Zehua Hong

Design and analysis of a phase modulator based on a metal–polymer–silicon hybrid plasmonic waveguide

A plasmonic-hybrid-waveguide-based optical phase modulator is proposed and analyzed. The field enhancement in the low-index high-nonlinear polymer layer provides nanoscale optical confinement and a fast optical modulation speed. At 2.5 V drive voltage, a π phase shift can be obtained for a 13-μm-long plasmonic waveguide. Because of its small capacitance and parasitic resistance, the modulation bandwidth can reach up to 100 GHz with a low power consumption of ∼9 fJ/bit. The plasmonic waveguide is connected to a silicon wire waveguide via an adiabatic taper with a coupling efficiency of ∼91%. The phase modulator can find potential applications in optical telecommunication and interconnects.

Temperature-Insensitive Microdisplacement Sensor Based on Locally Bent Microfiber Taper Modal Interferometer

We report a temperature-insensitive microdisplacement sensor with a locally bent microfiber taper interferometer. The microfiber taper waist diameter can be optimized to minimize the spectral shift of the sensor owing to the environmental temperature change. With a ~ 1.92-μm-diameter microfiber taper, a bimodal fiber interferometer is proposed and experimentally fabricated. The transmission spectrum shows substantially small temperature dependence matching well with the theoretical estimation. The transmission spectrum is red-shifted in response to microdisplacement with a high sensitivity of 102 pm/μm but without requirement for temperature compensation.

Experimental demonstration of self-coupled optical waveguide (SCOW)-based resonators

We experimentally demonstrate a self-coupled optical waveguide (SCOW)-based optical resonator. Transmission spectra reveal the resonators can exhibit split, broadened, or enhanced resonance dips. The SCOW resonators can be used for second-order optical filters.

Design and analysis of a highly efficient coupler between a micro/nano optical fiber and an SOI waveguide.

A compact coupling structure is proposed for highly efficient coupling between a micro/nano fiber and a silicon-on-insulator waveguide. The proposed structure is characterized by high coupling efficiency, wavelength insensitivity, large misalignment tolerance, and easy fabrication. Theoretical analysis and numerical simulation results show that coupling efficiency of >90% can be achieved with a taper length of ∼4.5  μm.

Characterization of DNA optical microfiber devices fabricated by drawing

We demonstrate the characterization of DNA optical microfiber devices fabricated by manually drawing. The strength, flexibility and optical loss are experimentally investigated. DNA optical microfiber devices are expected to be used as optical biosensors.

Miniature Intensity Modulator Based on a Silicon-Polymer Hybrid Plasmonic Waveguide

We present a novel micrometer-sized intensity modulator based on a silicon-polymer hybrid plasmonic waveguide. The field enhancement in the low-index high-nonlinear polymer layer provides a nano-scale optical confinement and a fast optical modulation speed. After applying a voltage, the surface plasmon waves experience different phase delays, resulting in an intensity variation at the output waveguide. Due to its small capacitance and parasitic resistance, the RC delay time is <6 ps, corresponding to a modulation bandwidth of >40 GHz. The intensity modulator can find potential applications in optical telecommunication and interconnect.

High-Resolution Measurement of Fiber Length Change with Optical Low-Coherence Reflectometer Based on a Fiber-Ring Structure

A simple approach is proposed and experimentally demonstrated to improve measurement precision of short fiber length or fiber length change with an optical low-coherence reflectometer (OLCR). A fiber-ring structure composed of a coupler and a circulator is introduced in the test arm of OLCR to virtually multiply the length of the fiber under test. By measuring the multiplied fiber length under test, the measurement precision is enhanced. A precision enhancement of 10 times is successfully achieved.

Highly efficient fiber-to-chip evanescent coupling based on subwavelength-diameter optical fibers

A novel, compact, and highly efficient fiber-to-chip evanescent coupling structure is proposed based on a subwavelength-diameter fiber. The coupling structure is characterized by a large misalignment tolerance and easy fabrication. The dependence of coupling efficiency on various parameters is calculated and analyzed. The simulation results show that a coupling efficiency as high as 95% can be obtained within a coupling length of <4 \mum.

A new fiber length measuement method with high precision and large absolute length based on FDL

We propose and demonstrate a new fiber length measurement method, which supports large absolute length and high accuracy measurement of fiber. This method is based on multi-stage optical fiber delay lines structure and self-calibration method with Precision Reflectometer. The precision maintains 20 µm and the enlarged measurement range reaches to 6395.43mm.

Transmission-line model for analyzing the coupling between two parallel micro/nano-fibers

The coupling behavior between two parallel micro/nano-fibers is investigated by extending the theory of transmission-lines (TL) to optical domain, Simulation result indicates that the energy transfer length of micro/nano-fibers based coupler is much shorter than that of conventional fiber based coupler. The experiment of the coupling behavior of micro/nano-fibers is demonstrated. It verifies the TL model of micro/nano-fiber coupler. This result may offer valuable reference for the investigation of nano-photonic devices.