Diode-pumped Terahertz laser source based on stimulated polariton scattering

Terahertz (THz) radiation has been referred to as the last frontier of the electromagnetic spectrum because it is one of the most difficult frequency bands to generate and detect. While the potential for THz radiation to be used in medicine, biology, security and other applications has been abundantly demonstrated [1], the widespread uptake of THz technologies is hampered by the need for practical, low-cost THz sources. Terahertz parametric oscillators (TPOs) make use of both second and third-order nonlinear processes ie optical parametric oscillation and stimulated Polariton scattering respectively [2] and are a promising solution to this problem. Recently Edwards et al [3] demonstrated a diode-pumped intracavity TPO which generated tunable, pulsed (10 ns) THz radiation, with average powers up to 10 W. Here we report on a system with similar overall architecture, but make use of CW diode pumping and a resonator design which provides higher cavity Q together with smaller mode size in the active crystals. The attractive features of this diode-pumped, intracavity TPO include its very low threshold (corresponding to 3.8 W diode pump power), together with its relative simplicity, compactness and the robust, cost-effective Nd solid-state laser technology on which it is based.