PCI set-up

I reinstalled the QWP and the HWP in order to get a circular polarization after the last mirror. And I add a polarizer on a motorized mount, just before the translation stage. Like this, we can get any linear polarization with enough power, without going into the clean room.

I put as sample a QWP, everything seems ready to start a measurement.

IMPORTANT : LIMIT VALUE ON Z AXIS == 23mm. (avoid to hit the polarizer)

AlGasAs coating measurement

[Shalika, Marc]

Measuring Jones Matrrix of AlGaAs coating

The sample is same as mentioned by Manuel in 746. We used the mounting technique as mentioned by Manuel in 746. But, we put in a mount where we can tune the alignment as well, i.e in  a 2inch mirror mount. We first practiced putting a sample with no polish to see if the mount is fine. After being fully assured that the mount was indeed fine(like the screw will not touch the wafer or the wafer will not fall off, etc.), we then put the 0.5mm thick sampple. (pic1, pic2)

We setup a small clean room (taken from PCI). The AlGaAs was kept inside it. (pic3, pic4)

saving measurement from LC voltage scan in   in:

C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\AlGaAs\20240621\Fri, Jun 21, 2024 3-12-57 PM.txt

Comment to Re-characterizing the BS and measuring mirror (Click here to view original report: 3611)

I rotated the sample. Although its on non rotatble mount, I took a picture of the back surface for a reference of Sample 2 BB1EO3, before and after rotation.

C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\BB1-EO3 Sample2\20240619\Wed, Jun 19, 2024 6-42-43 PM.txt

wifi issue in TAMA solved

With help of NOC

 

During last electrical shutdown a white CISCO wifi provider in TAMA storage stopped working.

Today we found out that its power supply got broken. Furthermore, NOC is not fully sure what are the 2 switches in the storage doing? Maybe old remnants.

In any case, NOC is responsible for the white CISCO wifi provider and the purple switch. The wifi source was moved and connected to the purple switch close to the DGS through POE and worked fine.

It can happen that the purple switch breaks during thunder or typhoon. A quick check would be to confirm if the LED is on on the white CISCO.

Comment to Re-characterizing the BS and measuring mirror (Click here to view original report: 3611)

Replaced mirror with another sample of BB1EO3

10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\BB1-EO3 Sample2\20240616\10 avg\Mon, Jun 17, 2024 11-30-53 AM.txt

100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\BB1-EO3 Sample2\20240616\100 avg\Mon, Jun 17, 2024 9-08-21 AM.txt

Re-characterizing the BS and measuring mirror

Coming across the recent issues with labview and the several modifications, we saw that the observed characteristics of other components look better. Hence, we also chose to re-calibrate the BS

Pol states after LC without BS:

10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Polarization states\20240613\Thu, Jun 13, 2024 4-52-27 PM.txt

100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Polarization states\20240613\Thu, Jun 13, 2024 5-35-00 PM.txt

Flipped the BS and measure

with 100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Beam Splitter Calibration\20240613\BackFaceRefl\10 avg\Fri, Jun 14, 2024 11-52-01 AM.txt

with 10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Beam Splitter Calibration\20240613\BackFaceRefl\100 avg\Fri, Jun 14, 2024 1-22-15 PM.txt

The BS was flipped back to its original position

Pol states with BS :

10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Polarization states\20240613\Sat, Jun 15, 2024 9-41-39 AM.txt

100 avg:C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Polarization states\20240613\Fri, Jun 14, 2024 10-54-07 PM.txt

Put camera in mirror reflection

I changed the mount of the mirror. Previously, I didn't notice, but I saw that when I rotated the mirror, the beam alignment changed(i.e the beam was rotating around a circumference of a circle) which could indicate that the way rotator mount is placed in the clamp mount, there is some inclination. To avoid discrepancy in considering normal incidence position, I changed the mount to using the mirror mount which is ideally used. 

