Eleonora P, Yuhang, and Aritomi
By keeping green always locked, we measured the power of all the higher order modes we could see from camera. The reason to keep green locked is that we have 'two different FSR' for IR. We found a lot of higher order modes. But the main higher order mode is HG10. This means our alignment needs to be improved for yaw direction. The power for each mode is reported as follows.(picture attached insequence without HG10 and TEM00)
AOM frequency | Transmission power | Mode |
108.93233MHz | 180mV | HG10 |
109.02030MHz | 62mV | HG50 |
109.02068MHz | 64mV | |
109.02125MHz | 54mV | |
109.03569MHz | 90mV | TEM00 |
109.20801MHz | 54mV | HG80 |
109.20911MHz | 54mV | HG81 |
109.22574MHz | 76mV | HG30 |
109.22632MHz | 56mV | LG11 |
109.41733MHz | 56mV | |
DC offset | 48mV |
Some modes I didn't write name seem so-called ince-gaussian modes. Maybe it comes from the combination of yaw misalignment and mode-mismatch.
We found the second HG10 at 109.4313MHz, which means FSR is 0.499MHz which is in agreement with our expectation.
We will do alignment of yaw for the next step.