Determining the population variation of an atomic level by a series of ultrashort light pulses

Hua Tang, Takashi Nakajima

Ya I Khanin, Olga A. Kocharovskaya

Yu. P. Malakyan, David G. Sarkisyan, A. S. Sarkisyan

A simple method of measuring atomic level populations was implemented by comparing the energies of the third harmonic generated by two identical ultrashort pulses. When the first ultrashort pulse induces a process that removes some of the atoms from the ground (initial) level for third harmonic generation, the energy of the second third-harmonic pulse Wth2 becomes lower than Wth1 as a result of a reduction in the number of atoms. In the experiments K = Wth1 / Wth2 increased as the ultrashort pulse intensity increased. Experimental investigations and theoretical estimates showed that the most probable process causing a reduction in the population of the 62S1/2 level of cesium atoms was multiphoton ionization. It was found that the degree of multiphoton ionization could be estimated from K.

Andrei I. Maimistov

Light pulse amplification in a fiber amplifier is analyzed using a two-level model of resonant impurity atoms in a preinverted state. A steady-state ultrashort pulse propagating in such an amplifier is predicted. The dispersion broadening of this pulse is compensated by a nonlinear compression due to self-interaction, whereas an increase in the amplitude is compensated by linear losses. The dependence of the total energy of a transient pulse on the fiber wavelength is determined and a study is made of the role of the spatial inhomogeneity of the population inversion of the impurity atoms. Quasicoherent amplification is discussed.

M. Gromovyi, V. I. Romanenko, Simon Mieth +2 more