Xin-Hong Jia

Nonuniform DFB-SOAs: dynamic Characteristics of bistability and a novel configuration based on linearly variable current injection

Starting from the coupled-mode equation and carrier rate equation, this paper has analyzed numerically the bistable dynamic characteristics of phased-shifted and chirped distributed-feedback semiconductor optical amplifiers (DFB-SOAs). The results show that phase shift first worsens the shape distortion of the falling edge of the output pulse and then alleviates it with the decreased initial detuning. This tendency can be suppressed by introducing chirp. We also proposed a novel configuration based on linearly variable current injection, which not only enhances the on-off switching ratio, but also has a similar transmission spectrum with phase-shift effects and similar bistable features, such as the wide frequency band and the flat upper branch of the hysteresis, with chirp effects.

Theoretical investigation on commanding the bistability and self-pulsation of bistable semiconductor laser diode using delayed optoelectronic feedback

Theoretical investigations on commanding the bistability and self-pulsation characteristics of two-segment bistable semiconductor laser diode (TBLD) using delayed optoelectronic feedback have been carried out in this paper. The effects of feedback gain and delayed time have been simulated numerically based on the rate equations. The results show that the stable region of TBLD varies periodically with delayed time, the bistable region shrinks with the increase of delayed time, stability can be enhanced for certain values of delayed time, and instability can be reached easily for negative delayed optoelectronic feedback. These conclusions establish the theoretical foundation to optimize and control the TBLD and may have potential applications in bistable switching and self-pulsation generation.

Detailed Theoretical Investigation on Enhanced Nondegenerate Four-Wave Mixing in Passive Mode-Locked Semiconductor Lasers

The passive mode-locked semiconductor laser (PMLL) can realize terahertz (THz) four-wave mixing (FWM) with high conversion efficiency and no need for pump input. Theoretical investigation on its FWM characteristics has been carried out by using the traveling wave and carrier rate equations combined with nonlinear dynamics of carrier density pulsation (CDP), carrier heating (CH), and spectral-hole burning (SHB). The stable mode-locked conjugate pulse with short-duration high-repetition frequency can be obtained by the PMLL. The pedestal-free conjugate pulse has narrower width and larger amplitude jitter compared with the pump wave. Smaller absorption recovery time is helpful to extend the stable conjugate output regime. There exists a down-limit for absorption recovery time to avoid self-pulsation (SP) instability. The larger injection current is required for smaller absorption recovery time to reach the given conversion efficiency. The larger conversion efficiency and narrower conjugate pulse can be obtained by proper design of distributed Bragg reflector (DBR) coupling strength. The DBR bandwidth must be designed to be within signal-pump detuning to avoid resonance-induced conjugate pulse distortion. The FWM in PMLL has considerable potential such as demultiplexing in optical time-division multiplexing systems.

Terahertz Wavelength Conversion Based on Four-Wave Mixing in

By using coupled mode equations, the characteristic of terahertz wavelength converter based on four-wave mixing in lambda/4-shifted distributed feedback lasers is analyzed. The numerical simulation indicates that, the larger biasing current and smaller detuning can expand the dynamic range of conversion efficiency and extinction ratio, but worsen the frequency chirp. Due to the lasing effect, the peak modulation frequency of extinction ratio and frequency chirp occurs at relaxation oscillation frequency. The good conversion characteristic can be obtained by selecting system parameters reasonably. This configuration could have potentials in optical communications because of wideband, high-speed, and no need for pump input

\lambda/4

The dynamic single-mode and modulation performance of λ/4 phase-shifted distributed feedback laser diode with chirped grating (QWS-CG-DFB) are analyzed theoretically. The numerical simulation shows that, In contrast to purely QWS-DFB laser, the enhanced dynamic single-mode suppression ratio (SMSR) can be reached by QWS-CG-DFB laser; Under the smaller biasing current, the modulation band-width in presence of chirped grating is narrower, this difference shrinks for larger biasing current; For large signal modulation, the chirped grating is helpful to increase the output extinction ratio, but worsens the frequency chirping.

-Shifted DFB Lasers: Dynamic Range and Performance Analysis

All-optical wavelength conversion based on four-wave mixing (FWM) is one of the key techniques for building dynamic optical networks. In this paper, the cavity enhancing effect of the residual F-P cavity mode on the non-degenerated four-wave mixing (NDFWM) in a distributed-feedback semiconductor laser diode (DFB-LD) have been investigated both experimentally and theoretically. The conversion efficiency of NDFWM is obtained at small or large frequency detuning range. The results show that the NDFWM can be enhanced obviously when the probe wavelength matches one of the F-P cavity modes, and the high conversion efficiency can be achieved even if the frequency detuning between the injection probe frequency and free-running frequency of the DFB-LD is up to THz.

λ/4 phase-shifted distributed feedback lasers with chirped grating: dynamic single-mode and modulation characteristics analyses

It is well known that the compressed pulse by the high-order soliton effect in dispersion-shifted fiber (DSF) accompanies by undesired pedestals. In this paper, a novel method by combining a nonlinear Fabry-Perot cavity (NLFPC) and EDFA is proposed for pedestal suppression, which is based on the optical bistability effect of the NLFPC. The numerical simulations demonstrate that obvious pedestal suppression can be realized by selecting reasonably the facet reflectivity of the NLFPC, and the detuning between the central frequency of the input pulse and the resonant frequency of the NLFPC.