Comment to T120#1 (Click here to view original report: 3520)

z edges seem to be at 39 and 90 mm. z_center = 64.5mm

The DC is still slowly decreasing with increasing z from aboiut 5 to 3 V... depending on measurements results I might aligned DC to specific z.

map at z_center : Fri, Apr 5, 2024 1-13-49 PM.txt

T120#1

Installed the 30mm diameter , 120mm thickness sample (1623048-4) called 120#1

I moved z_IU to 18.51mm

pink tape is at bottom towards IU

the sample is held roughly t its central thickness position to limit its tilt that could misaligned the beam on the sensors.

in that configuration, the DC is still varying between about 2 to 5V while changing z from 20 to 120mm...

Pt = 27.0mW ; Pin = 31.3mW

Pt = 4.72W

long z scan at x,y centers : Fri, Apr 5, 2024 11-52-43 AM.txt

OPO replacement PZT

During Yuhang's Christmas visit we attempted to replace the TAMA OPO. It was aligned but could not take a scan signal - the high voltage driver would just zero out then turn off, suggesting that the PZT on the input mirror is broken. I have to disassemble the "new" OPO and replace the PZT. The connectors for the PZT are soldered to our Dsub box - the OPO was kept in a zip lock bag during soldering. The Dsub box connects the OPO PZT and temperature actuator wires and puts them on a Dsub port, which then plugs into the controls of TAMA electronics.

I measured the output power vs current of the Coherent Mephisto laser in the ATC cleanroom used for the Taiwan and Korea experiments, using both standard Thorlabs (up to 500 mW) and thermal (several W) power meters. I fixed the laser temperature at 24.21 C. The output of the laser is about 47 mW at 0.8 A, up to 1.17 W at 1.5 A (it can go higher but I stopped here).

In the leadup to the Taiwan/Korean Christmas visit I designed the input beam path to: 1) inject collimated infrared p-polarized light into the Taiwan fiber SHG (~2.3mm diameter), and 2) send a small amount of s-polarized light to the Korea Faraday isolator. The actual beam profile was measured by Yi Ru Chen. There is a HWP and PBS setup which transmits p-pol to Taiwan (SHG) and reflects s-pol to Korea (Faraday). I set up to reflect a small amount of s-pol to Korea. At 0.800 A laser current, 30 mW reaches the HWP, with 3.8 mW s-pol going to Korea and 25.1 mW p-pol going to Taiwan. 3.8 mW is reasonable for our OPO characterization, it's about what we used last time. There is plenty of room to adjust up or down anyway, and since the beam size going to the OPO is around 20 micron the intensity is quite dangerous even at 4 mW.

I constructed a beam path to travel across the indicated line on the breadboard, cutting off from the Korean FI path (they aren't going to come back until October). The beam travels horizontally at 75mm, the height of the OPO crystal. In a previous iteration of this test we had a rotation stage below the OPO for rotation alignment but we found it to be unnecessary. It is better to set a beam at constant height, rough align the OPO case by hand then fine align with steering mirrors. We also did it this way in TAMA twice during the replacement/re-replacement episode and it works fine, could achieve > 90 % mode matching quickly. The beam path should be collimated at 2.3mm for quite some distance, so based on this I can set up a system to send the beam through an EOM. The lenses we originally used to mode match to the OPO (40 and 75 mm) are in the ATC unused.

I took a soldering iron from the elec shop and the Beam Master beam profiler from birefringence compensation. For other instruments the ATC KOACH cleanroom now has the 8 GHz function generator, PZT high voltage driver, Thorlabs temperature controller, resonant EOM, oscilloscope, old TAMA spectrum analyzer, PDA05CF2 RFPD, DET10N/M biased PD. We can scan the PZT of the reassembled OPO to test mode matching but to lock I would need another function generator or mokulab. The CCD and TV screen were taken to speed meter but maybe I don't need them. Locking is probably unnecessary though. It seems based on previous calculations that, due to the short length and low finesse, the storage time is too short to determine internal loss from cavity ring-down, even with a nanosecond scale off-switch. We will need to wait until the sqz/antisqz measurement to really see the optical loss.

Comment to T70#3 (Click here to view original report: 3514)

z = 73.75mm, Pt = 4.87W : Thu, Apr 4, 2024 10-28-30 PM.txt

Comment to T70#3 (Click here to view original report: 3514)

z = 53.75mm, Pt = 4.85W : Thu, Apr 4, 2024 6-30-57 PM.txt

Comment to T70#3 (Click here to view original report: 3514)

edges at 48.5 and 79 mm : z_center = 63.75 mm

map at z_center : Thu, Apr 4, 2024 2-23-48 PM.txt

T70#3

I installed the 30mm diameter; 70mm length, 4/6 sapphire (T70#3) with pink tape at bottom towards IU.

