Optical Characterization
This page is intended for summarizing the interferometer optical characterization results and discussions. See following pages and documents for iKAGRA and bKAGRA Phase-1 characterization summary:
See following pages for some design parameters
RF Sidebands
f1 frequency: 16.8732705 MHz https://klog.icrr.u-tokyo.ac.jp/osl/?r=4831
f2 frequency: 44.995388 MHz https://klog.icrr.u-tokyo.ac.jp/osl/?r=4831
- f1 modulation depth:
- f2 modulation depth:
Input Mode Cleaner
- Round-trip length
Design: 53.28708 m (FSR of 5.6269873 MHz)
Measured: 53.302985(9) m
Measurement method: FSR was measured to be 5.624308(1) MHz. https://klog.icrr.u-tokyo.ac.jp/osl/?r=4831
Notes: Measured on April 2018. Any re-installation after this? Needs to be adjusted to match with PRC length.
- Finesse
Design: 520
Measured: 409
Measurement method: Cavity pole was measured to be 6.86(2) kHz. https://klog.icrr.u-tokyo.ac.jp/osl/?r=14569
Notes: Lower than iKAGRA measurement of 540+/-70 http://klog.icrr.u-tokyo.ac.jp/osl/?r=618 Degraded?
- Mode-match
Measured:
Measurement method:
Notes:
Arm Cavities
- X-arm length
Design: 3000 m
Measured: 2999.990(2) m
Measurement method: Cavity scan FSR = 49.96557(4) kHz http://klog.icrr.u-tokyo.ac.jp/osl/?r=7332
Notes:
- X-arm Gouy phase
Design: 250.75 deg
Measured: 250.7(3) deg
Measurement method: Cavity scan TMS=34.79(5) kHz http://klog.icrr.u-tokyo.ac.jp/osl/?r=7332
Notes:
- X-arm finesse for IR
Design: 1530
Measured: 1410(30)
Measurement method: Ring down
Notes: There is temperature dependence due to frosting
https://klog.icrr.u-tokyo.ac.jp/osl/?r=10033
- X-arm round-trip loss
Design: 100 ppm
Measured: 86(3) ppm
Measurement method: From reflectivity change in locked and unlocked https://klog.icrr.u-tokyo.ac.jp/osl/?r=7307
Notes: The estimate might be wrong due to birefringence https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=11633
- X-arm mode-match
Measured: 91(1)%
Measurement method: Cavity scan https://klog.icrr.u-tokyo.ac.jp/osl/?r=7307
Notes:
- X-arm finesse for green
Design: 51
Measured: 41(2)
Measurement method: Calculated from reflectivity measurements by Hirose-san
Notes:
- Y-arm length
Design: 3000 m
Measured: 3000.015(1) m
Measurement method: Cavity scan, FSR = 49.96517(2) kHz https://klog.icrr.u-tokyo.ac.jp/osl/?r=9505
Notes:
- Y-arm Gouy phase
Design: 250.75 deg
Measured: 250.9(3) deg
Measurement method: Cavity scan, TMS = 34.82(5) kHz https://klog.icrr.u-tokyo.ac.jp/osl/?r=9505
Notes:
- Y-arm finesse for IR
Design: 1530
Measured: 1320(30)
Measurement method: Ring down, http://klog.icrr.u-tokyo.ac.jp/osl/?r=9052, http://klog.icrr.u-tokyo.ac.jp/osl/?r=9211, http://klog.icrr.u-tokyo.ac.jp/osl/?r=9496
Notes: There is temperature dependence due to frosting
https://klog.icrr.u-tokyo.ac.jp/osl/?r=10033
- Y-arm round-trip loss
Design: 100 ppm
Measured: NOT YET MEASURED?
