Optical Follower feedback control loop for the photon calibrator at LIGO
Document Type
Oral Presentation
Campus where you would like to present
SURC Ballroom A
Start Date
17-5-2012
End Date
17-5-2012
Abstract
The Advanced Laser Interferometer Gravitational wave Observatory (LIGO) calibration will rely on power-modulated auxiliary laser beams to induce time-varying displacements of the end test masses (ETMs). Photon calibration (Pcal) induces two kinds of displacement noise, relative power noise (RPN) and harmonic noise due to impurities in the modulated signal. To minimize the injection of displacement noise, the sinusoidal power modulation needs to be purified. To improve the spectral purity, we employ an "Optical Follower" feedback control system. The Optical Follower samples a fraction of the modulated power and compares it with a reference waveform. The difference is fed back to an acousto-optic modulator (AOM) to reduce differences between the generated and the reference waveforms. The servo was able to meet the requirements for harmonic noise and extended the linear range of the AOM. However more work needs to be done to improve RPN. This project was a proof of principle to design and fabricate an Optical Follower servo during a summer Research Experience for Undergraduate (REU) at LIGO in 2011.
Recommended Citation
Minton, Rolf, "Optical Follower feedback control loop for the photon calibrator at LIGO" (2012). Symposium Of University Research and Creative Expression (SOURCE). 93.
https://digitalcommons.cwu.edu/source/2012/posters/93
Poster Number
2
Additional Mentoring Department
Physics
Optical Follower feedback control loop for the photon calibrator at LIGO
SURC Ballroom A
The Advanced Laser Interferometer Gravitational wave Observatory (LIGO) calibration will rely on power-modulated auxiliary laser beams to induce time-varying displacements of the end test masses (ETMs). Photon calibration (Pcal) induces two kinds of displacement noise, relative power noise (RPN) and harmonic noise due to impurities in the modulated signal. To minimize the injection of displacement noise, the sinusoidal power modulation needs to be purified. To improve the spectral purity, we employ an "Optical Follower" feedback control system. The Optical Follower samples a fraction of the modulated power and compares it with a reference waveform. The difference is fed back to an acousto-optic modulator (AOM) to reduce differences between the generated and the reference waveforms. The servo was able to meet the requirements for harmonic noise and extended the linear range of the AOM. However more work needs to be done to improve RPN. This project was a proof of principle to design and fabricate an Optical Follower servo during a summer Research Experience for Undergraduate (REU) at LIGO in 2011.
Faculty Mentor(s)
Michael Braunstein, Rick Savage, Paul Schwinberg, Jonathan Berliner