Experiment basics

GENERAL RULES

1. Do not touch optic's surface with a hand, if it happened clean immediately (oils cause degradation of optics)
2. If you want to block a beam, use black paper, always block at half wave plates not on mirrors/lenses

LO = Local Oscilator

SWITCH ON PROCEDURE

MBR needs around 30 minutes to stabilize, so we start with it

1. Turn on the 2 Chillers and wait for them to stabilize (about 5 min, in the meantime everything else could be switched on)
2. MBR Power - switch key from standby to on
3. Wait for current to reach around 18A
4. Open the shutter
5. Wait until everything is locked (servo menu)
6. Switch to Power Level 2 (or 5W)
7. Switch on MBR scope (next to coherent), shows etalon and servo lock

1. Turn on cool & repump by flipping current switch to on and 3 scopes
2. Switch on Topica laser and scope, photodetectors (PD) (black box switch on back) and spectrum analyzer

Experiment preparation

look ListToDo.

1. Check cavity on MBR homodyne

Power on Cavity PD, Scope,Cavity SG & Amplifier. Might have to short the cable on top of scope

Check to make sure there's only one peak Make sure purple line stays above GND! Switch off Cavity SG & Amplifier

HOMODYNE'S ALIGNMENT PROCEDURE

TOPTICA

Block homodynes and photodetectors

Make sure only toptica is going to the fiber

Check Max power of LO, should be at least 10 mW

Check power of signal beam

Make Toptica signal 200+ µW using 1 HWP and 1 QWP

Block signal and match LO to be the same power looking on scope

Connect pink laptop to black camera, switch on power for the Camera using external power supply (12 V)

Draw line around the LO (near and far field, without lens/with a lens) using measure (right click to end) Near field = big blob, lens down Far field = small blob, lens up

Make sure location of signal and LO are the same, switch between near and far field and adjust signal(or LO) mirrors accordingly.

Turn on Toptica Signal Generator Open both signal and LO, make a central pulsing on the camera in near field.

Block the Camera! Block signal Send 10mW LO to homodynes and turn Homodyne Power on

Connect red cable (from colorful Scope) to homodyne Be sure both sides are gettin the same power (~5mW each) Put green line on ossiliscope to ground (10mV divisions) using half wave plate right before homodynes Make the beam from the right a minimum and beam from the top a maximum, ground again if needed.

Turn off Homodyne Power

MBR Block homodynes and photodetectors

Alignment of MBR's homodyne

1. Make sure only MBR is going into the fiber (block toptica, MBR+80MHz, yellow laser)
2. From the front side of the optical table(closer to door) make LO as low as possible, around 1.2mW.
3. From the same side (closer to door), make signal of the same power (adjust only HWP #4->#3->#2, in this sequence)

1. Connect pink laptop to blue camera, power on using button on the camera (red led will shine)
2. Run S-eye program and choose YW2310camera

If two beams are far away follow rough alignment procedure:

1. Block signal and draw line around the LO in the near and far field (flip lens to get far-field) using measure (right click to end)

//Near field = big blob, lens down //Far field = small blob, lens up

1. Make sure location of signal and LO are the same, switch between near and far field and adjust signal mirrors accordingly.

After rough alignment is done, we do fine adjust:

1. Turn on MBR Signal Generator.
2. Open both signal and LO
3. For low frequencies make a central pulsing(shrink and expand) on the camera for near field (use only near-field mirror)
4. check photo-detector and maximize interference with a far-field mirror

in detail, first make the same power on photo-detector from LO and signal.

1. block both signal and LO to find ground.
2. unblock signal to make it fixed (two divisions above the ground)
3. block signal and unblock LO to make same divisions(two) as the signal.
4. unblock both of them and you should see interference.
5. repeat procedure until required visibility is obtained (>90 %)

1. Make sure that signal an LO HWP (small HWP) are back in position, so all the power goes to HD
2. Block the Camera!
3.  !!! Block signal and flip PBS!
4. Increase LO power to 10mW
5. Connect homodyne to scope (Connect red cable from colorful oscilloscope), and turn power on
6. Be sure both sides are getting the same power (~5mW each)
7. Put green line on oscilloscope to ground (down to 10mV divisions) using half wave plate right before homodynes
8. Make the beam from the right a minimum and beam from the top a maximum,
9. ground again with HWP if needed

Turn off HDs -> 1. Diode laser Spectroscopy

1.1 Cooling spectroscopy
1.2 Repumper spectroscopy

2. Cavity alignment

2.1 Check cavity on PD

1. Homodyne MBR:

1.1  Balance of LO
1.2  Interference visibility >85% with PD
1.3 Check peaks on Spectrum Analyser

2. Homodyne Toptica:

2.1 Balance of LO
2.2 Maximize LO power (9.5 mW total)
2.3  Interference visibility >85% with PD

3. Fibers:

3.1 Maximize coupling for Toptica & MBR to blue fiber
3.2 Maximize coupling to yellow fiber

4. Waveplates

4.1 Waveplate for SPCM 258
4.2 Waveplate for Homodyne 304

5. MBR Spectroscopy

6. Phase lock

6.1 Check the power of MBR and Toptica going to PD (3mW each)
6.2 RF signal on a Spectrum Analyser should be > -10dBm
6.2 Set frequency difference to 6.864 GHz

7. Experiment

7.1 Get the MOT
7.2 Overlap (can be seen on MBR Homodyne if MBR+88 MHz is in resonance with F=2-> F'=2 )
7.3 Check Raman scattering on SPCM (3 kHz for MOT ambient light, 9-22 kHz when Write beam is on)