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:

• JGW-T160510 Summary of iKAGRA Test Run March 2016

• iKAGRA Channel List

• Phase 1 Measurements Summary

See following pages for some design parameters

• IOO related

• MIF related

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

  • Design: 10

  • Measured: 11-12

  • Measurement method: REFERENCE TO BE ADDED

  • 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: