Raman Echo Research Articles

Atmospheric Thermodynamic Profiling through the Use of a Micro-Pulse Raman Lidar System: Introducing the Compact Raman Lidar MARCO.

It was for a long time believed that lidar systems based on the use of high-repetition micro-pulse lasers could be effectively used to only stimulate atmospheric elastic backscatter echoes, and thus were only exploited in elastic backscatter lidar systems. Their application to stimulate rotational and roto-vibrational Raman echoes, and consequently, their exploitation in atmospheric thermodynamic profiling, was considered not feasible based on the technical specifications possessed by these laser sources until a few years ago. However, recent technological advances in the design and development of micro-pulse lasers, presently achieving high UV average powers (1-5 W) and small divergences (0.3-0.5 mrad), in combination with the use of large aperture telescopes (0.3-0.4 m diameter primary mirrors), allow one to presently develop micro-pulse laser-based Raman lidars capable of measuring the vertical profiles of atmospheric thermodynamic parameters, namely water vapor and temperature, both in the daytime and night-time. This paper is aimed at demonstrating the feasibility of these measurements and at illustrating and discussing the high achievable performance level, with a specific focus on water vapor profile measurements. The technical solutions identified in the design of the lidar system and their technological implementation within the experimental setup of the lidar prototype are also carefully illustrated and discussed.

Scalable time reversal of Raman echo quantum memory and quantum waveform conversion of light pulse

We have found a new hidden symmetry of time reversal light–atom interaction in the photon echo quantum memory with Raman atomic transition. The time-reversed quantum memory creates generalized conditions for the ideal compression/decompression of time duration of the input light pulses and its wavelength. Based on a general analytical approach to this scheme, we have studied the optimal conditions for the light field compression/decompression in resonant atomic systems characterized by realistic spectral properties. The demonstrated necessary conditions for the effective quantum conversion of the light waveform and wavelength are also discussed for various possible realizations of the quantum memory scheme. The performed study promises new capabilities for fundamental study of the light–atom interaction and deterministic quantum manipulation of the light field, significant for quantum communication and quantum computing.

Concentration dependence of absorption and optical and hyperfine transition dynamics in Pr3 +:La2(WO4)3

Optical and hyperfine parameters of the 3H4–1D2 transition are investigated in Pr3 +:La2(WO4)3 for doping concentrations ranging from 0.02 to 3 at.%, at liquid helium temperatures. This includes optical inhomogeneous and homogeneous linewidths, peak absorption, excited-state population decays, spectral hole lifetime and inhomogeneous and homogeneous hyperfine linewidths. Optical inhomogeneous broadening with increasing Pr3 + concentration is limited due to close atomic radii between Pr3 + and La3 +. The peak absorption coefficient increases with increasing Pr3 + doping, reaching up to 28 cm−1. At the highest Pr3 + concentration, optical coherence lifetime is 4.6 μs and hole lifetime 2 s, which should allow one to transfer coherences and tailor the optical inhomogeneous linewidth, as required for rare earth-based optical quantum memories. Raman echo experiments show that hyperfine inhomogeneous linewidth and coherence lifetime (50 kHz and 250 μs respectively) are independent of Pr3 + concentration. These results suggest that highly doped crystals are useful for efficient and long-storage time quantum memories.

Photon echoes upon Raman transitions

An analytical review of the development of the Raman echo technique is presented. We show that the use here of femtosecond extremely short pulses broadens the possibilities of Raman media.

Hyperfine structure and hyperfine coherent properties of praseodymium in single-crystallineLa2(WO4)3by hole-burning and photon-echo techniques

We studied the hyperfine structure and hyperfine coherent properties of the H-3(4)(0)-> D-1(2)(0) transition of Pr3+ ions in a tungstate single crystal La-2(WO4)(3) by hole-burning and photon-echo techniques. This work is motivated by the search of an efficient three level Lambda system in this new compound with which we could build up a quantum memory. By nonconventional hole-burning experiments, the ordering of the hyperfine splittings in the H-3(4)(0) ground state and in the D-1(2)(0) excited state is obtained. The hyperfine splittings are thus ordered: 24.6 and 14.9 MHz for the H-3(4)(0) level and 5.0 and 7.3 MHz for the D-1(2)(0) level. The relative and absolute transition strengths of individual hyperfine transitions are determined by comparing absorption strengths and by measuring the Rabi flopping frequency as the transition is coherently driven. Free induction and Raman echo decays give inhomogeneous and homogeneous hyperfine linewidths of 57 +/- 2 and 1.25 +/- 0.1 kHz, respectively. (Less)

Optical excitation of nuclear spin coherence in aTm3+:YAGcrystal

A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. The nuclear spin coherence is optically excited, detected, and characterized in such a crystal. The lifetime of the spin coherence---the potential storage entity---is measured by means of a new Raman echo protocol to be about $300\text{ }\ensuremath{\mu}\text{s}$ over a wide range of ground state splittings. This flexibility, which is attractive for broadband operation and well fitted to existing quantum sources, results from the simple hyperfine structure, which contrasts to Pr- and Eu-doped crystals.

