Arm Length Stabilization System

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

ALS Configuration

To Do

optical layout of PR2/SR2 chambers, POP/POS table
select AOM and AOM driver
- DONE
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
- DECIDED not to use fiber for PLL (Mar 5, 2018)
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)
  - first, try with digital switch and decide (Feb 6, 2018)
lock acquisition scheme

Common Mode Servo Board JGW-D1503705 (ready)
PLL Board (similar to CMB, ordered to AEL)
Phase Frequency Discriminator LIGO-D1002476 (prototype developed at UToyama)
Fast version of IQ Demodulator LIGO-E1100044 (ordered to AEL)
RF Oscillator for PDH Keysight N5181B MXG (ready)
- FM option N5181BU-UNT (not yet ordered)
VCO for PLL Keysight E8663D (ready)
Frequency counter Tektronix FCA3103 (ready)
Current driver for the thermal path ALS-X/Y servo

Broadband PD for PLL Newport 818-BB-21A (1.2 GHz bandwidth)
Resonant PD for green PDH JGW-D1201280
AOM G&H 3080-125 (80MHz) and AOM driver G&H 1075FM-1 (1W, 5MHz BW). (ordered)
EOM: Qubig EO-T38M3-VIS (ready)
- modulation frequencies are 32 MHz and 33 MHz JGW-T1605626
QPD for green beam pointing? (Use Oplev QPD?)
Picomotor mount? (ordered)

Faraday isolator Thorlabs IO-5-532-HP (ready)
Periscopes Thorlabs Ø1.5inch Post Assembly (ready)
Dichroic mirror for periscopes: LEO DRX-1064/532-45P-UF-2038 (ready: 8pcs(2 each for POP/POS/TRX/TRY))
Harmonic splitter: LEO LWP-45-R532-T1064-UF-2038 (ready: 8pcs(1 each for POP/POS/TRX/TRY, 4 spares))
Dichroic mirror in-vac: Sigma TFVMQ-50.8C10-20-W1D-532/1064-ARS-30-45D (ready: 4pcs(1 for PR2, 1 for SR2, 2 spares))

Fiber: Coastal Connections P-FAnskFAnsk-3.5nx/125/3-75 and -80 (under test at UToyama)
- probably with jacket, with endcap, without AR coating
- polarization maintaining
Fiber collimator (Thorlabs PAF-X-5-A? Thorlabs triplet lens collimator TC06APC-543?)