BB1EO3 sample old :

10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240615\10 avg\Sat, Jun 15, 2024 8-17-41 PM.txt

100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240615\100 avg\Sat, Jun 15, 2024 5-26-09 PM.txt

Comment to Labview modification for camera integration (Click here to view original report: 3575)

The format of saving is of the form:

X, Y, Azimuth, Ellipticity, Power, s1, s2, s3

Measurement of ILM sample

tuned input polarization to O ellipticity and 45 deg azimuth :

-took small map without sample for reference : Thu, Jun 13, 2024 1-42-34 PM.txt
-with a ILM sapphire as sample : Thu, Jun 13, 2024 1-49-37 PM.txt

tuned input polarization to 0 deg in azimuth and ellipticity :

-took small map without sample for reference : Thu, Jun 13, 2024 3-02-11 PM.txt
-with a ILM sapphire as sample : Thu, Jun 13, 2024 3-07-04 PM.txt

Comment to More Labview problems (Click here to view original report: 3609)

I took this subvi for granted and didn't notice this before. But, it seems there always has been a discrepancy in the voltage. It means that there is a high possibility that the input voltage used for calibration and for characterizing the optics were never same.

More Labview problems

I am not sure what was the logic used in making the "dual step voltage" VI to change the voltage of LC but it is very problematic. It doesn't have 1mV resolution. Whenever I want to change the voltage from  0-3.5 V with 0.1V step, all of a sudden the voltage supplied starts becoming random numbers like 0.214. I don't understand how can it happen!

This needs to be changed because it means voltage applied is random!

Also, for future its advisable to not add stuff in VI if it can't generate perfect requirements!

measurement of iLM sample

tuned input polarization to 0 deg in azimuth and ellipticity :

-took small map without sample for reference : Wed, Jun 12, 2024 2-27-13 PM.txt
-with a QWP as sample : Wed, Jun 12, 2024 2-47-47 PM.txt

tuned input polarization to O ellipticity and 45 deg azimuth :

-took small map without sample for reference :Wed, Jun 12, 2024 3-37-50 PM.txt
-with a QWP as sample : Wed, Jun 12, 2024 3-54-04 PM.txt

test of microscope

I checked the TAMA microscope.

It is Olympus model GX51 with light source U-LH100-3 and cooled CCD camera BU-50LN.

It also comes with few ND filters.

The microscope is working fine. The camera aswell. I could installed the japanese driver and software on my laptop (for some reason the english version did not work).

Comment to Coating measurement with more averaging (Click here to view original report: 3597)

HWP

at 0 deg with 10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Retarder\HWP\20240611\0 deg\10 avg\Tue, Jun 11, 2024 5-38-05 PM.txt

at 0 deg with 100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Retarder\HWP\20240611\0 deg\10 avg\Tue, Jun 11, 2024 9-18-38 PM.txt

at 38 deg with 10 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Retarder\HWP\20240611\38 deg\10 avg\Wed, Jun 12, 2024 12-31-12 PM.txt

at 38 deg with 100 avg: C:\Users\atama\Dropbox\LC-Experiment\Measurement Data\Retarder\HWP\20240611\38 deg\100 avg\Wed, Jun 12, 2024 9-56-56 AM.txt

Comment to Coating measurement with more averaging (Click here to view original report: 3597)

Coating :

at 0 deg with 10 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240606\0 deg\Sat, Jun 8, 2024 8-12-43 PM.txt

at 62 deg

10 avg:C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240606\62 deg\Mon, Jun 10, 2024 12-22-38 PM.txt

100 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240606\62 deg\Mon, Jun 10, 2024 9-26-34 AM.txt

Coating measurement with more averaging

I read a paper which said that Jones matrix measurement can be improved with more averaging. Although they measure a sample which was changing its properties in time. its quite different. But, still wanted to try to save with more averaging. So I did 100 averaging of each point. Also, had to take measurement again after amending flaws in the averaging./

So, I scan the LC voltage from 0-3.5V with 0.1V step.

