Simple system for generation and detection of tunable-frequency far infrared light

The system described in this paper has a simple optical configuration for g uiding far infrared light to a detector, and thus requires neither a Michel son-type diplexer nor a Fabry-Perot-type filter, both of which require fine adjustments. In this system, all the components that generate, guide, and detect far infrared light work at room temperature. It uses a Schottky barr ier diode for heterodyne detection rather than a conventional thermal detec tor, such as a cooled bolometer for direct detection. The system is simpler than the conventional system, yet it maintains high sensitivity to FIR rad iation. Experimental results demonstrate the principal behavior of this sys tem. The modulation factor and the tunable-frequency far infrared power is estimated by using an equivalent circuit model with a Schottky barrier diod e. The estimated far infrared power is compared with the values reported in other papers. The results of a gas absorption measurement with this system are also discussed.