Compact, submilliwatt, 2 × 2 silicon thermo-optic switch based on photonic crystal nanobeam cavities

We propose and experimentally demonstrate a 2×2 thermo-optic(TO) crossbar switch implemented by dual photonic crystal nanobeam(PCN)cavities within a silicon-on-insulator(SOI)platform.By thermally tuning the refractive index of silicon,the resonance wavelength of the PCN cavities can be red-shifted.With the help of the ultrasmall mode volumes of the PCN cavities,only～0.16 mW power is needed to change the switching state.With a spectral passband of 0.09 nm at the 1583.75 nm operation wavelength,the insertion loss(IL)and crosstalk(CT)performances were measured as IL(bar)=-0.2 dB,CT(bar)=-15 dB,IL(cross)=-1.5 dB,and CT(cross)=-15 dB.Furthermore,the thermal tuning efficiency of the fabricated device is as high as1.23 nm/mW.

Non-blocking 2×2 switching unit based on nested silicon microring resonators with high extinction ratios and low crosstalks

In this paper,we propose and demonstrate a2 9 2 optical Benes switching unit based on two nested silicon microring resonators(MRRs)monolithically integrated on a silicon-on-insulator(SOI)wafer.High extinction ratios(ERs)of about 44.7/38.0 dB and low crosstalk values of about-37.5/-45.2 dB at cross/bar states are obtained with the fabricated device.The operation principle is theoretically studied and the switching function is verified by system demonstration experiments with 10 and12.5 Gb/s non-return-to-zero(NRZ)signals.The switching speed on the order of gigahertz based on free carrier effect in silicon is also experimentally demonstrated.

High-efficiency and broadband four-wave mixing in a silicon-graphene strip waveguide with a windowed silica top layer

We experimentally demonstrate high-efficiency and broadband four-wave mixing in a silicon-graphene strip waveguide. A four-wave mixing conversion efficiency of -38.7 d B and a 3-dB conversion bandwidth of 35 nm are achieved in the silicon-graphene strip waveguide with an optimized light-graphene interaction length of 60 μm. The interaction length is controlled by a windowed area of silica layer on the silicon waveguide.Numerical simulations and experimental studies are carried out and show a nonlinear parameter γGOSas large as 10~4 W^(-1)· m^(-1).

On-chip silicon polarization and mode handling devices

Mode-and polarization-division multiplexing are new promising options to increase the transmission capacity of optical communications.On-chip silicon polarization and mode handling devices are key components in integrated mode-and polarization-division multi-plexed photonic circuits.In this paper,we review our recent progresses on silicon-based polarization beam splitters,polarization splitters and rotators,mode（de）multiplexers,and mode and polarization selective switches.Silicon polarization beam splitters and rotators are demonstrated with high extinction ratio,compact footprint and high fabrication tolerance.For on-chip mode multiplexing,we introduce a low loss and fabrication tolerant three-mode（de）multiplexer employing sub-wavelength grating structure.In analogy to a conventional wavelength selective switch in wavelength-division multi-plexing,we demonstrate a selective switch that can route mode-and polarization-multiplexed signals.