I measured the beam profile of the Alberto laser (that will be the ETMY end laser) as I found the data inconsistent with the measurements done earlier.
The laser was set to nominal current (ADJ =0) and the output measured 330mW. I used a 99% BS and measured the beam profile of the transmitted light at several points along propagation using Beamscan. I am attaching the data and matlab script for the fit for future reference.
1. ETMY oplev setup has been put together. Because of the shift in the TRY path, I had to modify the oplev path on the table as well.
2. Green laser setup coming together:
(i) Used a HWP after the NPRO to convert s-polarization to p-polarization. (Verified by introducing a PBS after the HWP and then removed later).
(ii) Lens focuses the beam into the Faraday.
(iii) Used steering mirrors to align the beam to the faraday. With 320mW before the Faraday, I was able to get 240mW after the output aperture. The spec sheet for the faraday specifies a 93% transmission; but what I measure is only 75%.
Enclosure is at the east end. It has it's bottom o-ring in place. It will be ready for optics tomorrow around 5pm
I have to shim out the enclosure, finish leveling the table and cut surgical tubing O-ring for the top.
Glued surgical latex tubing with super glue into O-ring shape. The existing in place tubing K-100, OD 0.125" (actual size 0.140"), wall 0.031", ID 0.062".
I have just found out that tolerances on tubing OD are + - 0.026" by the manufacturer. I'm getting larger tubing for better fit.
The table is ready for optics.
Things left to do:
1, finalize o-ring size 2, finish cable feedthrough 3, finalize window connection 4, IR-Thermashield strips for bridge sides 5, replace bridge support post with solid one
I'm working on to improve the quality of the enclosure.
The short comings are: more cable feedthroughs needed, latches to anchor top covers air tight and posts to support bending bridges.
Red triangles are compression latches at 10 places to hold the top air tight on surgical tubing
Green lines represent 4 posts of Al 1" OD to support the covers and maximize their eigenfrequencies.
Black crosses are 4 spring loaded push-bottom quick release pins to anchor the top covers to the bridges. This connection will not be air tight.
(quarter-turn wing head fastener have the same problem) I'm thinking of some solution to minimize the leak.
Violet _ steel plate (1" wide, 15" long, 0.125" thick) between the two posts will anchor the quick release pins and make bridge rigid.
Blue rectangle is an other cable feedthrough exiting on the chamber side.
Planning to substitute window with soft - air tight ( Aluminized thin wall hose ) connection to vacuum view port where white circle is representing the Al adaptor ring.
Updated after Wednesday meeting 4-24-2013
Are 4 of these spring loaded pins enough? I'm not sure how one pin can hold 2 lids at each point. It seems like we need 8 pins.
Steve has explained to me that the pins will go in between the 2 lids, with a big washer, so that one pin holds both lids at the same time. 4 is the right number.
Layout that will be improved upon over the next few days.
Things that need to be updated:
1. Waist size at all optics
2. Beam size at detectors and choice of lenses
3. IPANG & green PD proposed positions
I started to put together optics at the endtable. I am attaching the layout with the green blocks showing the optics that are assembled and will not be moved henceforth unless somebody contradicts.
1. Power after HWP = 314mW
Power before faraday = 310mW
Power after faraday = 300mW (the power loss while aligning the faraday earlier was due to the AR coating on the focusing lens before the faraday - it was AR coated for visible and that accounted to the power lost)
2. Since we do not know the length of TGG inside faraday, I measured the beam profile after the faraday so that I can trace the beam without any errors to calculate exact mode matching solutions.
3. The NPRO beam seems to be obviously elliptical as seen on the IR card and also from beam profile measurement. So we cannot skip including cylindrical lenses in the layout.
I have updated the waists (W) and beam diameters (D) at 1064nm optics on the endtable.
I am not able to locate the characteristics of QPD-Y and oplev PD and hence took the beam diameter to be half of the detector surface area to determine their positions.
Beam diameter on PDA520 used for TRY was calculated using the transimpedance and responsivity of the PD from an old elog in 2004.
Progress with end table:
Parts in green show assembled optics that will not require any changes. Parts in yellow are in place but will need either change of lenses in their optical path or change in position.
More optics have been put on the table. Direction of the rejected beam from the 532nm faraday estimated to be ~1.7 deg along -y axis.
Transmon QPD, TRY and camera have beams on them for locking Y arm. Oplev configuration is waiting for it's lens to arrive.
I rotated some mounts along the green beam path, and I started aligning the beam again.
The beam is aligned up to the waveplate just before the doubler crystal, even if I couldn't reach more than 88% transmission for the Faraday. Next week I will finish the alignment and I'll put the lenses that Manasa already ordered.
Yend table - Current status
Today the 2m focal length lens along the oplev path (just after the laser) has been added. In Manasa's layout it allows to have a beam waist of 3.8mm on the OPLEV QPD, even if it seems to be smaller.
The laser is closer to the box wall than the layout shows (it's on the line n.1 instead of line n.9), so maybe it has to be moved in the position shown in the layout, as Steve suggests, to leave empty space just before the window.
