Design of a Coating-less Optical Cavity based on Total Internal Reflection

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Abstract:: Gravitational Wave astronomy requires ultraprecise measurements of the miniscule changes in length scales, far smaller than the size of an atom. Present day laser interferometry promises to deliver the desired accuracy; However, noise from various sources is a major barrier towards this goal. In fact, the precision required for detecting strong signatures is to the level where the spontaneous thermal fluctuation in the test masses result in ‘Thermal Noise’ in the interferometer output. This project aims towards noise reduction by developing an optical cavity without the high reflecting coating layers and resorting to Total Internal Reflection (TIR) instead to obtain high reflectivity. Finite Element Analysis (FEA) using COMSOL and MATLAB is employed to calculate the Thermal noise for specific geometries. The results are crosschecked with certain analytic results for the correctness of the model. It is expected that suitable design and materials brings cancellation effects between the Thermo Elastic (TE) and Thermo Refractive (TR) noise.

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LIGO Document G1300821-v1