LIGO Document G2501539-v1
- Noise Characterizations in Table-top
Waveguided Optical Parametric
Amplification (WOPA) Process
Gravitational wave detectors such as Advanced LIGO rely on exquisite sensitivity to detect minuscule spacetime perturbations, making them susceptible to a variety of noise sources. Among the most fundamental is quantum noise, which arises from vacuum fluctuations entering the interferometer's antisymmetric port. To mitigate this limitation, frequency-dependent squeezed vacuum states quantum states with reduced uncertainty in one quadrature are injected to suppress the quantum noise. Currently, squeezing at LIGO is achieved via optical parametric oscillators (OPOs) using resonant cavities. This project explores Waveguided Optical Parametric Amplification (WOPA) as a cavity-free alternative that offers architectural simplicity and potential robustness against alignment instabilities. WOPA utilizes a single-pass configuration through a periodically poled lithium niobate (PPLN) waveguide, pumped with 532 nm light, to generate broadband squeezed vacuum states at 1064nm.
This work aims to develop a detailed noise and loss budget for the WOPA-based squeezing source. The analysis includes contributions from laser frequency and intensity noise, phase noise, polarization mismatch, propagation and coupling losses in the waveguide, imperfect mode matching, and gain imbalance at the balanced homodyne detector (BHD). The ultimate goal is to identify and limit these noise sources, thereby increasing the achievable level of squeezing.
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