To couple the spare NPRO into our Panda PM980 fibers, in order to carry out tests to characterize the fibers, in order to use them in FOL.
Manasa and I spent this morning building the setup to couple NPRO light into the fibers. We used two steering mirrors to precisely guide the beam into the coupler (collimator).
We also attached the lens to a moveable stage (in the z axis), so the setup could be fine tuned to put the beam waist precisely at the photodiode.
The fiber was attached to a fiber-coupled powermeter, so I would be able to tell the coupling efficiency.
During alignment, the NPRO was operating at 1.0 amps, roughly half of nominal current (2.1A).
I first placed the coupler at the distance that I believed the target waist of 231um to be.
Using the steering mirrors and the stage that holds the couple, I aligned the axes of the coupler and the beam.
Finally, I used the variable stage that the lens is attached to to fine tune the location of the target waist.
Once I was getting readings on the powermeter (~0.5nW), the laser was turned up to nominal current of 2.1A.
At this point, I and getting 120nW through the fiber.
While far from "good" coupling, it is enough to start measuring some fiber characteristics.
Tomorrow, I hope to borrow the beam profiler once again so as to measure the fiber mode.
Beyond this, I will be taking further measurements of the Polarization Extinction Ratio, the Frequency Noise within the fiber, and the effects of a temperature gradient upon the fiber.
Once these measurements are completed, the fiber will have been characterized, and will be ready for implementation in FOL.