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Devrim Tarhan

Publications and source records attributed to Devrim Tarhan.

17 recordsLinked to original sources
arXiv2019

Optomechanical cavity without a Stokes side-band

We investigate a theoretical demonstration of perfect frequency conversion in an optomechanical system in the weak coupling regime without a Stokes side-band. An optomechanical cavity illuminated by a weak probe field generates two side-modes, differentiating from the original signal by a phonon frequency. We report the presence of a special combination of parameters in the weak-coupling regime, where Stokes side-mode vanishes exactly. Only the anti-Stokes mode is observed with a few hundreds Hz spectral bandwidth of the probe field. Emergence of this special point is totally unrelated with the electromagnetically induced transparency (EIT) condition, where absorption (dip) cancellation is limited with the damping rate of the mechanical oscillator. Emergence is independent of the cavity type, i.e. single or double-sided, and takes place only for a single value of the effective coupling strength constant which is specific to the system parameters. At a specific effective coupling strength between the mirror and the cavity field, which can be tunable via the coupling field, only the anti-Stokes band is generated. At that specific coupling there appears no Stokes field. Hence, a filter, to eliminate the Stokes field, does not necessitate.

quant-ph↗
arXiv2015

Mutual emergence of noncausal optical response and nonclassicality in an optomechanical system

We show that single-mode nonclassicality of the output of an optomechanical cavity and the noncausal linear optical response of this cavity emerge at the same critical cavity-mechanical coupling. In other words, single-mode nonclassicality emerges when the barrier (in electromagnetism) avoiding faster-than-light communication is lifted off. The nature of the emergence of noncausal behavior does not depend on the length (boundary conditions) and the type of the cavity. Origin of the noncausal behavior is the temporal/frequency relations between the incident and reflected waves at the outer surface of the cavity. We further discuss the relations with the recent studies; (i) equivalence of the entanglement among identical particles to the nonclassicality of their quasiparticle excitations, (ii) necessity of superfluid behavior of vacuum, and (iii) entanglement-wormhole equivalence.

quant-ph↗
arXiv2013

Bose-Einstein Condensate in a Linear Trap With a Dimple Potential

We study Bose-Einstein condensation in a linear trap with a dimple potential where we model dimple potentials by Dirac \del function. Attractive and repulsive dimple potentials are taken into account. This model allows simple, explicit numerical and analytical investigations of noninteracting gases. Thus, the \Sch is used instead of the Gross-Pitaevski equation. We calculate the atomic density, the chemical potential, the critical temperature and the condensate fraction. The role of the relative depth of the dimple potential with respect to the linear trap in large condensate formation at enhanced temperatures is clearly revealed. Moreover, we also present a semi-classical method for calculating various quantities such as entropy analytically. Moreover, we compare the results of this paper with the results of a previous paper in which the harmonic trap with a dimple potential in 1D was investigated.

cond-mat.quant-gas↗
arXiv2013

Superluminal and Ultraslow Light Propagation in Optomechanical Systems

We consider an optomechanical double-ended cavity under the action of a coupling laser and a probe laser in electromagnetically induced transparency configuration. It is shown how the group delay and advance of the probe field can be controlled by the power of the coupling field. In contrast to single-ended cavities, only allowing for superluminal propagation, possibility of both superluminal and subluminal propagation regimes are found. The magnitudes of the group delay and the advance are calculated to be 1ms and -2s, respectively, at a very low pumping power of a few microwatts. In addition, interaction of the optomechanical cavity with a time dependent probe field is investigated for controlled excitations of mirror vibrations.

quant-ph↗
arXiv2013

Laser pulse amplification and dispersion compensation in an effectively extended optical cavity containing Bose-Einstein condensates

We review and critically evaluate our proposal of a pulse amplification scheme based on two Bose-Einstein condensates inside the resonator of a mode-locked laser. Two condensates are used for compensating the group velocity dispersion. Ultraslow light propagation through the condensate leads to a considerable increase in the cavity round-trip delay time, lowers the effective repetition rate of the laser, and hence scales up the output pulse energy. It has been recently argued that atom-atom interactions would make our proposal even more efficient. However, neither in our original proposal nor in the case of interactions, limitations due to heating of the condensates by optical energy absorption were taken into account. Our results show that there is a critical time of operation, $~0.3$ ms, for the optimal amplification factor, which is in the order of $\sim 10^2$ at effective condensate lengths in the order of $\sim 50$ $μ$m. The bandwidth limitation of the amplifier on the minimum temporal width of the pulse that can be amplified with this technique is also discussed.

physics.optics↗
arXiv2012

Effect of Dimple Potential on Ultraslow Light in a Bose-Einstein Condensate

We investigate the propagation of ultraslow optical pulse in atomic Bose-Einstein condensate in a harmonic trap decorated with a dimple potential. The role of dimple potential on the group velocity and time delay is studied. Since we consider the interatomic scattering interactions nonlinear Schrodinger equation or Gross-Pitaevskii equation is used in order to get the density profile of the atomic system. We find large group delays of order 1 msec in an atomic Bose-Einstein condensate in a harmonic trap with a deep dimple potential.

cond-mat.quant-gas↗
arXiv2012

Superluminal Pulse Propagation in a One-sided Nanomechanical Cavity System

We investigate the propagation of a pulse field in an optomechanical system. We examine the question of advance of the pulse under the conditions of electromagnetically induced transparency in the mechanical system contained in a high quality cavity. We show that the group delay can be controlled by the power of the coupling field. The time delay is negative which corresponds to superluminal light when there is a strong coupling between the nano-oscillator and the cavity.

