Refractive index variations induced by a microwave field interacting with the active medium of an FIR laser

Double-resonance effects due to irradiation of the active molecules of an FIR laser by a resonant microwave field are demonstrated. In particular, dispersion effects are shown to contribute to both AM and FM of the FIR laser output. By using double resonance in a metallic waveguide laser, amplitude modulation up to 30 percent and FM shift to 40 kHz were obtained with 50mW microwave driving power. Higher modulations could be obtained if stronger microwave power were used.