QPD#              QPD1       QPD2
Housing#          #004       #008
Diode#            #44        #46
Shim              (see OMC ELOG 323)
-------------------------------------
Power Incident    252.3 uW  266.0 uW
Sum Out           174.2 mV  176.0 mV   +0.3
Vertical Out      + 4.7 mV  +19.0 mV   +0.2
Horizontal Out    -16.1 mV  - 8.0 mV   +0.0
SEG1              -52.4 mV  -53.  mV   -0.1
SEG2              -37.6 mV  -47.  mV   -0.1
SEG3              -41.8 mV  -34.  mV   -0.1
SEG4              -43.7 mV  -36.  mV   -0.1
-------------------------------------
Spot position X   +39   um  +15. um  (positive = more power on SEG1 and SEG4)
Spot position Y   - 8.1 um  -56. um  (positive = more power on SEG3 and SEG4)
-------------------------------------
Responsivity[A/W] 0.69      0.66
Q.E.              0.80      0.77
-------------------------------------

Arrangement of the segments
View from the beam
/ 2 | 1 X
|---+---|
\ 3 | 4 /

---------------

I(w,x,y) = Exp[-2 (x^2 + y^2)/w^2]/(Pi w^2/2)

(SEG_A+SEG_B-SEG_C-SEG_D)/(SEG_A+SEG_B+SEG_C+SEG_D) = Erf[sqrt(2) d/w]

d: distance of the spot from the center
w: beam width

[Koji, Philip]

Today we tested the functionality of the four remaining PZTs (11,12,13 and 22) .  Each PZT was placed within a collimated 500um beam.
Roughly half of the beam was blocked by the PZT. The PZT and a PD then acted as shadow sensor. Each PZT was tested with 0 and
150 V. The resulting power change then could be converted into a displacement of the PZT using the beam diameter.

The open light value for each of these tests was 3.25 V.

PZT 11:
0 V supply voltage     --> 1.717 V on PD
150 V supply voltage --> 1.709 V on PD
delta = 0.008 V

PZT 12:
0 V supply voltage     --> 1.716 V on PD
150 V supply voltage --> 1.709 V on PD
delta = 0.007 V

PZT 13:
0 V supply voltage     --> 1.702 V on PD
150 V supply voltage --> 1.694 V on PD
delta = 0.008 V

PZT 22:
0 V supply voltage     --> 1.770 V on PD
150 V supply voltage --> 1.762 V on PD
delta = 0.008 V

0.008 V --> 0.24% change in power on PD --> about  3.8 um displacement assuming no light which is blocked
by the PZT is hitting the PD.

We further started to drive all four PZTs over night with 100 V (half of their range) at 100 Hz.
We additionally display the impedance to ensure none of them degrades.

All four PZTs seem to be connected to Teflon coated wires. It needs to be checked if these
fulfill the vacuum compatibility requirements.

Attachment 1: Shadow sensor setup for the PZT displacement test

Attachment 2: PZT endurance test. 4 PZTs were shaken at once.

Attachment 3~5: Function generator setup 100Hz, 3.5Vpp 1.75Voffset (meant be displayed for 50Ohm load)

Attachment 6: The above setting yields 7Vpp unipolar signal @Hi-Z load

Attachment 7: The output was monitored with a 1/10 probe with the PZTs connected. This shows 10Vmax 0Vin -> Good. This photo was taken at 17:35.

Attachment 8: The test is going well @9:15 next day. (t=15.7hours = 5.6Mcycles)

Attachment 9: The test went well. The modulation was stopped @15:35. (t=21hours = 7.6Mcycles)

D1200105 SN006 was selected as the breadboard for OMC(004).
The reason is the best parallelism among the unused ones.

The attached is the excerpt from T1500060 with the #006 highlighted.

We are going to use B6 for the DCPD BS (BS2), and B1 for the QPD BS (BS3). Their role can not be swapped.

B6 has the best loss among the available ones, while the perpendicularity is not so critical due to the short arm.

B1 has the OK perpendicularity, while the loss is also moderately good.

The attachment is the excerpt from T1500060 with some highlighting.

We are going to use E6, E9, E11, and E14 for BS1, SM1, SM2, and SM3. They (and E18) are all very similar.

The attachment is the excerpt from T1500060 with some highlighting

After having dug into the past email, it turned out that these wires were the ones already replaced from the original teflonwires. The length of them were confirmed to be ~19" (480mm). 

[Joe, Koji, Liyuan, Philip, Stephen]
Work done on 16.04.2019

Finishing assembly of transport box
Assembly worked fine except for the clamping structure to clamp the lid of the transport box to the bottom part.
It seemed that some of the plastic of these clamps became brittle during the baking. The plastic was removed and the
clamps where wiped clean. It appears that the clamps can't be locked as they should. Still the transport box should be fine
as the long screws will mainly clamp the two parts together.

Preparing the transport box to mount the breadboard
The lid of the the transport box was placed upside down and clamped to the table. All peak clamping structures where pulled back as far as possible.

Preparation and cleaning of the breadboard
We unpacked the breadboard and found lots of dust particles on it (most likely from the soft paper cover which was used). We used the ionized nitrogen gun
at 25 psi to get rid of the majority of particles and cross-checked with a bright green flash light before and after blowing. The second stage of cleaning was done
below the clean room tent and included the wiping of all surfaces. The breadboard was then placed into the prepared lid of the transport box and clamped with peak
screws.

Unpacking of the template
The previously cleaned template was unpacked while the last layer of coverage was removed below the cleanroom tent.

Template adjustment on the breadboard
All peak screws of the clamping structure of the template where removed. The template was placed onto the breadboard only seperated by peak spacers.
All peak screws have been inserted for horizontal clapming. A calipper was used to measure the distance of each edge of the template to the edge of the
breadboard. For documentation the labeled side of the bradboard (facing away from the persons on the pictures) of the upside down breadboard is defined to 
be the south side, continuing clockwise with west, north and east. First rough alignment was done by shifting the template on the breadboard and then the 
peak screws where used for fine tuning. The caliper values measured where:
North   C 8.32mm     E 8.52 mm     W 8.41 mm
East     C 8.08 mm
South   C 8.32 mm
West    C 8.02 mm
(E indicating east side position, W indicating west side position and C indicating center position)

[Joe, Phillip, Koji, Stephen]

*draft post, please add anymore info if I missed something*

• made initial alignment of the cavity. To do this we used the periscope mirrors to aim the incoming beam at the centre of the first mirror and second (1st curved mirror) mirror. Using the micrometers (initial positions was 0.20mm), we moved the first curved mirror so that it hit the third mirror. We then used a combination of the periscope and first curved mirror movements to start seeing 2 or 3 round trips. micrometer was set to roughly 0.11mm. We then only used  periscope mirrors to align the beam into the cavity.
• We set up a wincam at the transmission of the cavity. This was a useful was of seeing what mode was being transmitted through the cavity. We walked the beam with the periscope mirrors until we saw flashes of the TM00 mode.
• Once the cavity was transmitting TM00 modes, we started to lock it. Once it was locked we looked at the the spot positions of beam on the mirrors. Phillip looked with an IR viewer and could see that the spots were too high on both the curved mirrors
• We set up a CCD to capture an image of this. Two post holders have been left in place for easy movement of the CCD.

