Proton radiation effects on optically transduced silicon carbide microdisk resonators

Circular microdisk mechanical resonators vibrating in their various resonance modes have emerged as important platforms for a wide spectrum of technologies including photonics, cavity optomechanics, optical metrology, and quantum optics. Optically transduced microdisk resonators made of advanced materials such as silicon carbide (SiC), diamond, and other wideor ultrawide-bandgap materials are especially attractive. They are also of strong interest in the exploration of transducers or detectors for harsh environments and mission-oriented applications. Here we report on the first experimental investigation and analysis of energetic proton radiation effects on microdisk resonators made of 3C-SiC thin film grown on silicon substrate. We fabricate and study microdisks with diameters of -48 & mu;m and -36 & mu;m, and with multimode resonances in the -1 to 20 MHz range. We observe consistent downshifts of multimode resonance frequencies, and measure fractional frequency downshifts from the first three flexural resonance modes, up to --3420 and -1660 ppm for two devices, respectively, in response to 1.8 MeV proton radiation at a dosage of 1014/cm2. Such frequency changes are attributed to the radiation-induced Young's modulus change of -0.38% and -0.09%, respectively. These devices also exhibit proton detection responsivity of 2t & AP; -5 to -6 x 10-6 Hz/proton. The results provide new knowledge of proton radiation effects in SiC materials, and may lead to better understanding and exploitation of micro/nanoscale devices for harsh-environment sensing, optomechanics, and integrated photonics applications.