Rana suggests a 2mm diameter beam on the QPD, so a new calculation has to be done to add a second lens.
The beam has been aligned until the doubler, but after the crystal it it has a small tilt, so a better alignment has to be done.
Moreover, the beam waist has to be measured after the Faraday for the green, in way to choose the focal length of the lenses necessary for the mode matching.
Then the three steering mirrors to send the beam into the arm have to be put.
A lens which has to be put on the Transmon path (already ordered) has to be added, and the beam alignment on the QPD-y and on the PDA520 has to be done.
Koji noticed that earlier this afternoon the Yarm ASS was working, but then after dinner it was no longer working. I saw that the ETMY trans camera beam was clipped. These things precipitated a visit to the Yend station.
I saw that the beam on the optic that steers the camera beam to the camera was very, very low, almost falling off the optic. The only mirror which steers to this optic is the harmonic separator which reflects the IR, and transmits the green. I turned the pitch knobs on the harmonic separator until the beam was roughly centered on all 3 optics between the separator and the camera (BS to QPD, BS to TRYDC and Y1 for camera). The yaw was fine, so I didn't touch it.
I then adjusted the steering mirror to the camera, and the BS pointing to the DC PD. I have not touched the BS pointing to the QPD. Once the beam was on the TRY PD, Koji ran the ASS script, and I recentered the beam on the DC PD. During this time, Koji had the Yarm triggering using -1 in the POYDC element of the matrix.
The harmonic separator is not mounted in a nice way (I'm assuming that Annalisa is in the middle of things, and she'll get back to it after the green work), so the TRY PD and camera will need to be aligned again, so I didn't do any ASS-recentering-ASS iteration tonight.
The Yarm ASS works nicely again, getting TRY to ~0.89 .
I'm planning to remove the ETMY optical table enclosure and move it over to CES Shop 8am Thursday morning.
We'll install spring loaded lathes, hooks and quick release pins.
The bridge will be reinforced with steel plate to support release pins on posts.
There will be an other cut out for cable feedtrough as it is shown on elog #8472
Let me know if this timing does not fit your work.
The new lenses arrived, and I put the right 250mm before the doubler. I'm still not so confident with the alignment, because I cannot get more than 11-12 uW out from the "green" Faraday, with more than 200uW going in.
I replaced the Y1 mirror with an HR1064-HT532. The alignment has to be done. Today the 50cm focal length lens arrived, and I'm going to put in tomorrow.
I still have problems in maximizing the power out from the doubler. I realized that the real green power I obtain is about 30 uW, and it is the power which really enters the Faraday.
Before I was measuring it just after the Harmonic separator, and there was some residual IR beam which increased the power on the power meter, that's why I obtained about 200 uW.
I also tried to slightly vary the position of the mode matching lens, but I was not able to get more than 30 uW on the power meter.
The 50 cm focal length lens has been added in the position shown on Manasa's layout, and the beam has been focused on the PD.
Today, I moved the router from on top of the PSL into the control room in order to perform dark field tests on the GC650 (which I also moved). The GC750 along with the lens that was on it and the mount it was on has been lent to Ricardo's lab for the time being. I successfully triggered the GC650 externally and I also characterized the average electronic noise. For exposure times less than 1 microsecond, the average noise contribution appears to be a constant 15 on a 12-bit scale.
I found two ThorLabs PDA55 Si photodetectors that says detect visible light from DC to 10MHz that I'm going to use from now on. I don't know how low of a frequency they will actually be good to.
Rather than make a new elog post every time I move something, I'm going to just keep updating this Google spreadsheet, which ought to republish every time I change it. It's already got everything I've done for the past week-ish. The spreadsheet can be accessed here, as a website, or here, as a pdf. I will still post something nightly so that you don't have to search for this post, but I wanted to be able to provide more-or-less real-time information on where things are without carpet-bombing the elog.
I fit the data from the beam profile that Jenne measured on 5/21/2010. The distances are measured from halfway between MC1 and MC3 to the beam scanner. The fits give the following where w0 is the waist size and z0 is the distance from the waist to halfway between MC1 and MC3.
For the horizontal profile:
reduced chi^2 = 0.88
z0 = (1 ± 29) mm
z0 = (1
w0 = (1.51 ± 0.01) mm
w0 = (1.51
For the vertical profile:
reduced chi^2 = 0.94
z0 = (673 ± 28) mm
z0 = (
w0 = (1.59 ± 0.01) mm
w0 = (1.59
I calculated the radius of curvature of MC2 using these values of w0:
horizontal: (16.89 ± 0.06) m
vertical: (17.66 ± 0.07) m
For this calculation, I used the value of (13.546 ± .0005) m for the length of the mode cleaner measured on 6/10/2009. The specification for the radius of curvature of MC2 is (18.4 ± 0.1) m.
In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.
the lead spheres that were placed below the granite slab have been flattened by hammering to have lesser degree of wobbling of the slab.
the height of each piece, and the flatness of their surfaces was checked by placing another slab over them and checking by the spirit level.