Input file:

with 10 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240607\Fri, Jun 7, 2024 10-13-20 AM.txt

with 100 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240607\Fri, Jun 7, 2024 10-52-34 AM.txt

Output files of optics:

QWP:

at 0 deg with 10 avg C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\QWP\20240605\0 deg\Fri, Jun 7, 2024 3-13-11 PM.txt

at 62 deg with 10 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\QWP\20240605\62 deg\Fri, Jun 7, 2024 3-42-36 PM.txt

at 0 deg with 100 avg : C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\QWP\20240605\0 deg\Fri, Jun 7, 2024 1-30-40 PM.txt

at 62 deg with 100 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Retarder\QWP\20240605\62 deg\Fri, Jun 7, 2024 4-12-57 PM.txt

Coating BB1E03:

at 0 deg with 100 avg: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240606\0 deg\Fri, Jun 7, 2024 5-40-54 PM.txt

Comment to Labview modification (Click here to view original report: 3599)

The STD has reduced to around 0.08 deg in azi and 0.03 in ell at around lc voltage of 0.9V (where the flip happens in sign and ell in wrapped). At all the other voltages of LC the std is 2e-3 deg ish in ell and azi both. 

The uncertainity was reduced by adding a wait time(1s) before the polarization camera is read and after lc voltage changes. From my understanding at this voltage of 0.9 ish V the lc molecules take more time to stabilize as compared to other voltages, which was giving rise to high std at just this voltage. Also, the ellipticity getting wrapped was giving rise to high std.

Now, the setup is ready to take measurement with better averaging and more averaging. I have left the setup to warm up. Will start measurement in an hour.  

shg, irmc, mz/grmc recovery

[Logan, Marc]

We checked again SHG scan. Actually, we found that our HOMs were splitted in 2 due to mistuning of the input polarization.

This made our previous mode-matching estimation wrong. Retuning the HWP, we could properly recover the 91% mode-matching. It is not clear why the high order-mode that was spoiling 30% of mode-matching disappeared. Tuning the modulation phase and servo settings we could relock SHG. The DDS1 setting was saved.

We realigned MZ and GRMC and could also lock them without particular issue. Same for IRMC.

issue with polarization camera?

[Hugo, Marc, Shalika]

While trying to align the polarization camera on pci setup we found out that the power it measured was quite lower than expected.

We installed it on the translation stage to verify if the discrepancy was due to the beam size but whichever position gave similar result.

We also placed it on the LC beam that was used for birefringence compensation and Jones matrix measurement but still could see this discrepancy (we measure 75% of the real power).

This is true for vertical and horizontal linear polarization, elliptic, right/left circular polarization...

We are now discussing with Thorlabs support about this.

Labview modification

There were several issue related to data averging. The VI became too complicated due to unwise choices. modifications involved:

1. Previoulsy the averging and filling buffer was done in same labview. I separated both of them. Also made a subvi called delete buffer which resets the buffer before lc voltage is changed for new data.

2. removed PCI like complicated averging and now m using directly VI from NI for this. This made the labview very compact.

3. The only issue remains when the lc changes the azimuth from -45 to 45 kinda when the voltage is around 1V. The std is high at this point.

So, we have now a rather clean procedure

LC voltage change --->>>> create bufffer VI (initialized array of size equal to average order) --->>>> Fill Buffer VI by loading camera VI(number of times it loads is equal to averge order) --->>>> average VI (takes average of entire buffer) --->>>> Send data for saving --->>> delete buffer

On a good note: The VI datasaving speed is better now. With averging of 10th order the  data saving speed is 40Hz.

Comment to OPO characterization in ATC- beam profile (Click here to view original report: 3595)

I did some check based on fiber equations that you can find on Thorlabs or Newport.

The fiber to the SHG is PM980 (polarization maintaining 980nm in-fiber wavelength) with a mode field diameter 6.6 um. This gives f/D = pi*MFD/(4 lambda) = 4.8. Thorlabs FC/ACP connector fiber collimators are sold with f = 2.0, 4.6, 7.5, 11.0, 15.3, 18.4mm focal lengths, giving input beam diameters D = 0.41, 0.94, 1.53, 2.26, 3.14, 3.8 mm. The clear apertures are 2.0, 4.9, 4.5, 4.4, 5.0, 5.5 mm. In retrospect, maybe I should have picked the f = 4.6mm. But it's maybe not super important. exp(-2*(r/w0)^2) = 0.00051 (510 ppm diffraction loss) for the current coupler. r > 2.7 w0 gives < 1 ppm diffraction loss.