General notes about working with this set up. The lens on the CCD can come off quite easily, as you just change how much its screwed on to change the focus. Care should be taken that you don't know the template with this as well, as the camera is quite close to the template (and near the edge of the bench!). Also be mindful of the PZT wires, as they can pull the mirrors out of position.

Attachment 1 shows the position of the spots on the mirrors A14 and PZT11. The spots are about 3mm ish from the centre of the curved mirror in the vertical and horizontal direction. 

Attachment 2 sketch of mirror positions.

Attachment 3 shows the postion of the spot on PZT13. The spot is less near the edge than on PZT11, but its still 2mm ish from the centre of the curved mirror in both directions.

To move the beam horizontally we can use the alignment matrix in appendix C of T1500060. However since we don't have control over the pitch of the mirrors, moving the spots down could require us to inspect the glass breadboard/prisms for dust. We suspect that PZT could be the culprit, as we could not see newtonian rings between its base and the glass breadboard. One way to test this idea is just to clean the bottom of the PZT with acetone, and see if that improves the spot position. If we don't have to do any work to realign it, then this was not the issue.

Koji pointed out that the spot in attachment 1 is very near the edge of the optic, so shifting the beam horizontally could also fix the vertical issue. 

ach[Joe, Phillip, Koji, Stephen]

Work from 17.04.2019

First contact cleaning of OMC optics
We cleaned the OMC optic with first contact. After a first cleaning run all mirrors except for two looked
fine. One had some first contact residuals on the left at center height and another had some particle sitting
near the center area. As the ionized nitrogen gun didn't help we applied another round of first contact which resolved
the two issues. Unfortutanely the second run of cleaning again left some residuals of first contact at the edges.
We were able to peal these off with tweezers.

Placement of Optics at the breadboard
We cleaned the contact surfaces for the bonds using optic wipes and pure isopropanol. The placement wen't well for 3 of the 5 optics (low number of newtonian rings).
One was recleaned and placed on the breadboard again which seemed fine. For the 5th no newtonian rings could be seen (either verry ood or bad) we planed on trying it in the current set-up. Mirrors used can be seen in attachment 3.

 

The spot on CM1 was found displaced by 3.4mm (horiz.) and 3.0mm (vert.) in the upper right direction looking from the face side.
The spot on CM2 was found displaced by 1.2mm (horiz.) and 1.8mm (vert.) in the upper left direction looking from the face side.

The drawing on the left side of the attachment shows the estimated misalignment when we think they all come from the curved mirrors.
As for the yaw misalignment, CM1 and CM2 were 3.9mrad and 5.6mrad rotated (misaligned) in CW, respectively.
As for the pitch misalignment, CM1 and CM2 has 1.7mrad (narrowing) and 3.5mrad (widening), respectively. We have no adjustment for this.
Let's say if this comes from the dusts on the bottom of the prisms, CM1 has ~17um one, and CM2 has ~35um one beneath them. The question is if we can believe this or not? This should be checked with the Newton fringes we can see at the bottom of the prisms.

Similarly to OMC ELOG 349 the spot positions after the replacement of CM2 were measured (Attachment 1)
Also, the spot positions after the realignment were measured. (Attachment 2)

[Koji,Philip, Liyuan, Joe]

CM1:

We moved the curved mirrors to these positions:

inner = 0.807mm

outer = 0.983 mm

CM2:

inner = 0.92 mm

outer = 0.85 mm

To do this so that realignment was easier, we moved the screws in steps of 5um. We alternated which mirror we adjusted so that we could monitor with a wincam how well aligned the beam into the cavity was. We only moved the cavity mirrors a small amount so we could still see higher order mode flashes transmitted through the cavity (e.g.TM03 modes). We would then improve the input alignment, and then move the cavity mirrors some more. Once the mirrors were adjusted according to http://nodus.ligo.caltech.edu:8080/OMC_Lab/190422_195450/misalignment4.pdf the spot positions looked near the middle of the curved mirrors (using a beam card). We began beam walking but we ran  out of range of the bottom periscope screws in the yaw dof. We tried using the third screw to move the mirrror in both yaw and pitch, hopefully this will let move the mirror such that we can use the just the yaw screw. This screw also ran out of range, so we decided that the cavity needed a small adjustment.

The curved mirrors were moved slightly (>5um) and then we tried to get alignment. By using the fibre coupler translation stage, we move the beam side ways slightly, and then tried to get the periscope mirrors back to a position where the screws could move the mirrors. Once we had an ok alignment, we checked the beam. It looked like it was pretty close to the centre of the curved mirrors, which is where we wanted it to be.

We then tried locking the cavity, although the error signal was quite small. The adjusted the input offset and gain of the servo (there is apparently some problem to do with the input and output offsets). Once the cavity was locked we could make the final adjustments to aligning. We still ran out of range on the periscope. We decided to move the breadboard with the fibre coupler and mode matching lenses on it. Because we knew that the cavity was aligned such that the beam hits the centres of the curved mirrors, we could regain flashes quite quickly. We saw the error signal go down, but eventually this decrease was just to do with the beam clipping on the periscope mirrors. We moved the spot back to where we ok aligned, and slid the periscope so we were not clipping the mirror. This worked very well, and then optimised the alignment.

We then tried to improve the mode matching. 

We took photos of the spot positions (quite near the center) and made the detuned locking measurement. The fitting of the data (attachment 1) wsa 1.1318m (what error should we put here?).

I think the order we did things in was:

• turning anti clockwise on the fibre coupler and misalign the diode, we measured the modespacing.
• returned the alignment for the photodiode, and realign fibre couple.
• miss align the photodiode horizontally, and then used fibre coupler to maximise the peak higher order mode peak height. We then used the PD again to make the peak height bigger.
•  

[koji,philip,joe,liyuan,stephen]

need to add spot positions.

Mirrors: PZT11,PZT22, A14, A5

Mode matching = 97.72%

15.66-> 15.30mW coupled.

