Abstract

Dual-frequency lasers offer beat notes from DC to the terahertz range [1], leading to various applications such as remote sensing, lidars, and Doppler velocimetry. In order to stabilize the beat note in a dual-frequency laser, a new scheme consisting in feeding back one polarization mode into the other was recently developed [2]. Here, we investigate experimentally, numerically, and analytically the synchronization properties between the two polarization modes when the locking range is comparable to the relaxation oscillation frequency of the laser. An important parameter is the coupling coefficient β that measures the cross-saturation of the two polarization modes in the gain medium. If β → 0, the two-mode laser system reduces to a single mode laser subject to an injected signal [3]. On the other hand, if β → 1 (β = 0.8 in our experiments), we observe more complex forms of synchronizations that strongly depend on the intensities of the individual modes.

© 2011 IEEE