FiO/LS 2011 - Wednesday Sessions

    Today was quite the whirlwind, after getting breakfast in the morning, I went off to a room that I hadn't been to before. Unfortunately, I thought it was somewhere else, so I ended up circling the conference center and coming back to the room right above the coffee shop. And this was after I had my morning coffee... sigh...

    Anyway, there were a few gems of talks today. The first was a talk by Mark Foster on his work doing time lensing - essentially using an all fiber setup to shift the pattern in the spectrum of light into the time domain, and the time domain into the spectral domain. This is cool stuff because in telecom they have well developed methods for handling one type of signal but not the other, so by having an all fiber way of switching between the two makes it easy to modify either signal. This could lead to faster bandwidth with only minimal overhead. It turns out that you can use a similar method to do extra-precise analog to digital conversion by using a pulsed laser (which has very small timing jitter of about 5 fs, that's 5*10^-15 s) to do the sampling, then stretch the samples out a bit so that an electronic ADC can pick it up (these have timing jitter of about 100 fs). So you pick up a factor of 10-100 accuracy by this method.

    The rest of the morning wasn't particularly my field, so I didn't get a lot out of it. Consequently I went off to The Tech Museum to have some fun, but also decompress and get my brain ready for more talks. I had a really good time there, and to do it justice, I think I'll make a separate post (with pictures).

    By the time the afternoon rolled around, a few more talks popped up on my radar. First up was a talk by Eric Van Stryland's group on their work in seeding supercontinuum (SC) generation. I mentioned this briefly before, but the idea is that if you go through special optical fibers or, in this case, a krypton gas cell you can turn a short laser pulse of a few frequencies (about 100 nm bandwidth) into a longer pulse of many more frequencies (usually spanning the visible, from 400 nm (deep purple) to 800 nm (red) and even longer wavelengths). Since supercontinuum generation is the result from a plethora of nonlinear processes, you have to have very intense light to do it. Usually there is also a sharp turn on, from having no SC to having the SC by tuning the laser power very slightly. By seeding the supercontinuum, a process where you add a bit of light - his group used a pulse with 40,000 times less energy - to get the process started. Not only did they find it works, but it increases the amount of light you get out by a factor of 4 or so. They don't completely understand it yet, but this is a fantastic result, because having a bright light source that is continuously variable over such a broad range of spectrum really opens to door to many experiments, and is something I may be working on in the future.

    Then there were two talks on biology and biological optics. I'm going to save the one by Nicholas Roberts on polarized vision in animals for a later post - this was the research on Mantis Shrimp being able to see circularly polarized light, but there's so much more than just that. Instead I'd like to focus on Hui Cao's work on mimicking nature's optics... and then doing better! You may have heard that butterflies have a wing scale pattern that has very fine microstructure, acting like a diffraction grating and giving them their wing iridescence. Well, it turns out that some birds, and for some colors, have a similar effect that colors their wings. However, while the butterfly wing will seem to change colors as you change viewing angle, this does not happen for the birds. This is a result of having local structure but no large scale structure in the bird wing. By making similar structures, they were able to re-create the effect in the lab. But if that were all it would hardly be entertaining. They went a step further, and placed what are known as quantum dots into their structures, these are small metallic spheres that emit different colors based on how big they are. When they hit this structure with light, it would preferentially amplify a certain frequency - they had created a laser! Hopefully the birds don't figure this one out.

FiO/LS 2011 - Tuesday Sessions

    Wow! Today was absolutely packed and quite exciting. First off I just invented my "Most Amusing Talk" award so I could give it to John Dudley, whose talk (slides available here) was very entertaining. He started off with a case of how he was wrong, then moved into a recount of how he was observing super continuum generation (where you get white light from almost single color laser light using special optical fibers) as a solution to the nonlinear wave equation and couldn't get it published anywhere (Science, Nature, and on down the food chain), but eventually got it into Applied Optics. Now these types of results make the cover of Nature Photonics! He suggested they start the journal "Nature Reinterpretations" which got a good chuckle from the audience.
    This was mixed with a recount of how the first nuclear weapon design (gun type) was not actually tested, but the engineers who were building it had a good idea it would work, so while the physicists were busy testing their bomb (implosion type), the engineers just dropped theirs! I really have no idea how this fit in, but interesting trivia anyway. Another good quote; "Fluid dynamicists were divided into engineers who observed things that could not be explained and mathematicians who explained things that could not be observed …" (Sir James Lighthill). I can think of some other fields, where this is true.
    Finally, he ended by showing just why science is exciting - the solutions they were seeing in their nonlinear optics experiments should have been possible in water (where the equations the optics people used were first developed). Despite searching, no-one had been able to produce the effect in water until the optics folks showed the way. And now we have rogue wave type solitons in water;

    The best part of the day, however, was going by the '"Mission: Optical" Student Chapter Competition'. The goal was to build a project for under $25 (US) that demonstrated an optics principle. So many good and fun ideas - I'll definitely be stealing many of these! My favorites were a balloon stretched across the end of a tin can, the other end was cut off so you could speak into it. A laser pointer was then attached pointing at a mirror (or CD) that was glued to the balloon. When you spoke into it, the balloon drum would vibrate, and the reflected spot would trace out a pattern on the wall. A great way of 'visualizing sound', and much easier, more direct and more robust than having motors drive mirrors to deflect the laser beam. Another group used legos, LED's, CD's and some ingenuity to build a 3D stroboscopic viewer. It almost worked. But it was enough of an ingenious idea, that I'd really like to give them credit for it.
    Other groups used just a bucket of water, sugar and milk to demonstrate as many different optical principles as they could: Reflection and refraction, the later of which changes with the addition of sugar to the water, total internal reflection in the bucket and the addition of milk for scattering. And another had a great setup that really made it easy for students to get into the scientific principle (just don't tell the kids that). They had kids split into groups and try different ways to heat water. Yet another demonstration of just why I think these conferences are awesome - I never would have thought of some of these ideas on my own, but now I can use them to teach others about optics.