Sun Jun-qiang

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.

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.

Spectral broadening of ultrashort optical pulse due to birefringence in semiconductor optical amplifiers

The effect of birefringence on the spectrum characteristics of ultrashort optical pulse in semiconductor optical amplifier (SOA) is investigated. It is revealed that a considerable part of spectrum broadening arises from birefringence in SOA. The scheme of minimizing this bad effect is also discussed.

Double-Brillouin-Frequency Spaced Multiwavelength Generation in a Ring Brillouin-Erbium Fiber Laser

We demonstrate the double-Brillouin-frequency spaced multiwavelength generation at room temperature by using a simple ring Brillouin-erbium fiber laser. The Brillouin pump is pre-amplified before entering the single-mode fiber, the odd Stokes and even Stokes are amplified in two opposite directions. All amplification provided by a home-made bi-directional operation erbium-doped fiber may achieve high intensity of Brillouin Stokes that leads to the homogenous gain saturation. Twelve even Stokes and thirteen odd Stokes with a wavelength spacing of 0.172 nm (20 GHz) are simultaneously obtained for 6 dBm Brillouin pump power and 120 mW pump power at 980 nm. The influence of different Brillouin and erbium-doped-fiber pump powers on multiwavelength and tuning range are investigated in detail.

Enhancement of Photodetector Responsivity and Response Speed Using Cascaded-Cavity Structure with Subwavelength Metallic Slit

A cascaded-cavity photodetector with subwavelength metallic slit is proposed to enhance responsivity and response speed simultaneously. Responsivity enhancement depends on light transmittance increased by using a subwavelength metallic slit plasmonic mode resonant cavity; it also relies on quantum efficiency improved by adopting a resonant cavity enhanced structure. Response speed improvement is due to low capacitance of metal-slit-metal and thin absorption layers. In the cascaded-cavity structure, the subwavelength metallic slit plays a vital role in performance improvements. Simulation results show that, for the optimized slit structure, responsivity enhancement of 80 times can be achieved compared to the conventional structure. In addition, response bandwidth of the optimized structure can reach 150 GHz.

Study of temperature stability for fiber-optic Mach-Zehnder interferometer filter

The fiber-optic Mach-Zehnder (M-Z) interferometer can be used as wavelength-multiplexers and demultiplexers. The /spl Delta/L and /spl Delta//spl Phi/ directly influence the properties of M-Z. Through lengthening the /spl Delta/L, M-Z can demultiplex many more wavelengths. But the longer /spl Delta/L is, the more seriously the temperature will influence M-Z. We explored a method to solve this problem, making M-Z work stably. The wavelength spacing is 0.8 nm, and the extinction ratio is high.

Novel configuration for wavelength conversion based on cross-gain modulation in semiconductor optical amplifiers

Novel configuration for cross-gain modulation (XGM) wavelength conversion based on the single-port-coupled semiconductor optical amplifier (SOA), in which the input and the output share one port, has been demonstrated with the output extinction ratio as high as 15 dB, even in the 2.5 Gbit/s wavelength up conversion with a 12.8 nm span. Owing to the existence of double-pass gain and the transmission loss of the rear facet, the novel scheme can be achieved with simpler implementation and higher output extinction ratio, compared with the conventional schemes based on double-port-coupled SOA either with identical long chip or double long chip.

Novel XGM wavelength conversion scheme based on SLAOLM

A novel XGM wavelength conversion scheme exploiting semiconductor laser amplifier in a loop mirror (SLAOLM) has been demonstrated. Results showed that this scheme is helpful for extinction ratio and noise performance improvement simultaneously, due to the coexistence of gain saturation and phase modulation effect.

Multiwavelength erbium-doped fiber laser exploiting intracavity polarization inhomogeneity

Simultaneous multiwavelength lasing is demonstrated exploiting intracavity polarization inhomogeneity in an erbium-doped fiber laser. Experiments indicate that polarization hole burning can be enhanced by the changes of optical MQW waveguide bias current and the polarization states in the laser cavity. Ten wavelengths with 0.9 nm spacing are generated at room temperature.Simultaneous multiwavelength lasing is demonstrated exploiting intracavity polarization inhomogeneity in an erbium-doped fiber laser. Experiments indicate that polarization hole burning can be enhanced by the changes of optical MQW waveguide bias current and the polarization states in the laser cavity. Ten wavelengths with 0.9 nm spacing are generated at room temperature.