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Tarak Nath Dey

Publications and source records attributed to Tarak Nath Dey.

25 records · Page 2Linked to original sources
arXiv2019

Four-wave mixing based orbital angular momentum translation

We theoretically study the generation of orbital angular momentum(OAM) based on four-wave mixing (FWM) process in a diamond-type inhomogeneously broadened $^{85}$Rb atomic system. We use density matrix formalism at weak probe limit to explain the origin of vortex translation between different optical fields and generated signal. We show how the singularities which are omnipresent in phase of the input optical vortex beams can be profoundly mapped to atomic coherence in the transverse plane that hold the origin of OAM translation. This translation process works well even for moderately intense control field which enhances medium nonlinearity. Further we have manoeuvred an additional rotation of the phase wavefront in both clockwise and anti-clockwise direction controlled by the single photon detuning. The generation and manipulation of OAM of light beam in nonlinear medium may have important applications in optical tweezers and quantum information processing systems.

physics.optics↗
arXiv2018

Four wave mixing based generation and control of light pulse

We present an efficient scheme for the generation and control of a degenerate four-wave mixing (FWM) signal in a N-type inhomogeneously broadened 85Rb atomic system. We observe the propagation dynamics of the generated FWM signal along with the probe pulse under the condition of Electromagnetically Induced Transparency. The FWM signal clones the temporal shape of the probe pulse and travels through the medium without changing its shape and intensity. We have also shown that a time dependent control field permits the storage and retrieval of these optical signals without losing their identity. This work allows us to generate, control, store and retrieve FWM signal of any arbirary shape.

physics.optics↗
arXiv2004

Causality in Propagation of a Pulse in a Nonlinear Dispersive Medium

We investigate the causal propagation of the pulse through dispersive media by very precise numerical solution of the coupled Maxwell-Bloch equations without any approximations about the strength of the input field. We study full nonlinear behavior of the pulse propagation through solid state media like ruby and alexandrite. We have demonstrated that the information carried by the discontinuity, {\it i.e}, front of the pulse, moves inside the media with velocity $c$ even though the peak of the pulse can travel either with sub-luminal or with super-luminal velocity. We extend the argument of Levi-Civita to prove that the discontinuity would travel with velocity $c$ even in a nonlinear medium.

quant-ph↗
arXiv2003

Slow Light in Doppler Broadened Two level Systems

We show that the propagation of light in a Doppler broadened medium can be slowed down considerably eventhough such medium exhibits very flat dispersion. The slowing down is achieved by the application of a saturating counter propagating beam that produces a hole in the inhomogeneous line shape. In atomic vapors, we calculate group indices of the order of 10^3. The calculations include all coherence effects.

quant-ph↗
arXiv2002

From Storage and Retrieval of Pulses to Adiabatons

We investigate whether it is possible to store and retrieve the intense probe pulse from a $Λ$-type homogeneous medium of cold atoms. Through numerical simulations we show that it is possible to store and retrieve the probe pulse which are not necessarily weak. As the intensity of the probe pulse increases, the retrieved pulse remains a replica of the original pulse, however there is overall broadening and loss of the intensity. These effects can be understood in terms of the dependence of absorption on the intensity of the probe. We include the dynamics of the control field, which becomes especially important as the intensity of the probe pulse increases. We use the theory of adiabatons [Grobe {\it et al.} Phys. Rev. Lett. {\bf 73}, 3183 (1994)] to understand the storage and retrieval of light pulses at moderate powers.

quant-ph↗
arXiv2001

A Knob for Changing Light Propagation from Subluminal to Superluminal

We show how the application of a coupling field connecting the two lower metastable states of a lambda-system can produce a variety of new results on the propagation of a weak electromagnetic pulse. In principle the light propagation can be changed from subluminal to superluminal. The negative group index results from the regions of anomalous dispersion and gain in susceptibility.

quant-ph↗