SBIR-STTR Award

A mode-locked, far-infrared solid-state p-Ge laser, tunable from 2.1 to 4.2 THz (70 - 140 cm-1), will be developed. Innovative concepts include pulse-position modulation (PPM) of the mode-locked output and piezoelectric control of cavity length and intracavity tuning element. Our PPM scheme differs from usual PPM telemetry using mode-locked lasers by being analog modulation, giving potentially higher dynamic range and resolution. It also does not require synchronized clocks at the transmitter and reciever, which will be advantageous for secure local-area communications on a highly-directional free-space THz beam. Piezo control of an intracavity tuning element and of the overall external cavity length will allow continuous tuning (without mode hops), frequency stabilization, and frequency modulation. The tunable laser will feature 10 W peak output power within megahertz spectral width. A turn-key design will demonstrate the commercial viability of the p-Ge laser for communications, materials characterization, process monitoring, plasma diagnostics, atmospheric sensing, and spectroscopy, even in airborne, space, and field applications. The proposed design is much simpler and more compact than the free electron laser or even gas lasers. Applications include communications, telemetry, materials characterization, process monitoring, plasma diagnostics, atmospheric sensing, and spectroscopy

The terahertz (THz) region of the electromagnetic spectrum is under-utilized for lack of convenient sources. In particular, there is no commercial solid-state far-infrared laser at sub-millimeter wavelengths. The objective of this STTR Phase II project is to deliver well-defined far-infrared solid-state laser products based on the p-Ge active medium. Phase I feasibility demonstrations included electrically-controlled wavelength selectors, external semi-confocal cavitites, non-metallic mirrors, an improved process for broad-area high-power ohmic contacts, permanent magnetr assemblies, compact solid-state electronics, and a closed-cycle cooler for the active crystal. Phase II will accomplish the research and development to refine and integrate these innovations. Room temperature external cavities and tuning elements will be developed to improve performance and reliability. The configuration of cooler, magnet, and active crystal will be optimized to reduce cooler requirements. Electronics will be further integrated and miniaturized, and electromagnetic interfernce will be reduced for low-noise applications. Pulse modulation of mode-locked laser emission will be further develeoped for potential free-space telemetry applications. Contacts, mirrors, and magnet assemblies will be further tested and refined. Effort will be directed to exploring potential aerospace uses of the laser with assistance from consultants.

Keywords:
TERAHERTZ, FAR-INFRARED, SUB-MILLIMETER, LASER, COMMUNICATIONS, SENSING, INSPECTION, SATELLITE