We report the calculations of vectorial nonlinear properties of rubidium vapor for 87Rb D2 transition at moderate intensities. Different from Kerr nonlinearity, optimal intensity exists here, which depends on beam geometry. For intensities close to the optimal, the vectorial mechanism is much more efficient than a scalar one.
We investigate the enhancement of characteristic nonlinear phase shift in warm rubidium vapor for a signal beam using an additional pump laser at different frequency. A numerical model based on density matrix formalism is used. Experimental results of self-rotation and diffraction in a three-wave mixing process as well as beam amplification are shown. For 87Rb transition D2 line with Fg = 1, the nonlinearity to absorption ratio can be enhanced approximately two times with a pump beam tuned at Fg = 2 transition in a co-propagating scheme, which produces strong nonlinear interaction for Fg = 1 line at signal beam powers of ~10 mW.
We investigate the nonlinear refraction and absorption related to holographic writing in rubidium vapor at resonance with 87Rb D2 transition. The numerical model based on time-dependent density matrix formalism is used. The theory adequately describes nonlinear optical rotation and absorption at light intensities in the 0.1-30 mW/cm2 range. The basic configurations for obtaining amplitude and phase gratings for nearly equal frequencies of writing beams are investigated experimentally, and the writing time is estimated.
We investigate the nonlinear refraction and absorption related to holographic\nwriting in rubidium vapor at resonance with 87Rb D2 transition. The numerical\nmodel based on time-dependent density matrix formalism is used. The\ntheory adequately describes nonlinear optical rotation and absorption at light\nintensities in 0.1− 30mW / cm2 range.\nWe discuss two principal mechanisms. The first is based on absorption grating\nwriting and another grating formation mechanism based on Faraday rotation. It is\npromising for applications because it gives phase holograms with higher diffraction\nefficiency. The theory for both cases was developed.\nThe basic configurations for obtaining amplitude and phase gratings for nearly\nequal frequencies of writing beams are investigated experimentally, and the writing\ntime is estimated.\nWe also proposed a rapid solution algorithm for the calculation of the full density\nmatrix evolution for a multi-level atom. The calculation principle is similar to the\nsplit-step algorithm widely used for modeling the nonlinear propagation in media\nwith Kerr-type nonlinearity. The spectrum of nonlinear Faraday rotation in the D2\nnatural rubidium line is calculated and compared with the experiment. Good\nagreement is obtained.
An investigation of the resonant interaction of the rubidium atoms with an intensity (10 kWcm-2 ≤ I ≤ 2 MWcm-2) and a wavelength close to that of the D1 and D2 transitions of the rubidium atom (5S1/2 → 5P3/2 or 5S1/2 → 5P1/2, λD1 = 780 nm, λD2 = 795 nm), which has passes through rubidium vapor with density (1011 - 1014 cm-3) been studied theoretically. The system of equations describing the processes of Collisional ionization and multiphoton ionization of rubidium vapour resonantly excited with nanosecond pulsed laser is solved. The dependence of the ion density on the laser intensity and the atomic density of rubidium are considered. The result of calculations revealed that, both quadratic ion density dependence on laser intensity and linear behaviour of the ion density versus rubidium density for 5S1/2 → 5P3/2 transition is due to photoioization process. In contrast, for 5S1/2 → 5P1/2 transition, the ion density dependence is nonlinear and indicates that the collisional processes play the major contribution in the total ionization. Also, the obtained results showed reasonable agreement with the experimentally measured values of the ion density dependence given by Bakhramov et al. In addition, the analysis of mutual competition between the different ionization processes considered for the ion yield as a function of both laser intensity and atoms density are also presented this work.