Analytical approach on linear and nonlinear pulse propagations in an open Λ-type molecular system with Doppler broadening

Abstract

We develop a systematic analytical approach on linear and nonlinear pulse propagations in an open Λ-type molecular system with Doppler broadening. In the linear case, using a residue theorem and a spectrum decomposition method, we prove that a crossover from electromagnetically induced transparency (EIT) to Autler–Townes splitting (ATS) exists for a co-propagating configuration of probe and control fields. However, there is no EIT and hence no EIT–ATS crossover for a counter-propagating configuration. We give various explicit formulas, including probe-field spectrum decomposition, the EIT condition, the width of the EIT transparency window, as well as a comparison with the result of cold molecules. Our analytical result agrees well with the experimental one reported recently by Lazoudis et al (2010 Phys. Rev. A 82 023812). In the nonlinear case, using the method of multiple scales, we derive a nonlinear envelope equation for probe-field propagation. We show that stable ultraslow solitons can be realized in the open molecular system.

Theoretical analysis on quantum interference effect in fast-light media

“…Now we make a detailed analysis on the appearance of gain doublet in the gain spectrum of the signal field shown above by using the SDM developed recently for slow-light media [26][27][28][29][30][31][32][33][34][35][36].…”

“…In order to illustrate the QI effect in a simple and clear way, as done in Refs. [26][27][28][29][30][31][32][33][34][35][36], we decompose the gain spectrum −Im(K) for different regions of Ω c as follows.…”

“…Furthermore, the QI also results in a drastic change of dispersion and hence a large reduction of the group velocity of the signal field [1][2][3]. In addition, it has been discovered recently that in such systems there exists an interesting crossover from EIT to Autler-Townes splitting (ATS) [26][27][28][29][30][31][32][33][34][35][36]. It is natural to ask the question: Is it possible to have similar phenomena for fast-light media?…”

“…1). We carry out systematic theoretical analyses and give clear physical explanations on the QI effects occurring in these fast-light media by extending the spectrum-decomposition method (SDM) developed recently for the EIT-ATS crossover of slow light [26][27][28][29][30][31][32][33][34][35][36]. We show that such fast-light media are capable of not only completely eliminating the absorption but also suppressing the gain of signalmodulate field, and hence provide the possibility to realize a stable long-distance propagation of the signal field with a superluminal velocity.…”

Phase-controlled optical switching and slow- and weak-light solitons in a coherent molecular system with permanent dipole moments

“…Although most studies on EIT are focused on atomic systems, in recent years there has been much investigation of EIT in molecular systems both theoretically and experimentally [21][22][23][24][25][26][27][28][29][30][31]. However, up to now less attention has been paid to the EIT in molecules with permanent dipole moments (PDMs).…”