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
f2 frequency
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?
Finesse
- Design: ~500
- 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:
- Measurement method:
- 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:
- Measurement method:
- Notes:
Y-arm mode-match
- Measured:
- Measurement method:
- 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:
- Measured:
- Measurement method:
- Notes:
PRY length
- Design:
- Measured:
- Measurement method:
- Notes:
PRC Gouy phase
- Design:
- Measured:
- Measurement method:
- Notes:

Signal Recycling Cavity

SRX length
- Design:
- Measured:
- Measurement method:
- Notes:
SRY length
- Design:
- Measured:
- Measurement method:
- Notes:
SRC Gouy phase
- Design:
- Measured:
- Measurement method:
- Notes:

Michelson

Schnupp asymmetry
- Design:
- Measured:
- Measurement method:
- Notes:

Dual Recycled Michelson

Power recycling gain
- Design:
- Measured:
- Measurement method:
- Notes:

Power Recycled Fabry-Perot Michelson

Power recycling gain
- Design:
- Measured:
- Measurement method:
- Notes:
Power at each ISC detection ports when locked
- 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:
- Measured:
- Measurement method:
- Notes:
Finesse
- Design:
- Measured:
- Measurement method:
- Notes: