Line-narrowed, compact, and coherent source of widely tunable terahertz radiation

We report a technique for line-narrowing terahertz radiation produced through parametric generation. By incorporating an etalon within the idler-wave cavity of the parametric oscillator, radiation is generated with a linewidth of 1GHz (freerunning linewidth 50–100GHz) and with a center frequency continuously tunable over a band >50GHz, settable anywhere within the coarse tuning range of the device (1–3THz). When implemented within an intracavity cavity geometry, pulses of terahertz radiation of duration ∼10ns and energy ∼30nJ are generated at repetition rates up to 400Hz (implying mean powers of >10μW and peak powers of ∼3W) in a compact device.