Terahertz system exploits 1550 nm telecom technologies

The primary advantage of continuous-wave (CW) terahertz generation as opposed to femtosecond-pulse terahertz generation is the simplicity and tunability of its optical source: two CW lasers; one tunable and one fixed, with the possibility of monolithic integration.

The primary advantage of continuous-wave (CW) terahertz generation as opposed to femtosecond-pulse terahertz generation is the simplicity and tunability of its optical source: two CW lasers; one tunable and one fixed, with the possibility of monolithic integration. Unfortunately, the workhorse for the subsequent light-to-terahertz conversion—low-temperature gallium arsenide photoconductive antennas—exhibits significantly lower performance in CW operation compared to femtosecond pulsed operation due to its inherent nonlinearity.

Researchers at the Fraunhofer Institute for Telecommunications (Berlin, Germany) recognized the availability of compact, low-cost 1550 nm telecom technology and modified an existing telecom receiver design to create a waveguide-integrated photodiode antenna (WIN-PDA). With this linear device, they can overcome the limitations of photoconductive antennas in combination with CW illumination and thus increase the emitted terahertz power by more than an order of magnitude. For detection of the terahertz radiation emitted by this WIN-PDA, the Fraunhofer researchers developed a coherent photoconductive receiver made of low-temperature indium gallium arsenide. This combination of a high-power terahertz emitter with sensitive coherent detection was demonstrated for the first time. Analysis of water-vapor absorption lines showed significantly improved detection sensitivity and resolution compared to time-domain systems over an operating range from 0.1 to 1.6 THz. Contact Bernd Sartorius at bernd.sartorius@hhi.fraunhofer.de.

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