Participaint: Eleonora, Yuhang and Matteo

Motivation: Last week, we achieved the coupling of laser to fiber up to 50 percent. However, we find it has a large fluctuation. We guessed it might be caused by the back reflection laser. Anyway, we need to have this FI.

Simulation: I designed how to put them so that we can have a output beam which can match collimator and fiber. I also checked the beam going into FI is much smaller than the aperture of FI(5mm). See attached Figure. 1.

Installation: I collected all the necessary components and put them in sequency. I also checked the beam after the last lens seems fine. But I found the second half-wave plate is broken. I mean we cannot rotate it, so we cannot change polarization. I will change it tomorrow and make the light s-polarization. See attached Fig. 2.

Result:

The transmission of FI is 12.71/14.07 = 90.33%. See attached Fig. 3 and 4.

I used roughly 33 cm of space.