Tunable Narrow-Linewidth Fiber Laser Based on the Acoustically Controlled Polarization Conversion in Dispersion Compensation Fiber

Abstract

Researches on high coherence light sources always pursue fast tuning speed, linear tunability and persistence of narrow linewidths at different tuning channels. Fortunately, acousto-optical interaction (AOI) can be employed in the fast management of the lasing wavelength. Herein, we propose a fast tunable narrow-linewidth fiber laser assisted by the acoustically-induced polarization selection in dispersion compensation fiber (DCF). The lasing wavelength is determined by the acoustically-induced band-pass grating in DCF. The large dispersion slope of the DCF suppresses the bandwidth of the TM₀₁ peak to be less than 1 nm. The acousto-optic-controlled polarization conversion effectively restrains the acousto-optic frequency shift. With side longitudinal mode suppressions induced by the combintion of the self-injection feedback and saturable absorption filtering, the output laser successfully achieves the narrow-linewdith operation and owns a low relative intensity noise floor of −135 dB/Hz. By controlling the acoustic-wave frequency, the laser can be linearly tuned with a large wavelength range (over 20 nm, linear fitting R² reaches 0.99781), and the laser linewidths remain about ∼2 kHz in different tuning channels. The laser tuning dynamics under the acousto-optical controlling are experimentally revealed, and the lasing tuning response time is ∼800 μs.