FAR-INFRARED SPECTROSCOPY WITH HIGH-RESOLUTION CYCLOTRON-RESONANCE FILTERS

A new type of far infrared spectroscopy based on a cyclotron resonance notch filter is demonstrated. The resonant absorption energy of such a filter is tuned by an external magnetic field. GaAs/AlGaAs heterostr uctures with high mobility two-dimensional electron gas are used to ob tain an optimal cyclotron resonance filter. With such a filter, we can analyze far infrared radiation in the range 40-150 cm(-1) with a reso lution of up to 2 cm(-1). A procedure for the determination of the spe ctral characteristics of an unknown source from the detector signal is presented. We show that the cyclotron-resonance-notch-filter based sp ectrometer provides ultralow background radiation conditions for measu rements. We also demonstrate the performance of the spectrometer by an analysis of electrostimulated far infrared emission of InSb, GaAs bul k crystals as well as of selectively doped quantum wells. (C) 1998 Ame rican Institute of Physics.