Thursday, May 20, 2010

More about interesting talks

Time flies so fast that I cannot keep up with posting about everything. Here are some interesting talks that I have attended on Wednesday and Thursday.

I was very impressed with the tutorial talk on terahertz quantum cascade lasers given by Dr. Kumar on Wednesday afternoon (CWF1). Typically, these devices operate at very low temperatures and need to be criogenically cooled. However, the operation temperature of terahertz QCLs gets higher and higher thanks to the new progress in the field.

I have attended most of the session on Nonlinear Integrated Optics, as this subject is of my primary interest. I liked the presentation given by Dr. Pasquazi on Net Parametric Gain in a High Index Doped Silica Waveguide (QWE1). The materials they used in order to obtain phase-matched four-wave mixing with a good efficiency was a special kind of glass, doped with some ions to have a nonlinear refractive index five times greater than that of SiO2, retaining at the same time the low linear and nonlinear absorption in the telecom range.

An interesting talk was given by Dr. Labukhin, in which a new method for modeling and controlling the nonlinear spatiotemporal dynamics of a semiconductor laser has been proposed (CWN6). In particular, the authors considered mode hopping effect exhibited by many lab semiconductor lasers, and studied its behavior under different conditions.

Prof. Shalaev from Purdue University presented a very good tutorial, in which he overviewed the recent progress in the field of tunable and active metamaterials (QThB1). Having many interesting potential applications, metamaterials still suffer from very high losses. This problem has been recently addressed by making the metamaterials active to compensate and even over-compensate the strong attenuation. Very recently the group of Prof. Shalaev was able to demonstrate such structures in the visible range.

Recent progress on chalcogenide-glass-based integrated optics has been reported by Prof. Luther-Davies (CCthW7). In this work, the authors investigated a new type of chalcogenide glass, having higher linear and nonlinear refractive indices compared to the earlier used chalcogenide glass As2S3. The authors fabricated nanowires in the new type of chalcogenide glass. Due to a higher refractive index, the new material enabled tighter mode confinement and resulted in a huge nonlinear coefficient. The authors were able to successfully realize supercontinuum generation in the new type of chalcogenide glass. Despite the 10 times higher nonlinear absorption coefficient compared to that of As2S3, the new material seems promising for wavelength conversion and other applications. I am looking forward to the published paper on this topic which I hope will become available soon.

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