- Did more modeling for different levels of heating and different mesh densities for the SIS input.
- Lots of orientation stuff
- Started on progress report.
- Attended a lot of meetings (Safety, LIGO Orientation)
- Finished draft of week 3 report (images attached)
-Attented LIGO orientation meeting and safety session.
-Prepared 3 week report
- Paper edits and more data generation for the paper (lower resolution grid data)
- Attended a talk on LIGO
-Updated 3 week progress report with new additions and deletions.
-Attended LIGO lecture which was very interesting and full of information.
- Discussed the further project with Dr. Brooks.
-Tried to derive formula for the test mass inside cryogenic shield(infinitely long shield from one side)
Plan for building the model
- Find the fields that would be incident on the beam splitter from each arm (This is done already)
- Propagate these through until they get to the OMC using the TELESCOPE function in SIS
- Combine the fields incident on the OMC in MATLAB and minimize the power to get the input field for the OMC (Most of this is done, just waiting to figure out what kind of format we need to use it as an SIS input)
- Model the OMC as an FP cavity in SIS
+ Need to think about how to align the cavity in a sensible way in SIS (need to find out more about how they actually do it)
- Pick off the fields from both ends of the OMC-FP cavity for analysis
- Add thermal effects to one of the arms and see how that changes the fields, specifically how the signal to noise ratio changes
- Finished the MatLab code that both combines two fields and simulates the adjustment of the beamsplitter to minimize the power out (with a small offset).
- Added the signal recycling telescope to the SIS code that generates the fields
To Do: Make the OMC cavity in SIS
-Discussed the project outline for next 6 weeks.
-made a write up for the tasks. (attached)
-Analyzed the variation of temperature of the test mass with input power for different lengths of the shield.
Made a COMSOL model that can include CO2 laser heating, self heating, and ring heating
Figured out how to run SIS out of a script and set up commands to run the two SIS stages of the model
Borrowed thorlabs power meter on 21 Sep 2017. It is on the south table of the ATF lab.
I've started an 80C cure of two materials bonded by EPOTEK 353ND. The objective is to see (after curing) how much the apparent glass transition temperature is increased over a room-temperature cure.
Ian and I moved some new hardware into the lab, shown in the below photos. It is from the shipment of loaned equipment recently returned by Whitman College.
The ZnSe lenses and windows were put in the CO2 drawer of the optics cabinet. The CO2 laser, AOM, and modulator drivers were left packaged in boxes underneath the large laser table.
Koji: QIL/TCS entrance flooding. Check your lab
Anchal: Can someone take a look at CTN too?
Koij: TCS needs more people @aidan
Koji: CTN ok
Aidan: On my way
Shruti: Cryo seems fine
Aidan: There was a leak in a pipe in the wall of B265A. It was coming from the building air conditioner condensation overflow. Facilities has fixed the pipe and is working on clean-up
I checked the lab this morning. It was dry and there wall was in the same state as yesterday.
11:29AM - Lab has flooded again this morning. I'm calling PMA. Looks to be the same issue as before.
Some photos of water and clean-up.
Summary: I came into the lab around 11:30AM and found water on the floor in the changing room outside QIL/TCS. Turns out the condesation overflow pipe from the AC blew out again. This time near the ceiling. Water was on the floor but also had sprayed a little onto the tool chest and East optical table. A few optics got wet on the table. Initial inspection looks like electronics were spared with the exception of the "broken" spectrum analyzer that was on the floor.
Facilities came in and cleaned up the water. A small amount got into QIL but stayed near the door as the lab floor slopes up from the door area. They fixed the pipe and were looking into whether there was a blockage cuasing this problem. PMA was notified and John Denhart is coordinating follow-up.
Triage effort: given the AC was still active, John and I strung a temporary tarp across the two tables to block any spray.
Does this work?
I've been looking to see what the time constant of the ring heater is. The attached plot shows the voltage measured by the photodiode in response to the heater turning on and off with a period of 30 minutes.
The time constant looks to be on the order of 600s.
I just replaced the brass Hartmann plate with the Invar one. The camera was off during the process but has been turned on again. The camera is now warming up again. I've manually set the temperature in the EPICS channels by looking at the on-board temperature via the serial communications.
