Pradipta Panchadhyayee

Corrigendum: Coherent control of localization of a three-level atom by symmetric and asymmetric superpositions of two standing-wave fields

A scheme for one-dimensional localization of a three-level atom is proposed by employing a modified technique for the formation of a standing-wave regime using two standing-wave fields. In the present system, precise position information of the atom can be achieved by measuring the population of the excited state, which can be efficiently controlled by the symmetric and the asymmetric superpositions of two standing-wave fields in the presence of constructive quantum interference. Our results highlight that, depending upon the effect of asymmetric superposition, the proposed scheme may provide a promising way to obtain various types of single-peak and double-peak localizations of the atom either in a one-wavelength range or in a half-wavelength range with appropriate values of the Rabi frequencies, detunings and spatial phase shifts of the coupling fields.

Optical trapping with modified exponential decay in optical waveguides via dressed continuum

Simultaneous interaction of two side-coupled waveguides with the dressed continuum represented by a linear waveguide array causes cross-coupling between the two evanescent decay-channels and results in the phenomenon of trapping of the light field in the spatial domain during propagation through the waveguide system. For specific parameter values, it has been shown that the trapping effect is possible for all relative positions of the waveguides side-coupled to the dressed continuum. The model also demonstrates non-exponential decay characteristics of the optical field amplitudes in the waveguides. Depending on the values of the propagation mismatch, the nonlinearity arising in the decay-rate characteristics exhibits features like optical Zeno and anti-Zeno effects.

Optical analogue of double Fano resonance via dressed twin continua

A semiclassical model consisting of two noninteracting waveguide arrays along with three side-coupled waveguides is presented to demonstrate the optical analogue of double Fano resonance. The photonic system is configured so that it causes simultaneous cross coupling between two decay channels via one array and another two decay channels via the other array. Owing to the two individual interference effects, the decay-rate profile for the waveguide coupled directly to the continuum exhibits two asymmetric peaks, or dips, or a combination of one peak and one dip in the vicinity of the frequency mismatches. As far as the distribution of optical field amplitudes in the side-coupled waveguides is concerned, the present model also demonstrates the features of optical trapping (optical analogue of coherent population trapping) in side-coupled waveguides under certain symmetric parametric conditions.

Variable-coupling-induced optical trapping in optical waveguides via dressed continuum

We have studied a photonic structure, based on a semi-classical approach, considering simultaneous interaction of two side-coupled bent waveguides having variable coupling interactions (Gaussian and exponential-type) with a dressed continuum. We have examined the condition of optical trapping in spatial domain during propagation of a light field through the waveguide. The variation in parametric conditions leading to a typical trapping (quasi-trapping) phenomenon for both the cases of exponential and Gaussian coupling interactions is discussed. Simulation of such phenomenon of trapping in our macroscopic photonic structure is possible for all even relative positions of the side waveguides coupled to the dressed continuum. As far as the onset of quasi-trapping is concerned, the coupling width in the Gaussian coupling case is smaller than that in the exponential case. In this context, the Gaussian profile is found more tolerant than the exponential one so far as the separation between the side-coupled waveguides is concerned. Perfect trapping is observed to sustain by setting proper conditions while launching initial light in the side waveguides.

Modulation of spatial propagation dynamics in a three-core linear directional coupler

Abstract. A new class of three-core linear directional coupler is demonstrated, in which the centers of the cross-section of the waveguides (WGs) form the vertices of a triangle. Gaussian-type interaction is assumed to couple each WG directly to other WGs. By employing coupled mode equations under slowly varying envelope approximation, we numerically analyze the optical field dynamics in the three transmission channels. Under different parameter conditions, the coupler exhibits wide-ranging characteristics including nonadiabatic to adiabatic evolution of light transfer in versatile manners.

