Abstract
We present recent advances in modeling, design, and fabrication of in-plane
multilayer optical resonators fabricated by high aspect ratio etching of silicon. We
first revisit the model of Gaussian beam divergence proposed by A. Lipson to correct a
mistake that leads to an underestimation of the losses affecting this type of resonator.
Secondly, we discuss the influence of surface roughness at the silicon-air interfaces of
multilayered structures. Roughness profiles—measured by white light interferometry on
the sidewalls of silicon trenches etched by deep reactive ion etching (DRIE)—are
presented. The single absorbing layer model of Carniglia is used to predict the
influence of the measured roughness (30±5 nm RMS). This model is combined with the
corrected model for Gaussian beam divergence and is compared with recent experimental
results obtained for a new generation of deep-etched Fabry–Perot refractive index
sensors. These sensors are fabricated using the contour lithography method, which is
demonstrated to greatly improve the predictability of their optical characteristics. The
combined model for roughness and divergence is found to correspond remarkably well with
the experimental results, with predictions of loss and finesse of the resonances within
an average error of 1.3 dB and 25%, respectively. We therefore expect the models and the
simulations presented in this article to become a useful tool for the design of devices
based on deep-etched multilayer resonators.
© 2012 IEEE
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