~100uW for QPD

->15.2mW in cavity

Trans = 14.55mW -> 95.7% transmission

The flat mirrors were the ones with the most scattering, so we thought about how to improve it. We tried to move the first flat mirror by pushing it with our finger so that he beam would move along the optic. We tried this a couple of times, however the second time we moved it we lost our alignment and could not retrieve it. We looked at the mirror and we could see quite a lot of newtonian rings. We could see a small fibre on the glass bread board. We cleaned the optics base and the gbb, and we could get the alignment back. The beam was aligned to the cavity, the spots no longer hit the centre of the CM2. 

We measured the power budget again.

mode matching = 1-47/2680 = 0.9824, 98.2% mode matching

same p_normalise so

15.66-> 15.34mW coupled.

~15.24mW in cavity

transmission = 14.45, so 94.8% transmission.

Koji noticed that FM1 wasn't touching the template correctly, so he re-aligned the cavity.

Afternoon session - UV Bonding (E1300201-v1 procedure 6.4.4 "Gluing" using procedure in section 7.2 "UV Gluing")

Wiped down UV PPE, UV Illuminator, and UV Power Meter

Applied Optocast 3553-LV Epoxy to sample fused silica optics, to test quantity of glue needed and to become familiar with the process and tools. Philip and Joe each created a successful bond. Joe's had 3 visible spots in the bulk of the bond. Acetone was used to scrub some residue of epoxy from the surface near the OD, which was likely cured. Short duration exposure (seconds) to acetone at the perimeter of the bond did not yield any weakening of bond.

While test pieces were bonded, Koji was making some adjustments to the cavity alignment in preparation for gluing of the steering mirror BS1.

Koji noticed that the spring clamp was causing pitch in the BS1 mirror, so he recommended that we utilize the "restrain by allen key" technique to load the mirror during curing.

Once aligned, we tried taking the BS1 mirror out of the template and then putting it back. We did this twice and both times the cavity needed realigning (with the curved mirrors as well as the input steering periscope). Why is this? Since the mirror was touching the template it should not have become misaligned right? Maybe the template moves slightly? I think before glueing in the cavity mirrors we should find out why probably? Koji took a look and claimed that a few optics may have been unconstrained. 

Planning between Koji and Joe led to placement of 5 drops of epoxy on the BS1 surface, to match the bonding area. At this point we noticed that the template was not secured very well, by poking down on it we could see it move. This might explain why we are becoming misaligned very easily. Once the prism was back on the board, Koji used allen keys to move around the prism. This was done until we could align it again (i.t looked too pitched). The beam was aligned back into the cavity, and the UV light was used to cure the bond. The reflected DC when locked was

• pre-cured = 47mV
• cured = 55 mV

so it looks ok still.

[koji, joe]

The template or glass breadboard was wobbling, and we noticed that the caivty alignment became worse/better when it was pressed down. We saw that it was the glass breadboard, so it was fixed into the transport fixture more securely. Now its alignement didn't change when it was pressed down. We took a pzt mirror out and replaced it, the alignment din't change much so that was good. We set up posts to hold the pzt wires.

We noticed that the bottom of the mirrors were dirty, so we cleaned them, and once we were happy with the newton rings, we aligned the cavity

Took a photo of CM2, the spot is maybe 1 beam diameter vertically and horizontally from the centre, and quite a bright spot could be seen. The same problem with CM1. We thought it would be good to see a measurement of higher order mode spacing dependence on PZT DC voltage rather than doing the full characterisation since the alignment seems to change quite a lot when ever we do anything, and this cavity arrangement probably isn't very good anyway (can see scattering on both curved mirrors with the IR camera). 

did measurements of FSR, = 2.64835MHz

did HOM spacing for 0,75,150V on CM1 in pitch and yaw.

we want to come up with a work flow for how to do these measurements, and make automate parts of the analysis?

Tried a few things.

1. Replaced CM1 (PZT ASSY #10=M21+PZT#22+C12) with PZT ASSY #7 (=M1+PZT#13+C13)

We tried PZT ASSY #7 at the beginning and had the spots at almost at the top edge of the curved mirrors. As we found a particle on the bottom of the M1 prism (and removed it), I gave it a try again. Resulting spots are again very high. This results in rejecting PZT ASSY #7 and we set the combination of the PZT ASSYs as #8 (M7+P11+C11) and #10 (M21+P22+C12). This combination nominally gives the spot ~1mm above the center of the curved mirrors.

2. Swapped FM1 and FM2. Now FM1=A5 and FM2=A14.

No significant change of the scattering features on the FMs. The transmitted power was 14.85mW (Ref PD Vin = 3.42V), Reflection PD Vrefl,lock = 54.3mV and Vrefl,unlock = 2.89V (Vin=3.45V), Vrefl,offset = -6.39mV. The incident power was 17.43mW (Vin 3.69V).

==> Coupling 0.979 , OMC transmission 0.939 (This includes 0.6% loss to the QPD path) ...Not so great number

3. Built better camera setups to check the spot position and the scattering from the cavity mirrors.

Now the spot heights are fixed and safe to move the camera up for inches to obtain better views of the mirror faces. The camera was set 15" away from the mirrors with 1.5" height from the beam elevation. This is 0.1rad (~ 5 deg) and Cos(0.1)~0.995 so the distortion (compression) of the view is negligible. (Attachment) The spot photo were taken with the fixed CCD gain, the focus on the glass, and  lens aperture F=8.0. Later the focus and aperture were adjusted to have clear view of the scattring points.

The intensity of each scattering was constant at different views. I suppose this is because the scattering is coming from a spot smaller than the wavelength. The bright spots does not show any visible feature on the mirror surfaces when they were inspected with a green flash light.

CM2 has the excellent darkness and we want to keep this spot position. FM1, FM2, and CM1 showed bright scattering.

The spot at CM1 is not well centered on the mirror. And this is the way to avoid this scattering point. So let's think about to move the spot on CM1 by 1.3mm towards the center while the spot on the CM2 is fixed. Note that this is going to be done by the micrometers for CM1 and CM2.

By turning right micrometer of CM1 forward (50um = 5div = 1/10 turn) and the left micrometer of CM2 backward (60um = 6div) moves the spots on FM1, FM2, CM1, and CM2 by (0.43, 0.87, 1.3, 0)mm. This basically moves the spots toward the center of each mirror. Let's give it a try.

