Pulse propagation in the slow and stopped light regime

by Tal Weiss

at Quantum optics seminar

Thu, 11 Oct 2018, 15:30
Physics building (#54) room 207

Abstract

In recent decades slow light was studied at optical frequencies and it was shown that light can nearly be brought to complete standstill As a result various potential applications emerged including in particular optical memory in quantum computing In many studies pulse propagation in the slow light regime was studied via a somewhat phenomenological transport equation for the pulse envelope i e neglecting second and higher order dispersion terms More accurate models were based on envelope equations like the nonlinear Schr dinger equation NLSE However the validity of these models is limited to moderate levels of slow light Otherwise an exceeding number of dispersion terms in the form of high order time derivatives has to be taken into account because the various dispersion coefficients are proportional to the inverse of the group velocity and its powers In these cases one is forced to resort to finite difference time domain method which is far more demanding in terms of computational resources and hampers physical insights In this context in our work we derive an alternative formalism which is based on momentum basis expansion leading to different NLSE which is particularly accurate when the group velocity drops to zero Applying the new formalism to pulse propagation in the zero group velocity point ZGVP regime we observe various temporal nonlinear NL phenomena In particular our formulation shows that the relevant quantity is the propagation time rather than propagation space if measured in time the rate of phase accumulation is not different than in weakly dispersive systems Thus the apparent enhanced phase accumulation hence NL effect and absorption in the slow light regime are a direct result of the longer time spent in the system rather than of enhanced light matter interactions We then extend our formalism to allow for the study of interactions of multiple pulses Specifically we derive the coupled mode theory CMT to study light stopping by implementing a perturbation in the form of transient Bragg grating that couples the incoming pulse to the ZGVP regime We show that the spectra of the stopped pulse can easily be controlled by modulating the time envelope of the perturbation We conclude by presenting the limitations of our formalism

Created on 14-10-2018 by Bar Lev, Yevgeny (ybarlev)
Updaded on 14-10-2018 by Bar Lev, Yevgeny (ybarlev)