Optical analogue of Rabi oscillations in optical waveguides via structured continuum

In this article, simultaneous interaction of two side-coupled waveguides is considered with the dressed continuum represented by a linear waveguide array in which two consecutive pairs of waveguides are coupled in phase (positive coupling) and out-of-phase (negative coupling) alternately. It causes cross-coupling between the two evanescent decay-channels and results in the phenomenon of Rabi-like oscillations of the light field in spatial domain during propagation through the side waveguides. The profile of population exchange between the two side waveguides depends on the distinctive parameter conditions. It is interesting to note that, under no circumstances, light energy resides in the continuum.

Decay interference induced high precision localization in a multilevel atom via controlled spontaneous emission

A simple scheme for one-dimensional atom localization is proposed by employing a technique for the formation of the standing-wave regime using two unidirectional standing-wave fields. We consider a four-level atomic system similar to the one used by Paspalakis and Knight [Phys. Rev. Lett. 1998, 81, 293–296], with travelling-wave fields for the study of the phase control of emission in the presence of vacuum-induced interference between two spontaneous decay channels. In the present system precise position information of the atom can be achieved by measuring the frequency of spontaneous emission, which can be efficiently controlled by different system parameters and also by adjustment of the relative phase in the presence of the decay interference effect. The proposed scheme provides a potential technique to attain 100% detection probability of the atom in one wavelength range with generation of a sharp localization peak at low light level.

Resonance fluorescence microscopy via three-dimensional atom localization

A scheme is proposed to realize three-dimensional (3D) atom localization in a driven two-level atomic system via resonance fluorescence. The field arrangement for the atom localization involves the application of three mutually orthogonal standing-wave fields and an additional traveling-wave coupling field. We have shown the efficacy of such field arrangement in tuning the spatially modulated resonance in all directions. Under different parametric conditions, the 3D localization patterns originate with various shapes such as sphere, sheets, disk, bowling pin, snake flute, flower vase. High-precision localization is achieved when the radiation field detuning equals twice the combined Rabi frequencies of the standing-wave fields. Application of a traveling-wave field of suitable amplitude at optimum radiation field detuning under symmetric standing-wave configuration leads to 100% detection probability even in sub-wavelength domain. Asymmetric field configuration is also taken into consideration to exhibit atom localization with appreciable precision compared to that of the symmetric case. The momentum distribution of the localized atoms is found to follow the Heisenberg uncertainty principle under the validity of Raman–Nath approximation. The proposed field configuration is suitable for application in the study of atom localization in an optical lattice arrangement.

Modification and control of coherence effects in the spontaneous emission spectrum of a three-level atom at weak field regime

It has been shown that coherence effects have a marked influence in the spontaneous emission spectrum of a three-level -type atom driven by weak coherent and incoherent fields. Phase dependent evolution of interference effects leading to spectral narrowing, generation of spectral hole and dark line are exhibited in the present scheme when the atom does not interact with the incoherent fields. The basic mechanism underlying this scheme seems to be appropriate for a phaseonium. Apart from phase-coherence introduced in the system the phenomenon of line narrowing, in the presence of weak incoherent pumping, can be achieved in a different way as a consequence of two competitive resonant effects: sharp non-Lorentzian and symmetric Fano-like-resonance contributions to the line shape. In both the situations, the evolution of narrow structures in the line shape can be achieved even when the emission is influenced by the dephasing of Raman coherence.

Classical analogues of a quantum system in spatial and temporal domains: A probability amplitude approach

Abstract We have simulated the similar features of the well-known classical phenomena in quantum domain under the formalism of probability amplitude method. The identical pattern of interference fringes of a Fabry–Perot interferometer (especially on reflection mode) is obtained through the power-broadened spectral line shape of the population distribution in the excited state with careful delineation of a coherently driven two-level atomic model. In a unit wavelength domain, such pattern can be substantially modified by controlling typical spatial field arrangement in one and two dimensions, which is found complementary to the findings of recent research on atom localization in sub-wavelength domain. The spatial dependence of temporal dynamics has also been studied at a particular condition, which is equivalent to that could be obtained under Raman–Nath diffraction controlled by spatial phase.