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The asymmetry problem still occurs, and is very apparent depending on which beam's frequency I scan over. For a standing wave from 3 to 40 mW, scanning over the higher power coupling beam, around 16mW, causes a large slope in the standing wave data. The slope is also there if I turn the Lower power beam off, and use the high power coupling beam for two consecutive EIT pulses. If I scan over the weaker beam, I don't see this slope in the data.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 18:42, 1 October 2014 (CDT)
I've taken some good data from Sep. 24 to Oct 1. The data on the 24th is with larger coupling beams, approximately 2.2mm by 2.4mm. This was measured with the newport camera. Probe power was 3mW. The plots show a sine wave at lower power, and then some localization at higher powers. On the 26th I took some more scans at higher powers, but this time I had the probe power at 4 mW, this was a mistake, I wanted to mimic some of the results from the other day, but forgot to adjust this power to 3 mW. After taking the longer scans, I decided to reduce the beam size to 2mm so that I could got higher in power for testing 1 EIT pulse. The data on Sep 29th shows that as I increase the coupling power, the features get narrower and then this stops at even higher powers, I am not sure why.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 16:22, 22 October 2014 (CDT)
Taking scans from 0 to 10, 0 to 15, and 0 to 20. The power has been fluctuating on one of the beams, for 0 to 15, the power went from 3.75 at the beginning of the run to 4.2 at the end. The other beam stayed the same. At these lower powers I think these fluctuations might make a difference, but we should be able to test that with the simulations.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 11:05, 28 October 2014 (CDT)
The data I took Oct 22 looked very interesting, and I'm now trying to simulate it. I need to figure Out what things we'll need for the grant proposal in December. I think simulating these plots will be one of them.
I thought more about the coupling beam standing wave acting as a FORT for the ground state and we thought it might be heating up the atoms. I'm trying to prove it so I had the coupling beams on but no probe beam, and tried to measure the temperature of the atoms after the coupling beams were turned off. I didn't see any change in atom number or temperature with the beams on or off.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 10:13, 31 October 2014 (CDT)
Took Beam size measurement of Probe beam, it had a 1/e^2 of 2.6mm, although I wouldn't be surprised if it was between 2.55 and 2.65, maybe a litte more. The coupling beam were measured a few weeks ago and were each 1.5mm. I took these measurements with the Thorlabs beam profiler.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 16:38, 3 November 2014 (CST)
Interesting things about the localization. When the standing wave is traveling toward the probe beam, meaning the beam on channel ChC is larger than ChB, the data becomes broadened in that direction. I notice that for lower, power coupling beams, 0 to 20 mW. I took data to show this more closely on Oct 31.
[[https://wiki.physics.wisc.edu/yavuz/images/2/20/Proof_Of_Asymmetry_At_low_coupling_power_0_to_20mW.pdf Standing Wave Asymmetry]]
Weird things happen when I change the Shim current. The features look different but they're still there. Changing the shims affect the total atom number, but doesn't move the atoms in any way, so I don't think it's an alignment issue.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 14:32, 4 November 2014 (CST)
This data is from Oct 30, when I noticed that changing the shim current on #2 from 4 Amps made a difference in the features.
[[https://wiki.physics.wisc.edu/yavuz/images/d/da/0to20mWCoupling_3.7mWProbe_DifferentNo2ShimCurrents.pdf Shim Current Changes]]
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 14:00, 17 November 2014 (CST)
Since changing the shim currents changes the features and contrast, I think the problem is with the m levels. Not sure how to see that though, so we've but a large magnetic field on the FORT to split the shim levels by about 10 MHz. This takes 15 Amps with the current set up. The coils were already on the MOT chamber but haven't been used for awhile.
The idea is to seperate the m levels and only use 1 level to do the experiment. Then I'll change the shim currents slightly and see if I see the same thing.
The problem now is that I would need about 30 amps to separate the levels far enough using 100 ns pules. So I'm switching to 200 ns pulses, this cuts the width in frequency space by half.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 15:21, 2 December 2014 (CST)
I'll try to stick with the 100 ns pulses, but I want to make sure the levels are split enough with the current we have. We might make some more coils with 14 AWG wire instead of the 12 we're using now. We would use less current with 14 but be able to make a lot more turns, so I think we could still get a bigger B Field.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 15:54, 3 December 2014 (CST)
Checked the Beam size of the Coupling beams, I thought they hadn't changed since the last time, but ChB was ~2 mm diameter 1/e^2 and ChC was ~1.7 mm diameter 1/e^2. Probe was still about 2.6 mm. Bigger than the coupling beam but it makes alignment much easier, and there is plenty of power to use for the Probe.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 15:21, 9 January 2015 (CST)
We are trying the experiment with different m levels. Part of the hyperfine repumper is used as a pump to get most of the atoms into the m=0 F=1 level. This way we can more easily model what will happen with the EIT pulses.
