Arm Length Stabilization System

Wiki for ALS (Arm Length Stabilization; Auxiliary Lock System), a.k.a green lock system

Schematic (One Arm)

ALS Configuration

optical layout of PR2/SR2 chambers, POP/POS table
select AOM and AOM driver
fix green fiber specs, including how to do the laying
fiber collimators for green
green fiber after EOM/AOM or before EOM/AOM
- Not much difference from noise, cable length point of view.
- Alignment jitter noise from AOM will be less if fiber comes after AOM. So, let it so.
fiber for PLL beat or not
where to put frequency offset: PLL or arm length
more detailed noisebudget
initial alignment planning
comm/diff servo topology
- necessity of summing node for common mode servo (LIGO-D1300782)
lock acquisition scheme

Broadband PD for PLL Newport 818-BB-21A (1.2 GHz bandwidth)
Resonant PD for green PDH JGW-D1201280
AOM and AOM driver (to be determined)
EOM: Qubig xxxxxx (ready)
- modulation frequencies are 32 MHz and 33 MHz JGW-T1605626
QPD for green beam pointing? (Use Oplev QPD?)
Picomotor mount? (ordered)

Fiber (under test at UToyama)
- probably with jacket, with endcap, without AR coating
- polarization maintaining
Fiber collimator (Tholabs PAF? Fixed focus collimator?)