Evaluation of laser frequency offset locking using an electrical delay line.

Abstract

Frequency offset locking between two Nd:YAG lasers is performed using frequency locking with an electrical delay line. The relative frequency instability of the offset locking is measured to be 3.5×10-12 for an averaging time of 1s, which is approximately 77 times smaller than that of the free-running case. The frequency instability of the frequency locking is compared to that of the phase locking between the two Nd:YAG lasers. Furthermore, a compact solid-state laser is frequency locked to an optical frequency comb with a frequency instability of 8.2×10-11 for an averaging time of 1s, which is improved by approximately 20 times, with respect to the free-running case. The offset-locking scheme using a delay line is useful for various applications including a research on quantum optics, interferometric measurements, and experiments involving laser cooling, such as an optical lattice clock.