[Shalika, Mitsuhashi-san]

This elog is about us trying to improve lock time. In continuation to work in elog. 

Details:

1. Today we finalized our cavity mirror alignment. The TEM00 mode observed using PD at transmitted beam is of 10.4V ampitude and is as shown in Fig 1 during laser scan. The corresponding error signal looks is as shown in Fig 2. The demodulated signal's phase is set at 110º. All the higher order modes were less than 50% of TEM00 amplitude.

2. We found the laser temperature at which TEM00 mode appears. We set the laser temperature to 9100. 

3. We changed the offset voltage and around 0.7 to 0.8 V, the cavity was able to lock for 10 minutes(shown in Fig 3).The filter cut off frequency was 10 Hz and gain was 200. The amplitude of the locked signal was a bit less than the TEM00 mode amplitude. We are certain it was locked to TEM00 and was not locked to higher order mode, since no modes other than TEM00 were observed at an amplitude of more than 5V. To fix this we will change the filter cut off frequency and gain. 

Next Step:

We will try to change the filter properties and make the locked signal amplitude same as TEM00 mode amplitude(as in Fig 1).