Relaxation of Photon Density in a Resonant Medium

A. I. Alekseev

Rostislav M. Arkhipov, Mikhail V. Arkhipov, A. V. Pakhomov +4 more

We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this medium. Possible applications in the ultrafast optics such as optical switcher and laser beam deflector are discussed.

I A Poluéktov, Yurii M Popov, V S Roĭtberg

Numerical integration of a system of equations for a resonant medium and a field is used in a study of the influence of the relaxation of the phase memory of this medium on its coherent two-photon interaction with a light pulse. It is shown that the principal coherent effects occur right up to pulse durations equal to the phase relaxation time.

Yu. M. Kirin, Sergey G. Rautian, А. Э. Семенов +1 more

S. T. Gevorkyan, G. Yu. Kryuchkov

Jan Klaers

W present time-resolved studies of the thermalization and condensation process of a two-dimensional photon gas in an optical microcavity. In our experiment, a two-dimensional photon gas is confined in a high finesse microresonator containing a dye medium. If this system is operated in a regime in which reabsorption of cavity photons by the dye medium dominates over photon loss, e.g. by mirror transmission, a thermalization process of the photon gas to the temperature of the resonator (room temperature) takes place. In earlier work, we have experimentally observed both the thermalization process and, at sufficiently high photon densities, a condensation in the resonator ground mode. In recent experiments, we have studied the thermalization and condensation dynamics of the system after excitation with a short laser pulse. The timescale on which the photon gas becomes thermal (Bose-Einstein distribution) is found to be in the picosecond to nanosecond regime and is tunable by various system parameters e.g. by the dye concentration. Upon spatially displacing the pump spot from the optical axis, a transient laser-like oscillation of higher order cavity modes can be observed. These laser-like oscillations decay after several hundred picoseconds when the majority of photons have relaxed to the resonator ground state.