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A scheme, which allows one to select the shortest part from the Dubins set D directly, without the usual exhaustive calculation of its elements, is proposed. The results indicate that the problem of finding the shortest path between two configurations can be reduced to a logical manipulation of the set of appropriate path candidates, without their explicit calculation.

In this paper, we report latest developments in wafer-level micro-glassblowing paradigm for fabrication of highly symmetric, high Q-factor fused silica wineglass gyroscopes. Q-factors over 1 million have been demonstrated on both n = 2 wineglass modes with a high frequency symmetry (Δf/f) of 132 ppm. High Q-factor is enabled by a high aspect ratio, self-aligned glassblown stem structure, careful surface treatment of the perimeter area, and low internal loss fused silica material. Low frequency split is provided by the self-correcting behavior of the surface tension based micro-glassblowing process. Micro- glassblowing may enable batch-fabrication of high performance fused silica wineglass gyroscopes on a wafer surface at a significantly lower cost than their precision-machined macro-scale counterparts. [ABSTRACT FROM AUTHOR]

Abstract: This paper demonstrates spherical vapor cells intended to be used in chip-scale atomic devices. A micro glass blowing process is introduced, in which multiple glass spheres are simultaneously shaped on the top of a silicon wafer and subsequently filled with rubidium. In the presented fabrication process, an array of cylindrical cavities is first etched in silicon. Next, a thin glass wafer is anodically bonded to the silicon wafer. The bonded wafers are then placed inside a furnace set to 850 C. At this elevated temperature, the viscosity of the glass is decreased and the heated trapped gas in the cavities expands, thus causing the glass to be blown into spherical cells. Microscopic alkali vapor cells are achieved by evaporation of through a small glass nozzle into the cell cavities. The cells are then sealed by anodic bonding. The fabricated cells are characterized and the presence of rubidium vapor inside the cells is verified by observing an absorption spectrum. [Copyright &y& Elsevier]

Abstract: This paper reports on the design and implementation of high efficiency, nonmetallic reflectors integrated on the sidewalls of micromachined cavities. Due to shadowing from deposition within a cavity, significant variation in the thicknesses of the dielectric thin films composing the reflectors are encountered when the layers are deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). These gradients in thickness limit the performance of the reflector at the intended design wavelength. An optimized design procedure is described to maximize the performance of the reflector at the absorption wavelength of of 795nm for use in micromachined atomic vapor cells. The reflector design is based on multiple shifted quarter wave Bragg reflectors in series, which extends the reflective bandwidth for increased robustness to film thickness gradients. The extended reflectance range maintains high reflection at the design wavelength despite greater than 70% decrease in film thickness across the reflector surface. The reflector technology is ideally suited for use in atomic MEMS vapor cell applications by achieving high reflectance while maintaining light polarization. We demonstrate less than 2dB of return loss with circular polarization ellipticity maintained to . [Copyright &y& Elsevier]

Abstract: This paper reports a new MEMS vibratory rate gyroscope designed with increased robustness to fabrication imperfections and variations in environmental conditions. The proposed architecture utilizes a single degree-of-freedom (DOF) drive-mode and a fully coupled 2-DOF sense-mode. The drive-mode operational frequency and the sense-mode bandwidth can be set independently, relaxing the tradeoff between the gain, die size, and detection capacitance inherent to the previously reported robust gyroscopes with dynamic vibration absorber (DVA) architecture of the 2-DOF sense-mode. Prototypes with 2.5kHz operational frequency were extensively characterized in air and demonstrated sense-mode 3dB bandwidth of 250Hz. The uncompensated temperature coefficients of bias and scale factor were 313(/h)/C and 351ppm C, respectively. Using off-chip detection electronics, the rate sensitivity was 28 V/(/s), ARW – 0.09(/s)/, bias instability – 0.08(/s), and ARRW – 0.03(/s) . Detailed time domain, Allan variance, and probability density function analysis revealed that both ARW and ARRW are of Gaussian type and Coriolis-uncorrelated, showing stable in-operational noise performance of the reported gyroscope. [Copyright &y& Elsevier]

This paper presents a study on dynamics of a dual-mass MEMS vibratory gyroscope in presence of fabrication imperfections and reports a method for precision electrostatic frequency tuning of the operational modes. A number of multi-mass MEMS gyroscopes have emerged in recent years pursuing different goals, such as dynamically balanced structure, increased bandwidth, and dynamic amplification. Along with many perceived advantages of multi-mass devices, several challenges associated with mode-matching in a system with increased number of degrees-of-freedom (DOF) have to be considered. This work shows that it is possible to apply the DC tuning techniques, similar to tuning a conventional single-mass gyroscope, to achieve the precision tuning in a dual-mass sensor, without losing advantages of increased DOF of the system. The presented frequency trimming technique is based on assessing the modes mismatch and cross-coupling between modes by means of fitting the experimental frequency response curves to the analytical solutions of the dual-mass system in presence of imperfections. The tuning algorithm involves two steps. First, the stiffness mismatch along the two axes and the anisoelasticity angles α and β are identified, then the tuning DC voltages for modification of diagonal, off-diagonal, and coupling terms in the stiffness matrix are chosen. The method of electrostatic tuning was validated through the experimental characterization of a dual-mass dynamically amplified gyroscope, where the coupling between the two operational modes was minimized and frequency split was reduced from 26 Hz down to 50 mHz, resulting in 17.5× increase in the gyroscope scale factor and significantly improved noise characteristics. The presented electrostatic compensation method is suitable for both off-line and on-line calibration. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on a method for improving the optical efficiency of micromachined reflectors integrated in rubidium vapor cells for application in atomic MEMS sensors. A hybrid bulk micromachining and multilayer PECVD thin film process is used to form the Bragg reflectors on angled sidewalls, which redirect laser light through the vapor cell and back toward the plane of the source with reduced optical power loss. Integrated thin film Bragg reflectors are shown to improve the reflectance of the micromachined surface by almost three times, resulting in an optical return efficiency of two paired dielectric reflectors that is as much as eight times higher then uncoated silicon reflectors. Absorption of the absorption line at a wavelength of 795nm in a 1 vapor cell is demonstrated experimentally by use of two integrated thin film reflectors with a total optical return efficiency approaching 40%. [Copyright &y& Elsevier]