What's claimed to be the world's first room-temperature terahertz laser harnesses the optical equivalent of heterodyning to bridge the terahertz gap. Today, a terahertz-gap exists where most semiconductor lasers fail to operate--between microwave wavelengths (centimeters) and optical wavelengths (microns). In between are the millimeter wavelengths--terahertz frequencies (1-10 terahertz frequency or 30-300 microns wavelength). The only semiconductor lasers that run in the terahertz regime today are supercooled quantum cascade lasers (QCL). Now, the co-inventor of the QCL has demonstrated a heterodyning method cast in nonlinear materials that mixes two easy-to-generate optical frequencies spaced apart at the desired terahertz frequency, resulting in a room-temperature terahertz laser. In the photo, the laser is connected to the contact pad (left) by thin gold wires where a silicon hyper-hemispherical lens is attached to collimate its 5 terahertz output. Terahertz lasers enable scanning like x-rays, but are safe to use around people. Using a terahertz scanner, airports could detect hidden weapons under clothing, as well as hazardous and toxic materials inside luggage. Terahertz lasers could also remotely detect hazardous gases floating in the air, offering a potential solution to identifying improvised explosive devices from a distance.

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