ELOG ligo-ex

The set up for the next round of beam characterization measurements has begun. The beam is initially passing through a half waveplate, is split at a polarizing beam splitter, and then stirring mirrors are used to properly aim the beam into photodiodes (not yet installed). This is the current configuration of the set up.

Attachment 1: initial_Intens_measure_set_up.jpg

Thu Apr 6 10:20:43 2023

More optical components were added to the optical set up for laser intensity / polarization drift measurements. Both lenses and both PDs were added to the configuration, as seen in the image below. The beam is already well aligned into the center of both of PDs, and focused nicely by the lens. Both PD's take BNC connecting cables, and the Red Pitaya takes SMA connecting cables. Since we are currently without a BNC to SMA cable, and we do not want to cut, strip, and crimp what we have, then measurement process cannot proceed until we get the cables.

Attachment 1: Optical_Setup_4-6-23.jpg

Fri Apr 28 11:21:01 2023

The Digi-key cables have arrived, and I have began implementing them in the intensity drift measurements. There was a slight problem initially in connecting the SMA to BNC cables from the photodiode to the red pitaya, since the red pitaya was way on the other side of the lab. Cao and I connected the red pitaya to a new ethernet cable that extended far enough for the red pitaya to sit comfortably on the breadboard with the optics. Right now the PDAs are not connected to the red pitaya. I have connected them to the oscilloscope in order to read out how much voltage they produce upon incidence of 532nm laser light. This was done in order to make sure that they do not surpass the limit of the red pitaya (+-1V). I have not acquired a value for the readout voltage of the PDAs since I had to go to class. I will gather this preliminary data soon.

Attachment 1: IMG-0183.jpg

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Thu May 18 14:07:08 2023

I figured out a method in which to capture power measurements including the initial seconds in which the beam is first turned on. I first clear and restart the kernel of the python notebook. Then I run the command to connect the red pitaya oscilloscope package to the input data being taken in both channels. To my understanding, this allows for data acquisition as the code compiles. I then started looping the 1.074s trigger bunches, and then roughly 2 seconds after I ran that command, I went and turned on the laser. The first plot shown is a 2 minute practice trial of me trying this technique to make sure that the python package was correctly registering the input of the red pitaya. It is clear that initially the laser is off, and then as I turned it on, the voltage in each channel spikes, which is compelling evidence that the code is working. I then set the data collection to be 7518 seconds (7000 loops), which is about 2 hours and 5 minutes. I repeated the same technique as for the first plot, only changing the amount of time I collected data. The second plot shown here is the voltage being read in each channel as a function of time. As we can see, over a period of hours, the intensity drifts quite dramatically for the first several minutes, and then begins to stabilize slightly. However, there are still some strong sudden fluctuations in each channel.

Attachment 1: Time_Series_Trial_4.png

Attachment 2: Time_Series_Trial_5_2hrs.png

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Tue Jun 6 16:15:09 2023

Launch Optics for Visible Light Cavity

I assembled the first few components of the launch optics for the visible light cavity. Below is an image of the current table configuration, and the image is how the cavity will be oriented on the table.

Attachment 1: IMG-0882.jpg

Attachment 2: IMG-0883.jpg

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Thu Sep 7 19:24:25 2023

The launch optics up to the Faraday Isolator have been added to the breadboard. In the first image, the optics are (from L to R) the stirring mirror, half-wave plate, polarizing cube, 100mm f lens, electro-optical modulator, Faraday isolator, 50mm lens (not part of final design), stirring mirror (not part of final design)

Attachment 1: IMG-3404(1).jpg

Attachment 2: IMG-3408(1).jpg

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Mon Oct 9 11:06:17 2023

Implemented the new stage for the EOM. Took power data at different positions in the launch chain. Beam waist: 0.066mm (beam waist is inside EOM). Power before EOM: 0.473mW. Power after EOM: 0.452mW. Power after Faraday Isolator: 0.415mW. Might need to adjust better to configure for clipping losses. Images of setup are attached below.

Attachment 1: IMG-3540.jpg

Attachment 2: IMG-3538.jpg

Attachment 3: IMG-3533.jpg

Attachment 4: IMG-3522.jpg

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Mon Oct 23 07:28:57 2023

I have attached a pdf with slides of my latest updates.

Attachment 1: Carney_VLC_Update.pdf

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Mon Nov 6 11:31:25 2023

See Update Attached

Attachment 1: VLC_Update_11_6_23.pdf

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Mon Nov 13 06:15:45 2023

Weekly Updates Attached in pdf

Attachment 1: VLC_Mode_Matching_3.pdf

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Fri Dec 8 11:15:21 2023

The optics of the visible light cavity have been assembled. The mode matching telescope is folded through the two stirring mirrors at the corners shown in the image below, with the first lens (f=0.2m) before the first stirring mirror, and the second lens (f=0.5m) between the two stirring mirrors. The distance from the cavity to the edge of the table is 14cm. There is still some work to be done on the alignment of the cavity, as the beam does not seem to be completely centered on the two mirrors.

