Huaxiang Yi

Wavelength demultiplexing structure based on arrayed plasmonic slot cavities

A compact wavelength demultiplexing structure based on arrayed metal-insulator-metal (MIM) slot cavities is proposed and demonstrated numerically. The structure consists of a bus waveguide perpendicularly coupled with a series of slot cavities, each of which captures SPPs at the resonance frequency from the bus waveguide and tunes the transmission wavelength by changing its geometrical parameters. A cavity theory model is used to design the operating wavelengths of the structure. Moreover, single band transmission of each channel and the adjustable transmission bandwidth can be obtained by altering the drop waveguide positions and the coupling distance. The proposed arrayed slot cavity-based structure could be utilized to develop ultracompact optical wavelength demultiplexing device for large-scale photonic integration.

Band-pass plasmonic slot filter with band selection and spectrally splitting capabilities

An ultra-compact surface plasmon polaritons (SPPs) narrow band-pass filter based on a slot cavity is proposed and numerically investigated. Attributed to the coupled resonances in the cavity, the filter demonstrates pass-band selection capability. Also, by varying the positions of output waveguides, the filter shows the spectrally splitting function. Moreover, the combination of the adjustments to the length/width of the slot cavity and to the coupling distance provides more flexibility in design for the locations and widths of the pass-bands of the proposed filter.

Highly sensitive silicon microring sensor with sharp asymmetrical resonance.

We analyze the resonance spectrum in silicon microring resonators taking into account the end-facet reflection from a coupled waveguide, which can provide a dense set of Fabry-Perot resonances. Based on the simple configuration of a microring coupled with a waveguide, the resulting asymmetric Fano-like non-Lorentzian resonance is obtained by scattering theory and experiment. Enhanced sensing performance with steeper slope to the resonance is theoretically predicted and experimentally demonstrated for a 10-microm racetrack silicon microring resonator. A high sensitivity of approximately 10(-8) RIU in terms of the detection limit is obtained in a 30-dB signal-to-noise ratio (SNR) system.

Low-voltage, high speed, compact silicon modulator for BPSK modulation.

A low voltage, high speed, compact silicon Mach-Zehnder Interferometer (MZI) modulator for Binary Phase Shift Keying (BPSK) modulation has been demonstrated. High modulation efficiency, VπLπ equals to 0.45V·cm, was obtained in a 1mm length device owing to a higher doping concentration and low-loss traveling-wave electrode. 25 Gb/s non-return-to-zero(NRZ)-BPSK with 6Vpp RF driving signal was achieved. Driven by a very low 3Vpp RF signal, the 10 Gb/s NRZ-BPSK was also realized benefiting from the high modulation efficiency and the low-voltage driving scheme. The power consumption for the BPSK modulation was as low as 0.118 W. These results prove that the silicon modulator is suitable for advanced communication system with low power consumption.

Demonstration of low power penalty of silicon Mach–Zehnder modulator in long-haul transmission

We demonstrate error-free 80km transmission by a silicon carrier-depletion Mach-Zehnder modulator at 10Gbps and the power penalty is as low as 1.15dB. The devices were evaluated through the bit-error-rate characterizations under the system-level analysis. The silicon Mach-Zehnder modulator was also analyzed comparatively with a lithium niobate Mach-Zehnder modulator in back-to-back transmission and long-haul transmission, respectively, and verified the negative chirp parameter of the silicon modulator through the experiment. The result of low power penalty indicates a practical application for the silicon modulator in the middle- or long-distance transmission systems.

Dual-microring-resonator interference sensor

Dual-microring-resonator interference with the microrings on separate arms of a Mach–Zehnder interferometer is shown to provide the basis for high-performance sensors. The output spectrum, which depends on the overlap of the resonances of the two microring resonators, depends sensitively on the resonance shift of one of the microrings due to the presence of an analyte. The sensitivity and detection limit are obtained theoretically and found to be as large as 0.31 nm overlap resonance shift according to 2×10−6 refractive index units for Si-based sensors.

Development trends in silicon photonics

Silicon photonics has become one of the major technologies in this very information age. It has been intensively pursued by researchers and entrepreneurs all over the world in recent years. Achieving the large scale silicon photonic integration, particularly monolithic integration, is the final goal so that high density data communication will become much cheaper, more reliable, and less energy consuming. Comparing with the developed countries, China may need to invest more to develop top down nanoscale integration capability (more on processing technology) to sustain the development in silicon photonics and to elevate its own industry structure.

Highly Sensitive Athermal Optical Microring Sensor Based on Intensity Detection

An athermal optical sensor using intensity detection based on silicon microring resonators (MRs) is presented. The thermally independent sensing is realized in the sensing zone within the temperature range ±5 K. The significant phase difference in the presence of an analyte between the low-Q coupled MRs is further sensitized through an interference-based intensity sensing scheme. Better performance of the coupled MR sensor compared to conventional microring sensors is demonstrated using transfer-matrix theory. For a measurement system of 30 dB signal-to-noise ratio, a detection limit of 6.8 ×10-7 recognition indexing unit is predicted.

Silicon nanophotonic devices based on resonance enhancement

In recent years, silicon nanophotonic devices have attracted more and more attention due to their compactness, low power consumption, and easy integration with other functions. In addition to the higher index of silicon material providing stronger light confinement, the optical resonance associated with the novel structure design also enhances the performance of nanophotonic devices and offers stronger light-matter interaction. Silicon nanophotonic devices such as polarization beamsplitters, mirrors and reflectors, slow light waveguides, and microring sensors are studied, and all of them demonstrate much better performances due to the incorporated optical resonance enhancement.

Polarization beam splitter based on cascaded step-size multimode interference coupler

Abstract. A polarization beam splitter (PBS) based on cascaded step-size multimode interference (MMI) coupler is demonstrated on silicon on insulator. The total area of MMI sections is smaller than 7×600  μm2. This PBS shows 25-nm bandwidth for transverse-electric polarization and 20-nm bandwidth for transverse-magnetic polarization with an extinction ratio more than 20 dB. The length of this PBS is reduced to about one ninth of that of the conventional design in MMI sections.