We (rana, yehonathan and i) briefly talked about having high power going into the IFO. I worked on some calcs a couple of years ago, that are summarized here. There is some discussion in the linked page about how much power we even need. In summary, if we can have

• T_PMC ~85% which is what I measured it to be back in 2019
• T_IMC * T_inputFaraday ~60% which is what I estimate it to be now
• 98% mode matching into the IMC
• power recycling gain of 40-45 once we improve the folding mirror situation in the recycling cavities
• and a gain of 270-280 in the arm cavities (20-30ppm round trip loss)

then we can have an overall gain of ~2400 from laser to each arm cavity (since the BS divides the power equally between the two arms). The easiest place to get some improvement is to improve T_IMC * T_inputFaraday. If we can get that up to ~90%, then we can have an overall gain of ~4000, which is I think the limit of what is possible with what we have.

We also talked about the EOM. At the same time, I had also looked into the damage threshold as well as clipping losses associated with the finite aperture of our EOM, which is a NewFocus 4064 (KTP is the Pockel medium). The results are summarized in Attachments #1 and #2 respectively. Rana thinks the EOM can handle factor of ~3 greater power than the rated damage threshold of 20W/mm^2.