Vineet Bharti

• Ph.D.
• Senior Research Associate at University of Bristol

We demonstrate a technique for continuous tuning of the Hanle effect from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) by changing the polarization ellipticity of a control beam. In contrast to previous work in this field, we use spatially separated probe and control beams. The experiments are done...

An array of ultracold atoms in an optical lattice (Mott insulator) excited to a state where single electron wave-functions spatially overlap would represent a new and ideal platform to simulate exotic electronic many-body phenomena in the condensed phase. However, this highly excited non-equilibrium system is expected to be so short-lived that it h...

We report the observation and control of ultrafast many-body dynamics of electrons in ultracold Rydberg-excited atoms, spatially ordered in a three-dimensional Mott insulator (MI) with unity filling in an optical lattice. By mapping out the time-domain Ramsey interferometry in the picosecond timescale, we can deduce entanglement growth indicating t...

Rydberg atoms in optical lattices and tweezers is now a well-established platform for simulating quantum spin systems. However, the role of the atoms’ spatial wave function has not been examined in detail experimentally. Here, we show a strong spin-motion coupling emerging from the large variation of the interaction potential over the wave function...

We present a theoretical study to investigate sub- and super-luminal light propagation in a rubidium atomic system consisting of a Rydberg state by using density matrix formalism. The analysis is performed in a 4-level vee+ladder system interacting with a weak probe, and strong control and switching fields. The dispersion and absorption profiles ar...

We realized ~10 ¹¹ cm ⁻³ high density Rydberg gas of ultracold ⁸⁷ Rb atoms by ultrafast excitation using improved picosecond pulse laser system, and observed the spontaneous ionization induced by Rydberg-Rydberg interactions.

We report the observation and control of ultrafast non-equilibrium many-body electron dynamics in Rydberg-excited spatially-ordered ultracold atoms created from a three-dimensional unity-filling atomic Mott insulator. By implementing time-domain Ramsey interferometry with attosecond precision in our Rydberg atomic system, we observe picosecond-scal...

We experimentally demonstrate electromagnetically induced absorption (EIA) in a vee + ladder system. The experiment is done using the low-lying energy levels of $^{87}$Rb. A theoretical model of the system is made that reproduces the experimental results. We study the dependence of the characteristics of the EIA resonance on various combinations of...

We demonstrate---experimentally and theoretically---that resonances obtained in electromagnetically induced transparency (EIT) can be both bright and dark. The experiments are done using magnetic sublevels of a hyperfine transition in the D$_1$ line of $^{87}$Rb. The degeneracy of the sublevels is removed by having a magnetic field of value 27 G. T...

We use the technique of coherent population trapping (CPT) to access the ground hyperfine interval (clock transition) in 133Cs. The probe and control beams required for CPT are obtained from a single compact diode lasers system. The phase coherence between the beams, whose frequency difference is the clock frequency, is obtained by frequency modula...

We demonstrate resonances due to coherent population pumping in a bright state (CBS), using magnetic sublevels of the closed $ F_g = 2 \rightarrow F_e = 3 $ transition in $^{87}$Rb. The experiments are performed at room temperature vapor in two kinds of cells---one that is pure and the second that contains a buffer gas of Ne at 20 torr. We also pre...

We demonstrate---experimentally and theoretically---that resonances obtained in electromagnetically induced transparency (EIT) can be both bright and dark. The experiments are done using magnetic sublevels of a hyperfine transition in the D$_1$ line of $^{87}$Rb. The degeneracy of the sublevels is removed by having a magnetic field of value 27 G. T...

We study coherent population oscillations (CPO) in an odd isotope of the two-electron atom ${\rm ^{173}Yb} $. The experiments are done using magnetic sublevels of the $ F_g = 5/2 \rightarrow F_e = 3/2 $ hyperfine transition of the $ {\rm {^1S_0} \rightarrow {^3P_1}} $ intercombination line. The experiments are done both with and without a magnetic...

We demonstrate a technique for continuous tuning of the Hanle effect from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) by changing the polarization ellipticity of a control beam. In contrast to previous work in this field, we use spatially separated probe and control beams. The experiments are done...