Attachment 1: IMG_4194.jpg

Attachment 2: IMG_4195.jpg

Attachment 3: IMG_4197.jpg

Attachment 4: IMG_4196.jpg

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Tue Jan 16 10:01:21 2024

VLC Faraday Isolator and Mode Matching

Attached is a PDF of my weekly updates.

Attachment 1: VLC_Mode_Matching_Design_-_Remastered.pdf

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Mon Apr 15 11:51:03 2024

An update on the VLC project is attached below:

Attachment 1: VLC_Update_April_15_2024.pdf

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Mon May 13 14:53:29 2024

VLC Update WEEK 7 attached below

Attachment 1: VLC_Update.pdf

Sat Feb 4 17:01:03 2023

Peter and Ryan took laser beam data. Configuration: 100mm focal length lens is ~100mm from lens. 150mm focal length lens is ~200mm from first lens. Beam waist is ~420mm from second lens. Beam waist is very small still. Had to input large amounts of error in data collection. Took width data successively at points near waist and at >= Rayleigh range. Plots are shown below. Key points: Took a while to figure out optimum configuration for lenses to be placed so that an accessible beam waist could be obtained. Beam waist is still very small. May need to do an ABCD calculation to see if there is anything bigger that can be obtained.

Attachment 1: OmegaX_M2_Fit_3.png

Attachment 2: OmegaY_M2_Fit_3.png

Tue Feb 28 19:31:05 2023

Took M2 measurements today. Configuration: Lens 1 (f = 50mm) at 0mm. Lens 2 (f = 150mm) at 200mm, camera at 350mm. The laser beam was being moved in -z direction on track (so further away from the first lens). Quick data shown in the sheets plot. Not a real fit. I was trying to see where the beam waist was if there even was one. Seems that it is much further than we have room for on the track. Will need to come back and take more data. I suggest maybe Dr. Richardson or Cao come and see the configuration in person and how the beam diverges for themselves on the detector card. Maybe they can offer pointers to make this go smoother.

Attachment 1: X_width_and_Y_width.png

Thu Mar 9 12:03:59 2023

Took more M2 Data today. Picture of the optical set up is shown below. lens1 f = 100mm, lens2 f = 50mm, lens3 f = 150mm. There was a nice converging/diverging beam profile, and the beam waist was able to be read by the camera. I took as much data as I could before clipping loss. The M2 value is quite high.

Attachment 1: OmegaY_M2_Fit_3.png

Attachment 2: OmegaX_M2_Fit_3.png

Attachment 3: optical_setup.jpg

Fri Mar 10 12:08:09 2023

Took more M2 laser data today. The configuration is the same as before except now the beam camera is the only component moving. Pictures can be seen below. The beam shape in x and y is very consistent with low error. However, the M2 value is still a bit high.

Attachment 1: OmegaX_M2_Fit_4.png

Attachment 2: OmegaY_M2_Fit_4.png

Tue Apr 4 09:39:58 2023

Final M squared measurements were taken Wednesday, 3/29/23 by Peter and Ryan Hinosawa. 5 separate sets of data were taken, and upon discussion, we declared the plots shown below in attachment 1 and 2 as the final plots of our M squared measurements. The optical design of the M squared measurement process is given in attachment 3. The laser and three lenses shown below are mounted on the optical table. The track is placed behind the third lens, and the camera is moved along the track to take successive measurements of the beam's width. This will allow us to see a change in the beam's width over its propagation direction. The raw data is given in attachment 4 as a Beam_Data_8_3lens.txt file. This is eventually what gets used to generate the plots shown below. The code to run the analysis on these measurements (as well as analysis on the Gaussian intensity profile fitting) can be found: git@git.ligo.org:uc_riverside/visible-light-cavity.git

Attachment 1: OmegaY_M2_Fit_8.pdf

Attachment 2: OmegaX_M2_Fit_8.pdf

Attachment 3: M2_Measurements_Set_Up.svg

Attachment 4: Beam_Data_8_3lens.txt

z-z0	x_width	y_width	x_error	y_error
-50	267	304	30	30
-40	227	261	30	30
-30	192	223	30	30
-20	167	194	30	30
-10	153	169	50	50
0	149	154	50	50
10	166	152	50	50
20	198	169	50	50
30	233	195	50	50

... 17 more lines ...

Tue Apr 4 16:43:53 2023

Jon

Additional Thorlabs PDA10A2

I ordered a second PDA10A2 and mounting post + spacer (which puts the aperture at the VLC's standard 3" beam height). These arrived today and I delivered them to the lab. They are sitting on the VLC table near the laser.