Experiment on 5/1
- CM1 right knob was moved 1div (10um) backward such that the spots were better centered on the mirrors 
FM1 (A5): h=-0.2mm -> 0.4mm made the spot much darker but still it has a few scattering spots.
FM2 (A14): h=-0.8mm -> 0.2mm reduced the number of spots from 2 to 1. And it is darker. The remaining spot at the center.
CM1 (C11): h=-1.3mm -> +1.0mm made the spot much darker.
CM2 (C12): h=-0.7mm -> +0.2mm remains dark.

Note: CM1 h=1mm and CM2 h~0mm are good locations. h+ is the good direction to move. Avoid h-.
FM1 and FM2 has the scat spots at the center. Want to go h+ more.

Uniformly go h+ is the good move. => This can be done by rotate CM1 positive => CM1 right knob CCW.

Improvement of the transmission from 93.9%->95.3%

- Further moved CM1 right knob 0.5div (0.5um) backward such that the spots were moved to h+ directions.
FM1 (A5): h=0.4mm -> 1.1mm (there is only one spot rather than multiple spots)
FM2 (A14): h=0.2mm -> 1.1mm (darker but multiple spots)
CM1 (C11): h=1.0mm -> 1.8mm (brighter but single spot)
CM2 (C12): h=0.2mm -> 1.5mm (dark multiple spots)

Not much improvement of the transmission but kept 95% level.

- Replaced FM1 (A5) with A1 mirror (No photo)

Good news: This did not change the cavity alignment at all.

Transmission 95.4%

- Tweaked the CM1 angle

Transmission 95.3%

=> A1 mirror does not improve the transmission much.

Next Plan: Use A5 (or something else) as FM2 and see if A14 caused the dominant loss.

Notes on the OMC cavity alignment strategy

- x3=1.17 γ + 1.40 δ, x4=1.40 γ + 1.17 δ
- This means that the effect of the two curved mirrors (i.e. gouy phases) are very similar. To move x3 and x4 in common is easy, but to do differentially is not simple.
- 1div of a micrometer is 10um. This corresponds to the angular motion of 0.5mrad (10e-6/20e-3 = 5e-4). ~0.5mm spot motion.
- ~10um displacement of the mirror longitudinal position has infinitesimal effect on the FSR. Just use either micrometer (-x side).
- 1div of micrometer motion is just barely small enough to keep the cavity flashing. => Easier alignment recovery. Larger step causes longer time for the alignment recovery due to the loss of the flashes.

- After micrometer action, the first move should be done by the bottom mirror of the periscope. And this is the correct direction for beam walking.

- If x3 should be moved more than x4, use CM2, and vise versa.
- If you want to move x3 to +x and keep x4 at a certain place, 1) Move CM2 in (+). This moves x3 and x4 but x3>x4. 2) Compensate x4 by turning CM1 in (-). This returnes x4 to the original position (approximately), but leave x3 still moved. Remember the increment is <1div of a micrometer and everytime the cavity alignment is lost, recover it before loosing the flashes.

(Now the CCD image is captured as a movie and the screen capture is easier!)

Various spot positions on CM1 and CM2 were tried to test how the transmission is dependent on the spot positions. CM1 has a few bright spots while CM2 shows very dark scattering most of the case. Attachment 1 is the example images of one of the best alignment that realized the transmission of ~96%. FM1 and FM2 also showed bright spots. The replacement of the FM mirrors does not improve nor degrade the transmission significantly. The transmission is still sensitive to the spot positions on the alignment. This indicates that the loss is likely to be limited by CM1.

Attachment 2 shows the distribution of the (known) scattering spots on CM1. The bright spots are distributed every ~1mm on the spot height and the beam (with beam radius of .5mmm) can't find a place where there is no prominent spots.

We will be able to examine if the transmission can be improved or not by replacing this CM1 mirror.

We want to perform a damage test of OMC DCPDs with high power beam. The OMC DCPD is the 3mm InGaAs photodiodes with high quantum efficiency, delivered by Laser Components.
The sites want to know the allowed input power during the OMC scan for beam mode analysis. The nominal bias voltage of the PDs is +12V. Therefore, 30mA of photocurrent with the transimpedance of 400 Ohm is already enough to saturate the circuit. This means that the test is intended to check the damage of the photodiode mainly by the optical power.

The test procedure is as follows:

1. Illuminate the diode with certain optical power.
2. Measure the dark current and dark noise of the PD with no light on it.
3. Check the condition of the PD surface with a digital camera.
4. Repeat 1~3 with larger optical power.

The beam from an NPRO laser is delivered to the photodiode. The maximum power available is 300~400mW. The beam shape was regulated to have the beam radius of ~500um.

- When the PD is exposed to the high power beam, the circuit setup A) is used. This setup is intended to mimic the bias and transimpedance configuration used in the DCPD amp at the site.

- When the dark noise is measured, the circuit setup B) is used. This setup is low noise enough to measure the dark noise (and current) of the PD.

- The test procedure is going to be tested with an Excelitas 3mm InGaAs PD (C30665), and then tested with the high QE PD.

C30665 (3mm) camera test. The camera was Canon PowerShot G7X MkII. Exposure 1/15s, F 5.6, ISO 125, MF (~the closest), no zoom.
This image was taken before the beam illumination. Will tune the green lighting to have some gradient on the surface so that we can see any deformation of the surface.

An Excelitas C30665 PD with the cap removed (SN07 in Case H slot #2) was exposed to the beam with the optical power of 1.4mW to 334mW.
After each illumination, the dark current and the dark noise level were tested. Also the photo image of the PD surface was taken each time.

- No significant change of the dark current after each illumination.

- No significant change of the dark noise after each illumination.

- No visible change of the surface observed.

LaserComponents IGHQEX3000 (Cage B2: Serial# B1-23) was exposed to the beam with the optical power from 1.6mW to 332mW.
After each illumination, the dark current and the dark noise level were measured. Also the photo image of the PD surface was taken each time.

- No significant change of the dark current after each illumination.

- No significant change of the dark noise after each illumination.

- No visible change of the surface observed.

(During this dark noise measurement, the current amp gain was set to be 1e8 V/A, instead of 1e7 for the measurements yesterday.)

[LiyuanZ, StephenA]

Downs B119

Summary: Beginning on 20 May 2019, two CM PZT assemblies were soaked in Acetone in an effort to debond the EP30-2 bonds between tombstone-PZT and between PZT-optic. Debonding was straightforward after 8 days of soaking. 24 hours of additional acetone soaking will now be conducted in an attempt to remove remnant EP30-2 from bonding surfaces.

Procedure: The assemblies were allowed to soak in acetone for 8 days, with acetone level below the HR surface of the optic. No agitation of the solution, mechanical abrasion of the bond, or other disturbance was needed for the bond to soften.

