Tony Y. Abi-Salloum

Phase dynamics and interference in EIT

In this paper, we investigate various aspects of electro-magnetically induced transparency (EIT) that are associated with quantum interference. In the first half of this paper, we investigate two cascade schemes and demonstrate two possible absorption pathways in one, which leads to interference, and only one pathway in the other scheme, which does not exhibit EIT. In the second part of this paper, we demonstrate how EIT can be changed into enhanced absorption by changing the phase of either the coupling or probe fields.

Interference between competing pathways in the interaction of three-level ladder atoms and radiation

In this paper we explore the physical origin of the transparency induced in absorbing three-level cascade atoms by the simultaneous interplay of two coherent beams of light. By utilizing the scattering technique we offer what we believe is a very convincing physical evidence for the existence, or for the absence, of quantum interference effects in the two considered ladder systems. Bare and dressed states pictures are adopted in two different field regimes when applicable. The conclusions are drawn based on the existence of different excitation pathways and their relative orders of magnitudes. The presented study includes a distinction between the Autler–Townes (AT) and electromagnetically induced transparency (EIT) phenomena.

Four-level ‘N-scheme’ in bare and quasi-dressed states pictures

In this work, we consider a four-level ‘N-scheme’ (three radiation fields coupling four atomic levels) that has previously been shown to feature different group velocity regimes (sub-luminal, super-luminal, and negative) controlled by the strength of the third interacting field, which is referred to as the control field. Another interesting aspect of the N-scheme is the ‘appearance’ and ‘disappearance’ of an electromagnetically induced transparency (EIT) window at resonance. In this paper, based on a study in the bare states picture, we point out differences and similarities between two settings (different strengths of the acting fields) of this four-level N-scheme. Conclusions are drawn based on a work in a simplified quasi-dressed states picture. We find that the four-level N-scheme under study can be approached as either a one or two three-level lambda-like system(s) that display the same physics regardless of the relative strength between the two fields that form the EIT portion of the system.

Variations of dispersion and transparency in four level N-scheme atomic systems

Systems that exhibit positive and negative dispersion are of interest for numerous applications especially when accompanied by transparency. In this work, we study the variation of the sign of the dispersion in the case of a four-level ‘N-Scheme’ system. The different dynamics of the sign and value of dispersion and transparency are first explored in light of three resonances that we have previously introduced, then studied as a function of the varying strengths of the fields. As an application we consider in this work both passive and active optical gyroscopes.

Double-Raman gain for realizing a superluminal ring laser

We show how a dual-peak gain produced via optical pumping and non-degenerate Raman pumps in a single vapor cell can be used to realize a superluminal ring laser with enhanced sensitivity for gyroscopy and accelerometry.

Enhanced sensing in a double-Raman superluminal ring laser

We investigate the feasibility of realizing a superluminal ring laser with enhanced sensitivity by using the gain produced via double-Raman pumping in an inverted three-level system. If the laser cavity is tuned to the center between the two gain peaks produced in such a system, it is expected to experience an effective negative dispersion, which can be tuned to the condition necessary for enhancing the sensitivity of the laser frequency to a change in the cavity length. Using a model of two idealized, independent Lorentzian gains, we solve the laser equations to show the enhancement of sensitivity. We then extend our analysis to calculate the gain profile in a real lambda system. Unlike the idealized system mentioned above, where the dual gain peaks are modeled as two adjacent Lorentzians in a manner that ignores the relative coherence between the Raman pumps, we present a more accurate model where this coherence is not neglected. As such, the Hamiltonian remains time dependent after making the rotating wave transformation. Using an approximation --- valid for practical systems --- where higher order terms in the density matrix are neglected, we determine the gain experienced by a weak probe beam. Numerical techniques are needed to incorporate the resulting gain and dispersion profiles into the laser equation to determine accurately the behavior of the superluminal laser. This work will be carried out in the near future. Experimental realization of a superluminal laser based on this approach may prove to be easier than other approaches proposed previously.

Effective dispersion in an inhomogeneously broadened single mode laser

Recently, we have been investigating the development of a superluminal ring laser, where finely tuned anomalous dispersion leads to an enhancement in the sensitivity of the laser frequency to a change in the cavity length, by as much as six orders of magnitude, for applications such as hypersensitive rotation sensing and accelerometry, as well as for gravitational wave detection. For such a laser, as well as other lasers that are used for precision metrology, the effective dispersion – manifested in the manner in which the lasing frequency varies as a function of a change in the cavity length due to the index induced by the medium under saturated gain corresponding to steady-state lasing – is of utmost significance. In determining the effective dispersion, the role of inhomogeneous broadening (IB) must be taken into consideration carefully. In this work, we consider an inhomogeneously broadened gain medium in a single mode optical cavity, and study the effective dispersion experienced by the lasing field. It is well known that the steady state index for such a laser cannot be expressed analytically. Previous studies have employed approximate models to interpret the effective dispersion, in two limits: IB is much larger than homogeneous broadening (HB), and IB is insignificant compared to HB. Here, we use an iterative but quickly converging numerical code to determine the exact behavior of the effective dispersion under all conditions, and show that the results agree with the expected behavior in these two limits. This technique paves the way for taking into account the effective dispersion in any inhomogeneously broadened laser, including the superluminal laser, in determining accurately its sensitivity to change in cavity length, as well as it quantum noise limited linewidth.

Effect of inhomogeneous broadening on a DPAL based superluminal laser for precision sensing

In several applications such as optical gyroscopes, gravitational wave detection, and vibrometry, the precision sensing of the effective length of the optical cavity is key. In this work we show how an active single mode laser with a negatively dispersive medium can enhance the sensitivity of measuring the alteration of the length of the cavity in the practical case of a warm medium. We also state how a Rubidium based Diode Pump Alkali Laser satisfies the requirements of the proposed model.