I've updated the PSOMA optical layout. I still have some questions on locking, and there are a few additional configurations that we could try. In particular:
- Amplifier cavity as a 2-port device (signal and pump mixed before reaching an overcoupled amplifier cavity)
- Amplifier cavity as a 4-port device (signal and pump enter the cavity through different ports)
- Overcoupled case -- 'signal out' at the same mirror as 'signal in'
- Critically coupled case -- 'signal out' through the 'pump in' port
Each of these configurations also has a couple different ways to pickoff an LO for homodyne readout. Shruti and I enumerated these configurations on a zoom whiteboard a couple weeks ago, and I've attached them (the zip contains png).
Chris also mentioned last week that we may run into a frequency-dependent loss in the critically coupled cavity configurations. The pdf I've attached shows a configuration that I think is a minimal modification of the Mach-Zehnder amplifier described in PSOMA. One of the ring cavities is replaced with a tunable steering mirror, and the LO is picked off before the pump reaches the MZ.
In the new diagram, I'm thinking about controlling the following degrees of freedom:
- Signal phase relative to pump phase
- Pump frequency relative to amplifier cavity resonance
- pump intensity
- MZ relative path length
- Homodyne mixing angle
- Signal and pump spatial mode
Some things I'm unsure about:
- I am not currently controlling signal laser intensity -- can this be done by sending the first order AOM beam to a PD rather than dumping it as shown?
- Not sure about the right place to place several of the EOM
- If we have transmission through the cavity's curved mirror, is the associated loss acceptable?
Shruti and I are now tracking our work on git issues in the PSOMA repo. |