Coherent Control of Electromagnetically Induced Grating

Abstract

In this PhD thesis, we investigate the coherent control of electromagnetically induced grating (EIG) through different atomic media under distinct conditions of coherence. An atom-field system which exhibits EIT acts as an EIG (atomic grating) when the traveling wave control field is replaced by a standing-wave field. The spatial modulation of the standing-wave changes the amplitude of the incident probe light field in a periodic manner similar to that as hybrid grating. The EIG and its applications have attracted researchers in various fields of science to study, for example, diffracting and switching a quantized probe field, probing the optical properties of a material, and all optical switching, routing, and light storage. Initially, we investigated the role of spatial coherence on diffraction intensity for a partially coherent incident Gaussian Schell model (GSM) beam which is diffracted from a two-level atomic grating. It is shown that the performance of the atomic grating is greatly influenced by the spectral coherence width of the partially coherent fields. It is observed that relatively large intensity of the diffracted light can be obtained via spatial coherence, beam width, interaction length, and mode index of partially coherent incident light. The scheme provides possibilities for the potential applications of atomic grating in lensless imaging using the partially coherent light field. Next, we present a scheme to realize electromagnetically induced grating in an ensemble of strongly interacting Rydberg atoms, which act as superatoms (SAs) due to the dipole blockade mechanism. The ensemble of three-level cold Rydberg-dressed (87Rb) atoms follows a cascade configuration where a strong standing-wave control field and a weak probe pulse are employed. The diffraction intensity is influenced by the strength of the probe intensity, the control field strength, and the van der Waals (vdW) interaction. It is noticed that relatively large first-order diffraction can be obtained for low-input intensity with a small vdW shift and a strong control field. The scheme can be considered as an amicable solution to realize the atomic grating at the microscopic level, which can provide background- and dark-current-free diffraction. Finally, we extend the idea of electromagnetically induced grating to exploit the realization of one-dimensional (1D) and two-dimensional (2D) electromagnetically induced holographic imaging (EIHI) in an ensemble of strongly interacting Rydberg atoms. Here, we consider two schemes for holographic imaging; the first scheme is the direct detection of holographic imaging pattern and called as electromagnetically induced classical holographic imaging (EICHI), whereas in the second scheme entangled photon pairs are employed for the imaging and it is called as electromagnetically induced quantum holographic imaging (EIQHI). Both schemes are employed to obtain 1D and 2D holographic imaging. In EICHI and EIQHI, amplitude and phase information of EIG can be imaged with controllable image variation in size. It is noticed that holographic imaging is also influenced by vdW effect present in Rydberg atoms.