Able to couple into four input couplers on the same line, waveguiding throughout sample starting at first grating input coupler.

After having ground the first column of input grating couplers off of the sample, the laser was able to couple into all four remaining input couplers.

The laser wasn't straight vertically, however leading to the possibility of coupling into later gratings without ever coupling into earlier ones:

It is interesting that this time, we could couple into four input grating couplers and not just the three that we coupled into originally. Perhaps the angle of the sample increased spacing just enough to reach the fourth grating. Or perhaps the fact that the sample is wave guiding allows the spacing to variate slightly. The entrance point to the coupler is clearly farther each time, so some expansion is still necessary.

Judging from lack of waveguiding wholy and ccompletely with our first test with this sample, my angle may have been off initially. This is likely the reason our spacing is better this time.

Further adjustments should be between 6.25 and 6.75 mm for fine tuning.

Confirmed that the first edge of the sample wasn't covered during proton exchange. Able to actual waveguide and couple over two couplers.

Scott mentioned that he thinks this sample wasn't completely submerged during proton exchanged, and for that reason our tests showed no waveguiding. With that knowledge, after polishing the reverse side, we entered the sample backward to try to waveguide. The spacing wasn't perfect, but we were able to couple into the second input grating coupler (from light entry) on the second row. Here you can see the guided light stops before the last grating coupler (from light entry) confirming that this part was not submerged during proton exchange.

Here, despite the imperfect spacing the light was able to couple in on both the second and third input coupler showing that we were able to repeat our earlier results. Note also, how the next bounce is just past the fourth input coupler.

Going forward, we will grind off the first column of couplers to get better spacing between the light input and the first grading couplers in an attempt to couple through 3 input grading couplers.

Able to hit three couplers on third row of sample, though spacing too short for further hits. Unable to couple into waveguiding because around the first column of input grating couplers was not proton exchanged.

Tested Dr. Smalley's second bounce test sample, containing three rows of five leaky mode couplers each, with red laser.

The maximum number of coupler hits on the first row is just two.

Similarly, I could only hit two couplers on the second row as well.

By moving the point the laser enters the first coupler on the third line to be the edge of the coupler closest to the laser assembly, I could hit three input grading couplers. This did produce a less than desired line of light guided through the waveguide, but showed the bounce distance results I was testing for.

This image shows the displacement of the point of entrance on the couplers in each bounce.

I think about half a millimeter wider spacing will allow for better results both in more bouncing and better guided lines when actually waveguiding. For the next sample, I'll test spacings between 6.5 and 7 millimeters.