1. Test of EOM
We conducted the test about fiber-coupled EOM which are going to be used in KAGRA phase-2 (See attached picture.).
1-a. Transmittance
We measured the power of transmitted light after each optical components by power meter.
The results are...
NPRO 400mW -> FI (old one) 140mW -> EOM B 50mW -> EOM A 25mW -> Fiber amplifier
Thus, we estimated the transmittance of
EOM B as 35% ,
EOM A as 50%.
1-b. Phase modulation depth
According to data sheet from Jenoptik, half wave voltage is 6V at typical modulation frequency(I don't know which frequency this 'typical' means...).
We measured the phase modulation depth with applied voltage of 16MHz.
Seed laser after EOM A and EOM B was injected to high-Q Fabry Perot cavity, of which length we swept by its PZT and transmitted light was obtained by PD.
The experimental setup and calculation method are presented in an attached PDF.
The results about each EOM are attached.
we can say that datasheet's value(6V) as half wave voltage is valid also at 16MHz.
2. Test of new fiber isolator
New fiber-coupled Faraday isolator was arrived(Transmittance of the isolator we have used, had declined suddenly to 35% ).
Picture of it is attached.
We measured the power of transmitted light after each optical components by power meter.
NPRO 400mW -> FI (old one) 220mW -> EOM A,B 35mW -> Fiber amplifier
The transmittance of new fiber isolator are estimated as 55%.
Also, we confirmed that fiber amplifier can work in this optical setup.
