Formation of optical field inside a transparent spherical particle irradiated by train of ultrashort laser pulses

摘要

Diffraction of a train of femtosecond laser pulses at a weakly absorbing aerosol particle is considered based on the analytical solution of the Maxwell equations obtained through representation of light fields as series expansion in terms of electromagnetic eigenmodes of a dielectric sphere. The dynamics of formation of an optical field inside a transparent spherical particle irradiated by a single pulse and a train of ultrashort laser pulses is comparatively analyzed. It is found that when the particle is exposed to a series of laser pulses, both the evolution of the field inside the particle and its energy characteristics vary depending on the pulse repetition frequency. The analysis shows that the decrease of the gap between the acting laser pulses leads to the increase in the intensity of the internal field in the zone of its maximum. As this takes place, the lifetime of the field inside the particle increases because the spectrum of the acting radiation becomes richer as compared to a single pulse and the probability of excitation of high-Q resonance modes in the particle is higher.