Tuesday, May 18, 2010

Lasers and Waveguide Arrays

There are so many things per unit time happen at the conference that I cannot keep up with writing. So many interesting talks and events that it is not possible to write about everything and (I have to confess) recall all the details.

Yesterday and today I've been attending very interesting sections on novel phenomena. There have been a lot of works done in waveguide arrays lately, especially in 2D arrays, produced by femtosecond laser writing. I would like to especially mention the talk on 2D Dynamic Localization of Light, given by Dr. Alexander Szameit on Monday (QMA7). In that presentation, he told us about the observation of approximate dynamic localization in a 2D waveguide array, in which there were two layers of periodic structures, staggered with respect to each other. Optical analog of Bloch oscillations and dynamic localizations can be observed in coupled waveguide arrays under the condition of a gradient in the effective index from waveguide to waveguide, produced by the change of the waveguide width or by curving the waveguide array. You can excite one waveguide, and the light, instead of spreading all over the array because of diffraction, would relocalize in that initially excited waveguide periodically. This phenomenon has both fundamental and practical implications. E. g., one can make a narrow-band filter by properly design the waveguide array to exhibit the relocalization for a certain wavelength, so that at the output of the structure all the light would exit through the initially excited waveguide.

The soliton sections were expecially interesting. There is an increase in the number of experimental demonstrations of spatial solitons. I enjoyed the talk given by Y. Lamhot, Hot Particle Solitons (QTuC2). I have learned about a way of soliton formation by strong coupling between light and nanoparticles. The light heats the fluid containing the nanoparticles, which accummulate in the heated area and induce the effective refractive index change, influencing the guidance and causing the light self-trapping. I also enjoyed the talk given by Dr. Marco Peccianti, Optical Bullet Trains via Modulation Instability in Nonlocal Solitons (QTuC4). It is very impressive that it is now possible to experimentally observe such effects.

There were a lot interesting talks on semiconductor lasers. I found the morning section on 3-5 um Semiconductor Lasers very interesting. I've learned a lot about quantum cascade lasers and the recent developments and improvements to their performance. Another demonstration of a successful realization of a new semiconductor laser based on a Bragg reflection waveguide, which is a 1D vertical photonic bandgap structure with a defect supporting guided modes, was given by Bhavin Bijlani (CTuO5). He also gave a very interesting report on New Modality of Second-Order Nonlinearity in Bulk AlGaAs Bragg Reflection Waveguides later in the afternoon (CTuEE2). These reports together hold promise to realize the first electrically injected, self-pumped higher harmonic generation for applications including quantum optics. Using the sample platform for a difference-frequency generation process can also provide electrically injected sources to cover wide ranges of wavelengths in the infra-red. Don't miss another related talk tomorrow (QWE2)!

As I am finishing, it is time for the CLEO Welcome reception and the Lasers Rock! concert. More networking, more fun!

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