Glass-blown Pyrex resonator with compensating Ti coating for reduction of TCF

This paper demonstrates that the Thermal Coefficient of resonant Frequency (TCF) of a micro glass-blown Pyrex spherical resonator can be substantially reduced by the application of a titanium (Ti) coating. Finite Elements Analysis (FEA) is used to demonstrate that the temperature dependence of the Young´s modulus of the shell material is the dominant parameter affecting the TCF of the resonator, clearly suggesting the use of a metallic compensating layer. Experimental characterization demonstrates that the TCF of a Pyrex glass-blown resonator is reduced by 70% (from 73 ppm/°C to 24 ppm/°C) by the application of a 1.33 μm thick layer of Ti. It is predicted by FEM that for a Ti layer thickness on the order of 2.5 μm the TCF will fall below 10 ppm an acceptable value for high performance resonators. This investigation is a step forward in the quest to employ the desirable properties of micro-blown resonators, such as high symmetry, manufacturing tolerances and environmental robustness.