Librational echo: Subpicosecond intermolecular interactions in liquid

The ultrafast optical Kerr effect observed in liquids upon two-pulse laser excitation is studied theoretically. It is shown that a Raman echo on librational frequencies (librational echo) can be excited in liquid. The librational echo has the following features: its shape and amplitude strongly depend on the local inhomogeneity of a medium and the form of local potentials; and the echo signal can be separated into the contributions of the phase and irreversible relaxation of coherent molecular librations. These properties of the librational echo can be used for studying the specific features of the local structure of liquids by the method of selective subpicosecond spectroscopy of molecular librations.

Optical investigation of nuclear spin coherence in Tm:YAG

With all-optical means, the nuclear spin coherence lifetime is measured for the first time in a crystal doped with low-concentration thulium. A novel Raman echo scheme is demonstrated. The hyperfine splitting is varied over a 15 MHz-wide range with the help of an external magnetic field. Over this range the spin coherence lifetime remains close to 350 μs in the electronic ground state. Thulium-doped materials are proved to be interesting substitutes to other rare earth ion-doped crystals as quantum memory candidates, thanks to their convenient wavelength, their adjustable three-level system and their stable and long spin coherence lifetime.

Erratum: “Two Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System–Bath Interactions: I. Gaussian-White Case”

The quantum Fokker-Planck equation is derived for a system nonlinearly coupled to a harmonic oscillator bath. The system-bath interaction is assumed to be linear in the bath coordinates but quadratic in the system coordinate. The relaxation induced dynamics of a harmonic system are investigated by simulating the higher-order correlation functions of the Raman polarizability and the dipole moment, which represent the nonlinear optical responses of Raman or infrared spectroscopy. The 5th-order Raman response shows that, in addition to the frequency fluctuations induced by the bath, higher-order energy transfer between the system and bath plays a role. The nonlinearity of the system-bath interaction yields also an interesting feature in the 7th-order Raman echo or the 3rd-order infrared photon echo response: The calculations predict a finite signal for the case of a harmonic potential and a linear coordinate dependence of the polarizability or dipole while for linear system-bath coupling this response vanishes completely due to destructive interference of different Liouville space pathways.

Controlled rotational Raman echo recurrences and modulation of high-intensity ultrashort laser pulses by molecular rotations in the gas phase

We show that sequences of femtosecond laser pulses can control the rotational Raman response of a gas mixture, giving rise to a tunable manifold of echo recurrences in the retarded nonlinear-optical response of the gas. Tailored phase masks for high-intensity ultrashort laser pulses are experimentally demonstrated using molecular rotations in the gas phase driven by optimally time-ordered pulse sequences.

Raman echo under medium excitation by extremely short pulses

A generalization of the Bloembergen-Shen model to Raman active molecules with an arbitrary number of normal modes was suggested. The generalized model was used to study Raman echo signal characteristics when a system of molecules was excited by pulses of widths up to one period of optical oscillations. It was shown that a large number of echo responses on Stokes and anti-Stokes components could arise even under a two-pulse action in a continuous monochromatic pumping field. The number of echo responses depended on the number of molecular normal modes and the geometry of measurements. At small exciting pulse “areas,” the echo responses whose Stokes and anti-Stokes components corresponded to normal vibrational modes of a molecule had the highest intensity, whereas the components formed by normal mode combinations were strongly suppressed.

Raman echo induced by ultimately short pulses under conditions of strong nonresonant pumping

On the basis of quantum-mechanical approach, a theoretical study of the primary Raman photon echo was carried out under conditions of excitation of a medium by pulses with a duration on the order of one period of electromagnetic oscillations (ultimately short pulses) and by strong quasi-monochromatic nonresonant pumping. It is shown that the intensities of the pumps determine to a considerable extent the time of formation of the echo signal, its duration, the direction of emission, and the power and that the use of ultimately short pulses promotes the substantial simplification of the schemes of prospective experiments. The possibilities of echo generation at the Stokes and anti-Stokes frequencies in the regimes of two-, one-, and zero-pulse excitations are revealed. In the last case, the Raman-active transitions are excited by two pumps with different intensities.

