the silicon and aluminum layers to produce large vertical deflection due to their distinct coefficients of thermal expansion (CTE). The micromotor fabrication procedures involve standard CMOS-MEMS processes. Rolling and spinning motions of the spherical rotor are performed by driving the electrothermal actuators with multi-phase signals, and the piston motion can be achieved by synchronizing the drive signals to all actuators without phase difference. The dynamic behavior of this micromotor has been successfully predicted by multibody dynamics simulation software. Such unique dynamic motions of this planar micromotor device show promising capabilities in Optical Coherence Tomography (OCT) and Optical Coherence Microscope (OCM) applications. If this sphere is mounted with a highly-reflective mirror platform, it can be used to divert the light beam to achieve a full 360° circumferential scan about the optical axis.

Abstract: In this paper, we present a Fourier Transform micro-spectrometer which works based on a lamellar grating interferometer. The spectrometer model is electrostatically driven by parallel plate actuators which change the optical path difference (OPD) between movable grating facets and fixed ones. With a 200V input voltage, a maximum OPD of 48.7μm is achieved. The spectrum of a combined light source of a diode-pumped solid-state (DPSS) laser (λ=532.0nm) and a laser diode (λ=637.2nm) is experimentally acquired to demonstrate the performance of the model. The reconstructed spectrum displays two separate spectral peaks at 530.5nm and 635.2nm and the corresponding full-width at half-maximum (FWHM) resolutions are 9.8nm and 12.8nm respectively, indicating good wavelength accuracy and optical resolution.

Abstract: A liquid tunable diffractive/refractive hybrid lens which combines the use of high precision diamond turning and soft lithography is developed in this work. This diffractive/refractive hybrid lens comprises a Fresnel lens and a tunable refractive lens automatically aligned during the fabrication process. Multiple PDMS hybrid lens devices can be fabricated from the diamond-turned master mould and AFM results show that the surface quality of the PDMS lenses meets the requirements for optical purposes. The hybrid lens is tested with a green laser (λ = 532nm) and experimental results demonstrate a tunability of more than 20mm.