GariLynn contributed the glassware and fume hood, and advised on the process (similar to debonding of CM and PZT from OMC SN002 after damaging event). The equipment list was (WIP, more detail / part numbers will be gathered today and tomorrow):

• crystallizing dish (no spout, like a deep petri dish)
• curved lid
• wax sheet (to seal)
• acetone
• fume hood

Results: Today, 28 May 2019, I went to the lab to check on the optics after 8 days of soaking. Liyuan had monitored the acetone level during the first 4 days, topping up once on 24 May. All bonds were fully submerged for 8 days.

There were 2 assemblies soaked in one crystallizing dish. Debonded assemblies - ref OMC eLOG 328 for specified orientations and components:

PZT Assy #9 - ref. OMC eLOG 334 - M17+PZT#12+C10

PZT Assy #7 - ref. OMC eLOG 332 - M1+PZT#13+C13

PZT Assy #7 was investigated first.

• C13 was removed with no force required.
• PZT#13 was removed with no force required.
• EP30-2 remained at the bond surfaces and tracing the diameters of each bond on each of the 3 bonding surfaces of the PZT and tombstone - these components were returned to the dish to soak.
• No EP30-2 remained on the surface of the curved mirror - C13 was removed and stored.

A video of removal of C10 and PZT#12 from PZT Assy #9 was collected (See Attachment 8), showing the ease with which the debonded components could be separated.

• C10 was removed with no force required.
• A slight force - applied by gripping the barrel of the PZT and pushing with the index finger on the surface of the tombstone - was required to separate PZT#12 from M17,
  • likely due to excess glue at the barrel of the PZT
• EP30-2 remained at the bond surfaces and tracing the diameters of each bond on each of the 3 bonding surfaces of the PZT and tombstone - these components were returned to the dish to soak.
• No EP30-2 remained on the surface of the curved mirror - C13 was removed and stored.

Photos and video have been be added to supplement this report (edit 2019/07/08).

[Stephen, Koji]

The perpendicularity of some of the A and M prisms were tested.

Results

- The measurement results are listed as Attachment 1 and 2 together with the comparisons to the measurement in 2013 and the spec provided from the vendor.
- Here, the positive number means that the front side of the prism has larger angle than 90deg for the air side. (i.e. positive number = facing up)
- The RoC of the curved mirrors is 2.5m. Therefore, roughly speaking, 83arcsec corresponds to ~1mm beam spot shift. The requirement is 30 arcsec.
- The A prisms tend to have positive and small angle deviations while the M prisms to have negative and large (~50arcsec) angle deviations.
- The consistency: The measurements in 2013 and 2019 have some descrepancy but not too big. This variation tells us the reliability of the measurements, say +/-30arcsec.

Setup

- The photos of the setup is shown as Attachments 3/4/5. Basically this follows the procedure described in Sec 2.2.2 of T1500060.
- The autocollimator (AC) is held with the V holders + posts.
- The periscope post for the turning Al mirror was brought from Downs by Stephen.
- The turning mirror is a 2" Al mirror. The alignment of the turning mirror was initially aligned using the retroreflection to the AC. Then the pitching of the holder was rotated by 22.5deg so that the AC beam goes down to the prism.
- The prism is held on a Al mirror using the post taken from a prism mount.
- If the maximum illumination (8V) is used, the greenish light becomes visible and the alignment becomes easier.
- There are two reflections 1) The beam which hits the prism first, and then the bottom mirror second, 2) The beam which hits the bottom mirror first and then the prism second. Each beam gains 2 theta compared to the perfect retroreflection case. Therefore the two beams have 4 theta of their relative angle difference. The AC is calibrated to detect 2 theta and tells you theta (1div = 1 arcmin = 60 arcsec). So just read the angle defferencein the AC and divide the number by 2 (not 4).

Liyuan's scattering measurement for the A and C mirrors.

Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it format).

These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material while mechanically removing glue. It is also possible that there is systematic error between the two sets of measurements. I did not run any calculations of wedge ange or orientation on these data.

Note that cleaning of debonded PZTs involved mechanically separating glue from the planar faces of PZTs. The second image shows the razer blade used to scrape the glue away.

There were thick rings of glue where there had been excess squeezed out of the bond region, and there was also a difficult-to-remove bond layer that was thinner. I observed the presence of the thin layer by its reflectivity. The thick glue came off in patches, while the thin glue came off with a bit of a powdery appearance. It was hard to be certain that all of the thin bond layer came off, but I made many passes on each of the faces of the 2 PZTs that had been in the bonded CM assemblies. I found it was easiest to remove the glue in the bonded

I was anticipating that the expected 75-90 micron bond layer would affect the micrometer thickness measurements if it was still present, but I did not notice any irregularities (and certainly not at the 10 micron level), indicating that the glue was removed successfully (at least to the ~1 micron level).

I attempted to fit the data taken by Koji of the beam spot precession at the CCD in order to find the location of the curvature bottom in terms of its distance (d) and angle () from the centre of the mirror. This was done using the method described in a previous similar measurement  and Section 2.1.3 of T1500060.

Initially, I attempted doing a circle_fit on python as seen in Attachment 1, and even though more points seem to coincide with the circle, Koji pointed out that the more appropriate way of doing it would be to fit the following function:

since that would allow us to measure the angle more accurately; is the anti-clockwise measured angle that the curvature bottom makes with the positive x direction.

As seen on the face of the CCD, x is positive up and y is positive right, thus, plotting it as the reflection (ref. Attachment 2) would make sure that  is measured anti-clockwise from the positive x direction.

The distance from the curvature bottom is calculated as 

r: radius of precession on CCD screen (value obtained from fit parameters, uncertainty in this taken from the std dev provided by fit function)

R: radius of curvature of the mirror 

L: Distance between mirror and CCD

R = 2.575  0.005 m (taken from testing procedure doc referenced earlier) and L = 0.644  0.005 m (value taken from testing doc, uncertainty from Koji)

	d (mm)	(deg)
C7	0.554  0.004	-80.028  0.005
C10	0.257  0.002	-135.55  0.02
C13	0.161  0.001	-79.31  0.06

Using the measurements of PZTs 12,13 taken by Stephen, I estimated the wedging angle and orientation following Section 2.3.1 of T1500060. The results can be found in Attachment1 and is summarised as follows.

