LIGO Document G2501538-v1
- The next-generation gravitational wave detectors aim to surpass current sensitivity limits by reducing thermal
noise through operating in longer wavelength, cryogenic cooled temperatures and the use of crystalline silicon
optics. This requires transitioning from 1064 nm lasers, as used in the current LIGO detectors, to longer
wavelengths around 2 m, where silicon exhibits low optical absorption. However one of the challenges at 2 m
is the lack of high quantum-efficiency (Q.E) photo detectors. We explore to set up a cavity enhanced Sum
frequency generation (SFG) configuration for the indirect detection of 2 m signal. This involves 2 micron
signal combined with 1064 nm pump to yield 700 nm up-converted photons which can then be detected by the
high Q.E detectors. For SFG, We set up a mode-matched, pump resonant, bowtie cavity with PPLN crystal as
nonlinear material inside cavity for high power build up to achieve higher Up-conversion efficiency.
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