Microtech Instruments (Eugene, OR) launched its terahertz parametric oscillator TPO-850, a 0.85 THz source that propagates over long distances. The device complements a previously released version that emits at 1.5 THz; both sources target the 0.85 and 1.5 THz atmospheric-transmission windows that have low water absorption, making them ideal for imaging and spectroscopy applications. Unlike heterodyne photomixing-based terahertz sources that have limited output power (typically less than 10–20 µW), the TPO sources are based on intracavity difference frequency generation (DFG) and are a factor of 10 more powerful at 0.1 mW average power (more than 150 mW peak power) and narrowband at 100 GHz spectral width for high spectral power density.
In the type II double resonant ring-cavity optical parametric oscillator (OPO), a periodically poled lithium niobate (PPLN) crystal is pumped by a 1064 nm, 5 W fiber-laser source with 6 ps pulse duration and 109 MHz pulse repetition rate. Terahertz radiation is generated through DFG between signal and idler pulses by placing a quasi-phase-matched (QPM) crystal—a stack of gallium arsenide wafers rotated 180º with respect to each other—at a second focal point in the cavity. By using different QPM periods, the terahertz output can be tuned from 0.8 to 2.8 THz and reaches milliwatt power levels. Contact Patrick Tekavec at [email protected].