Attachment 1: PDA10A2.png

Tue Apr 25 11:56:37 2023

Jon

Red Pataya has arrived

The Red Pataya 125-14 starter kit that we ordered for locking the 532 nm cavity has arrived. I left it laying on the optical table near the laser.

Attachment 1: Red_Pataya.jpg

Mon May 1 18:56:57 2023

I've configured the two PDA's to the Red Pitaya. I put a 50 ohm resistor connector to each red pitaya input port. This was because the oscilloscope showed that the voltage reading from the P polarization PDA was almost at 1V, which was the limit of the red pitaya. Once both S and P polarization PDA's were connected, I opened the red pitaya's oscilloscope. A screenshot of the voltage readings is shared below. Channel 1 (Yellow) is for S polarization. Channel 2 (Green) is for P polarization. It would seem that there is a significant amount of polarization in the P direction as opposed to the S direction. I then tried running the template time series measurement within the python notebook from channel 1 only. The python notebook graph is shown below. I have not figured out what are the units of time on the x axis, and I have not figured out how to change the amount of time that the red pitaya takes data. A plot of the time series measurement is shown below.

Attachment 1: graphs.jpg

Attachment 2: Time_Series_Trial_1.png

Tue May 2 15:55:33 2023

I changed the 1/2 wave plate from the lens mount to the rotational optic mount. This allowed me to rotate the 1/2 wave plate, which changed the respective polarization power transmitting through S and P polarization. Initially, more power was coupled into the P polarization. Now, with the 1/2 plate rotated, both channels are experiencing the same voltage reading. Before feeding the PDA signals into the red pitaya, a 50 ohm terminator had to be placed at the SMA connection port so that the input power into the red pitaya did not exceed 1V. With this configuration, both channels experience about 0.35mV. (See attached) I then opened the Jupyter notebook, and ran a demo time series measurement from the red pitaya. This time, I was able to get a plot featuring both channels (green is P polarization. Blue is S polarization). The plots are consistent with what is shown in the red pitaya oscilloscope. However, the time collection (I'm assuming) only runs for about 0.018s. I will have to write some of my own code to loop over this measurement, and collect more data.

Attachment 1: IMG-0221.jpg

Attachment 2: IMG-0222.jpg

Attachment 3: graphs(1).jpg

Attachment 4: Time_Series_Trial_2.png

Thu May 4 14:01:10 2023

I adjusted the rotational mount of the wave plate to see if the power can be 100% coupled into either S or P polarization. The images shown below of the oscilloscope indicate that this is not possible. The minimum transmitted power we can obtain in either S or P polarization is 75mV. The maximum voltage we obtain in either S or P polarization is ~ 740mV. This means that at a maximum, we can obtain ~ 90% polarization in either direction, indicating that our laser has a slightly elliptical polarization.

Attachment 1: graphs(3).jpg

Attachment 2: graphs(2).jpg

Tue May 16 11:56:33 2023

With the configuration the exact same as before, I used the Jupyter notebook in the red pitaya's development package to collect data from both input channels. Last week, I was able to take data, yet only for a very short period of time, and I did not know how to change it. I went online to the red pitaya's user manual to figure out how to change the sampling period for longer. The link to the page is here: https://redpitaya.readthedocs.io/en/latest/appsFeatures/examples/acqRF-samp-and-dec.html#s-rate-and-dec Though I now know how to change the period of time for which data is taken, the maximum amount of time is still only about 8 seconds. So with help from Cao, we looped over the data taking samples, and got a mean value for each iteration. We then put all those mean values in an array, and plotted it. Below, we see a plot of both the S and P polarizations, and a sum of both of them. As seen in the graph, I have set the time to be able to take data for almost 2 minutes. There is some slight drift in the respective intensities. The next steps I believe are to convert the units into watts, and take data for longer periods of time.

Attachment 1: Time_Series_Trial_3.png

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Mon May 22 16:43:28 2023

In order to fully analyze the polarization data taken last Thursday, I needed to convert the signal output (which is in volts) to power (units of watts). I used the power meter to accomplish this. Keeping the exact same configuration of PD's and beam splitting, opened the red pitaya's oscilloscope package. I then took the power meter, and held it in front of the PD to measure the amount of Watts at each PD. I then wrote down the corresponding voltage being seen in the red pitaya. I took 5 sets of measurements for each PD to get experimental accuracy. I then used a simple y = mx + b fit to find out the constant m that converts the input wattage into voltage. For the s polarization, the conversion factor is 0.83. For the p polarization, the conversion factor is 1.12. I then used this data to plot polarization angle as a function of time, and the relative intensity drift as a function of time. The plots are shown below. The physical meaning of the polarization angle is shown in the unit circle diagram below, in which P is the total power.

Attachment 1: S-P_Polarization_Diagram.svg

Attachment 2: Polar_angle_vs_time.png

Attachment 3: Rel_Intens_vs_time.png

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Wed May 24 14:28:26 2023