Comment to OPO replacement ATC beam setup (Click here to view original report: 3556)

Yesterday I prepared a new beam path to measure the beam profile directly from the laser. Today I measured the beam profile and at first it looks normal. So as we thought, the problem seems to be with the Faraday Isolator. I need to finish making the beam profile with all measurements to be sure of that but for now, it looks normal (at least with the W profile values).

Comment to OPO replacement ATC beam setup (Click here to view original report: 3556)

We took a Thorlabs IO-5-1064-HP from a box of miscalleneous optics for KAGRA filter cavity testing (next to Mitsuhashi Roberts linkage experiment, purchased end of FY23).

We put it on a micro tilt adjustment stage and made sure it could be adjusted to the beam height from the Mephisto (72-73 mm). Actually the Faraday isolator that was already there was just put on a pedestal post instead of an adjustment stage, so it is likely that the vertical alignment through the FI was not good, generating a visible higher order mode and causing the improper beam profile.

OPO replacement ATC beam setup

Logan, Michael

We once again found that the beam profile is showing some strange behavior with the asymmetry of the beam divergence. By using the profiler camera we see that it is probably due to misalignment of the Faraday isolator.

Comment to Compensation of BB1EO3 at 0 deg (Click here to view original report: 3544)

Did scans from

LC1, LC1step, LC2, LC2Step, averaging

0-25V, 0.2V, 0-25V, 0.2V

then observed and put a constraint on ell and azi of 2 deg

second scan 

0-1V, 0.01V, 0-25V, 0.1V

15-25V, 0.1V, 0-25V, 0.1V

third scan

0-0.06V, 0.01V, 0-8V, 0.05V

15-25V, 0.01V, 0-5.2V, 0.01V

15-25V, 0.01V, 5.2-8V, 0.05V

0-0.06V, 0.01V, 0-4.3V, 0.01V

4th scan

0-0.04V, 0.005V, 0.83-1.2V, 0.001V

15-25V, 0.005V, 0.83-1.2V, 0.001V

5th scan

14.99-15.02, 0.001, 0-2V, 0.001V

24-25V, 0.001V, 0.95-0.994V, 0.001V

Comment to Compensation of BB1EO3 at 0 deg (Click here to view original report: 3544)

Even though the voltages are being used from the file, it seems there could be a deviation, considering we did the calibration of LC 2 months ago. I can't see a zero crossing in azi and ell, also the file is a bit huge, so it will take longer than expected.

I am going to instead do scan using the voltage range estimated but without using the file, and doing first a rough scan, and then will later do a finer scan.

The voltage range estimated from characterization is 7-8 V for LC 1 and 0-25V for LC2 with condition of 2 degrees on azi and ell. 

So, doing a scan from 6-9V with 0.2V step, and 0-25V, 0,2V step. 

measurement file:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\AfterCompensation\Sun, May 5, 2024 2-44-03 PM.txt

(could see zero crossing in labview, still need to plot, measurement finished by the time I finished writing this elog)

Comment to Compensation of BB1EO3 at 0 deg (Click here to view original report: 3544)

Couldn't transfer voltage file , a bit too huge

decreased condition to 20mV, 2mV and 2 degrees.

Also, I had made a mistake in conversion from rad to degree in the previous one , at one instance

voltage file:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\CompensationVoltage\voltagecompensating_0.02_0.002_2.txt

measurement file :

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\AfterCompensation\Sat, May 4, 2024 6-05-39 PM.txt

Comment to Compensation of BB1EO3 at 0 deg (Click here to view original report: 3544)

The measurement stopped because of windows update. I have paused windows update for next 5 weeks.

Started another one with new voltage set of radius 50mV, step 5mV. The condition on ell and azi was 5 degrees.The measurment is being saved with 1 average.

voltage file is here:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\CompensationVoltage\voltagecompensating_0.05_0.005.txt

find the measurment file here:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\AfterCompensation\Sat, May 4, 2024 5-10-32 PM.txt

Comment to ATC OPO input PZT replacement - beam profile characterization (Click here to view original report: 3547)

We tried to calculate the beam profile but it seems that the beam divergence going in does not match the beam divergence going out.

i.e. approaching the beam waist, the beam shrinks ~ 100 um diameter per screw hole, but going past, it increases only ~ 50 um per screw hole.

We will look again for the source of this odd behaviour.

ATC OPO input PZT replacement - beam profile characterization

Logan, Michael

I showed Logan the use of the ATC clean room and the experiment setups we have there.

I showed and supervised the use of the Coherent Beam Master BM-3 UV beam profiler. Although I dropped and broke the included NG9 ND filter (0.5% transmission). The manual says to use below 5 mW and 200 W/mm^2 without the filter so it's fine in this case (3.8 mW).

