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

Parametric down-conversion techniques provide an effective means for producing terahertz radiation. A novel device, based on an intra-cavity geometry, has been developed that is both compact and widely tunable over the range 1-3 THz. Reduction of the free-running linewidth of this device (typically 50-100 GHz) to <5 GHz accompanied by continuous and smooth tuning over a band extending over 50-100 GHz where this band may be set anywhere within the above tuning range is described. A significant increase in the mean terahertz power generated to >10 muW is attained by increasing the pulse repetition rate up to 350 Hz. Applications in spectroscopy and imaging are discussed.