Photo Echo and Optical Nutation in Molecules

Brewer, Richard G.; Shoemaker, R. L.

doi:10.1103/physrevlett.27.631

Cited by 335 publications

(76 citation statements)

References 23 publications

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“…A detailed understanding of this behaviour is crucial to analyze pumpprobe experiments in which dynamics takes place on the same time scale as laser interaction. Due to the difficulty to control properly the laser pulses, the effects of CT are most often ignored [11].Similarities can be found with optical CT observed in the experiments of free induction decay or photon echoes which provide relaxation rates [12][13][14]. In these experiments, they observed on the transmitted optical signal, a beat between initially induced polarisation of the medium at resonance and a near-resonant laser.…”

supporting

confidence: 63%

Observation of Coherent Transients in Ultrashort Chirped Excitation of an Undamped Two-Level System

et al. 2001

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The effects of Coherent excitation of a two level system with a linearly chirped pulse are studied theoretically and experimentally (in Rb (5s -5p)) in the low field regime. The Coherent Transients are measured directly on the excited state population on an ultrashort time scale. A sharp step corresponds to the passage through resonance. It is followed by oscillations resulting from interferences between off-resonant and resonant contributions. We finally show the equivalence between this experiment and Fresnel diffraction by a sharp edge.Coherent excitation of atomic transitions is a general phenomenon occurring whenever electromagnetic radiation interacts with atoms. This interaction may result in various kinds of processes, for example Rabi oscillations, free induction decay, adiabatic population transfer and Coherent Transients (CT) [1]. By simply varying the temporal shape of the pulses, a great variety of systems can be manipulated such as spins in Nuclear Magnetic Resonance [2] or atomic and molecular systems in coherent control schemes [3]. We consider here the simplest case of linearly chirped pulses where the "instantaneous frequency" drifts in time.Depending on the frequency sweep and on the intensity, adiabatic following can be observed with a significant population transfer. For example total population transfer has been achieved via multilevel ladder climbing [4][5][6][7][8][9] and Stimulated Raman Adiabatic Passage [10].On the contrary if the adiabaticity criterion is not fulfilled, the final population depends crucially on the pulse integral and CT dominate the interaction. This letter presents theoretical and experimental studies of these Coherent Transients. Although many works have dealt with the transfer efficiency into the final state, we report here the first direct observation of these transients on a subpicosecond time scale. The CT result in oscillating population. This is a signature of interferences between resonant and non-resonant excitation. A detailed understanding of this behaviour is crucial to analyze pumpprobe experiments in which dynamics takes place on the same time scale as laser interaction. Due to the difficulty to control properly the laser pulses, the effects of CT are most often ignored [11].Similarities can be found with optical CT observed in the experiments of free induction decay or photon echoes which provide relaxation rates [12][13][14]. In these experiments, they observed on the transmitted optical signal, a beat between initially induced polarisation of the medium at resonance and a near-resonant laser. In the particular case of a single chirped optical pulse, the beat frequency increases linearly after passage through resonance, following the increase of resonance mismatch [15]. On the contrary to these previous studies, the present report involves CT directly observed on the population before relaxation becomes significant. The beats result here from interferences between the resonant and non-resonance excitation paths. The passage through resonance does not ...

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supporting

confidence: 63%

Observation of Coherent Transients in Ultrashort Chirped Excitation of an Undamped Two-Level System

et al. 2001

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“…2b or 8c). The mathematical description follows earlier work on two-level systems by Brewer and coworkers [55,56], or the work on commensurate echoes in THz time-domain spectroscopy [11] or rotational recurrences in pump probe spectroscopy [57,58]. Of course, there is no particular reason to view the signature in the purely time or frequency domains, and in Fig.…”

