Nick Brewer

5/9/14

The fibers that we were using to clean up the tapered amplifier output were introducing power fluctuations, over the course of this week we tried three fibers:

- The first fiber we tried was single mode but not polarization maintaining (and not angle polished?) and there were power fluctuations >20%.

- The next fiber was single mode and polarization maintaining but not angle polished from Oz Optics. The same power fluctuations were occurring. We determined back reflected light was getting back through the isolators and that was causing the power fluctuations.

- We borrowed a single mode, polarization maintaining, angle polished fiber that had previously been repaired from Saffman's group. This fixed the power fluctuations seen earlier, but the output polarization rotated causing the output power to drift by 50% after a beam cube. I tried to find the correct input polarization by jiggling the fiber and watching the output power fluctuate after a beam cube, but I couldn't find a good polarization. Jared said he's seen output polarization rotate due to the wrong input polarization, but it was not as extreme as this, it only caused the power to fluctuate by ~10%. I suspect this fiber is just damaged and the repair that was previously made did not completely restore the fiber (and possibly caused the current problems?).

Jared ordered some new polarization maintaining, single mode, angle polished fibers from Oz Optics so hopefully that fixes the problems we are seeing. In the mean time I just used the output of the TA to do the single pass texts on the PPKTP crystal. The results were surprisingly close to what was expected:

Single pass efficiency: E_NL=P_out/P_in²=0.0027 (Simulated E_NL=0.0029)

Temperature bandwidth = ~2.4 °C (In Kumar's paper they report a temp bandwidth of 3 °C for a 19 mm PPKTP crystal at 1064 nm)

Temperature tuning coefficient = 0.0591 nm/°C (The salesman from Raicol said they measured 0.053 nm/°C for SHG at 1064 nm)

For the single pass efficiency and temperature tuning bandwidth measurements the TA was set to 1799mA and had a power of 478 mW right after the TA. While determining the temperature coefficient the TA was set at 1500 mA and had a power of 350 mW right after the TA. This power changed from wavelength to wavelength a little bit though.

5/7/14

Re-centered fiber scope lens; avoided forking fiber to the table.