Measurement method: https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=11633
Notes:
- Y-arm mode-match
Measured: 87(2) %
Measurement method: Cavity scan https://klog.icrr.u-tokyo.ac.jp/osl/?r=9505
Notes:
- Y-arm finesse for green
Design: 51
Measured: 53(3)
Measurement method: Calculated from reflectivity measurements by Hirose-san
Notes:
Power Recycling Cavity
- PRX length
Design: 68.2563 m (PRC length = 66.591 m)
Measured: 68 m
Measurement method: Using dnu/nu=dL/L https://klog.icrr.u-tokyo.ac.jp/osl/?r=14633
Notes: Compare it with PRY.
- PRY length
Design: 64.9265 m
Measured: 70.2 m
Measurement method: Using dnu/nu=dL/L https://klog.icrr.u-tokyo.ac.jp/osl/?r=14565
Notes: In consistent results between different methods and not compatible with Schnupp asymmetry measurement
- PRC Gouy phase
Design: 33.0 deg
Measured: 31(1) deg
Measurement method: Cavity scan with the inertia locking method http://klog.icrr.u-tokyo.ac.jp/osl/?r=9276
Notes: After PR2 was moved.
Signal Recycling Cavity
- SRX length
Design: 68.2563 m (SRC length = 66.591 m)
Measured:
Measurement method:
Notes:
- SRY length
Design: 64.9265 m
Measured:
Measurement method:
Notes:
- SRC Gouy phase
Design: 35.0
Measured: 48(2)
Measurement method: Cavity scan with the inertia locking method http://klog.icrr.u-tokyo.ac.jp/osl/?r=9246
Notes:
Michelson
- Schnupp asymmetry
Design: 3.3299 m
Measured: 3.36(1) m
Measurement method: Demodulation phase difference in locking X-arm and Y-arm https://klog.icrr.u-tokyo.ac.jp/osl/?r=14575
Notes: Not consistent with PRX and PRY measurements.
Dual Recycled Michelson
- Power recycling gain
Design:
Measured: ~3
Measurement method: REFERENCE TO BE ADDED
Notes:
- Power at each ISC detection ports when DRFPMI is locked
- IMC output:
- REFL:
- POP p-pol:
- POP s-pol:
- POS p-pol:
- POS s-pol:
- AS RF:
- OMC REFL:
- OMC TRANS:
- TRX:
- TRY:
Power Recycled Fabry-Perot Michelson
- Power recycling gain for carrier
Design: 10
Measured: 11-12
Measurement method: REFERENCE TO BE ADDED
Notes:
- Power recycling gain for f1 sideband
Design:
Measured:
Measurement method:
Notes:
- Power recycling gain for f2 sideband
Design:
Measured:
Measurement method:
Notes:
- Power at each ISC detection ports when PRFPMI is locked
- IMC output:
- REFL:
- POP p-pol:
- POP s-pol:
- POS p-pol:
- POS s-pol:
- AS RF:
- OMC REFL:
- OMC TRANS:
- TRX:
- TRY:
Output Mode Cleaner
- Round-trip length
Design: 1.5 m
Measured: 2 * 0.717(2) m = 1.434(4) m
Measurement method: Cavity scan FSR of 208.99(65) MHz https://klog.icrr.u-tokyo.ac.jp//?r=14696
Notes:
- Finesse
Design: 780
Measured: 616(62)
Measurement method: Cavity scan https://klog.icrr.u-tokyo.ac.jp//?r=14696
Notes:
- AS mode content
Sensing Matrix Measurements
- LSC
- ASC
Optical Tables
I think we need a power budget here.
http://gwwiki.icrr.u-tokyo.ac.jp/JGWwiki/KAGRA/Subgroups/IOO/OutputTables/Optics
POP table lauyout (POP s-pol and p-pol)
POS table layout (POS s-pol and p-pol) https://klog.icrr.u-tokyo.ac.jp/osl/?r=14622
Others
- Laser intensity/frequency noise coupling
- MICH/PRCL/SRCL to DARM coupling
- MICH contrast defect
- Type-A, B, Bp actuation efficiency measurements