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MarcEisenmann - 17:52, Wednesday 16 May 2018 (776)Get code to link to this report
FC scan

Participants : Marc, Yuefan, Yuhang

 

Here is presented the FC scan.

Compared to entries 771 and 775 few corrections have been implemented.

There was a mistake in the first estimation of the mode-mismatch (2 order 0 have been taken into account as well as the 2 sidebands).

There was another mistake done while doing the fitting : Now we used 1 Airy function defined by the 2 order 0 and then only changed the normalization value (T0).

We obtain the following results :

r : 0.9992

FSR : 125 s (the AOM frequency modulation have been changed but we still have FSR=500 kHz)

T0 (normalization factor) : 3.6374    0.0164    0.0604    0.0274    0.0119    0.0262    3.3774

x0 : 65.62 89.52 115.155 115.208 164.78 164.88 190.62

The mode-mismatch was evaluated using the ratio sum of higher order modes T0/ fundamental mode T0.

This leads to a mode-mismatch of 3.9%.

 

Few things to notice :

The position of the sidebands needs to be confirmed

While modulating the AOM frequency to realize the scan, the beam exiting the AOM is tilted which leads to the different heights of the fundamental order peak (?)

Images attached to this report
776_20180516105215_fcscan.png
Comments related to this report
YuhangZhao - 21:40, Wednesday 16 May 2018 (779)

According to the signal we send to DDS board, the modulation frequency of we give to EOM is 15.2MHz. The FSR is 0.5MHz.

15.2/0.5=30.4

So we will have additional 0.4 of FSR. This exactly explains the result we have on the oscilloscope.

MarcEisenmann - 17:38, Monday 21 May 2018 (783)

The total amount of power not coupled inside the FC is composed of the mode-mismatch and the sidebands.

The sidebands maximum are respectively : 0.1462 and 0.1422 mV (this takes into account the background value).

This means that 11.84% of the light is not coupled inside the FC.