I also made sure the front plate was secured tightly.
Here's a plot of the 15-day output of the SLED.
Currently there is an 980nm FC/APC fiber-optic patch-cord attached to the SLED. It occurred to me this morning that even though the patch cord is angle-cleaved, there may be some back-reflection than desired because the SLED output is 830nm (or thereabouts) while the patch cord is rated for 980nm.
I'm going to turn off the SLED until I get an 830nm patch-cord and try it then.
Correction: I removed the fiber-optic connector and put the plastic cap back on the SLED output. The mode over-lap (in terms of area) from the reflection off the cap with the output from the fiber is about 1 part in 1000. So even with 100% reflection, there is less than the 0.3% danger level coupled back into the fiber. The SLED is on again.
I've assembled the box Mindy ordered from Newport that will house the Hartmann sensor. It's mainly to reduce ambient light, air currents and to keep the table cleaner than it would otherwise be.
We need to add a few more holes to allow access for extra cables.
I'm in the process of aligning the cross-sampling experiment for the HWS. I've put the 1" PBS cube into the beam from the fiber-coupled SLED and found that the split between s- and p-polarizations is not 50-50. In fact, it looks more like 80% reflected and 20% transmitted. This will, probably, be due to the polarization-maintaining patch-cord that connects to the SLED. I'll try switching it out with a non-PM maintaining fiber.
I've set up a crude alignment of the cross-sampling system (optical layout to come). This was just a sanity check to make sure that the beam could successfully get to the Hartmann sensor. The next step is to replace the crappy beam-splitter with one that is actually 50/50.
Attached is an image from the Hartmann sensor.
I've been setting up the cross-sampling test of the Hartmann sensor, Right now I'm waiting on a 50/50 BS so I'm improvising with a BS for 1064nm.
The output from the SLED (green-beam @ 980nm) is around 420uW (the beam completely falls on the power meter.) There are a couple of irises shortly afterwards that cut out a lot of the power - apparently down to 77uW (but the beam is larger than the detection area of the power meter at this point - by ~50%). The BS is not very efficient on reflection and cuts down the power to 27uW (overfilled power meter). The measurement of 39uW is near a focus and the power meter captures the whole beam. There is a PBS cube that is splitting the beam unequally between s- and p-polarizations (I think this is due to uneven reflections for s- and p-polarizations from the 1064nm BS). The beam is retro-reflected back to the HWS where about 0.95uW makes it to the detector.
There is a 1mW 633nm laser diode that is used to align the optical axis. There are two irises that are used to match the optical axis of the laser diode and the SLED output.
I've set up the HWS with the probe beam sampling two optics in a Michelson configuration (source = SLED, beamsplitter = PBS cube). The return beams from the Michelson interferometer are incident on the HWS. I misaligned the reflected beam from the transmitted beam to create two Hartmann patterns, as shown below.
The next step is to show that the centroiding is a linear superposition of these two wavefronts.
The SLED in the cross-sampling experiment produces unpolarized light at 980nm. So I added a PBS after the output and then a HWP (for 1064nm sadly) after that. In this way I produced linearly p-polarized light from the PBS. Then I could rotate it to any angle by rotating the HWP. The only drawback was that the HWP was only close to half a wave of retardation at 980nm. As a result, the output from this plate became slightly elliptically polarized.
The beam then went into another PBS which split it into two beams in a Michelson-type configuration (REFL and TRANS beams) - see attached image. By rotating the HWP I could vary the relative amount of power in the two arms of the Michelson. The two beams were retro-reflected and we then incident onto a HWS.
I measured the power in the REFL beam relative to the total power as a function of the HWP angle. The results are shown in the attached plot.
I got the LTG CO2 laser to deliver 50.02W as measured by the Thorlabs 200W power head today. This required running the Glassman HV supply at full power (30.0kV, 31.1mA), tweaking the end grating and output coupler alignments, and cleaning the ZnSe Brewster windows on the laser tubes, and it only lasted a few seconds before dropping back to ~48W, but the laser delivered the specified power. In the factory it delivered 55W at the 10.6 micron line I am using now- I checked it with the CO2 laser spectrum analyzer- so there is more work to do.
