Chirped optical pulses in nonlinear absorbers

Valentin P. Petrov, Wolfgang Rudolph, B. Wilhelmi

姚海凤, 钮月萍, 彭延东 +1 more

Boris D. Fainberg, Vladimir N. Nazarov

Changes in the modulus and phase of a slowly varying envelope of an ultrashort pulse are calculated for the case of propagation across a saturable absorber. Vibronic relaxation of the optical transition in the absorber is allowed for. A study is made of the dependences of the duration of a pulse transmitted by a nonlinear absorber on the vibrational relaxation time of dye molecules and on the detuning of the carrier frequency of a pulse relative to the maximum of the equilibrium absorption spectrum. It is shown that a chirp appears even in the absence of such detuning provided the energy of lf quanta of optically active vibrations is comparable with the thermal excitation energy. This chirp originates from partial completion of the vibrational relaxation process during a pulse, so that absorption and refraction occur in a system which is not in a vibrational equilibrium.

Angelo Turrin

A. Turrin

Aminul I. Talukder, Makoto Tomita

We experimentally measure the propagation delays for chirped optical pulses with asymmetric temporal envelope functions, through a resonantly absorbing dye solution. The transmitted pulses suffer a strong deformation and the arrival times are dramatically modified by the interaction between the chirp and the absorption effect of the sample. It is shown that the arrival time, represented by the centroid of energy of the transmitted pulse, can be well described by the reshaping delay and has a greater significance than the peak of the pulse.