Two-Dimensional Raman Echoes: Femtosecond View of Molecular Structure and Vibrational Coherence

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTwo-Dimensional Raman Echoes: Femtosecond View of Molecular Structure and Vibrational CoherenceShaul Mukamel, Andrei Piryatinski, and Vladimir ChernyakView Author Information Department of Chemistry, University of Rochester, P.O. RC Box 270216, Rochester, New York 14627-0216 Cite this: Acc. Chem. Res. 1999, 32, 2, 145–154Publication Date (Web):November 6, 1998Publication History Received6 March 1998Published online6 November 1998Published inissue 1 February 1999https://doi.org/10.1021/ar960206yCopyright © 1999 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views570Altmetric-Citations135LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (172 KB) Get e-AlertsSUBJECTS:Molecules,Nuclear magnetic resonance spectroscopy,Oscillation,Probes,Quantum mechanics Get e-Alerts

Spin coherence excitation and rephasing with optically shelved atoms

We investigate the use of resonant optical Raman pulses to excite and rephase ground state spin coherences via the partial storage or shelving of atoms. Unlike direct-rf-excited spin echoes or off-resonant Raman echoes, the resonant Raman optical field efficiently excites and rephases the spin coherence using \ensuremath{\pi} and 2\ensuremath{\pi} pulses, respectively. In a crystal of ${\mathrm{Pr}}^{3+}$ doped ${\mathrm{Y}}_{2}{\mathrm{SiO}}_{5},$ we experimentally observe spin echo efficiency as high as 46% of the free induction decay signal.

Perturbation analysis of Raman echo

A time-dependent perturbational approach is used to study the Raman echo generated by an inhomogeneous ensemble of three-level atomic systems in the Λ configuration. The sixth-order perturbative solution for coherence between the two lower states contains eight echo terms that are visualized with double Feynman diagrams. The echo is interpreted as a response of the ensemble to six short single-frequency optical pulses whose timing satisfies a special condition. Nonperturbative numerical simulation confirms the predictions of the perturbation analysis about the main characteristics of the echo. When the excitation pulses vary adiabatically with respect to fast optical coherence decay the echo amplitude depends on interference of the eight terms. A computational scheme developed for the higher-order perturbative analysis is also discussed.

Fifth and seventh order nonlinear spectroscopy with femtosecond pulses

Temporally two-dimensional non-resonant Raman spectroscopies, which are based on higher order susceptibilities, have been developed to distinguish homogeneous and inhomogeneous contributions to vibrational dephasing. We have performed five-pulse correlation experiments to study low frequency intermolecular vibrational dephasing of liquid CS 2 and estimated the inhomogeneous width for the underdamped mode. By the Raman echo experiment we found the C≡N stretching of benzonitrile is homogeneously broadened.

Liquid dynamics studied by higher order non-linear optical spectroscopy

Temporally two-dimensional non-resonant Raman spectroscopies, which are based on higher order susceptibilities, have been developed to distinguish homogeneous and inhomogeneous contributions to vibrational dephasing. The five-pulse correlation experiment was performed to study low frequency intermolecular vibrational dephasing of liquid CS 2, and the Raman echo experiment was conducted to investigate the CN stretching of benzonitrile. In the both cases it is found that homogeneous dephasing is dominant.

Ultrafast Raman echo experiments in liquids

AbstractThe Raman echo is the first of the eight‐wave mixing spectroscopic techniques to be experimentally demonstrated in molecular systems. Practical results achievable in such high‐order experiments are described. Signal levels, competing non‐linear effects, phase‐matching requirements and other experimental design considerations are discussed. Results needed to predict the success of experiments at different power levels, Raman cross‐sections and concentrations are presented.

Rapid, homogeneous vibrational dephasing in ethanol at low temperatures determined by Raman echo measurements

Raman echo and Raman free-induction decay experiments on the broad Raman transition of the sym-methyl stretch ofethanol-1,1- d 2 were performed in the room-temperature liquid, just below the glass transition (80 K) and in the low-temperature glass (12 K). Contrary to standard theories, the dephasing remains both rapid and homogeneous at low temperatures. We suggest that the dephasing is caused by very rapid (225–365 fs), solvent-assisted intramolecular vibrational redistribution.

Observation of homogeneous vibrational dephasing in benzonitrile by ultrafast Raman echoes

Raman echoes are observed for the C  N stretching of benzonitrile in the liquid phase. It is found that the vibrational line broadening of C  N stretching is mainly due to a homogeneous effect. An experimental method involving amplified ultrafast laser pulses of two colors at a high repetition rate and phase sensitive detection of the echo signal is described.