Spatial mapping of multimode Brownian motions in high-frequency silicon carbide microdisk resonators.

High-order and multiple modes in high-frequency micro/nanomechanical resonators are attractive for empowering signal processing and sensing with multi-modalities, yet many challenges remain in identifying and manipulating these modes, and in developing constitutive materials and structures that efficiently support high-order modes. Here we demonstrate high-frequency multimode silicon carbide microdisk resonators and spatial mapping of the intrinsic Brownian thermomechanical vibrations, up to the ninth flexural mode, with displacement sensitivities of ~7-14 fm Hz(-1/2). The microdisks are made in a 500-nm-carbide on 500-nm-oxide thin-film technology that facilitates ultrasensitive motion detection via scanning laser interferometry with high spectral and spatial resolutions. Mapping of these thermomechanical vibrations vividly visualizes the shapes and textures of high-order Brownian motions in the microdisks. Measurements on devices with varying dimensions provide deterministic information for precisely identifying the mode sequence and characteristics, and for examining mode degeneracy, spatial asymmetry and other effects, which can be exploited for encoding information with increasing complexity.