Dielectric microwave resonator with large optical apertures for spin-based quantum devices

Abstract

We demonstrate a low-loss dielectric microwave resonator with an internal quality factor of 2.30×104 while accommodating optical apertures with a diameter of 8 mm. The two seemingly conflicting requirements, high quality factor and large optical apertures, are satisfied, thanks to the large dielectric constant of rutile (TiO2). The quality factor is limited by radiation loss, and we confirmed by numerical simulation that this radiation loss can be suppressed by extending the enclosure height of the resonator; the resonator can potentially achieve a dielectric loss-limited quality factor, exceeding 106. Using this resonator, we performed both continuous-wave (cw) and pulse electron spin resonance (ESR) spectroscopy on 2,2-diphenyl-1-picrylhydrazyl (DPPH) crystalline powder and P1 centers in a diamond crystal in a dilution refrigerator. The cw ESR spectroscopy demonstrated high-cooperativity and strong spin-resonator coupling with the DPPH and P1 centers, respectively, while the pulse ESR spectroscopy successfully measured longitudinal and transverse relaxation times. This optically accessible low-loss microwave resonator enables the implementation of a spin-based quantum device, such as a microwave-optical photon transducer.