Matteo, Satoshi, Kiwamu,
Now that we confirmed that green laser S/N 2143A has been back up and running without an issue (8395), we wanted to measure the absolute frequecy of the laser. Such piece of information is critical because it determines whether 2143A can produce beatnote with the main laser at a reasonable frequency at around several tens of MHz.
[Measurement result]
The overall behavior of the temperature-frequency trace for 2143A was measured to be almost identical to the X arm Prometheus or 2143B (c.f., 6239). Since our lasers (i.e., the main and X arm green lasers) are now operating somewhere at around 281630 GHz, we expected that this laser should run at a crystal temperature of either 23 degrees or 25 degrees. Indeed, beanote was found later in the evening by Sugimoto et al., at 23.5 deg (8394). From the point of view of avoiding to be too close to a mode-hop, we think that the choice of 23.5 deg is better than that of 25 deg.
The raw data in txt format is attached as well.
[The set up]
Here are some pictures of the measurement setup which is meant to be temporary and is built nearby the free-space Mephisto on the PSL table.
The setup is super simple; we had a half-wave plate, PBS and the fiber-coupler in transmission of the PBS. The fiber is directly connected to the wavelenght meter (Highfinesse WS Ultimate 30). We manually adjusted the waveplate angle in such a way that the laser wavelength meter doesn't saturate. We intentionally didn't calibrate the wavelength meter. Obviously, we were coupling the 1064 nm light into the fiber and not the 532 nm.
