Sub-THz spectroscopic system using a multimode laser diode and photoconductive antenna

A system for measuring transmittance of electromagnetic waves in the sub-TH z region is proposed. The electromagnetic radiation is generated by the exc itation of a photoconductive antenna with a commercially available multimod e laser diode. The spectral coverage of the radiation is increased by defoc using the light spot on the photoconductive antenna. Transmitted radiation is detected by a hot-electron bolometer through a Martin-Puplett-type inter ferometer. Transmittance is measured for n-type Si wafers with various dopi ng levels. The carrier densities calculated from the transmittance agree we ll with those obtained from the dc conductivity measurement. (C) 1999 Ameri can Institute of Physics. [S0003-6951(99)01748-9].