arXiv subjects

Charles S. Adams

Publications and source records attributed to Charles S. Adams.

At least 55 records · Page 3Linked to original sources

arXiv2015

Observation of interference effects via four photon excitation of highly excited Rydberg states in thermal cesium vapor

We report on the observation of electromagnetically induced transparency (EIT) and absorption (EIA) of highly excited Rydberg states in thermal Cs vapor using a four-step excitation scheme. The advantage of this four-step scheme is that the final transition to the Rydberg state has a large dipole moment and one can achieve similar Rabi frequencies to two- or three-step excitation schemes using two orders of magnitude less laser power. This scheme enables new applications such as dephasing free Rydberg excitation. The observed lineshapes are in good agreement with simulations based on multilevel optical Bloch equations.

physics.atom-ph↗

arXiv2015

Electromagnetically induced absorption in a non-degenerate three-level ladder system

We investigate, theoretically and experimentally, the transmission of light through a thermal vapour of three-level ladder-type atoms, in the presence of 2 counter-propagating control fields. A simple theoretical model predicts the presence of electromagnetically induced absorption (EIA) in this pure three-level system when the control field is resonant. Experimentally, we use $^{87}$Rb in a large magnetic field of 0.62~T to reach the hyperfine Paschen-Back regime and realise a non-degenerate three-level system. Experimental observations verify the predictions over a wide range of detunings.

physics.atom-ph↗

arXiv2015

Effect of line broadening on the performance of Faraday filters

We show that homogeneous line broadening drastically affects the performance of atomic Faraday filters. We use a computerized optimization algorithm to find the best magnetic field and temperature for Faraday filters with a range of cell lengths. The effect of self-broadening is found to be particularly important for short vapour cells, and for `wing-type' filters. Experimentally we realize a Faraday filter using a micro-fabricated $^{87}$Rb vapour cell. By modelling the filter spectrum using the ElecSus program we show that additional homogeneous line broadening due to the background buffer-gas pressure must also be included for an accurate fit.

physics.atom-ph↗

arXiv2015

Coherent Excitation Transfer in a Spin Chain of Three Rydberg Atoms

We study coherent excitation hopping in a spin chain realized using highly excited individually addressable Rydberg atoms. The dynamics are fully described in terms of an XY spin Hamiltonian with a long range resonant dipole-dipole coupling that scales as the inverse third power of the lattice spacing, $C_3/R^3$. The experimental data demonstrate the importance of next neighbor interactions which are manifest as revivals in the excitation dynamics. The results suggest that arrays of Rydberg atoms are ideally suited to large scale, high-fidelity quantum simulation of spin dynamics.

quant-ph↗

arXiv2015

Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz

We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D$_1$ line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities the cesium D$_1$ line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 gauss and a temperature of 68.0$\,^\circ$C. Experimentally, the prediction from the model is verified. The experiment and theoretical predictions show excellent agreement.

physics.atom-ph↗

arXiv2015

ElecSus: A program to calculate the electric susceptibility of an atomic ensemble

We present a computer program and underlying model to calculate the electric susceptibility of a gas, which is essential to predict its absorptive and dispersive properties. Our program focusses on alkali-metal vapours where we use a matrix representation of the atomic Hamiltonian in the completely uncoupled basis in order to calculate transition frequencies and strengths. The program calculates various spectra for a weak-probe laser beam in an atomic medium with an applied axial magnetic field. This allows many optical devices to be designed, such as Faraday rotators/filters, optical isolators and circular polarisation filters. Fitting routines are also provided with the program which allows the user to perform optical metrology by fitting to experimental data.

physics.atom-ph↗

arXiv2014

Probing an excited-state atomic transition using hyperfine quantum beat spectroscopy

We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

physics.atom-ph↗

arXiv2014

Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapour

Electromagnetically induced transparency (EIT) resonances using the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}\rightarrow5\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}$ transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to four-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to $100\%$ and a linewidth of 15 MHz. In addition, the large line narrowing effect allows resolution of $^{85}$Rb $5\rm{D}_{5/2}$ hyperfine structure even in the presence of strong power broadening.

physics.atom-ph↗

arXiv2012

Absolute absorption and dispersion of a rubidium vapour in the hyperfine Paschen-Back regime

Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen- Back regime for fields greater than 0.33 T on the Rb D2 line. The experiment uses a compact 1 mm3 microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.

physics.atom-ph↗

arXiv2012

Three-photon electromagnetically induced transparency using Rydberg states

We demonstrate electromagnetically induced transparency (EIT) in a four-level cascade system where the upper level is a Rydberg state. The observed spectral features are sub-Doppler and can be enhanced due to the compensation of Doppler shifts with AC Stark shifts. A theoretical description of the system is developed which agrees well with the experimental results and an expression for the optimum parameters is derived.

physics.atom-ph↗

arXiv2012

The cooperative Lamb shift in an atomic nanolayer

We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using an atomic nanolayer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift which has a spatial frequency equal to $2k$, i.e. twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for non-linear optics.

