In recent past, considerable success has been achieved in the precise control over the optical properties of the medium. The fundamental properties of a medium like dispersion and absorption can be manipulated by using appropriate coherent fields. In particular, one could get distortionless propagation of pulses even through an absorbing medium. An appropriate management of the dispersive and absorptive properties of a medium has led to remarkably very large number of applications. For example it is now possible to produce ultraslow light and even stop the light. It is also possible to store light in atomic coherences and to retrieve the light on demand. Furthermore the coherent control can also produce superluminal propagation of light as well as cloning of light pulses. The recent demonstration on storage and retrieval of light in resonant media has tremendous technological implications. The ability to slow down the propagation velocity of light and to coherently stop and store it, holds the key to the ultimate control of light. This will have revolutionary impact in the area of optical communications and quantum information processing.

Improving the resolution of an image has been a fundamental problem. The well-known limitation comes from the Rayleigh criterion which does not allow resolution of the features of an image beyond half of the optical wavelength with the use of conventional optics. Further the transmission of an image without much loss of resolution as a result of diffraction is an important issue. We have shown how the effect of paraxial diffraction can be partially eliminated during the propagation of optical images in a medium by pumping under the conditions of saturated absorption. Proper considerations of spatial profiles of the pump beams are important as it enables us to produce appropriate complex refractive index profile. We have also shown that super Gaussian pump are better for attaining diffraction free propagation of images. Further we have analyzed how the probe beam acquires the characteristic shape of Laguerre Gaussian pump when the pump beam is much wider than probe beam. We expect that similar conclusions would apply for propagation of images through in-homogeneously broadened solid state systems where one comes across a very wide range of relaxation times.

Optical Imaging beyond Diffraction Limits

We present first ever analytical solutions for shape-preserving pulses in a Kerr nonlinear two-mode fiber doped with 3-level Ëatoms. The two modes are near-resonant with the two transitions of the atomic system. We show the existence of quasi-stable coupled bright-dark pairs if the group velocity dispersion has opposite signs at the two mode frequencies. We demonstrate the remarkable possibility allowed by the fiber dispersion for the existence of a new class of solutions for unequal coupling constants for the two modes. We present the conditions for existence and the analytical form of these solutions in presence of atomic detuning. We confirm numerically the analytical solutions for the spatio-temporal evolution of coupled solitary waves.

Optical Soliton

Coherent Control

Recently, superconducting qubits have been used in state-of-the-art quantum information processors because of their high coherence time,  tunability and miniaturization. Realizing the controllable strong interaction of superconducting qubits with the microwave photons in the high-quality superconducting resonators led to circuit quantum electrodynamics. Inspired by cavity QED, the interaction of the superconducting artificial atoms (SAAs)/qubits with the quantized electromagnetic fields (microwave photon) in various coupling regimes ( dispersive, strong, ultra-strong, deep-sling, strong, etc.) is studied under the framework of circuit QED. Furthermore, there has been a continuous effort to study quantum mechanical/quantum optical phenomena in hybrid superconducting quantum circuits (SQCs), where other physical systems such as quantum dots, magnons, and mechanical systems are interfaced with the SQCs. Recent advancements with superconducting artificial atoms also led to the realization of giant atoms. Unlike the point-like atoms in quantum optics, the giant atoms can couple to an electromagnetic field at multiple points, giving rise to unconventional quantum interference effects absent in quantum optics with tiny atoms. Coherent control of circuit QED can  increase the lifetime and robustness of quantum memory that is capable of performing deterministic complex gate operations

Coherent Circuit Quantum Dynamics

One PhD position for an M.Sc. student joining the PhD program at IIT Guwahati from Aug-2024 and One Research Associate position for PhD holder with expertise on "Vector Beam" is available for working on a sponsored project entitled "Customization and characterization of vector beams beyond paraxial approximation by coherent control."

Research Opening