Stable actively Q-switched single-frequency fiber laser at 1.5 µm based on self-injecting polarization modulation.

ABSTRACT

A new technique for the realization of a stable Q-switched operation in a single-frequency fiber laser based on self-injecting polarization modulation is demonstrated, for the first time to the best of our knowledge. A piezoelectric fiber stretcher was utilized to introduce periodic stress-induced polarization changes. Then the modulation of polarization state transformed into Q switching by virtue of a designed distributed Bragg reflector (DBR) resonant cavity with polarizations loss anisotropy. Finally, a stable actively Q-switched single-frequency fiber laser at 1.5 µm with Gaussian-shape pulse output was achieved. We experimentally found that, the repetition frequency (several hundred kHz) coincided with the working frequency of the polarization modulation, and the pulse width (several hundred ns) reduced with the increasing of the modulating frequency, the modulating amplitude, as well as the pump power. This stable Q-switched single-frequency fiber laser is promising for applications in optical time-domain reflectometry, coherent Doppler wind radar, and optical coherent detection. More importantly, this novel Q-switched technology may be applicable to other DBR single-frequency fiber lasers.