Huang De-Xiu

PPLN-Based Flexible Optical Logic and Gate

All-optical flexible 20-Gb/s logic and gate based on cascaded sum- and difference-frequency generation in a periodically poled lithium niobate waveguide is proposed and experimentally demonstrated. The theoretical analyses further indicate that 40-, 80-, and 160-Gb/s ultrahigh-speed logic and operations can potentially be performed. Moreover, it is expected that the and output can be tuned in a wide wavelength range (67 nm) with slight fluctuation of the Q-factor and extinction ratio.

Numerical simulation of recovery enhancement by a CW pump light in semiconductor optical amplifiers

This paper aims at numerically simulating gain recovery enhancement effect in semiconductor optical amplifiers (SOAs) when a CW pump light is applied. The effective carrier lifetime reduction behaviors are simulated for different CW wavelengths. Gain saturation behaviors at the signal wavelength as well as gain and phase-shift dynamics introduced by short pulse amplification in presence of the CW pump light are also simulated for different CW wavelengths and powers. The results confirms the feasibility of enhancing the recovery rate of SOA by a CW pump light near the material transparency wavelength.

Enhancement of gain recovery rate and cross-gain modulation bandwidth using a two-electrode quantum-dot semiconductor optical amplifier

A two-electrode quantum-dot semiconductor optical amplifier (QD-SOA) is proposed to enhance gain recovery rate and cross-gain modulation (XGM) bandwidth. In the theoretical model, electron and hole dynamics as well as the carrier diffusion are accounted for in the quantum-dot rate equations, which are solved with forward and backward propagation equations of signal and amplified spontaneous emission. The simulation results show that two-electrode QD-SOA can distribute injection current density nonuniformly to maintain carriers in carrier reservoirs of quantum dot sufficient along the entire cavity length of the semiconductor optical amplifier, thus making gain saturation dynamics dominated by spectral hole burning at lower bias current than common QD-SOA. Besides, distributing more current density in the second section of the two-electrode QD-SOA at higher bias can greatly accelerate gain recovery as well as expand the XGM bandwidth.

A Microwave Photonic Notch Filter Using a Microfiber Ring Resonator

A novel tunable microwave photonic filter based on a microfiber ring resonator is proposed and experimentally demonstrated. A fiber ring laser based on the microfiber ring resonator is employed to generate two single-longitudinal-mode carriers, then the dispersive element introduces the delay between two modulated carriers. By adjusting the diameter of the microfiber ring resonator, the proposed microwave photonic notch filter can be continuously and widely tuned. The measured notch rejection ratio is greater than 35 dB, and there is good agreement between the experimental result and the theoretical analysis.

All-Optical Temporal Differentiator Using a High Resolution Optical Arbitrary Waveform Shaper

We experimentally demonstrate an all-optical temporal differentiator using a high resolution optical arbitrary waveform shaper, which is based on liquid crystal on silicon switching elements, and both amplitude and phase of the spectrum are programmable. By designing specific transfer functions with the optical waveform shaper, we obtain first-, second-, and third-order differentiators for periodic pulses with small average errors. We also theoretically analyze the bandwidth limitation of optical waveform shaper on the differentiator.

Single-to-Multiple Channel Wavelength Conversions and Tuning of Picosecond Pulses in Quasi-Phase-Matched Waveguides

We report the single-to-multiple channel wavelength conversions of 1.57-ps pulses based on cascaded second-harmonic generation and difference frequency generation in quasi-phase-matched periodically poled lithium niobate waveguides. For single-to-single channel wavelength conversion, no external cavity laser is required with use of a fibre ring laser. The conversion efficiency is about -21.44 dB. The converted idler wavelength can be tuned from 1526.4 nm to 1537.5 nm as the lasing pump wavelength is varied from 1566.1 nm to 1555.0 nm. By employing several input pumps, tunable single-to-dual and single-to-triple channel wavelength conversions are experimentally demonstrated.

Influence of Size of ZnO Nanorods on Light Extraction Enhancement of GaN-Based Light-Emitting Diodes

We investigate the influence of size of ZnO nanorods on the light extraction efficiency (LEE) enhancement of GaN-based light-emitting diodes (GaN-LEDs). ZnO nanorods with different sizes are hydrothermally grown on patterned indium-doped tin oxide (ITO) electrodes of the GaN-LEDs in zinc acetate aqueous solutions of different concentrations. Measurements are conducted for the LEE enhancement of the LEDs with ZnO nanorods, compared to these without ZnO nanorods. The results suggest that the LEE of the LEDs with ZnO nanorods increases with the increasing size of ZnO nanorods. However, a saturation trend for the LEE improvement is also observed, which is attributed to the maximum limitation of light coupled into ZnO nanorods from GaN-based LEDs, and the reflection is increased by the increasing top surface of the ZnO nanorods.

Hybrid Active-Passive Microwave Photonic Filter with High Quality Factor

A hybrid high quality factor (Q-factor) microwave photonic filter with a cascaded active filter and a passive filter is presented and experimentally demonstrated. The active infinite impulse response filter is realized by a recirculating delay line loop with a semiconductor optical amplifier, and a much narrower 3 dB bandwidth of response peaks can be achieved. A passive finite impulse response filter is realized by an unbalance Mach–Zehnder interferometer, and it is cascaded to select the desired filter frequencies and to suppress the intermediate peaks. Compared with the purely active filter scheme, the free spectrum range and the Q-factor of the hybrid structure can be doubled. Stable operation and a high Q-factor of 362 are experimentally demonstrated.

All-Optical RZ-to-NRZ Format Conversion with a Tunable Fibre Based Delay Interferometer

All-optical format conversion from return-to-zero (RZ) to non-return-to-zero (NRZ) is demonstrated with temperature-controlled all-fibre delay interferometer (DI) at 20 Gb/s. The operation principle is theoretical analysed with the help of numerical simulation and spectra analysis. Theoretical analysis results are consistent well with the experimental results. The format conversion can be achieved with power penalty of 0.54 dB and with output extinction ratio 20 dB.

Polarization Maintaining Fibre Loop Mirror for NRZ-to-PRZ Conversion in All-Optical Clock Recovery

We propose a novel configuration for clock extraction by converting the NRZ data into the PRZ data and by employing a polarization-maintaining fibre loop mirror (PMFLM) which is usually used as an optical comb filter. It is found that the PMFLM can simply be constructed by a polarization controller and polarization-maintaining fibre (PMF). We theoretically analyse the principle of PMFLM for the NRZ-to-PRZ conversion. Experimentally we demonstrate 10 Gbit/s all-optical clock recovery through our proposed setup. It is shown that recovered clock signal with an extinction ratio above 10 dB can be achieved.