We report a compact 2×2 Mach-Zehnder interferometer （MZI） electro-optic switch fabricated on a silicon- on-insulator using standard complementary metal-oxide semiconductor （CMOS） processes. With a short modu- lation arm length of 200μm, the crosstalk is reduced to -22 dB by the new modulation scheme of push-pull modulation with a pre-biased π2 phase shift. The new modulation scheme can also work with a fast switching time of about 5.4 ns.
This paper investigated the design and the characterization of a photonic delay line based on passive cascaded silicon-on-insulator （SOI） microrings. We considered the compromise of group delay, bandwidth and insertion loss. A 3-stage double channel side-coupled integrated spaced sequence of resonator （SCISSOR） device was optimized by shifting the resonance of each microring and fabricated with electron beam lithography and dry etching. The group delay was measured to be 17 ps for non-return-to-zero signals at different bit rates and the bandwidth of 78 GHz was achieved. The experiment result agreed well with our simulation.
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.
A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.
The first path-independent insertion-loss（PILOSS） strictly non-blocking 4×4 silicon electro–optic switch matrix is reported. The footprint of this switch matrix is only 4.6 mm×1.0 mm. Using single-arm modulation, the crosstalk measured in this test is-13 dB --27 dB. And a maximum crosstalk deterioration of 6d B caused by two-path interference is also found.
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.