For PZT 12, PZT 13 respectively:

Avg. height = 2.0063 mm, 2.0035 mm

Wedge direction (from the same direction as in the doc: positive right) = 120 deg, 120 deg

Wedge angles = 45.8 arcsec, 30.6 arcsec

This was done assuming that the measurements were taken uniformly at intervals of 60deg along the inner rim of the PZT. The diameter (2r) of the inner rim, according to T1500060, is 9mm. The measured heights were fitted with the function

as depicted in Attachment2 to find wedging angle and orientation .

Aim: To find the combinations of mounting prism+PZT+curved mirror to build two PZT sub-assemblies that best minimises the total vertical beam deviation.

(In short, attachment 1 shows the two chosen sets of components and the configuration according which they must be bonded to minimize the total vertical angular deviation.)

The specfic components and configuration were chosen as follows, closely following Section 2.3.3 of T1500060:

Available components:

Mounting prisms: 1,2,12,14,15 (Even though there is mention of M17 in the attachments, it can not be used because it was chipped earlier.)

PZTs: 12,13

Curved mirrors: 10,13

Method:

For a given choice of prism, PZT and mirror, the PZT can be placed either at 0deg or 180deg, and the mirror can rotated. This allows us to choose an optimal mirror rotation and PZT orientation which minimises the vertical deviation.

Total vertical angle 

 was measured by Koji as described in elog 369.

,              are the wedge angle and orientation respectively and were measured earlier and shown in elog 373 . 

,               The measurement of the location of the curvature bottom (d, ) of the mirrors is shown in elog 372 . The optimal  is to be found.

These steps were followed:

1. For every combination of prism, PZT, and mirror, the total vertical deviation was minimized with respect to the angle of rotation of the curved mirror computationally (SciPy.optimize.minimize). The results of this computation can be found in Attachment 2: where Tables 1.1 and 2.1 show the minimum achievable deviations for mirrors C10 and C13 respectively, and Tables 1.2 and 2.2 show the corresponding angle of rotation of the mirrors  .
2. From the combinations that show low total deviations (highlighted in red in Attachment 2), the tolerances for 5 arcsec and 10 arcsec deviations with mirror rotation were calculated, and is shown in Tables 1.3, 1.4, 2.3, 2.4 of Attachment 2.
3. While calculating the tolerances, the dependence of the vertical deviations with rotation were also plotted (refer Attachment 3).
4. Two sets from available components with low total deviation and high tolerance were chosen. 

Result:

These are the ones that were chosen:

1. M14 + PZT13 at 0deg + C13 rotated by 169deg anticlockwise (tot vertical dev ~ -3 arcsec)
2. M12 + PZT12 at 0deg + C10 rotated by 88deg clockwise (tot vertical dev ~0 arcsec)

The method of attaching them is depicted in Attachment 1.

[Stephen, Shruti, Koji]

We worked on the gluing of the PZT sub-assy (#9 and #10) along with the designed arrangement by Shruti (OMC ELOG 374).

The detailed procedures are described in E1300201 Section 6.2 PZT subassembly and Section 7.3 EP30-2 gluing.

We found that the PZTs, which were debonded from the previous PZT sub assy with acetone, has some copper wires oxidized. However, we confirmed that this does not affect the conductivity of the wires, as expected.

The glue test piece cooked in the toaster oven showed excellent curing. GO SIGNAL

Stephen painted the PZT as shown in Attachment 1.

The fixtures were closed with the retaining plate and confirmed that the optics are not moving in the fixtures.

At this point, we checked the situation of the air-bake oven. And we realized that the oven controller was moved to another vacuum oven and in use with a different setting.

Stephen is going to retrieve the controller to the air bake oven and test the temp profile overnight. Once we confirm the setting is correct, the PZT sub assys will be heat cured in the oven.  Hopefully, this will happen tomorrow. Until then, the sub-assys are resting on the south flow bench in the cleanroom.

Friday: [Stephen, Koji]

As the oven setting has qualified, we brought the PZT assys in the air bake oven.

Monday: [Stephen, Shruti, Koji]

We brought the PZT assys to the clean room. There was not bonding between the flexture and the PZT subassy (Good!). Also the bonding o at each side looks completely wetted and looks good. The package was brought to the OMC lab to be tested in the optical setup.

[Stephen, Koji]

20 glass beamdumps were bonded at the 40m cleanroom.

Attachment 1: We had 20 fused silica disks with a V-groove and 40 black glass pieces
Attachment 2: The black glass pieces had (usual) foggy features. It is well known to be very stubborn. We had to use IPA/acetone and wiping with pressure. Most of the feature was removed, but we could still see some. We decided to use the better side for the inner V surfaces.
Attachment 3: EP30-2 expiration date was 1/22/2020 👍. 7.66g of EP30-2 was poured and 0.38g of glass sphere was added. Total glue weight was 8.04g
Attachment 4: Glue test piece was baked at 200F in a toaster oven for ~12min. It had no stickiness. It was totally crisp. 👍👍👍
Attachment 5: Painted glue on the V-groove and put the glass pieces in. Then gave a dub of blue at the top and bottom of the V from the outside. In the end, we mostly had the glue went through the V part due to capillary action.
Attachment 6: The 20 BDs were stored in stainless vats. We looked at them for a while to confirm there is no drift and opening of the V part. Because the air bake oven was not available at the time, we decided to leave the assys there for the room temp curing, and then later bake them for the completion of the curing.
 

[Camille, Koji]

Began setting up fiber assembly for OMC testing:
-Aligned fiber mount to maximize transmission through fiber
-Adjusted polarization at output of fiber to minimize s-polarized output.

Power measurements:
fiber input: 56.7 mW
fiber output:43.2 mW
s-polarized output: 700 uW

Fiber matching: 43.2/56.7 = 76%
S/P-pol ratio 0.7/43.2 = 1.6%

[Camille, Koji]

Friday, Nov 11th, 2022

Setting up OMC #1 for transmission measurements:

The laser beam was aligned to the OMC cavity. The OMC cavity was locked and the transmission measurements were recorded.

The measured total optical loss of the OMC was

1st:   0.015 +/- 0.003
2nd: 0.085  +/- 0.005
3rd:  0.0585+/- 0.0008
4th:  0.047  +/- 0.002

In avegrage the estimated loss is
Loss = 0.055 +/- 0.014

This is unchanged from the measurement at LLO after the FC cleaning
Loss = 0.053 +/- 0.010

Monday, November 14, 2022

Camille and Koji did a "deep cleaning" of OMC#1:
1) Applied First Contact to the mirror surfaces. Removed first contact after ~10 minutes.
2) Acetone scrub of the mirror surfaces with a cotton swab.
3) Applied First Contact again. Removed after ~10 minutes. We left the FC paint on for the work on Thu.

The foggy spot on the input mirror was unchanged after the first round of First Contact. But the foggy spot came off during the acetone scrub.

