karmeng.kwan@LIGO.ORG - posted 13:26, Thursday 20 June 2024 - last comment - 09:51, Friday 21 June 2024(78556)
SHG-2 escape efficiency
Added a beamsplitter and photodetector at the input of the SHG cavity to measure the escape efficiency.
The reflected beam from the SHG (blue trace) gives an escape efficiency of 98.1%. The theoretical escape efficiency of the SHG is 98.5% for mirror reflectivity of 90% and 99.85%.
The escape efficiency is calculated via Ptrans/Prefl = (2nesc - 1)2. From the reflected beam, the Ptrans/Prefl = 3.19/3.45.
The escape efficiency calculated from the mirror transmissivity is, nesc = Tinput / Ttotal = 0.985
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After tweaking the cavity allignment, I managed to obtain an escape efficiency of 98.6% after taking into account of the higher order mode.
The new Ptrans / Prefl = (3.43 - 0.3) / (3.61 - 0.3) & nesc = 0.986
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