I measured the IR injection mode matching with new beam spot which has more stable IR transmission.
First I optimized IR injection alignment with new beam spot. I checked the IR injection alignment by changing AOM frequency. The mode matching is 95.6%. Note that AA and BS pointing were engaged during this measurement.
After the IR injection alignment, IR transmission was 460 with 430uW injection. According to our experience, the IR transmission should be 490 with 430uW injection. The possible reason of the smaller IR transmission is that the IR transmission is off centered in transmission PD with new beam spot.
AOM frequency (MHz) | mode | IR transmission |
109.53805 | TEM00 | 460 |
109.93494 | pitch | 100 |
110.33183 | LG | 105 |
offset | 94 |