Low-distortion slow light using two absorption resonances

We consider group delay and broadening using two strongly absorbing and widely spaced resonances. We derive relations which show that very large pulse bandwidths coupled with large group delays and small broadening can be achieved. Unlike single resonance systems, the dispersive broadening dominates the absorptive broadening which leads to a dramatic increase in the possible group delay. We show that the double resonance systems are excellent candidates for realizing all-optical delay lines. We report on an experiment which achieved up to 50 pulse delays with 40% broadening.Comment: 4 pages 4 figure

Rapidly reconfigurable slow-light system based on off-resonant Raman absorption

We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant Λ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates

Realization of an all-optical zero to π cross-phase modulation jump

We report on the experimental demonstration of an all-optical π cross-phase modulation jump. By performing a preselection, an optically induced unitary transformation, and then a postselection on the polarization degree of freedom, the phase of the output beam acquires either a zero or π phase shift (with no other possible values). The postselection results in optical loss in the output beam. An input state may be chosen near the resulting phase singularity, yielding a pi phase shift even for weak interaction strengths. The scheme is experimentally demonstrated using a coherently prepared dark state in a warm atomic cesium vapor

Transients of the Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity

We report observations of the dynamics of electromagnetically induced transparency (EIT) in a Λ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well with theory

Electromagnetically Induced Transparency Line Shapes for Large Probe Fields and Optically Thick Media

We calculate the line shape and linewidths for electromagnetically induced transparency (EIT) in optically thick, Doppler broadened media (buffer gasses are also considered). In generalizing the definition of the EIT linewidth to optically thick media, we find two different linewidth definitions apply depending on whether the experiment is pulsed or continuous wave (cw). Using the cw definition for the EIT line shape we derive analytic expressions describing the linewidth as a function of optical depth. We also review the EIT line shapes in optically thin media and provide physical arguments for how the line shapes change as a function of various parameters

Transients of the Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity: Theory

We present a theory describing the transients and rise times of the refractive Kerr nonlinearity which is enhanced using electromagnetically induced transparency (EIT). We restrict our analysis to the case of a pulsed signal field with continuous-wave EIT fields, and all fields are well below saturation. These restrictions enable the reduction of an EIT Kerr, four-level, density-matrix equation to a two-level Bloch-vector equation which has a simple and physically intuitive algebraic solution. The physically intuitive picture of a two-level Bloch vector provides insights that are easily generalized to more complex and experimentally realistic models. We consider generalization to the cases of Doppler broadening, many-level EIT systems (we consider the D1 line of 87Rb), and optically thick media. For the case of optically thick media we find that the rise time of the refractive EIT Kerr effect is proportional to the optical thickness. The rise time of the refractive EIT Kerr effect sets important limitations for potential few-photon applications

Three-dimensional characterisation of sedimentary heterogeneity and its impact on subsurface flow behaviour through the braided-to-meandering fluvial deposits of the Castissent Formation (late Ypresian, Tremp-Graus Basin, Spain)

Thanks, are given to Schlumberger for the donation of the Petrel E&P licenses, to the Virtual Outcrop Geology Group for the donation of LIME licenses, to Petroleum Experts for the donation of MOVE licenses, to Innovmetric for the donation of the Polyworks license and to Agisoft for the donation of the Agisoft Photoscan license. Magda Chmielewska is acknowledged for the technical support during the virtual outcrop processing. Support from the Ministerio de Economía y Competitividad (Project SEROS CGL2014-55900-P) and from the Generalitat de Catalunya (2017SGR596) is gratefully acknowledged. Thanks to reviewers Brian Willis and César Viseras and also to the Associate Editor Luca Colombera for their constructive comments, which have improved the content of this paper.Peer reviewedPostprin

Storage and Retrieval of Multimode Transverse Images in Hot Atomic Rubidium Vapor

We report on the experimental realization of the storage of images in a hot vapor of Rubidium atoms. The images are stored in and retrieved from the long-lived ground state atomic coherences. We show that an image impressed onto a 500 ns pulse can be stored and retrieved up to 30  μs later. The image storage is made robust to diffusion by storing the Fourier transform of the image

Slow Light with Large Fractional Delays By Spectral Hole-Burning in Rubidium Vapor

We report on the experimental realization of large fractional pulse delays in a hot, Doppler-broadened rubidium vapor. A pump laser burns a deep spectral hole in the inhomogeneously broadened vapor. The delay is shown to be widely tunable by both power broadening the resonance and frequency modulating the pump laser. The simplicity of the scheme opens up the possibility for practical optical delays and buffers

Child Care Needs of Low- Income Employed Parents in Milwaukee County Under W-2

This report assesses the current use and availability of child care as well as estimating potential demand for child care under W-2. The analysis focuses on Milwaukee County and examines the challenges facing local agencies and community organizations as they seek to provide adequate child care for parents entering the labor force, expanding their work hours, or participating in mandatory community service activities. To provide an analysis of current child care openings and capacity, the Employment and Training Institute conducted a survey of all regulated day care providers in Milwaukee County central city neighborhoods and a sample survey of the certified child care providers currently active with the Milwaukee County Department of Human Services. The Institute analyzed current usage in subsidized child care programs using data on all Milwaukee County child care payments for the month of February 1996 and all child care deductions taken for Milwaukee County children receiving AFDC or food stamps. Estimates of the current and potential demand for child care under W-2 were constructed using a database of all children and families on public assistance in Milwaukee County and U.S. Census data on employed low-income families in Milwaukee County not receiving public assistance