HOME SBOX THOMX MINICAV Utilities
SBOX orders SBOX installation SBOX commissioning SBOX control command
  Status of commissioning, report also here plots are reports.  Not logged in ELOG logo
Entry   2 Mirror Setup @ 216.6 MHz, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 20220706_Setup.jpgScreenshot_2022-07-06_1_181116.pngFinesse_Fit.jpg00mode.jpg00mode_diameter.jpg
    Reply   2 Mirror Setup @ 216.6 MHz, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 00mode.jpg00mode_diameter.jpgScreenshot_2022-07-08_0_164115.pngSlide1.JPGSlide2.JPG
       Reply   2 Mirror Setup @ 216.6 MHz, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics Screenshot_2022-07-08_2_182405.png
          Reply   FSR change & Finesse Measurements , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 00mode.jpg00mode_diameter.jpg00mode_diameter_fit.jpg
             Reply   FSR change & Finesse Measurements , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics Screenshot_2022-07-11_1_204143.pngScreenshot_2022-07-11_0_203646.png
                Reply   FSR change & Finesse Measurements , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 
                   Reply   Installation of D-shaped mirror / Alignment, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 
                      Reply   Installation of D-shaped mirror / Alignment, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 
    Reply   2 Mirror Setup @ 216.6 MHz, posted by Manar Amer at Optical room about lasers and optics manip2miroirs.pptx2mirror_plan_shperical_beam_size.png
Message ID: 112     Entry time: Tue Jul 12 10:19:30 2022     In reply to: 111     Reply to this: 113
 Author: Manar Amer 
 Status: Fixed 
 Type: report 
 Category: lasers and optics | detectors and electronics 
 Location: Optical room 
 Title: FSR change & Finesse Measurements  

Yesterday evening the cavity was Vacuum pumped up to pressure of 5.5*10^-2 and locked 

changed FSR to be 216.662 MHz and alignment a little and measured the Finesse

in Vacuum we have average Finesse = 30341.6265

FWHM (KHz) = 7.0592
Finesse = 30692.1961

FWHM (KHz) = 7.2186
Finesse = 30014.556

FWHM (KHz) = 7.1051
Finesse = 30493.7635

FWHM (KHz) = 7.1079
Finesse = 30481.9812

FWHM (KHz) = 7.1413
Finesse = 30339.2695

FWHM (KHz) = 7.1624
Finesse = 30249.776

FWHM (KHz) = 7.0239
Finesse = 30846.2719

FWHM (KHz) = 7.2614
Finesse = 29837.6477

FWHM (KHz) = 7.1935
Finesse = 30119.1768

 

Manar Amer wrote:

The FSR of the 2 mirror (plan-spherical) Cavity was adjusted from 210 MHz to reach 216.643 MHz

it was done by having two reference irises, one at the injection point and one at the reflection 

then changing the position of injection plan mirror to slightly closer distance and monitoring the reflection on the oscilloscope to be max.

The cavity modes were still seen, and we had to only improve the injection alignment after.

Me and Ronic locked in air and measured the Finesse, which was bigger by ~ 20%

average Finesse = 30208.53614

FWHM (KHz) = 7.0179
Finesse = 30869.9522

FWHM (KHz) = 7.1257
Finesse = 30403.005

FWHM (KHz) = 7.1287
Finesse = 30390.4014

FWHM (KHz) = 7.2884
Finesse = 29724.5531

FWHM (KHz) = 7.3055
Finesse = 29654.769

 

 

Manar Amer wrote:

Update for Finesse measurement, The cavity was put under vacuum ~ 1.1*10^-1 mbar

and the alignment and coupling improved.

FSR = 210.1 MHz

Average Finesse = 25686.46222

 FWHM (KHz) = 8.2387
Finesse = 25501.5659

FWHM (KHz) = 8.2028
Finesse = 25613.2858

FWHM (KHz) = 8.0978
Finesse = 25945.3289

FWHM (KHz) = 8.1744
Finesse = 25702.3142

FWHM (KHz) = 8.1847
Finesse = 25669.8163

Concluded from Ronic's calculations, this could be the maximum finesse we might be able to obtain with this setup

with Gain ~ 8000

On Monday we adjust the frequency to match 2160.66 MHz and lock the Pulsed,

at the same time start we start with the CELIA amplifier.

 

 

 

Manar Amer wrote:

The cavity was realigned using irises instead of pinholes, gave a better alignment.

The inside of the box, the spherical and the injection mirror were cleaned and placed back inside the box.

we see beating of fundamental mode, previously at the transmission point we placed a wedge to split the beam which resulted in an elliptical mode

we removed it and placed a very thin beam splitter, the beam is circular now.

The cavity was locked in air at a coupling of ~ 60-70 %

Finesse and line width measured five readings with a Finesse average 25095.08884  of a Gain ~ 8000

FWHM (KHz) = 8.2928
Finesse = 25323.0544

FWHM (KHz) = 7.9202
Finesse = 26514.4395

FWHM (KHz) = 8.5834
Finesse = 24465.8636

FWHM (KHz) = 8.4571
Finesse = 24831.2419

FWHM (KHz) = 8.6275
Finesse = 24340.8448

Theoretical and expected Finesse for the 2 mirror setup with the losses is calculated by Ronic for comparison between four and 2 mirror setup.

 

 

Manar Amer wrote:

The SBox cavity setup was changed to have only 2 mirrors M1 plane and M2 spherical, both from ThomX

Distance between the mirror ~ 72 cm , increased from 70 cm to take into account the thickness of the ThomX mirrors

Two lenses (300 mm @ 50 cm , 200 @ 104 cm) were placed to have the beam radius ~ 0.55 mm.

The cavity was locked with a coupling of 60 %, for Finesse measurement the sweep was taken over 100 KHz of 2 seconds.

FSR ~ 210.00 MHz, line width ~ 8.56 KHz, Finesse ~ 24 500 .

 

 

 

 

 

 

Attachment 1: Screenshot_2022-07-11_1_204143.png  36 kB  | Show | Show all
Attachment 2: Screenshot_2022-07-11_0_203646.png  42 kB  | Show | Show all
ELOG V3.1.4-395e101