Cheryl Vorvick, Chris Guido, Phil Willems
Attached is a PDF with some initial noise testing. There are 5 spectrum plots (not including the PreAmp spectrum) of the laser. The first two are with V_DC around 100 mV, and the other three are with V_DC around 200 mV. (As measured with the 100X gain preamplifier, so ideally 1 and 2 mV actual) We did one spectrum (at each power level) with no attempt of noise reduction and one spectrum with the lights off and a make shift tent to reduce air flow. The 5th plot is at 200mv with the tent and the PZT on. (The other 4 have the PZT off).
The second plot is just the spectrums divided by their respectives V_DC to get an idea of the RIN.
I've set up a quick experiment to modulate the angle of the Hartmann sensor probe beam at 10mHz and to monitor the measured prism. The beam from the SLED is collimated by a lens and this is incident on a galvo mirror. The reflection travels around 19" and is incident on the HWS. When the galvo mirror is sent a 1.1Vpp sine wave, then beam moves around +/- 0.5" on the surface of the Hartmann sensor, giving around 50mrad per Vpp.
The galvo is currently being sent a 0.02Vpp sine wave at 10mHz.
I changed the drive amplitude on the function generator to 0.05Vpp and have measured the angle of deflection by bouncing a laser off the laser mirror and projecting it 5.23m onto the wall. The total displacement of the spot was ~3.3mm +/- 0.4mm, so the amplitude of the angular signal is 1.6mm/5.23m ~ 3.1E-4 radians. The Hartmann Sensor should measure a prism of corresponding magnitude.
The frequency is still 10mHz.
I've set up an experiment to test the HWS intensity distribution displacement measurement code. Basically the beam from a SLED is just reflecting off a galvo mirror onto the HWS. The mirror is being fed a 0.02Vpp *10 gain, 10mHz sinewave from the function generator.
The experimental setup is shown below.
I hacked the HWS code to export the Gaussian X and Y centers to Seidel Alpha and Beta channels in EPICS (C4:TCS-HWSX_PSC_ALPHA, C4:TCS-HWSX_PSC_BETA)
I've had the output from a fiber projected about 400mm onto the Hartmann sensor for around 5 days now. (The divergence angle from the fiber is around 86 mrad).
I played around with the temperature of the lab to induce some defocus changes in the Hartmann sensor. The system is mostly linear, but there are relatively frequent jumps in the defocus of the order of 1E-4 m^-1. This may be due to a number of things - the Hartmann plate may be moving, the fiber holder may be shifting back and forth, there may be some issue with the source wavelength shifting.
Sun 30th May 2011 - 11:40AM - the z-axis control on the NewFocus 9091 fiber coupling mount was not tightened. I tightened that to secure the control.
I ran through the procedure to calibrate the lever arm of the Hartmann sensor. The beam from a 632.8nm HeNe laser was expanded to approximately 12mm diameter and injected into a Michelson interferometer. The Hartmann sensor was placed at the output port of the Michelson.
The 50W Access Laser is now in the lab. We need to wire up the interlock to the laser, plumb the chiller lines to the power supply and to the laser head and also wire up all the electrical and electronics cables. Additionally, we will need to plumb the flow meter and attach a circuit to it that triggers the interlock if the flow falls too low.
The data from the long-term measurement of the HWS is presented here. The beam envelope moves by, at most, about 0.3 pixels, or around 3.6 microns. The fiber-launcher is about 5" away from the HWS. Therefore, the motion corresponds to around 30 micro-radians (if it is a tilt). The beam displacement is around 4 microns.
The optical properties change very little over the full 38 days (about 2 micro-radians for tilt and around 2 micro-diopters for spherical power).
The glitches are from when the SLED drivers were turned off temporarily for other use (with the 2004nm laser).
There were known to be huge (65%) heating beam power losses on the SRM AWC table, somewhere between the CO2 laser and the test optic. Today I profiled the setup with a power meter, looking for the dominant source of losses. It turned out to be a 10" focusing lens which had the incorrect coating for 10.2 microns. I swapped this lens with a known ZnSe 10" FL lens (Laser Research Optics LX-15A0-Z-ET6.0) and confirmed the power transmittance to be >99%, as spec'd. There is now ~310 mW maximum reaching the test optic, meaning that the table losses are now only 10%.