We measured the beam profile from the s-polarized beam split off in the Taiwan/Korea experiment setups. I thought this beam was to be collimated at 2.3mm over some distance, but it doesn't maintain that size for long and turns out to have a waist of ~ 200 um radius about 30-40in from the PBS. So I also question a bit the Taiwan fiber SHG beam size, but we can look at that later. I tasked Logan with fitting the beam shape and redetermining the mode matching elements for the OPO.

Comment to Compensation of BB!EO3 at 0 deg (Click here to view original report: 3544)

File is being saved here after setting up new voltages

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\AfterCompensation\Thu, May 2, 2024 12-12-22 PM.txt

Comment to Compensation of BB!EO3 at 0 deg (Click here to view original report: 3544)

The voltages for compensation can be found here:

foldername='C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240417\0 deg\CompensationVoltage'

filename='voltagecompensating_0.02_0.002.txt'

Compensation of BB1EO3 at 0 deg

The Jones matrix of the coating BB1EO3 was measured at 3 position 0,14,62 deg. This matrix alongwith BS was used to combine with the input polarization states to find the optimum voltages for compenstion. The desired voltage afterwards were saved in the format where there were range of other voltages obatined using the first set of voltage as locus to create a square of half edge 20mV with step size 2mV.

The coating was moved to 0 deg.

The voltage file was fed to the labview "Complete Integration-File Choice"

The measurement will be started after stable temperature of LC is attained. (warm up time is ususally 30mins)

The laser will be kept on till next week. So, kindly don't turn it off.

recabling and DDS2 issue

[Logan,Marc,Michael]

We took time to check all electronic connections and are now preparing a summary scheme.

During this activity, we also reconnected the 2 missing GRMC/CCFC cables.

We also replaced the broken CC PLL MON cable that was previously broken.

We could lock SHG in similar condition as before (large HOM) but could not lock GRMC despite relatively reasonable alignment.

THe issue is that DDS2 is not detecting the 500MHz clock signal while it is fine for DDS1 and 3.

We are now sending -20.5dBm clock to DDS2. To be further investigated

Comment to issue with LC pc python (Click here to view original report: 3541)

[Hugo,Logan,Marc]

We resetted the previous spyder environnement.

The unloadable libraries issues was solve by doing the appropriate pip install directly in the spyder console.

All usual python codes are working fine now.

issue with LC pc python

There were issues to properly load python libraries on the pc so I resetted spyder settings to default.

Might be an issue for cv2?

Reconnecting after cable management operation

Logan, Michael

I introduced Logan to the squeezer clean room and mostly introduced FP cavity, FSR mode spectrum and PDH locking in the context of the green path.

I realigned the green mode cleaner/Mach Zender assembly to 92% mode matching. But the GRMC PD is not connected to the Cable Management Box. It's a bit hard to find in the giant mess of cables (seems to be unlabelled) so we will try next time.

Labview modification

The labview "Complete Integration for Camera" was modified to save data properly. The issue now was that the VI was too fast with averging of 1st order and there were same points being repeated in the dataset. Some changes were done as follows:

1. Added clear buffer for the averaging filter which is triggered when the number of iterations of averaging loop equals the averging order.

2. Added timer inside the averaging loop to make it a bit slower depending on what averging order you do. So, for different order you have different speed. Because the data saving was fine with averging order of 10, but was saving same data 4 times for averging order 1.

Comment to Manipulation 2D polarization (Click here to view original report: 3537)

1 LCD à 0° : Thu, Apr 18, 2024 11-14-30 AM.txt
1 LCD à 90° : Wed, Apr 24, 2024 3-40-14 PM.txt
1st 45° 2nd 0° : Wed, Apr 24, 2024 6-57-43 PM

Manipulation 2D polarization

After I've finished colimate my beam in the camera, I changed the orientation of my HWP and QWP to get 90° for the azymuthal angle and 0° for my elipticity.

Then, I made measurement with only 1 LCD of the polarization when we put a video on the LCD (video = all the 256 RGB value).
I did the same with 1 LCD oriented at 90°.

After doing this, I put the two different LCD and adapt my setup in order to get two different video, which allows you to combine the 256*256 different combinations.

All the setups seems to work.

Note : The camera is not synchronized with the 2 video make with a python.

HWP measurement at different positions

Mounted HWP on roator mount and measured the transmission using polcam. The measurement was taken at the following mentioned positions of the rotator mount.

The LC voltage was scanned from 0-3.5V with 0.1V step.

0deg:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\HWP\0 deg

Tue, Apr 23, 2024 4-45-43 PM.txt

38 deg:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\HWP\38 deg

Tue, Apr 23, 2024 5-10-09 PM.txt

The choice of position of rotator mount is random. The measurement is being taken to check if I can reconstruct rotation using the same method as being used for coating.