Characterizing Bulk Scatter in Crystalline Silicon

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Abstract:: The LIGO Voyager update is especially concerned with the material of the detectors optics. Current detectors use fused silica for the test mass mirrors; however, silica is not ideal for use in Voyager due to its thermal and mechanical properties at 123K. Silicon, however, works beautifully at 123K with low mechanical and thermal losses. Whats more important is that silicon mirrors can be made extremely pure at large volumes. However, there are still some expected defects in the silicon crystal. This project is focused on measuring the scatter as a diagnostic tool to measure the defect concentration in Michael Czochralski Magnetic Silicon. Beyond just using the scatter to understand the defect population in the Silicon, understanding the scatter by itself is important. Scatter from the mirrors can add phase noise, contribute to cavity loss, and disrupt squeeze states. In order to analyze scatter from silicon at 1550nm, a scatterometer was built to measure the scattered light as a function of angle. In order to characterize the defects that cause the scatter, these measurements are then compared to Mie scatter simulations of different expected populations of defects.

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Notes and Changes:: This is an node for collecting links to documents for Amani Garvin's 2017 SURF project on Scatter in a Silicon Sample (SSS). Reports and relevant documents will be linked back to this document number for a central reference point.

LIGO Document T1700337-v1