Devrim Tarhan

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.

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 offcenter dimple potential. We specifically consider the case of a tight and deep dimple potential, which is modeled by a point interaction. This point interaction is represented by a Dirac delta function. The atomic density, chemical potential, critical temperature and condensate fraction, and the role of the relative depth and the position of the dimple potential are analyzed by performing numerical calculations.

Dispersive effects on optical information storage in Bose-Einstein condensates with ultraslow 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.

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 Wentzel-Kramers-Brillouin analysis. Mode profiles are found numerically.

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.

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 argued recently that atom?atom interactions would make our proposal even more efficient. However, neither in our original proposal nor in the case of interactions, were limitations due to heating of the condensates by optical energy absorption taken into account. Our results show that there is a critical time of operation, 0.3 ms, for the optimal amplification factor, which is of the order of ?102 at effective condensate lengths of the order of ?50 ?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.

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.

Lensing and waveguiding of ultraslow pulses in an atomic Bose–Einstein condensate

Abstract 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.

Control of optical dynamic memory capacity of an atomic Bose-Einstein condensate

Abstract.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.

Ultraslow optical modes in Bose-Einstein condensates

Light can be slowed down to ultraslow speeds v ia electromagnetically induced transparency in atomic Bose-Einstein condensates. This is thought to be useful for storage of quantum information for weak probe pulses. We investigate the effects of inhomogeneous density profile of the condensate on propagation of such ultraslow pulses. We find that spatial density of an atomic condensate leads to a graded refractive index profile, for an off-resonant probe pulse when condensate parameters are suitably chosen. Within the window of negligible absorption, conditions for degenerate multiple waveguide modes are determined. Both analytical and numerical studies are presented to reveal the effects of experimentally controllable parameters, such as temperature and interatomic interaction strength on the number of modes. Group velocity dispersion and modal dispersion are discussed. The effect of waveguide dispersion, in addition to usual material dispersion, on ultraslow pulses is pointed out.