Reflective and transmissive film interference colors were calculated for DLC films on the Si and SiO 2 substrates.The calculated interference colors were compared with photographed colors of the prepared DLC samples.The observed film colors were found to match reasonably well with the corresponding calculated colors,indicating that DLC film colors come from interference instead of color center effects.Color charts for DLC films on the Si and SiO 2 substrates with various optical gaps were constructed,and the relationship between interference color and film properties such as optical gap,thickness and substrate were investigated.Usefulness of the calculated color charts in estimating optical gap or thickness of DLC films were demonstrated.
A silicon-on-insulator-based adiabatic waveguide taper with a high coupling efficiency and small footprint is presented.The taper was designed to reduce the incidence of mode conversion to higher-order and radiation modes inside the waveguide.In connecting a 0.5-μm-wide output waveguide and a 12-μm-wide input waveguide of a grating coupler,a compact 120-μm-long taper was demonstrated,achieving a transmission of 98.3%.Previously,this transmission level could only be achieved using a conventional linear taper with a length of more than 300μm.
We propose a novel resonator containing an elliptical microring based on a silicon-on-insulator platform. Simu- lations using the three-dimensional finite-difference time-domain method show that the novel elliptical microring can efficiently enhance the mode coupling between straight bus waveguides and resonator waveguides or between adjacent resonators while preserving relatively high intrinsic quality factors with large free spectral range. The proposed resonator would be an alternative choice for future high-density integrated photonic circuits.
Silicon photonic devices based on complementary-metal-oxide-semiconductor(CMOS) compatible technologies have shown attractive performances on very-large-scale monolithic optoelectronic integration,high speed modulation and switching,and efficient off-chip optical coupling.This paper presents the recent progress on fast silicon optical modulation,wavelength-insensitive optical switching and efficient optical coupling techniques in our group.Several CMOS-compatible silicon optical couplers with different structures have been developed,showing the highest coupling efficiency of 65%.Broadband silicon-based optical switches with sub-nanosecond switching on-off time are experimentally realized.Silicon modulators with novel PN junctions are demonstrated with the speed up to 50 Gb s-1.
