Boston University

BOSTON UNIVERSITY
CENTER FOR NANOSCIENCE AND NANOBIOTECHNOLOGY

Nanophotonics Symposium

Wednesday, May 16th 2007, 7:30am - 5:30pm

Photonics Center, 9th Floor Colloquium Room • 8 St. Mary’s Street • Boston, MA 02215

This event is cosponsored by the Central New England Chapter of the
IEEE Lasers and Electro-Optics Society as part of the LEOS 30th Anniversary Celebration

Vladimir Bulovic, MIT
Strong QED Coupling in Organic Thin Film Structures
Abstract:

J-aggregated molecular crystals of cyanine dyes are today’s best choice of excitonic materials for realization of polariton devices that operate in the strong coupling regime, at room temperature conditions.  From the earliest days of cavity QED, research efforts aimed to construct solid state optical devices that operate in the limit where strong light-matter interactions dominate the dynamics.  Through research with inorganic quantum well structures, such devices have been successfully constructed in 1990’s, but their operation was limited to cryogenic temperatures, because of the small binding energies of the typical excitonic materials.  The talk will demonstrate that when J aggregates are used as the excitonic material, the large exciton binding energy enables demonstration of QED strong coupling even at room temperature conditions.  The very large optical transition dipole of J-aggregates is itself the result of strong coupling amongst monomeric dye elements that form the J-aggregated crystal, so that the oscillator strength of the J-aggregate is derived from cooperative, coupled, response of constituent monomers.  In the presented work, the strong interaction of J-aggregates with the cavity confined electromagnetic field is clearly manifested, even at room temperature, by the emergence of discernable exciton-polariton states of the coupled light-matter system.  Although a number of materials can form J-aggregated crystals with emission and absorption spectra that span the visible spectrum, and a number of different methods can be used to assemble to J-aggregates into strongly coupled structures, the talk will focus on a specific J-aggregated dye and a specific, versatile method for incorporating J-aggregates in solid state devices.  For the uncoupled J-aggregated thin films the talk will demonstrate record-large peak optical absorption coefficient, which is applied to construction of critically-coupled resonators that absorb 97% of incident light in lambda/100 = 6 nm thick J aggregate films.  For J-aggregate films assembled inside a microcavity, the talk will demonstrate strong coupling at room temperature, as characterized by a light matter coupling strength, Rabi-splitting, that significantly exceeds the dephasing processes competing against the coherence of the interaction.  The first demonstration of electrically pumped polariton emission will also be reported for a J-aggregate resonantly coupled microcavity LED, with the discussion of prospects for realizing a polariton laser at room temperature.

Biography

Vladimir Bulovic joined the faculty of MIT in July 2000 as an Assistant Professor in the Electrical Engineering and Computer Science Department.  Just prior to joining MIT, he was a Senior Scientist and Project Head of Strategic Technology Development at Universal Display Corporation (UDC).  At UDC he worked on on the application of organic materials to LEDs for full color flat panel displays and thin film photovoltaics for solar cell and detector applications.  Prior to joining UDC he worked in Princeton's POEM Center as a graduate researcher (1993-1998) and research associate (1998-1999).  At Princeton, Prof. Bulovic participated in a series of projects examining the optical and electrical properties of vacuum deposited amorphous and crystalline molecular organic thin films and devices.  From 1991-1993, Prof. Bulovic worked at Columbia University's Microelectronics Sciences Laboratory, where he examined image-potential states and resonances on metal surfaces utilizing nonlinear two-photon photoemission spectroscopy.

Co-hosted by:
Boston University CNN The Boston University Photonics Center IEEE LEOS

This Symposium is the annual Spring event for the Boston University Center for Nanoscience and Nanobiotechnology. The annual Symposium alternates between Nanophotonics and Nanomedicine.