Using a single-axis micrometer stage I also made an occlusion measurement of the heating beam radius just in front of the test optic. I moved the 10" focusing lens back three inches away from the test optic to slightly enlarge the beam size. In this position, I measure a beam radius of 3.5+/-0.25 mm at 1.5" in front of the test optic (the closest I can place the power meter). The test optic is approximately 20" from the 10" FL lens, so the beam has gone through its waist and is again expanding approaching the test optic. I believe that at the test optic, the beam is very close to 4 mm.
For archive purposes, attached is a write-up of all the HWS measurements I've made to date for the SRM CO2 projector mock-up.
The 400 mW CO2 laser on the Hartmann table is currently configured for a measurement of its relative intensity noise. It is aligned to a TCS CO2P photodetector powered by a dual DC power supply beside the light enclosure. I got some data last night with the laser current dialed back for low output power (0.5-10 mW incident), but still need to analyze it. In the meantime please don't remove parts from the setup, as I may need to repeat the measurement with better power control.
Attached for reference is the RIN measurement from the initial data.
I did a beam size/beam propagation measurement of the low power CO2 laser (Access Laser L3, SN:154507-154935)
% 400mW CO2 laser beam propagation measurement
% measurements of Access Laser L3 CO2 output power (at about 30% PWM)
% SN: 154507-154935
% Aidan Brooks, 8-Feb-2018
xposn = 10.5:-0.5:5.0;
dataIN = [25 113.2 113.2 112.7 112.3 110.2 108.6 98.2 74.6 40.6 13.5 2.3 0.3
50 114.5 114.5 114.9 115 114.9 112.1 100 74.2 38.8 12.5 2 -0.1
We tested the output of the fiber launcher D1800125-v3. We were using a 6mm spacer in the SM1 lens tube and 11mm spacer in the SM05 lens tube and the 50 micron core fiber.
The output of the fiber launcher was projected directly onto the CCD. Images of these are attached (coordinates are in pixels where 100 pixels = 1.2mm)
There is a lot of high-spatial frequency light on the output. It looks like there is core and cladding modes in addition to a more uniform background. There was an indication that we could clear up these annular modes with an iris immediately after the fiber launcher but I didn't get any images. We're going to test this next week when we get an SM1 mountable iris.
And here's the output of the fiber launcher when I fixed it at 313mm from the camera, attached an iris to the front and slowly reduced the aperture of the iris.
The titles reflect the calculated second moment of the intensity profiles (an estimate of the equivalent Gaussian beam radius). The iris is successful in spatially filtering the central annular mode at first and then the outer annular mode.
We'll need to determine the optimum diameter to get good transmission spatially without sacrificing too much power.
Here is the output from D1800125-v5_SN01.
% get the beam size from the HWS ETM source D1800125-v5_sn01
[out,r] = system('tar -xf HWS*.tar');
% load the files
dist = [1,10,29,51,84,105,140,180,240,295,351,435,490,565]; % beam propagation distance
files = dir('*.raw');
Title was wrong - this is actually config [12,2,4,125]
I'm considering the 86-711 2" 532nm PBS from Edmund Optics for the ETM HWS at the sites.
The effect on the transmission through the system, compared to the THorlabs PBS, is shown in the attached plot.
Conclusion: it looks almost as effective as the Thorlabs PBS with the added benefit of being 2" in diameter.
Went down to the lab and showed Rana the setup. He's fine with me being down there as long as I let someone know. He also recommended using an adjustable mount (three screws) for the test mirror instead of the mount with top bolt and two nubs on the bottom - he thinks the one with three screws as constraints for the silica will be easier to model (and be more symmetric constraints)
Mounted the f=8" lens (used a 2" pedestal) and placed it on the table so the image fit well on the CCD and so a sharp object in front of the lens resulted in a sharp image. The beam was clipping the f=4" lens (between gold mirror and test mirror) so I spent time moving that gold mirror and the f=4" lens around. I'll still need to finish up that setup.