Generation of tunable continuous-wave terahertz radiation by photomixing the signal waves of a dual-crystal optical parametric oscillator

We present a continuous-wave dual-crystal optical parametric oscillator that generates signal waves of about 1.4 μm wavelength with a tunable difference frequency Δν between 0.64 and 5.3 THz. A model of the parametric gain in such a system indicates that the lowest reachable value for Δν depends on the refractive index dispersion of the nonlinear material used. As a proof of principle, we demonstrate the generation of terahertz radiation by photomixing the signal waves. Frequencies between 0.64 and 0.85 THz are created and detected coherently with ion-irradiated InGaAs interdigitated photomixers.