Nonlinear exciton dynamics in a new near-infrared molecular J-aggregate system

Summary form only given.It is known that in isotropic solutions some types of cyanine dye molecules can organize themselves spontaneously into long one-dimensional (1D) chains, called J-aggregates. Recently, J-aggregates have attracted much attention as potential materials for optical switching and other nonlinear optical devices. High values of resonant nonlinear /spl chi//sup (3)/ coefficients of J-aggregates originate form excitonic character of optical absorption and emission, resulting in an N-fold enhancement of the transition oscillator strength, where N is the number of coherently coupled molecules. Large oscillator strength manifests itself also as a drastic shortening of spontaneous radiative decay time. The lifetime of the exciton can be further reduced by an exciton-exciton annihilation process, resulting in a picosecond- or sub-picosecond relaxation rate. The unique combination of high optical nonlinearity with a very fast relaxation rate makes J-aggregates attractive as a new material for ultrafast optical logic and signal processing. For these applications it is important to have systems operating at wavelengths accessible to common diode lasers, /spl lambda/>800 nm. However, the majority of I-aggregates studied so far show an exciton absorption band in the range /spl lambda/=570-700 nm. In our paper we describe and characterize a new J-aggregate system, which absorbs and emits light in near-infrared wavelength range of 806-825 nm, well suited for commercial diode laser applications.