Method of resonant matching in diffraction radiation oscillator with a double comb

The resonant matching instead of the traditional phase matching of the double periodic grating substantially changes the resonant oscillation field structure in the ORS as DRO part. On the other hand, the double periodic grating at the bottom of the rectangular groove acting as a quarter-wave transformer enhances the resonance field utilization by the electron beam and effectively removes high-order modes, enabling us to further advance to the terahertz region. When the matching groove height is chosen to be b = 0.75λ , quite a wide tuning range is possible to achieve for the working oscillation with a high radiation quality. A larger factor of resonance field utilization in the ORS is due to the resonance field contraction to the ORS axis in the mirror space rather than the field amplitude growth in the double periodic structure, and it will not increase the ORS ohmic loss.