Stochastic Resonance in Quantum-Well Semiconductor Lasers

The quantum well （QW） semiconductor lasers have become main optical sources for optical fibre communication systems because of their higher modulation speed, broader modulation bandwidth and better temperature characteristics. In order to improve the quality of direct-modulation by means of the stochastic resonance （SR） mechanism in QW semiconductor lasers, we investigate the behaviour of the SR in dlrect-modulated QW semiconductor laser systems. Considering the cross-correlated carrier noise and photon noise, we calculate the power spectrum of the photon density and the signal-to-noise ratio （SNR） of the direct-modulated laser system by using the linear approximation method. The results indicate that the SR always appears in the dependence of the SNR on the bias current density, and is strongly affected by the cross-correlation coefficient of the carrier and photon noises, the frequency of modulation signal, and the photon lifetime in the laser cavity.     

Self-Starting Passively Mode-Locking All-Solid-State Laser with GaAs Absorber Grown at Low Temperature

We realize a stable self-starting passively mode-locking all-solid-state laser by using novel GaAs mirrors as the absorber and output coupler. The GaAs mirror is grown by the technology of metal organic chemical vapour deposition at low temperature. With such an absorber as the output coupler in the laser resonator, laser pulses with duration of 42ps were generated at a repetition rate of 400MHz, corresponding to the average power of 590mW.     

Passive Q-Switching Modelocked Yb^3＋ -Doped Fibre Laser with GaAs Absorber Grown at Low Temperature

GaAs absorber was grown at low temperature (550℃) by metal organic chemical vapour deposition (MOCVD)and was used as an output coupler with which we realized Q-switching modelocked yb^3 -doped fibre laser. The shortest period of the envelope of the Q-switched modelocking is about 31μs. The modelocking threshold is 4.27 W and the highest average output pulse power is 290mW. The modelocking frequency is 12 MHz.