[Camille, Koji]

The damaged black glass was removed from the OMC breadboard leaving the glass base.
The black glass pieces were bonded very tightly on the FS base with EP30-2. The apparent amount of the bond was not so much but it was such hard that removal by hand was not possible.
We decided to give drips of Acetone on the base hoping the gradual dissolving of EP30-2. Using a knife edge, the "filets" of the bonds were removed, but the BD was still tight.

By wedging the black glass-black glass bonding with the nife edge, the left side (the directly damaged one) was taken off from the structure leaving a tiny fragment of the glass on the base.

The remaining one was even stronger. We patiently kept dripping Acetone on the base and finally, the black glass piece was knocked off and removed from the base.

Attachment 1: The base right after the black glass removal.

Attachment 2: The black glass pieces were stored in a container with Al foil + clean cloth bed. The damaged and fogged surfaces faced up.

Attachment 3: The zoom-in shot of the black glass pieces.

Attachment 4: The base was wiped with Acetone and cleaned with FC. We will bond another BD assembly on the base, presumably using the UV epoxy.

[Camille, Koji]

Photo of the BS1 AR cleaning process

Attachment 1: Before cleaning. Foggy surface is visible.

Attachment 2: After FC cleaning. The structure of the deposited material is still quite visible.

Attachment 3: Acetone scrubbing. Cotton Q-tip was used so that the stick does not melt with acetone.

Attachment 4: After acetone scrubbing. Nicely clean!

Acetone scrubbing was applied to HR/AR of BS1, FM1, FM2, BS2, and HR of CM1 and CM2. (total 10 surfaces)
Then final FC paint was applied to these 10 surfaces.

We'll come back to the setup on Thu for FC peeling and loss measurement.

[Camille, Koji]

- Removed the first contact we left on Monday.

- Measured transmission (Set1) Very high loss! Total optical loss of 18.5%! Observation with the IR viewer indicated that CM1 has bright scattering. We suspencted a remnant of FC.

- Applied the second FC on the four cavity mirrors. This made the CM1 sport darker.

- Measured the transmission (Set1~Set3). We had consistent loss of 4.2~5.0%. We concluded that this is the limitation of this OMC even with the cleaning.

Conclusion on the cleaning of OMC #001

- After a couple of first contact cleaning trials and deep cleaning, the total loss was measured to be 0.045+/-0.004.
  This indicated a slight improvement from the loss measured at LLO before any cleaning (0.064+/-0.004).
  However, the number did not improve to the level we marked in 2013 (0.028+/-0.004).

- This loss level of 4.5% is comparable to the loss level of OMC #3, which is currently used at LHO.
  Therefore, this OMC #1 is still a useful spare for the site use.

- Some notes / to-do regarding this unit:
  1) The beam dump with melted black glass was removed. A new beam dump needs to be bonded on the base.
  2) The connector bracket still needs to be replaced with the PEEK version.
  3) The PZT of CM1 has been defunct since 2013. Combining LV and HV drivers is necessary upon use at the site. (LLO used to do it).

• Cleaning is based on this: LIGO-E1200326-v2
• Your effort will look more like this:  LIGO-T1800350-v1

Another set of FC cleaning was applied to FM1/FM2/CM1/CM2 and SM2. Some FC strings are visible on SM2. So I decided to clean SM2 as well as the cavity mirrors close to SM2 (i.e. FM2 and CM2)

As a result, the bright scattering spot on CM1 is now very dim. And the loss was reduced to 4.0%. This is 0.4% better than the value before the water cleaning.

It'd be interesting to repeat the water cleaning, at least on FM1. FM1 is the closest cavity mirror to the beam dump damaged by the high-power laser pulse.
Maybe we should also clean the AR side of FM1 and BS1, as they were right next to the damaged beam dump. It is not for the loss but for reducing the scattering.

The second trial of the water scrub

A bright scatter is visible on FM1, so I tried water scrub on FM1. This time, both surfaces of FM1 and both surfaces of BS1 were cleaned.

Smaller Vectra swabs were used for the scrub. Then the water was purged by IPA splashed from a syringe. Right after that FC was applied.
This was a bit messy process as the mixture of water/IPA/FC was splattered on the breadboard.
Nevertheless, all the mess was cleaned by FC in the end.

The transmission measurements are shown in Attachment 1, and the analyzed result is shown together with the past results.

The 2nd water scrub didn't improve the transmission and it is equivalent to the one after the two times of deep cleaning.
I concluded that the water scrub didn't change the transmission much (or at all). We reached the cleaning limit.

[Camille Koji]

We started buikding the OMC #4.

• Removed OMC #1 from the optical setup and placed it at a safe side on the optical table/
• Fixed OMC #4 in the optical setup
• Cleaned the OMC cavity mirrors
• Placed the OMC cavity mirrors
  • FM1: A1
  • FM2: A3
  • CM1: PZT #11
  • CM2: PZT #12
• Aligned the beam to the cavity
• Locked the cavity on TEM00
• Finely aligned the beam to the cavity

[Camille Koji]

We quickly measured the basic parameters of the OMC as is.

=== FSR ===
Used the technique to find a dip in the transmission transfer function (TF) with offset locking + phase modulation. The FSR was 264.79003MHz = The cavity length of 1.13219 [m] (requirement 1.132+/-0.005 [m])

=== TMS ===

Used the technique to find the peaks in the trans TF with phase modulation + input misalignment + trans PD clipping.
TMS_V: 58.0727 / TMS_H: 58.3070 => TMS/FSR V:0.219316 H:0.220201

This makes the 9th-order modes nicely avoided (Attachment 1). A slightly longer FSR may makes the numbers close to the nominal.

=== Spot positions ===

The image/video capture board turned out not functional with the new Apple silicon mac. We decided to use a small CCD monitor and took a photo of the display.

All the spots are within the acceptable range. The scattering on CM2 was particularly bright on the CCD image and also in the image with the IR viewr.

The spot on FM1/2 are right at the expected location. The spot on CM1 is 0.5mm low and 0.7mm inside (left). The spot on CM2 is ~0.25mm too high and 0.3mm outside.
(Attachment 2, a small grid is 1 mm/div)

== Transmission ==

We made a quick simplified measurement (Attachment 3).

Assuming the reflectivity of the matched beam to be ~0, the mode matching is M=1-(59.2e-3-(-6.5e-3))/(3.074-(-6.5e-3))=0.979
==> The power of the coupled mode is M x 21.28mW = 20.83 mW
The measued transmission was 19.88 mW
==> The OMC transmission (total) was 0.954 (4.5% loss)

This number is not too bad. But the spot on CM2 has too bright scattering. Next week, we want to check if swapping CM2 may improve the situation or not.

