Yuaurihara, K. Tanaka

We analized yesterday's measurement data and obtained the FSR = 5.62 +/- 0.03 MHz, round-trip length = 53.3 +/- 0.3 m and finesse: 461 +/- 28. FSR and the round-trip length are consistent with the design valu, previous measurement (klog615) and Akutsu-sans' estimation (klog18002). On the other hands, finesse is lower than these results.

 # What we did

1. The time series data we have used is attached Fig. 1. Of this data, the data from 13 to 18 seconds was used.
2. Got the interval it takes to sweep between FSR (t_FSR) = 0.7485+/- 0.016 sec from the fitting (Fig. 2).
3. Got the interval it takes to sweep from TEM00 peak to sideband peak( t_sb00) = 0.337 +/- 0.010 sec from the time stamp from upper and lower sideband
4. we can do the calibration from the time to the laser frequency by 13.78 MHz/(2*t_FSR+t_sb00). So FSR is calibrated to be 5.62 +/- 0.03 MHz
5. Which correspond to the roundtrip length of 53.3 +/- 0.3 m.
6. Got t_FWHM = 0.0016 +/- 0.0001 sec from the Lorentzian fitting of the transmitted beam peak. One example plot of the result of the fitting is attached (Fig. 3).
7. By t_FSR/t_FWHM, we got IMC finesse to be 461 +/- 28