Optical Spectrum Smoothing Phenomena in Harmonically Mode-Locked Semiconductor-Optical-Amplifier-Introduced Hybrid-Type Fiber Ring Laser

概要

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Optical spectrum smoothing phenomena have been investigated in semiconductor optical amplifier (SOA)-introduced hybrid-type fiber ring lasers. In the hybrid-type fiber ring lasers, a very stable, harmonically mode-locked operation is achievable owing to a high-pass filtering effect caused by a gain saturation as well as a fast carrier recovery time (ns) of an SOA. In this operation, very small detuning of the modulation RF signal induces optical spectrum smoothing phenomena, while generating very stable optical pulses with more than 55 dB supermode noise suppression ratio and less than 150 fs timing jitter. By measuring the beat signal of output pulse trains with and without a continuous wave (CW) single-mode external cavity laser, it has been concluded that the smoothing phenomena are assumed to originate from fast and random hopping between several sets of the harmonically mode-locked longitudinal modes, that is, the possible supermodes in the hybrid-type fiber ring lasers.
2009-02-25