Quasi-optical cw mm-wave electron spin resonance spectrometer

We describe a novel cw millimeter-wave electron spin resonance (ESR) spectrometer designed to operate in the frequency range of 80-200 GHz and in the temperature range of 2.5-300 K, which may be easily scaled to higher frequencies. The spectrometer uses a bimodal reflection cavity coupled to a circular corrugated guide and uses Gaussian quasi-optics for most of the front-end signal processing. This technique has very low insertion loss and allows a number of sophisticated measurement techniques to be employed including induction operation, which significantly reduces the effect of microphonics and stray reflections. A number of examples are given illustrating the sensitivity of the instrument and the advantages of using ESR at high fields. (C) 1998 American Institute of Physics. [S0034-6748(98)00311-6].