Coherent terahertz radiation has historically been very difficult to generate, and the search for an easy-to-use, compact source continues today.
Northwestern University researchers recently developed a simpler way to generate single-chip terahertz radiation — a discovery that could benefit security screening, border protection, high-sensitivity biological/chemical analysis, agricultural inspection, and astronomical applications. The research addresses two key issues that have limited the usefulness of initial demonstrations of terahertz systems.
First, by increasing the power and beam quality of the mid-infrared pumps, the researchers were able to increase the terahertz power by more than a factor of 30 to ~10 microwatts.
The researchers also incorporated a dual-wavelength diffraction grating within the laser cavity to create single mode (narrow spectrum) mid-infrared sources, which in turn has led to very narrow linewidth terahertz emission near 4 terahertz.
Because of the novel generation mechanism, the terahertz spectrum is extremely stable with respect to current and/or temperature — which could make it valuable as a local oscillator for low light level receivers needed for astronomical applications.
This research is partially supported by the Defense Advanced Research Projects Agency (DARPA). The researchers plan to continue working toward achieving milliwatt power levels, and would also like to incorporate tuning within the device.
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