We demonstrate that the Hanle effect can be tuned between magnetically induced absorption (MIA) and magnetically induced transmission (MIT) simply by changing the polarization of the input laser beam. The experiments are done using closed hyperfine transitions of the D2 line of 133Cs —F g = 3 → F e = 2 and F g = 4 → F e = 5. The former shows a tran...

We present a theoretical model, using density matrix approach, to study the effect of weak as well as strong probe field on the optical properties of an inhomogeneously broadened multilevel V-system of the $^{87}$Rb D2 line. We consider the case of stationary as well as moving atoms and perform thermal averaging at room temperature. The presence of...

We discuss the differences between two well-studied and related phenomena – coherent population trapping (CPT) and electromagnetically induced transparency (EIT). Many differences between the two – such as the effect of power in the beams, detuning of the beams from resonance, and the use of vapor cells filled with buffer gas – are demonstrated exp...

We present a theoretical study to investigate sub- and super-luminal light propagation in a rubidium atomic system consisting of a Rydberg state by using density matrix formalism. The analysis is performed in a 4-level vee+ladder system interacting with a weak probe, and strong control and switching fields. The dispersion and absorption profiles ar...

Electromagnetically induced transparency (EIT) in three-level systems uses a strong control laser on one transition to modify the absorption of a weak probe laser on a second transition. The control laser creates dressed states whose decay pathways show interference. We study the role of dressed-state interference in causing EIT in the three types...

We study coherent population oscillations (CPO) in an odd isotope of the two-electron atom Yb. The experiments are done using magnetic sublevels of the $ F_g = 5/2 \rightarrow F_e = 3/2 $ hyperfine transition in $^{173}$Yb of the $ {\rm {^1S_0} \rightarrow {^3P_1}} $ intercombination line. The experiments are done both with and without an appied ma...

Electromagnetically induced transparency (EIT) in three-level systems uses a strong control laser on one transition to modify the absorption of a weak probe laser on a second transition. The control laser creates dressed states whose decay pathways show interference. We study the role of dressed-state interference in causing EIT in the three types...

We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with...

We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with...

We present the results of a theoretical study of a four-level atomic system in vee + ladder configuration using a density matrix analysis. The absorption and dispersion profiles are derived for a weak probe field and for varying strengths of the two strong control fields. For specificity, we choose energy levels of $^{87}$Rb, and present results fo...

We present a theoretical study of the Doppler broadened Y-type six-level atomic system, using a density matrix approach, to investigate the effect of varying control field wavelengths and closely spaced hyperfine levels in the 5P3/25P3/2 state of 87Rb. The closely spaced hyperfine levels in our six-level system affect the optical properties of Y-ty...

We present a theoretical model using a density matrix approach to show the influence of multiple excited states on the optical properties of an inhomogeneously broadened V-system of the Rb D2 line. These closely spaced multiple excited states cause asymmetry in absorption and dispersion profiles. We observe the reduced absorption profiles, due to d...

We demonstrate extremely narrow resonances for polarization rotation in an atomic vapor. The resonances are created using a strong control laser on the same transition, which polarizes the atoms due to optical pumping among the magnetic sublevels. As the power in the control laser is increased, successively higher-order nested polarization rotation...

The main objective of the work reported in this thesis is to study the phenomenon of electromagnetically induced transparency (EIT) in Doppler broadened multilevel atomic systems. EIT is a quantum interference phenomenon that leads to the cancellation of absorption for the weak probe field in the presence of the strong control field. EIT was first...

We present a six-level atomic system using a density matrix approach to show variation of the optical properties in an -type Doppler-broadened system for the D2 line of alkali atoms with the nuclear spin I = 3/2, i.e. 87Rb, 23Na and 7Li. The variation in optical properties arises due to the presence of multiple excited states with varying separatio...

A theoretical model using the density matrix approach has been presented to show the influence of multiple excited states on electromagnetically induced transparency (EIT) in a cascade-type Doppler broadened medium. A five-level system has been considered that is a simple case of the 87Rb atom. In a room temperature vapour, when the Doppler broaden...

A theoretical model using density matrix approach has been presented to show the polarization dependence of Electromagnetically Induced Transparency (EIT) in cascade multilevel atomic system. EIT has already been investigated both theoretically and experimentally by using three-level system in lambda (Λ), vee (V), and cascade (Ξ) configurations. Ho...