Upload
sophia-horn
View
217
Download
1
Tags:
Embed Size (px)
Citation preview
Ponderomotive amplifier to reduce shot noise
GWADW @ Kyoto
May. 2010
Kentaro Somiya1 and Yanbei Chen2
Waseda Inst. for Adv. Study1 and Caltech2
High-freq sensitivity of GWD
RSE
HighFinesse
anti-reso
reso reso
SR gain could be higher if the arms were shorter.
Optical-bar regime by Braginsky and Khalili
SRM
PRM
Optical-bar regime
locked by opt spring
local-readout (high SRG)
ITM ETM
• Dual Recycling instead of PR+RSE (f<spring)• Signal enhancement at spring frequency• High power required to increase spring frequency
[Braginsky 98] [Rehbein 07]
local-readout
interpretation
Optical lever[Khalili 02][Danilishin 06]
• Reasonable power on the small mirrors• Chen-type optical lever is rather an amplifier• GW signal converts to radiation pressure in PA
interpretation
more signal less power
[Chen 03]
Ponderomotive amplifier
locked free
40kg
4km 1g
1m
Ponderomotive amplifier40kg
4km 1g
1m sig (phase)
sig (amp)
pump (amp)
RP sig (phase)
RP sig (amp)
sig (phase)
carrier (amp)
GW signal
coupled with pump
RP signal reenters
coupled with carrier• Vacuum enters from the pick-off• Optimized combination of the two outputs in the best quadrature
Ponderomotive amplifier
A
B
I1 I2
A=B=
……
I1 x … + I2 x … + …
maximize SNR
I2 x [vacuum + signal + disp-noise]GWD
Amp
Shot noiseSignal
4TcosI1(1-T)
: detune phase T: transmittance of input coupler
input coupler
If I2-term is dominant…
Signal is amplified and SNR increases
Sensitivity gain
GWD L=4km, m=40kg, I0=1kW, F=120
PA L=10cm, m=1g, I0=100W, F=6000
IC R=81%, =1.5rad
• Big reduction of shot noise up to kHz• Strong against PD losses• Power on PA might be a bit high…
PA displacement noise
• The small-mirror IFO will be noisy• The motion is suppressed by the optical spring
Sensitivity curve
• Not yet fully optimized• Good sensitivity with low power• PA noise limits the sensitivity at high freq
PBS
Single-path ponderomotive amplifier
I1 I2
GWD
Amp
vacuum
(TF and QN of DRSE)
• It turns out this one doesn’t work• Signal and noise increases at once• Recall the situation with detuned RSE…
Summary• Ponderomotive amplifier based on optical lever
• Reduction of shot noise
• Strong against optical losses
• PA displacement noise is suppressed by spring
• Possible combinations: LIGO + MIT 1g IFO Virgo + LKB micro-mirror GEO + membrane TAMA + NAO 20mg IFO… etc.