Refractive index, dispersion, and birefringence of silicon carbide polytypes.
The refractive index of each of the four common silicon carbide polytypes has been measured over the visible range. The data were analyzed in an attempt to relate the birefringence to the relative hexagonal character of the polytype. A general relationship exists, namely, that the birefringence increases with increasing hexagonal character of the polytype. This relationship is not sufficiently precise to use for the identification of polytypes.
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.
Joint University Program for Air Transportation Research, 1982
A summary of the research on air transportation is addressed including navigation; guidance, control and display concepts; and hardware, with special emphasis on applications to general aviation aircraft. Completed works and status reports are presented also included are annotated bibliographies of all published research sponsored on these grants since 1972.