HOMODYNE AND HETERODYNE READOUT OF A SIGNAL-RECYCLED GRAVITATIONAL WAVE DETECTOR S. Hild, H. Grote, J. Degallaix, A. Freise, M. Hewitson, H. Lück, K.A. Strain, J.R. Smith in addition to B. Willke Motivation as long as DC-readout Definitions Simulated shot noise

HOMODYNE AND HETERODYNE READOUT OF A SIGNAL-RECYCLED GRAVITATIONAL WAVE DETECTOR S. Hild, H. Grote, J. Degallaix, A. Freise, M. Hewitson, H. Lück, K.A. Strain, J.R. Smith in addition to B. Willke Motivation as long as DC-readout Definitions Simulated shot noise www.phwiki.com

HOMODYNE AND HETERODYNE READOUT OF A SIGNAL-RECYCLED GRAVITATIONAL WAVE DETECTOR S. Hild, H. Grote, J. Degallaix, A. Freise, M. Hewitson, H. Lück, K.A. Strain, J.R. Smith in addition to B. Willke Motivation as long as DC-readout Definitions Simulated shot noise

Asakawa, Bruce, Florists, Garden Centers, and Nurseries Editor;Host has reference to this Academic Journal, PHwiki organized this Journal HOMODYNE AND HETERODYNE READOUT OF A SIGNAL-RECYCLED GRAVITATIONAL WAVE DETECTOR S. Hild, H. Grote, J. Degallaix, A. Freise, M. Hewitson, H. Lück, K.A. Strain, J.R. Smith in addition to B. Willke Motivation as long as DC-readout LIGO-G070443-00-Z Reduced shot noise (no contributing terms from 2 times the heterodyne frequency) Reduction of oscillator phase noise in addition to oscillator amplitude noise Stronger low pass filtering of local oscillator (due to PR cavity pole) Simplify the GW detector Simpler calibration (GW-signal in a single data-stream, even as long as detuned SR) Simpler circuits as long as photodiodes in addition to readout electronics Possibility to use photodiodes with larger area => reduced coupling of pointing Reduced number of beating light fields at the output photodiode => simpler couplings of technical noise Requires less ef as long as t as long as injecting squeezed light (=> useful precursor as long as GEO-HF) LO in addition to GW pass the same optical system (identical delay, filtering, spatial profile) => This advantage is especially important as long as detectors with arm cavities. Increased coupling of laser power noise. Usually an output mode cleaner (OMC) is required. Very sensitive to imbalances of the interferometer arms. Definitions Tuning/detuning of the Signal-Recycling cavity (microscopic length) tuned: carrier is resonant in SR-cavity detuned: carrier is off resonance in SR-cavity (550 Hz or 1 kHz) Readout system heterodyne: LO from RF sideb in addition to s (Schnupp modulation) DC-readout / homodyne: Carrier from dark fringe offset serves as LO Optical gain Transfer function from differential dis-placement to signal at the detection point. Simulated shot noise Rotation of optical response ( as long as detuned SR) Tuned Signal-Recycling Detuned Signal-Recycling (550Hz) Summary Frequency [Hz] Darkport power [W/sqrt(Hz)} Heterodyne 550 Hz Red. MI modulation Red. MI modulation + carrier from dfo Turning down the radio frequency modulation (stable operation is possible with 10 lower sideb in addition to s) Dark port is dominated by carrier light (TEM00) from a 50 pm dark fringe offset We demonstrated a DC-readout scheme without output mode cleaner in GEO600. DC-readout in addition to heterodyne detection has been compared as long as several Signal-Recycling tunings. Using DC-readout a displacement sen-sitivity of 2·10-19m/sqrt(Hz) is achieved. Simulations were per as long as med with FINESSE. DC-readout gives a better peak sensitivity than hetero-dyne readout, independent of the SR tuning. For detuned SR: A “rotation” of the detector response is observed, when going from heterodyne to DC-readout The predicted rotation of the detector response is confirmed by the measurements. This phenomenon can be explained by the opposite phase of the two heterodyne sideb in addition to s. Shot noise Increased in DC-readout Roughly same as with heterodyne (2e-19m/sqrt(Hz)) Increased technical noise Laser power noise limits the sensitivity at some frequencies below 300 Hz. Above 300 Hz laser power noise seems not to be a problem. Optical gain increases with the size of the dark fringe offset. Optical gain as long as + in addition to – dark fringe offset have 180 degree different phase. Sensitivity seems to independent of sign in addition to size of the dark fringe offset. Tuned SR is realized by using a fast jumping technique. Two different operation modes: resonant in addition to non resonant RF modulation frequency. Simulation of Laser power noise DC-readout in GEO without OMC How to achieve DC-readout

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