Xiaobei Zhang

Expression of endothelial nitric oxide synthase and vascular endothelial growth factor in human malignant melanoma and their relation to angiogenesis

Background.  Angiogenesis is the major and key factor for growth and invasion of tumours, including malignant melanoma (MM), but the factors that contribute to tumour angiogenesis are still unclear. 

Active microring optical integrator associated with electroabsorption modulators for high speed low light power loadable and erasable optical memory unit

We propose and analyze a novel loadable and erasable optical memory unit based on an active microring optical integrator associated with electroabsorption modulators (EAM) on III-V material system. The gain of the active microring is characterized by the two energy band model with amplified spontaneous emission noises taken into account. Based on the light field propagation equation in the active microring waveguide and the transfer function of the EAM-MZI switch, the step function performances of the optical memory under the gain matching condition are discussed for different injection light powers. After that, the memory operation of the novel optical memory unit is analyzed in detail. Simulations show that, the step function response and memory performances are affected by the carrier consumption. However, such influence will be released, and the memory operates well for the low light power injection case. The novel optical memory unit is promising to be cascaded connected and densely integrated for high speed low power optical data stream storage and buffer.

Transmission characteristics of dual microring resonators coupled via 3×3 couplers

New types of dual microring resonators coupled via 3x3 couplers are proposed. By employing the transfer matrix method, a model for these four types is developed and analytical expressions for characterizing their transmissions are derived. The first two types show a coupled-resonator-induced-transparency-like transmission spectrum at the through port. The third type holds the same transmission spectrum, while the last type simultaneously realizes a first-order and a second-order filters at two drop ports. The effects of coupling coefficients on their transmission spectra are investigated in more detail. Moreover, the effects of loss are also discussed. These proposed types can be found applications in fields such as sensors and filters.

Elastic Polarization Converter Based on Dual Microring Resonators

A proposal for a silicon-based elastic polarization converter consisting of dual microring resonators and a phase shifter is presented and theoretically investigated. By utilizing a microring resonator for polarization splitting, a phase shifter for phase controlling, and another microring resonator for TE- and TM-polarized light combination, this proposed polarization converter can realize polarization conversions between any two linear, circular, and elliptic polarization states. The proposed scheme is also designed and numerically studied by performing the 3-D full vectorial film mode matching method and coupled mode theory. Simulation results show that the capacity factor of polarization conversion is wavelength-dependent and can be high up to 1 when the polarization converter operates at the resonance condition of the microring resonators. Finally, the linear-circular polarization conversion performances are also analyzed.

Fano resonances in cone-shaped inwall capillary based microsphere resonator

In this paper, we demonstrate a cone-shaped inwall coupler for excitation of the whispering-gallery modes (WGMs) of a microsphere resonator. The coupler is composed of a single mode fiber (SMF) and a capillary with an inner diameter of 5 μm. After immersing the capillary front end vertically into Hydrofluoric acid to obtain a cone inside the capillary, light in the SMF couples into the capillary efficiently while the hollow core is wide enough for a microsphere to be inserted. Because the front end face of the capillary acts as a reflector, a Fano resonance with an asymmetric line shape and a Q-factor of 2.57 × 104 is observed in the reflection spectrum using a barium titanite glass microsphere with a diameter of 45 μm. The integrated resonator structure has the advantages such as the reflective type, alignment-free and mechanically robust, making it have great potential in sensing applications and optical switching.

Sensing properties of intrinsic Fabry-Perot interferometers in fiber tapers

A sensing configuration of the fiber taper intrinsic Fabry-Perot interferometer (FTIFPI) was presented and developed. Direct inscription method of intrinsic Fabry-Perot interferometers in optical fiber tapers with a femtosecond laser has been fabricated experimentally. Fabry-Perot interferometers are firstly realized in the waist of fiber tapers. The experimental results indicate that the change in wavelength has a good linear relationship with temperature, while the fringe visibility keeps the same approximately. In the range of 0°C~100°C, the interference spectrum sensitivity is 12pm/°C. The fringe visibility decreases linearly with the liquid refractive index increasing, while extremes keep the same approximately.

Intrinsic fiber Fabry-Perot temperature sensor fabricated by a femtosecond laser

A Fabry-Perot (F-P) interferometer was inscribed in a standard single mode fiber by inducing refractive index changes in the core. It was written directly by using a femtosecond laser. The reflection spectrum of the F-P interferometer was measured, and was investigated as a temperature sensor. The sensitivity is 9.2pm/°C in the range of −20∼80°C.

Raman based silicon photonic integrator

We analyzed a silicon photonic integrator based on active ring resonator utilizing Raman gain for loss compensation. Excellent photonic integral performance can be obtained in a large range of input light power.

NRZ-DPSK to RZ-BPSK all-optical format conversion using optical filter and SOA-MZI

We propose and demonstrate all-optical format conversion from nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) to return-to-zero binary PSK (RZ-BPSK) at different bit-rates, using a tunable band-pass filter, a semiconductor optical amplifier (SOA) fiber ring laser and an SOA based Mach-Zehnder interferometer (SOA-MZI). The filter acts as the DPSK demodulator and also as the differential decoder. It converts the NRZ-DPSK into the RZ signals, which is equivalent to the data information before differential encoding. The SOA fiber ring laser is used to recover the clock signals from the demodulated RZ signals at different bit-rates. In the subsequent SOA-MZI, the RZ signal is used to modulate the recovered clock signal which is synchronous to the demodulated RZ signal. Thus, the amplitude information is encoded onto the phase of the clock signal, through cross gain modulation (XGM) and cross phase modulation (XPM) effects in the SOA-MZI. The converter can be operated at flexible bit-rates and used as the interface between long-haul WDM and OTDM systems.

A Fiber-Optic Sensor for Acoustic Emission Detection in a High Voltage Cable System

We have proposed and demonstrated a Michelson interferometer-based fiber sensor for detecting acoustic emission generated from the partial discharge (PD) of the accessories of a high-voltage cable system. The developed sensor head is integrated with a compact and relatively high sensitivity cylindrical elastomer. Such a sensor has a broadband frequency response and a relatively high sensitivity in a harsh environment under a high-voltage electric field. The design and fabrication of the sensor head integrated with the cylindrical elastomer is described, and a series of experiments was conducted to evaluate the sensing performance. The experimental results demonstrate that the sensitivity of our developed sensor for acoustic detection of partial discharges is 1.7 rad/(m⋅Pa). A high frequency response up to 150 kHz is achieved. Moreover, the relatively high sensitivity for the detection of PD is verified in both the laboratory environment and gas insulated switchgear. The obtained results show the great potential application of a Michelson interferometer-based fiber sensor integrated with a cylindrical elastomer for in-situ monitoring high-voltage cable accessories for safety work.