Metasurfaces, which are two-dimensional equivalent of metamaterials, offer a unique and efficient platform to study and control light-matter interactions in the sub-wavelength limit. When combined with semiconductor heterostructures, the metasurfaces can be coupled to fundamental excitations such as intersubband transitions in quantum wells. Such hybrid devices can provide opportunities for both fundamental studies of light-matter interactions as well as for new ultrathin optical devices such as voltage tunable optical modulators and nonlinear frequency generators. In the first part of this talk, I will present a low dissipation optical modulator using a hybrid plasmonic metasurface where the tuning mechanism relies on field induced tunneling of electrons in semiconductor heterostructures. In the second part of the talk, I will concentrate on hybrid dielectric metasurfaces  coupled to intersubband transitions for high efficiency  second harmonic generation. I will finally conclude by presenting fundamental studies of strong-light matter interaction between Mie modes in dielectric resonators and intersubband transitions in semiconductor quantum wells.

Biography:

Raktim Sarma is a Senior Member of Technical Staff at Sandia National Laboratories. He received a BS degree (magna cum laude honors) in Physics in 2010 from the University of Texas at Dallas and became both an Academic Distinction Scholar and a Van Ness Scholar of the Department of Physics. During his undergraduate degree, he was a research intern at Fermi National Accelerator Laboratory and at Laboratory for Atmospheric and Space Physics. He received his MS, MPhil, and PhD degrees in Applied Physics from Yale University in 2012, 2013, and 2017, respectively. His PhD thesis work was in mesoscopic physics of photons in disordered photonic systems and in developing miniature on-chip spectrometers and gyroscopes. His work on optical gyroscopes was recognized by Photonics.com as one of the top ten research stories of 2015 and was highlighted by numerous media outlets including Optical Society of America as “World’s Smallest Gyroscope”. Dr. Sarma joined Sandia National Laboratories in Dec 2016 as a Postdoctoral Appointee and worked in the area of low-loss, tunable, nonlinear, ultrathin metasurfaces and advanced optical devices to support Sandia’s nanophotonics strategy and BES-MSE thrust.  To date, Dr. Sarma has authored over 80 publications and conference papers. 

Please find a link below to Dr. Sarma's Google scholar page.

Google Scholar Link:  https://scholar.google.com/citations?user=jja_ZR8AAAAJ&hl=en