Spatial evolution of short laser pulses under coherent population trapping

Abstract

Spatial and temporal evolution is studied of two powerful short laser pulses having different wavelengths and interacting with a dense three-level Lambdatype optical medium under coherent population trapping. A general case of unequal oscillator strengths of the transitions is considered. Durations of the probe pulse and the coupling pulse T 1,2 (T 2 > T 1 ) are assumed to be shorter than any of the relevant atomic relaxation times. We propose analytical and numerical solutions of a self-consistent set of coupled Schrödinger equations and reduced wave equations in the adiabatic limit with the account of the first non-adiabatic correction. The adiabaticity criterion is also discussed with the account of the pulse propagation. The dynamics of propagation is found to be strongly dependent on the ratio of the transition oscillator strengths. It is shown that envelopes of the pulses slightly change throughout the medium length at the initial stage of propagation. This distance can be large compared to the one-photon resonant absorption length. Eventually, the probe pulse is completely reemitted into the coupling pulse during propagation. The effect of localization of the atomic coherence has been observed similar to the one predicted by Fleischhauer and Lukin (PRL, 84, 5094 (2000).

Selective preparation of the maximum coherent superposition state in four-level atoms

“…The conclusion is clarified in Fig. 4, where the amplitudes of ρ 13 and ρ 14 as a function of the interval are plotted. The figure shows that the periodic structure appears for both of the two coherence terms.…”

“…Many schemes can prepare the coherent superposition state. For instance, the fractional stimulated Raman adiabatic passage(F-STIRAP) [12] and the coherent population trapping [13] can obtain the maximum coherent superposition state of the two lower levels in lambda-type atoms. Our group also proposed several schemes to achieve this goal, such as the methods based on the STIRAP [14,15] and the pulse train method [16] .…”

Recording and reading of intense optical pulses based on the induced transparency

“…On the basis of this phenomenon, a new mechanism of quantum memory, based on coherent recording and reading of light, was proposed [5,[21][22][23]. It was shown in our papers [14,24] that under similar conditions, spatial localization of atomic (Raman) coherence, which carries information on the interacting pulses, takes place in the medium. The possibility of reversible recording and reading of a probing (signal) pulse was also demonstrated.…”

“…In the case of electromagnetically induced transparency, the initially optically dense medium becomes transparent in the region of one-photon resonance, and the dispersion of the refractive index strongly increases. As a result, the laws of propagation of light pulses are radically changed [7][8][9][10][11][12][13][14][15][16] (matched pulses, dressed field pulses, adiabatons, etc.). A tremendous decrease (to a factor of 10 7 or more) in the group velocity of a probing pulse [4,5] is one of the most prominent examples.…”

Stimulated Raman adiabatic passage via bright state in Λ medium of unequal oscillator strengths

“…Note that the propagation effects for counterintuitive sequences of pulses and population transfer via STIRAP in media have been investigated in many papers (see for example Refs. [16,[20][21][22][23]). One of the main results of [16] is that during pulse propagation in the STIRAP regime the interaction adiabaticity as well as the spatial evolution of propagating pulses are strongly affected by the relationship between the oscillator strengths of the corresponding atomic transitions.…”