Jon P. Davis

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.

A proposal for a gradient magnetometer atom interferometer

We propose the utilization of atom interferometry techniques for the measurement of magnetic fields in noisy environments. We find that the interferometer we propose is insensitive (to first order) to the magnetic field but is sensitive to the field gradient. We propose a technique by which a superposition of magnetically sensitive states (a beam splitter) can be achieved. We experimentally demonstrate our techniques to null the magnetic field at the location of a cold atom cloud and how we can probe the population of magnetic sublevels.

Controlling Raman resonances with magnetic fields

We utilize the tools already presented in a previous publication [DeSavage, S.A; Gordon, K.H; Clifton, E.M.; Davis, J.P.; Narducci, F.A. J. Mod. Opt. 2011, 58 (21), 2028--2035] to theoretically and experimentally investigate in detail Raman transitions in a sample of laser cooled 85Rb. Using cross-linearly polarized Raman fields, we find that, for an arbitrarily oriented magnetic field, the Raman spectrum consists of up to eleven peaks. However, by judicious choice of magnetic field direction, the spectrum can be reduced to a five peaked spectrum (transverse magnetic field) or a six peaked spectrum (longitudinal magnetic field). We present cases in which the full spectrum can not be thought of as the incoherent sum of the five and six peaked spectra.

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.

Raman resonances in arbitrary magnetic fields

We study the general problem of Raman resonances in arbitrary magnetic fields for realistic alkali atoms. We first present the details of a model that includes all magnetic sub-levels and their appropriate coupling strengths to two laser fields. The numerical implementation of this model and some of the results are also presented. Our experimental arrangement is described and preliminary measurements are presented.

Quantum optic techniques for diagnostics of a gradient magnetometer atom interferometer

In this article, we highlight some of the problems inherent in fielding an atom interferometer sensor, specifically an atom interferometer gradient magnetometer of the type recently proposed [Davis, J.P.; Narducci, F.A. J. Mod. Opt. 2008, 55, 3173–3185]. In particular, we focus on the problems created by stray magnetic fields. We review some of the quantum optic techniques to measure local magnetic fields for the purpose of nulling them. We also present our implementation of a technique to non-destructively measure the temperature of an atom cloud. We highlight our implementation of these techniques and present our measurements.

A frequency selective atom interferometer magnetometer

In this article, we discuss the magnetic-field frequency selectivity of a time-domain interferometer based on the number and timing of intermediate pulses. We theoretically show that by adjusting the number of pulses and the -pulse timing, we can control the frequency selectivity of the interferometer to time varying and DC magnetic fields. We present experimental data demonstrating increased coherence time due to bandwidth filtering with the inclusion of a pulse between the initial and final pulses, which mitigates sensitivity to low frequency magnetic fields.

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.

Recoil-induced resonances for optical switching

We have investigated recoil-induced resonances in laser-cooled atoms for the purpose of developing an optical switch. In contrast to our earlier experiments 8, we employ a system in which the trapping beams are left on during the course of the measurement. We not only find the expected narrow resonance but also a much wider resonance. The widths of the wide and narrow resonances differ by three orders of magnitude. In addition, the two resonances show different temporal dynamics. We explore the utility of each resonance as an optical switch.

Raman spectroscopy using a continuous beam from a 2D MOT

Atom interferometers consist of light pulses designed to create coherent superpositions of atomic states (“π/2” or “beam splitting” pulses) and that coherently interchange states (“π” or “mirror” pulses). In this article, we investigate the effects of imperfect pulses for a geometry specific to our apparatus. Atoms emerge from a 2-dimensional magneto-optical trap (2D MOT) in a continuous beam and cross continuous laser beams that drive stimulated Raman transitions. We use the atoms’ transit time through the laser field as the “pulse” time. We describe the impact of various effects on the contrast of the Rabi cycling, specifically the longitudinal velocity spread, the laser beam diameter and the spacing between the laser beams.