Laser current set to 1.5 amps.
IR output 1.125W (after the laser head), 50.0mW (after Faraday, we're using wave plate to intentionally dump some power), 10mW after PBS (another attenuation, we can decrease this, or increase this up to 50mW)
With 10mW going to the PLL diode, we have about -3dBm beat note.
green output 22.9mW (right after the laser head), 17.5mW (after the first Faraday), 13.85 (after the second Faraday), 12mW (just before the bottom periscope mirror)
Retroreflection (measured after 10:90 splitter) 0.73mW, this means that the retroreflection is 7.3mW.
Apparent table efficiency is 7.3/12 = 61%.
Aluminum mirror reflectivity is probably not that good (95%-ish if they're good) (turns out that they're silver, not aluminum, coated, thanks Matt for pointing it out, and this means that the reflectivity of these is 98% or so rather than 95), and there are four such mirrors (TMS telescope mirrors), double path, meaning there are 8 reflections. This should amount to 0.98^8 = 85%-ish.
There is a splitter for QPD (5%? I don't remember), again double path, so if it's 5% splitter this removes 10%.
0.85*0.9 = 77%-ish.
References: D1201457, E1000870, E1000669, E1000652, E1000425, C1103229
On a closer look, there is two E1000669 "IR HR, Green HT" mirrors (M4 and M7) in the green TMS path. Transmission of these is 98.6% according to the vendor measurement.
5% transmission is really 5.0% measured (E1000870), high reflectors are measured to be really high reflective (E1000652, E1000425).
Also, though there's no reflectivity measurement for TMS telescope silver mirrors, various vendos offer "protected silver" coating reflectivity data in tiny tiny plots, and Thorlabs data looks as if the reflectivity is 97% rather than 98 for 532nm, Newport quite similar, CVI looking lower. None of these three vendors are used for TMSY, we used two Edmund optics (the reflectivity data I wasn't able to find) and two custom optics coated by a coating vendor in California, but it sounds safe to assume that the reflectivity is 0.97 or lower per silver mirror.
ETMY uses ETM04 (C1103229) which has a ITM HR with a transmission of 1% for 532nm.
Including 98.6% transmission twice, 95% reflection once and 97% reflection four times, we have:
0.986^2 * 0.95 * 0.97^4*0.99 = 0.82 single path, or
(0.986^2 * 0.95 * 0.97^4)^2 = 0.67 double path for TMS itself.
Including 99% ETM, we have 0.66 total.
Double path was measured to be 61%, so there's still 5% discrepancy but this might easily be the silver mirror reflectivity.
If we put everything into the silver mirror, its reflectivity should be 96% per mirror.