[Camille Koji]

We replaced CM2 with a PZT mirror subassembly serialized by PZT "13" (Attachment 1).
This made the transmission increase to 96.x%. Therefore the quick measurement of FSR and TSM were done. Also more careful measurement of the transmission was done.

Next time

== Alignment ==

• CM2 was replaced from PZT "12" to PZT "13".
• The resulting position of the cavity spot were all over 1mm too "+" (convention T1500060 Appendix C).
• So we decided to rotate CM2 by 1mrad in CW. This was done with (-) micrometer of CM2 "pushed" by 20um (2 rotational div).
• The resulting spot positions were checked with CCD. (Attachment 2). The spot positions seemed to be within +/-1mm from the center as far as we can see from the images. (good)
• CM2 spot looks much darker. CM1 spot is almost invisible with a CCD and also an IR viewer. FM1/2 spots were nominal bright level. (Looks OK)

== Quick measurement of the transmission ==

Transmission: 20.30 mW
Reflection Voltage (locked): 65.0 mV
Reflection Voltage (unlocked): 3.094 V
Reflection Voltage (dark): -6.5 mV
Incident Power: 21.64 mW

---> Mode matching 1-0.023 / Pcoupled = 21.14 / OMC Transmission 0.96

96% transmission is not the best but OK level. We decided to proceed with this mirror combination.

== Quick measurement of FSR/TMS ==

FSR: 264.7837MHz
TMS_V = 58.2105MHz
TMS_H = 58.1080MHz

The HOM structure (with PZT Vs = 0) is shown in Attachment 3. 9th order modes look just fine. The excplicit coincidence is 19th order 45MHz lower sideband. (Looks good)

== Transmission measurement ==

The raw measurements are shown in Attachment 4. The processed result is shown in Attachment 5.
We found that data set 2 has exceptionally low transmission. So we decided to run the 4th measurement excluding the set 2.

Over all OMC loss
Set1: 0.029 +/- 0.014
Set3: 0.041 +/- 0.0014
Set4: 0.038 +/- 0.001

--> 0.036 +/- 0.004
(0.964 Transmission)
 

[Camille, Koji] Log of the work on Dec 15, 2023

The vertical and horizontal TMSs for OMC #4 were measured with the PZT voltages scanned from 0V to 200V.

We concluded that this alignment nicely avoids the higher-order mode structure up to ~19th order. We are ready for the cavity mirror bonding.

The RF transfer functions to the trans RF PD from the modulation on the BB EOM were taken with the presence of the vertical misalignment of the incident beam and the vertical clipping of the beam on the RFPD.

The typical measurement results and the fitting results are shown in Attachments 1/2.

The TFs were taken with the voltage 0, 50, 100, 150, and 200V applied to PZT1 while PZT2 were left open. The measurement was repeated with the role of PZT1 and PZT2 swapped.

The ratio between the TMS and FSR was evaluated for each PZT voltage setting. (Attachment 3)

When the PZTs are open, the first coincident resonance is the 19th-order mode of the 45MHz lower sideband. (Attachment 4)

When the PZT2 voltage is scanned with PZT1 kept at ~0V, no low-order sidebands come into the resonance (Attachment 5) until the PZT1 voltage is above 100V.

We found that the high voltage on PZT1 misaligns the cavity in yaw and the spot (presumably) moves to an undesirable area regarding the cavity loss.
This does not happen to PZT2. Therefore the recommendation here is that the PZT2 is used as the high voltage PTZ, while PZT1 is for the low voltage actuation.

[Koji, Camille]

We worked on the bonding of the flat mirrors for the OMC cavity with UV epoxy.

- Prepared the UV illumination setup. Cleaned up the table a bit to spare some space for the illuminator.
- Checked the output power of the illuminator. The foot pedal worked fine. The timer was set to be 10s. The UV output from the fiber was nominally 6W. This is after some warming up for ~1min. (Checked the output power continuously with the UV power meter.)

- Checked the cavity alignment / FSR / TMS - it looked good at this moment

- We confirmed that the UV epoxy has an expiration of July 3, 2023. The bond capsule was brought from Downs right before the work started, and thawed at the lab.

FM1 bonding

- The bottom of FM1 and the breadboard were cleaned. Cleaning with lens cleaning paper + IPA remained a few specks of dust on the surface. We decided to use Vectra swabs to wipe the breadboard surface. This worked pretty well.
- Applied a tap of UV epoxy to FM1 and placed it on the template. The optic was constrained by a retainer clip.
- We found that the spot positions were significantly moved. Probably FM1 was not well touching the template before. We tried to recover the previous optical axis by aligning CM1 and CM2.
- Here is the tip: align the beam on CM1 at the desired spot. Move CM1 to bring the spot on CM2 to the desired spot. CM2 is aligned to have TEM00 as much as possible.

- We recovered reasonable spots on the mirrors. Measured the FSR and TMS (vertical and horizontal) to be 264.73MHz, 58.18MHz, and 58.37MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.

- Gave UV illumination 10s x 2. Confirmed that the mirror is rigidly bonded.

FM2 bonding

- Continued to bond the other flat mirror. The same process was repeated.
- The bottom of FM2 and the breadboard were cleaned.
- Applied a tap of UV epoxy to FM2 and placed it on the template. The optic was constrained by a retainer clip.
- Measured the FSR and TMS (vertical and horizontal) to be 264.7925MHz, 58.15MHz, and 58.3725MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.

- Gave UV illumination 10s x 2. Confirmed that the mirror is rigidly bonded.

SM1/BS2/BS3 bonding

- Continued to bond some less important mirrors.
- SM1 was placed on the template with the same step as above. BS2 (for QPD) and a dummy QPD housing were also placed just to check if the optical axis has any inconsistency. The good beam alignment on the QPD housing was confirmed.
- Applied a bond to SM1 and blasted the UV (20s)
- Applied a bond to BS2. Checked the alignment on QPD1 again. It looked good. UV illumination was applied.

- Placed BS3 to the cavity transmission. A dummy DCPD housing was placed at the reflection side of BS3. There was no inconsistency with the beam alignment.
- The UV illumination was applied (20s).

Optic Inventory

Breadboard: #6
BS1: E6
FM1: A1
FM2: A3
CM1: PZT ASSY #8 (M7+PZT11+C11)
CM2: PZT ASSY #11 (M14+PZT13+C13)
SM1: E9
BS2: B8
SM2:
SM3:
BS3: B6