I'm also trying the experiment with higher intensity lasers. My model shows less oscillations in the populations of the three levels over time, and therefore the system reaches a steady state faster
Some data taken today shows that there is a difference with EIT between the two coupling beams. I want took transfer data from 1 of the coupling beams. Then I put the beam into the other fiber launch, so it's propagating in the opposite direction. The two transfer curves did not look the same, but I didn't check the beam sizes. I want to try this again more thoroughly because this could be a big deal... I don't know why they would be different though.
I check to see if either beam was clipping the chamber, and it seems that both are missing the chamber and a large amount of the power is going out the otherside.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 15:49, 11 January 2015 (CST)
I think something is wrong with the beam coming from ChB. I can move the ChC beam to the ChB fiber launch and get very similar data. I took some data on Jan 9 about this. I should look at the fiber output and make sure it's anice gaussian mode. I might switch fibers and redo timings too. The output looks fine on the camera, but it's still something to try. The ChB beam was not transferring as many atoms with EIT as the ChC beam was. the powers were the same and the fact the ChC beam did similar transfers and similar powers from each fiber launch means the beam sizes are correct.
I checked the timings of the ChB beam and it looked really good.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 15:44, 12 January 2015 (CST)
Light from the ChB AOM set up transfers less atoms the the ChC set up. It's something with the AOM timings or something with the fiber.
I'm convinced that CHC transfers better, but I'm not sure why. I'm going to move the circuit that pumps everything to F=1 to the CHB AOM to see if that circuit is messing things up.
After I did this both seemed to working fine. Not sure what was happening but I did notice that the lock on the diode for the EIT lasers was not that great. It would move around a little when locked. To fix it I turned down the sensitivity of the lock in amplifier.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 21:23, 28 January 2015 (CST)
Today I took some scans from 0 to 4 mW and 0 to 2 mW. A coulple of days ago I took very good data on the EIT transfer of both beams with each of there pulses. The figure has all 4 plots on it, and are very similar. I'm not getting good narrow data though. Not really sure why, I get coupling from ChB control beam into ChC fiber. I used thorlabs differential screws to better align the CHC coupling beam and the probe to the fort atoms.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 17:17, 5 February 2015 (CST)
I get a standing wave with more than 10% contrast when I optically pump to m=0. I also narrowing when I went from 2 mW to 50 mW, but not from 2 to 30. The simulations say both of these regions should get a narrow feature, but the simulation has not been matching the experiment very well. I was trying to get the optical pumping even better, but I think I will take a long scan of this narrow data, with the majority of the atoms starting in m=0, this would be a new data set.
Then I'm going to make the pulses rise times longer by changing their size through the AOM's. This should put us more in the dark state and eliminate the oscillations we see in the simulatinos for the transfer data.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 17:00, 24 February 2015 (CST)
Changed the pulse times by using a longer focal length, approximately twice the focal length of the original lenses. the rise times are closer to 50 ns, rather than 25 ns.
The FORT power decreased the other, tried to fix it but couldn't get the same amount of power out, maybe something is wrong with this Chinese laser. Got the FORT back though with similar atom number, now trying to get optical pumping to work better. I get EIT, but I'd like to do EIT closer on resonance.
Need to do standing wave closer to resonance to ensure that we're better in the dark state. This will match simulations better.
I checked the beam sizes, The probe is 1650X1500um +- 50 um Both coupling beams are about 1600X 1600 +- 50 um.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 16:10, 31 March 2015 (CDT)
I keep seeing some asymmetric stuff with the standing wave depending on which way I move the standing wave. We're moving the probe beam to be perpendicular to the coupling beams. We'll need to change the polarizations to so they are perpendicular to each other and the B field which defines our z axis.
We used to use vertically polarized coupling beams and horizontally polarized probe beam, now we'll be using vertically probe and horizonatll coupling.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 13:39, 24 April 2015 (CDT)
I've been trying to get narrower data, but no luck. I checked the beam sizes and they were all around 1700x1700 um. easily + or - 50 um though. I will got through the data I have and put some of it together to try and put together the paper.
I used 10 Amps on the coils for optical pumping, and I have proof that this does pump atoms into the m=0 level.
--[[User:Jmiles2|Jmiles2]] ([[User talk:Jmiles2|talk]]) 14:49, 3 May 2015 (CDT)
I'm trying to make some figures in Matlab for the paper, if you go into more properties when having the figure open with "plot tools" you can manually set the size of the figure through PlotBoxAspectRatio. Useful for getting all graphs to be the same for the paper.
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