Precise frequency tuning in the millimeter-wave FEL-oscillator with the Bragg resonator

A FEL-oscillator with the traditional Bragg resonator consisting of the wav eguide with corrugated ends (mirrors) allows to obtain single-mode generati on with high efficiency. However, the output radiation frequency cannot be fixed more precisely than the mirror's reflection band, typically at 2-3%. There exists another scheme of the Bragg resonator without the smooth tube between mirrors Depending on the corrugation phase shift between the mirror s this resonator has a single high-quality mode inside the reflection band or two modes near the ends of the reflection band. Variation of the corruga tion phase shift from 0 to 2 pi tunes the mode frequency from higher to low er limit of the reflection band. Bragg resonators of this type were designe d both for high-efficiency FEL-oscillator and for precise radiation frequen cy meter. Experimental investigation of the tunable EEL-oscillator is now i n progress. (C) 2000 Elsevier Science B.V. All rights reserved.