Section: Nsec 46 Nsecmentioning

confidence: 99%

Coherent dual-comb spectroscopy at high signal-to-noise ratio

2010

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Two coherent frequency combs are used to measure the full complex response of a sample in a configuration analogous to a dispersive Fourier transform spectrometer, infrared time domain spectrometer, or a multiheterodyne laser spectrometer. This dual comb spectrometer retains the frequency accuracy and resolution of the reference underlying the stabilized combs. We discuss the specific design of our coherent dual-comb spectrometer and demonstrate the potential of this technique by measuring the overtone vibration of hydrogen cyanide, centered at 194 THz (1545 nm). We measure the fully normalized, complex response of the gas over a 9 THz bandwidth at 220 MHz frequency resolution yielding 41,000 resolution elements. The average spectral signal-to-noise ratio (SNR) over the 9 THz bandwidth is 2,500 for both the magnitude and phase of the measured spectral response and the peak SNR is 4,000. This peak SNR corresponds to a fractional absorption sensitivity of 0.05% and a phase sensitivity of 250 microradians. As the spectral coverage of combs expands, coherent dual-comb spectroscopy could provide high frequency accuracy and resolution measurements of a complex sample response across a range of spectral regions.Work of U.S. government, not subject to copyright.

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“…The pulses must be nearly collinear to observe any T 2 effects, since otherwise Acf> will vary rapidly over a small volume, cos(Acf>) and sin(Acf>) will average to 0, and then Eq. (39) shows that C will vanish. In addition, if B 1 = 8 2 , ~1 = ~2 , and Acf> = ir/2, then C = 0 and only T 1 decay is observed.…”

Section: A Pulse Sequences For T 1 and T 2 Measurements: Fluorescencmentioning

confidence: 99%

“…Finally, Eqs. (38) and (39) show that, in the general case, incrementing Acf> by ir (i.e., inverting the second pulse) has no effect on B but multiplies C by -1. This could also be seen by noting that the a .. coefficient of u• a• U is unaffected by a 180° phase shift, but the a" and ay coefficients are inverted (Fig.…”

Section: A Pulse Sequences For T 1 and T 2 Measurements: Fluorescencmentioning

confidence: 99%

Multiple phase-coherent laser pulses in optical spectroscopy I: The technique and experimental applications

Warren¹,

Zewail²

1994

World Scientific Series in 20th Century Chemistry

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In this series of papers we report on the generation and application of multiple pulse phase coherent sequences in optical spectroscopy. In this paper the effects of intense pulse trains on systems with only two resonant energy levels are analyzed, with particular attention to the effects of extreme inhomogeneous broadening and population depletion to nonresonant levels. It is shown that these effects, which are present in virtually all optical systems, make the simple gyroscopic model of optical coherent transients invalid. Exact calculations show, e.g., that a two-pulse photon echo is not maximized by a 1:2 length ratio for the pulses; that the maximum excited state population is not created by a 180" pulse; and that three equal pulses are almost as effective as a 1:2:1 ratio for producing three pulse echoes. The role of pulse phase is extensively analyzed. Pulse sequences are proposed and experimentally demonstrated which permit optical phase sensitive detection and measurement of ground state relaxation parameters. The experimental results are based on an extension of the acousto-optic modulation and fluoresence detection techniques of Zewail and Orlowski [Zewail et al., Chem. Phys. Lett. 48, 256 (1977); Orlowski et al., ibid. 54, 197 (1978)). The relative merits offluorescence and transverse polarization detection are discussed, and fluorescence detection is shown to be more generally useful for these new sequences. Finally, composite pulse trains are shown to be capable of substantially increasing the signal available from highly inhomogenously broadened transitions. In paper II we extend the treatment to multilevel systems with some emphasis on solid state applications.

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Photo Echo and Optical Nutation in Molecules

Cited by 335 publications

References 23 publications

Observation of Coherent Transients in Ultrashort Chirped Excitation of an Undamped Two-Level System

Observation of Coherent Transients in Ultrashort Chirped Excitation of an Undamped Two-Level System

Coherent dual-comb spectroscopy at high signal-to-noise ratio

Multiple phase-coherent laser pulses in optical spectroscopy I: The technique and experimental applications

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