physics.atom-ph↗

arXiv2011

Manipulating ultracold atoms with a reconfigurable nanomagnetic system of domain walls

The divide between the realms of atomic-scale quantum particles and lithographically-defined nanostructures is rapidly being bridged. Hybrid quantum systems comprising ultracold gas-phase atoms and substrate-bound devices already offer exciting prospects for quantum sensors, quantum information and quantum control. Ideally, such devices should be scalable, versatile and support quantum interactions with long coherence times. Fulfilling these criteria is extremely challenging as it demands a stable and tractable interface between two disparate regimes. Here we demonstrate an architecture for atomic control based on domain walls (DWs) in planar magnetic nanowires that provides a tunable atomic interaction, manifested experimentally as the reflection of ultracold atoms from a nanowire array. We exploit the magnetic reconfigurability of the nanowires to quickly and remotely tune the interaction with high reliability. This proof-of-principle study shows the practicability of more elaborate atom chips based on magnetic nanowires being used to perform atom optics on the nanometre scale.

physics.atom-ph↗

arXiv2011

Optical preparation and measurement of atomic coherence at gigahertz bandwidth

We detail a method for the preparation of atomic coherence in a high density atomic medium, utilising a coherent preparation scheme of gigahertz bandwidth pulses. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing coherent states is found to be close to unity at the entrance to the medium. The coherence is then measured non-invasively with a probe field.

physics.atom-ph↗

arXiv2011

Optical transmission through a dipolar layer

The interaction between light and matter is fundamental to developments in quantum optics and information. Over recent years enormous progress has been made in controlling the interface between light and single emitters including ions, atoms, molecules, quantum dots and ensembles. For many systems, inter-particle interactions are typically negligible. However, if the emitters are separated by less than the emission wavelength, resonant dipole--dipole interactions modify the radiative decay rate and induce a splitting or shift of the resonance. Here we map out the transition between individual dipoles and a strongly interacting ensemble by increasing the density of atoms confined in a layer with thickness much less than the emission wavelength. We find two surprising results: whereas for a non-interacting ensemble the opacity increases linearly with atomic density, for an interacting ensemble the opacity saturates, i.e., a thin dipolar layer never becomes opaque regardless of how many scatterers are added. Secondly, the relative phase of the dipoles produces an abrupt change in the optical transmission around the thickness λ/4.

physics.atom-ph↗

arXiv2011

Polarization spectroscopy of an excited state transition

We demonstrate polarization spectroscopy of an excited state transition in room temperature cesium vapor. An anisotropy induced by a circularly polarized pump beam on the D2 transition is observed using a weak probe on the 6P3/2 to 7S1/2 transition. When the D2 transition is saturated, a sub-natural linewidth feature is observed which theoretical modeling shows is enhanced by Doppler averaging. Polarization spectroscopy provides a simple modulation-free signal suitable for laser frequency stabilization to excited state transitions.

physics.atom-ph↗

arXiv2009

Optical control of Faraday rotation in hot Rb vapor

We demonstrate controlled polarization rotation of an optical field conditional on the presence of a second field. Induced rotations of greater than pi/2 rad are seen with a transmission of 95%, corresponding to a ratio of phase shift to absorption of 40 pi. This combination of large, controlled rotation and low loss is well-suited for the manipulation of both classical and quantum light pulses.

physics.atom-ph↗

arXiv2009

Faraday filtering of Raman light in an isotopically pure alkali metal vapor

We present an application of the Faraday effect to produce a narrow band atomic filter in an alkali metal vapor. In our experiment two Raman beams separated in frequency by the ground state hyperfine splitting in 87Rb are produced using an EOM and then filtered using the Faraday effect in an isotopically pure 85Rb thermal vapor. An experimental transmission spectra for the filter is presented along with a theoretical calculation. The performance of the filter is then demonstrated and characterized using a Fabry-Perot etalon. For a temperature of 70 degrees and a longitudinal magnetic field of 80 G a suppression to -18 dB is achieved, limited by the quality of the polarizers.

physics.atom-ph↗

arXiv2008

Absolute absorption on the rubidium D lines: comparison between theory and experiment

We study the Doppler-broadened absorption of a weak monochromatic probe beam in a thermal rubidium vapour cell on the D lines. A detailed model of the susceptibility is developed which takes into account the absolute linestrengths of the allowed electric dipole transitions and the motion of the atoms parallel to the probe beam. All transitions from both hyperfine levels of the ground term of both isotopes are incorporated. The absorption and refractive index as a function of frequency are expressed in terms of the complementary error function. The absolute absorption profiles are compared with experiment, and are found to be in excellent agreement provided a sufficiently weak probe beam with an intensity under one thousandth of the saturation intensity is used. The importance of hyperfine pumping for open transitions is discussed in the context of achieving the weak-probe limit. Theory and experiment show excellent agreement, with an rms error better than 0.2% for the D2 line at 16.5 degrees C.

physics.atom-ph↗