[Aritomi, Eleonora P., Matteo]

 

Today we recovered parametric gain by tuning of OPO temperature and alignment of green. To check parametric amplification clearly, green phase is scanned with 50 mHz, 3 Vpp. Measured parametric (de)amplification is

 

Amp: 6.32, De-amp: 0.112, without green: 0.308

 

Parametric gain is 20.5, which is good.

 

Current parameter:

p pol PLL frequency: 138 MHz

OPO temperature: 7.156 kOhm

 

Then we injected CC. We checked CC power before homodyne BS. It was 52 uW. Since CC power before OPO is 12mW, CC power before homodyne BS should be around 120 uW considering OPO transmission is around 1%. The discrepancy of CC power should be investigated.

 

CC error signal

Attached picture shows error signals of coherent control. Yellow one is OPO reflection and blue one is homodyne RF. Green phase is scanned with 100Hz, 1Vpp. The amplitude of the error signals are

OPO reflection: 11.8 mVpp

Homodyne RF: 61.6 mVpp

 

Squeezing with/without coherent control

We measured squeezing with/without CC. The attached graph shows squeezing with/without CC and shot noise without squeezing. The center frequency is 100kHz. Squeezing with/without CC seem to be almost same, so this CC power will be good for shot noise of LO.

 

Then we locked both of CC loops, but OPO reflection loop is not stable. Control filter has to be optimized and it might be better to increase CC power a bit (replace OD1 with other OD) or use PD which has better responsivity.

 

Current filter parameter:

OPO reflection: lowpass 1Hz, gain 1000

Homodyne RF: lowpass 1Hz, gain 50

Today we recovered parametric gain by tuning of OPO temperature and alignment of green.

To check parametric amplification clearly, green phase is scanned with 50 mHz,3 Vpp.

Today we recovered parametric gain by tuning of OPO temperature and alignment of green.

To check parametric amplification clearly, green phase is scanned with 50 mHz,3 Vpp.