b KAGRA PSL EOM Layout 180 W Laser

b. KAGRA PSL EOM Layout ~180 W ? Laser (Master+Amp) EOM (f. PMC, PM) PMC EOM (f. IMC, PM) WB-EOM (wideband, PM) ~100 m. W Ref. Cav AOM • Modulation frequencies and requirements for modulations JGWwiki/MIFIOOInterfaces • Abbreviations EOM: electro-optic modulator PM: phase modulation AM: amplitude modulation WB: wideband Multiple EOMs? (f 1, PM-AM) (f 2, PM) (f 3, AM) to IMC

Requirements for f 1, f 2, f 3 • f 1 PM and AM (ratio should be adjusted with respect to detuning) • f 2 PM only • f 3 AM only (turned off once the IFO is locked) • Series modulation is OK • Detailed requirements are summarized in JGWwiki/MIFIOOInterfaces 2

Layout 1 • Simple but lose half the power ~ oscillator mixer phase shifter ~ f 2 EOM (f 1, f 2, f 3) to IMC ~ EOM (f 1, f 2, f 3) f 1 ~ f 3 3

Layout 2 ~ oscillator mixer • Saves the whole power phase shifter ~ f 2 EOM (f 2) ~ EOM (f 1) EOM (f 3) to IMC f 1 delay line ~ f 3 • f 1 = 16. 880962 MHz → 17. 76*(n+1/2) m It is not possible to use the same delay line for f 1 and f 3 if we want to save all the sidebands because f 3/f 1=10/3 (it is possible if f 3/f 1 = odd/odd, but this is not the case for b. KAGRA) EOM (f 3) delay line f 3 = 56. 269873 MHz → 5. 33*(m+1/2) m 4

Layout 3 • Simpler, but loses some f 3 AM ~ oscillator mixer phase shifter ~ f 2 EOM (f 2) EOM (f 1, f 3) to IMC ~ EOM (f 1, f 3) f 1 delay line ~ f 3 f 1 = 16. 880962 MHz → 17. 76*1/2 = 8. 88 m → 2. 66 m (see JGW-T 1706748) 5

Layout 3. 5 ~ mixer • Possible configuration for b. KAGRA Phase 2? NO ~ PBS f 2 EOM (f 2) ~ f 1 ~ f 3 EOM (f 1, f 3) oscillator phase shifter to IMC EOM (f 1, f 3) 45 deg tilted • EOM has wedges and AM generation is not possible with wedged EOM (even with two EOMs) • AM generation with tilted EOM requires severe temperature control • Possible effect on interferometer controls due to unwanted f 3 PM (we cancel f 3 PM with two EOMs, but we don’t have enough EOMs) and unwanted f 2, f 1 AM 6