Mechanism of dual-wavelength line-width synchronous narrow-modulation Q-switched laser based on gain control

An orthogonally polarized dual-wavelength single longitudinal mode Q-switched laser under the synchronous line-width narrowing technology is reported for the first time, to the best of our knowledge. We established a theoretical model that revealed the oscillation mechanism of the dual-wavelength SLM Q-switched laser operation. Fabry-Perot (F-P) etalons were used as auxiliary mode-selection elements, which not only enabled gain control for the two wavelengths, but also enhanced the side-mode suppression capability of the pre-laser Q-switching process. This narrowed the synchronized line-width for the two different wavelengths. The results of the theoretical analysis were experimentally validated. At a frequency repetition of 20 kHz, the spectral line-widths at 639- and 720-nm were 27 MHz and 37 MHz, respectively. The results of this study can provide guidance for future research on dual-wavelength, highly coherent, and integrated light sources. We believe that such a laser will have a number of potential applications, including multiple wavelength interferometry and microscopy imaging.