Two-frequency stimulated emission of radiation with orthogonal polarizations from an HCN laser

Simultaneous emission of two orthogonally polarized fundamental EH₁₁ modes was observed for a waveguide electric-discharge HCN laser (λ = 337 μm). The difference between the frequencies of these modes was continuously tunable in the range from 100 kHz to 4.5 MHz. A change in the beat frequency was observed as a result of a change in the discharge current.