Realigned DC

Pt = 26.3mW ; Pin = 30.7 mW

Pt = 4.87W ; long z scan (as for all previous z scan at x,y center ie 327,119 mm) : Thu, Apr 4, 2024 11-59-20 AM.txt

Comment to t70#2 (Click here to view original report: 3509)

z = 66.5mm, Pt = 4.83W : Wed, Apr 3, 2024 9-59-53 PM.txt

Comment to tidying up electronics (Click here to view original report: 3508)

I swapped the R and L cables for the OPO mixer.

During this process a cable for CC PLL monitor was quite damagedd but it's a bit tedious to replace alone and not priority for now so I left it as is for now.

I finalized the new box connections and little cable tidy up.

I could lock SHG after changing the DDS1 DAC1 phase from 20 to 240deg and the servo gain from 0.9 to 0.1 to avoid ringing. I measured about 30% HOM still present and 235mW of green produced.

The MZ/GRMC are heavily misaligned and I'll recover them tomorrow.

Manipulation 2D polarization

I choose and align two different lenses in order to extend my initial beam : - 1 inch ; f=25.4mm . - 2 inches ; f=750mm.

I've installed my two supports, made using a 3D printer, for the LCD (from the screen of a monitor).

The beam of the setup is too low to path throw the LCD screen. So I added to more mirrors (2 inches) to get the beam higher, and I started to align them.

Comment to t70#2 (Click here to view original report: 3509)

z = 46.5m, Pt = 4.73W : Wed, Apr 3, 2024 5-28-27 PM.txt

t70#2

Installed T70#2 (30; 70 mm 5/6)

pink tape at bottom towardsiu

realigned DC

Pt = 27.4mW ; Pin = 31.5mW

long z scan Pt = 4.77W ; Wed, Apr 3, 2024 12-31-34 PM.txt

z edges at 36 and 77 mm : z_center = 56.5 mm

map at z_center : Wed, Apr 3, 2024 1-11-48 PM.txt

tidying up electronics

I finalized the mixers box and installed it in the bottom NIM rack.

A little issue is that the BNC mixers are a bit too large to close the box... However we still have quite some space in the NIM racks so I'll leave the box open for now.

I'm also taking this opportunity to change cables for more appropriate ones and passing them through the cable clamp.

One thing I'm not sure about is that OPO RF signal was sent to the 'L' port of one mixer which I thought was for LO..

I'll correct this.

aircon of central building to cool mode

Today I switched aircon of central building to cooling mode at 22degC.

Still need to be done for END.

Comment to 30mm ; 70 mm 6/6 (Click here to view original report: 3504)

z = 47 mm ; Pt = 4.82 W ; Tue, Apr 2, 2024 6-27-00 PM.txt

Comment to 30mm ; 70 mm 6/6 (Click here to view original report: 3504)

z = 67 mm, Pt = 4.81W : Tue, Apr 2, 2024 2-29-08 PM.txt

30mm ; 70 mm 6/6

this sample is t70#1.

Moved zIU to 40.01 mm

Pt = 25.5mW ; Pin = 30.0mW

There is definitely an issue with the holder : the sample is fixed by 2 set screws which can induce a slight tilt of the sample with respect to the input beam.... However there seems to exist a roll angle that compensate this...

Recentered DC with pink tape at bottom towards IU this time.

z scan with 4.81 W : Tue, Apr 2, 2024 10-17-23 AM.txt

z edges at 37 and 77 mm : center at 57mm

map at z_center : Tue, Apr 2, 2024 10-31-32 AM.txt

Comment to 30mm ; 50mmL : 6/6 (Click here to view original report: 3499)

z = 54mm, Pt = 4.85W  : Mon, Apr 1, 2024 11-58-05 PM.txt

this sample is t50#2

30mm ; 50mmL : 6/6

DC was quite misaligned after changing sample..

after realignment

Pt = 26.1mW ; Pin = 30.0mW

rotated HWP to 28deg : Pt = 4.82W

long z scan : Mon, Apr 1, 2024 9-05-41 AM.txt

z edges at 29.5 and 58.5 mm : z_center = 44 mm

Pt = 4.84W

map at z_center : Mon, Apr 1, 2024 10-26-52 AM.txt

after visit break Pt~4.9W

z = 34 mm : Mon, Apr 1, 2024 4-44-36 PM.txt

Comment to 30mm diameter sapphire absorption (Click here to view original report: 3497)

pt _ 4.65W

map at z_53 mm , Pt _ 4.65W; Sat, Mar 30, 2024 11-35-05 AM.txt

map at 33mm ' Sat, Mar 30, 2024 8-01-36 PM.txt