Diode lasers detect terahertz radiation

Although great advances have been made in terahertz sources based on Ti:sapphire lasers and in terahertz detectors based on bolometers, these systems are expensive and complex. Building on recent research that realized cost-effective terahertz sources and imaging systems by photomixing of diode lasers, researchers at Ruhr-Universität (Bochum, Germany), TU Braunschweig (Braunschweig, Germany), Ferdinand-Braun Institute (Berlin, Germany), and Philipps-Universität (Marburg, Germany) have demonstrated that diode lasers can also be used as terahertz detectors.

To demonstrate terahertz detection, a methanol terahertz laser pumped by a carbon-dioxide laser is coupled into the active region of a diode laser. The diode laser is a single-quantum-well 840 nm laser grown by low-pressure metal-organic vapor-phase epitaxy. Upon terahertz injection, the voltage variations of the p-n junction of the diode laser are measured using a lock-in technique and found to vary as a function of the changing terahertz input. To increase the detection efficiency of this room-temperature detector, antenna structures could be implemented to increase the terahertz-radiation coupling into the laser-diode waveguide, and a diode laser with a weakly doped semi-insulating substrate could be substituted to avoid terahertz power absorption in the highly doped substrate used. Contact Carsten Brenner at [email protected]