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 heterostructures with high mobility two-dimensional electron gas are used to obtain an optimal cyclotron resonance filter. With such a filter, we can analyze far infrared radiation in the range 40-150 cm(-1) with a resolution of up to 2 cm(-1). A procedure for the determination of the spectral characteristics of an unknown source from the detector signal is presented. We show that the cyclotron-resonance-notch-filter based spectrometer provides ultralow background radiation conditions for measurements. We also demonstrate the performance of the spectrometer by an analysis of electrostimulated far infrared emission of InSb, GaAs bulk crystals as well as of selectively doped quantum wells. (C) 1998 American Institute of Physics.