Dual-polarization frequency-modulated laser source

Diode-pumped 1.3-μm as well as 1.06-μm Nd:YAG lasers have been operated with two orthogonally polarized modes at slightly different frequencies. The frequency difference, controlled by an intracavity electrooptic crystal, may be modulated. Thus, two polarized-outputs are obtained; one at a constant frequency, and the other frequency-modulated. This is a novel source for frequency-modulated heterodyne detection systems where the reference (local oscillator) frequency originates from the signal laser itself and is automatically locked to it.