Nick Brewer: Difference between revisions

 

I'm interested in measuring how well the cavity is mode matched. According to Jinlu's thesis, to measure the mode matching coefficient <math>m</math>, you can use the formula

Once the cavity was tuned and the temperature was adjusted to be at the optimal value, we measured 5.5 mW of green (I'm almost positive we used the right wavelength settings on the power meter). The input power was ~45 mW. That is an efficiency of ~12%. If I take <math>\eta=1.01/1.21 \rightarrow I_R/I_{in}=0.165</math> and figure out the mode matching coefficient with the other measured values above, I get m=0.84 (very well mode matched...almost too well). If there is 45 mW of power before the cavity, and the mode matching coefficient is 0.84, that means that 36 mW of power is being coupled into the cavity. When I ran the Matlab code I wrote to simulate the cavity enhancement, I find that for and input coupler with T=0.05, we should expect ~12% efficiency. This result is so close to what we measured that I almost certainly calculated something wrong. If I use <math>I_R/I_{in}=1.01/1.21=0.83</math>, I get a mode matching coefficient of m=0.12, which corresponds to 5.4 mW getting coupled into the fiber, which is less than the green power we got out.

 

 

We are still using the fiber we borrowed from Saffman's group but we are anxiously awaiting the arrival of the fibers we ordered from Oz Optics.

The polarization that generates the most green is vertical, I determined that with a Glan Taylor polarizer. We determined that in order to properly align the cavity we need to have the temperature far out of tune so we can see the cavity peaks produced from the vertically polarized light. Otherwise there is too much loss at that polarization due to the generation of green light.

 

 

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:

 

 

 

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