quant-ph↗
arXiv2011

Lensing and Waveguiding of Ultraslow Pulses in an Atomic Bose-Einstein Condensate

We investigate lensing and waveguiding properties of an atomic Bose-Einstein condensate for ultraslow pulse generated by electromagnetically induced transparency method. We show that a significant time delay can be controllably introduced between the lensed and guided components of the ultraslow pulse. In addition, we present how the number of guided modes supported by the condensate and the focal length can be controlled by the trap parameters or temperature.

physics.optics↗
arXiv2009

Dispersion Management of Ultraslow Light in a Bose-Einstein Condensate via Trap Curvature

One dimensional propagation of ultraslow optical pulses in an atomic Bose-Einstein condensate taking into account the dispersion and the spatial inhomogeneity is investigated. Analytical and semi-analytical solutions of the dispersive inhomogeneous wave equation modeling the ultraslow pulse propagation are developed and compared against the standard wave equation solvers based upon Cranck-Nicholson and pseudo-spectral methods. The role of curvature of the trapping potential of the condensate on the amount of dispersion of the ultraslow pulse is pointed out.

physics.optics↗
arXiv2008

Control of Optical Dynamic Memory Capacity of an Atomic Bose-Einstein Condensate

Light storage in an atomic Bose-Einstein condensate is one of the most practical usage of these coherent atom-optical systems. In order to make them even more practical, it is necessary to enhance our ability to inject multiple pulses into the condensate. In this paper, we report that dispersion of pulses injected into the condensate can be compensated by optical nonlinearity. In addition, we will present a brief review of our earlier results in which enhancement of light storage capacity is accomplished by utilizing multi-mode light propagation or choosing an optimal set of experimental parameters.

quant-ph↗
arXiv2007

Bose-Einstein condensate in a harmonic trap with an eccentric dimple potential

We investigate Bose-Einstein condensation of noninteracting gases in a harmonic trap with an off-center dimple potential. We specifically consider the case of a tight and deep dimple potential which is modelled by a point interaction. This point interaction is represented by a Dirac delta function. The atomic density, chemical potential, critical temperature and condensate fraction, the role of the relative depth and the position of the dimple potential are analyzed by performing numerical calculations.

quant-ph↗
arXiv2007

Bose-Einstein condensate in a harmonic trap decorated with Dirac delta functions

We study Bose-Einstein condensation in a harmonic trap with a dimple potential. We specifically consider the case of a tight and deep dimple potential which is modelled by a Dirac delta function. This allows for simpler, explicit numerical and analytical investigations of noninteracting gases. Thus, the Schrodinger equation is used instead of the Gross-Pitaevski equation. Calculating the atomic density, chemical potential, critical temperature and condensate fraction, the role of the relative depth of the dimple potential with respect to the harmonic trap in large condensate formation at enhanced temperatures is clearly revealed.

cond-mat.other↗
arXiv2007

Ultraslow optical waveguiding in an atomic Bose-Einstein condensate

We investigate waveguiding of ultraslow light pulses in an atomic Bose-Einstein condensate. We show that under the conditions of off-resonant electromagnetically induced transparency, waveguiding with a few ultraslow modes can be realized. The number of modes that can be supported by the condensate can be controlled by means of experimentally accessible parameters. Propagation constants and the mode conditions are determined analytically using a WKB analysis. Mode profiles are found numerically.

cond-mat.other↗
arXiv2007

Enhancing capacity of coherent optical information storage and transfer in a Bose-Einstein condensate

Coherent optical information storage capacity of an atomic Bose-Einstein condensate is examined. Theory of slow light propagation in atomic clouds is generalized to short pulse regime by taking into account group velocity dispersion. It is shown that the number of stored pulses in the condensate can be optimized for a particular coupling laser power, temperature and interatomic interaction strength. Analytical results are derived for semi-ideal model of the condensate using effective uniform density zone approximation. Detailed numerical simulations are also performed. It is found that axial density profile of the condensate protects the pulse against the group velocity dispersion. Furthermore, taking into account finite radial size of the condensate, multi-mode light propagation in atomic Bose-Einstein condensate is investigated. The number of modes that can be supported by a condensate is found. Single mode condition is determined as a function of experimentally accessible parameters including trap size, temperature, condensate number density and scattering length. Quantum coherent atom-light interaction schemes are proposed for enhancing multi-mode light propagation effects.

cond-mat.other↗
arXiv2007

Propagation of short pulses through a Bose-Einstein condensate

We study propagation of short laser pulses in a Bose-Einstein condensate taking into account dispersive effects under the conditions for electromagnetically induced transparency. We calculate dispersion coefficients using typical experimental parameters of slow-light schemes in condensates. By numerically propagating the laser pulse, and referring to theoretical estimations, we determine the conditions for which dispersion starts to introduce distortions on the pulse shape.

cond-mat.other↗
arXiv2007

Dispersive effects on optical information storage in Bose-Einstein condensates with ultra-slow short pulses

We investigate the potential of atomic Bose-Einstein condensates as dynamic memory devices for coherent optical information processing. Specifically, the number of ultraslow pulses that can be simultaneously present within the storage time in the condensate has been analyzed. By modeling short-pulse propagation through the condensate, taking into account high-order dispersive properties, constraints on the information storage capacity are discussed. The roles of temperature, spatial inhomogeneity, the interatomic interactions, and the coupling laser on the pulse shape are pointed out. For a restricted set of parameters, it has been found that coherent optical information storage capacity would be optimized.

cond-mat.other↗