LIGO Document T1600388-x0

Imaging Optical Scatter in Advanced LIGO

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T - Technical notes
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01 Jan 2017, 16:41
Due to surface imperfections, some laser radiation will deviate from its original, desired path—making the light disperse and appear as a deterministic angular distribution of intensity rather than a single, sharp reflection. A percentage of light is thus lost, or scattered away from the specular beam, causing a loss in energy and thereby decreasing the sensitivity of the laser. Concerns over the apparent deterioration of power stemming from the Pre-Mode Cleaner (PMC) led to an investigation focusing on characterizing this scatter by calibrating a CCD and modeling a bidirectional scattering distribution function of the data. In addition to the PMC, various optics (test masses and mode cleaners) were also analyzed, this time using a High Dynamic Range (HDR) computer program that takes images at different exposures and merges them together. By comparing HDR data with theoretical models, one can easily indicate any beam irregularities, thus my ongoing research further develops a better understanding of the total amount of noise optical scattering inflicts, and finds a way to decrease its influence on the detection of gravitational waves.
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