Exploring, tailoring, and traversing the solution landscape of a phase-shaped CARS process

Rhijn, A.C.W. van; Offerhaus, Herman L.; Walle, Peter van der; Herek, Jennifer Lynn; Jafarpour, Aliakbar

doi:10.1364/oe.18.002695

Cited by 15 publications

(18 citation statements)

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“…The present diagram may be extended to include more elaborate pulse sequences 20 as well as pulse shaping effects. 21 We have shown that electronically off resonant stimulated Raman measurements cannot possess both high temporal and spectral resolution, beyond the transform limit. The signal is determined by the evolution during a single time interval, representing backward propagation from t to T .…”

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confidence: 99%

Communication: Comment on the effective temporal and spectral resolution of impulsive stimulated Raman signals

Mukamel

Biggs

2011

The Journal of Chemical Physics

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A compact correlation-function expression for time-resolved stimulated Raman signals, generated by combining a spectrally narrow (picosecond) with a broad (femtosecond) pulse, is derived using a closed time path loop diagrammatic technique that represents forward and backward time evolution of the vibrational wave function. We show that even though the external spectral and temporal parameters of the pulses may be independently controlled, the effective temporal and spectral resolution of the experiment may not exceed the fundamental bandwidth limitation.

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confidence: 99%

Communication: Comment on the effective temporal and spectral resolution of impulsive stimulated Raman signals

Mukamel

Biggs

2011

The Journal of Chemical Physics

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“…Various methods developed so far include exploiting the polarization dependences of the resonant and nonresonant components of χ (3) [1][2][3][4][5], directly measuring [6][7][8] or extracting [9][10][11] the vibrational phase of the oscillators, shaping the phase of a broadband optical pulse to match that of the molecule [12][13][14][15], or introducing temporal delays to probe the resonant vibrational state after the nonresonant coherence has decayed [16,17].…”

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confidence: 99%

Background-free nonlinear microspectroscopy with vibrational molecular interferometry

et al. 2012

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We demonstrate a method for performing nonlinear microspectroscopy that provides an intuitive and unified description of the various signal contributions, and allows the direct extraction of the vibrational response. Three optical fields create a pair of Stokes Raman pathways that interfere in the same vibrational state. Frequency modulating one of the fields leads to amplitude modulations on all of the fields. This vibrational molecular interferometry technique allows imaging at high speed free of nonresonant background, and is able to distinguish between electronic and vibrational contributions to the total signal.For a number of decades much of the development of new coherent anti-Stokes Raman scattering (CARS) techniques has been focused on suppressing or eliminating the persistent nonresonant background that reduces contrast and can render experiments involving low concentrations of resonant oscillators impossible. Various methods developed so far include exploiting the polarization dependences of the resonant and nonresonant components of χ (3) [1][2][3][4][5], directly measuring [6][7][8] or extracting [9][10][11] the vibrational phase of the oscillators, shaping the phase of a broadband optical pulse to match that of the molecule [12][13][14][15], or introducing temporal delays to probe the resonant vibrational state after the nonresonant coherence has decayed [16,17].Recent work by Rahav and Mukamel [18] introduced a new paradigm regarding coherent Raman scattering experiments. Rather than operating in the common semiclassical field perspective, they focus on energy transfer from a molecular quantum mechanical point of view. The semiclassical approach of nonlinear optics assumes classical fields interacting with quantum matter. The detected mode is singled out from the outset and is described using the macroscopic Maxwell's equations. Heterodyne detection is viewed as an interference of the signal field with a local oscillator field, which makes it hard to establish connections between different experiments with the same pulse configuration where different modes are detected. The quantum description of heterodyne-detected four-wave mixing is much more transparent. We consider a steady state of the molecule with ground state |a〉 and vibrational state |c〉, and four modes of the radiation field (ω 1 − ω 2 = ω 4 − ω 3 = ω ca , with ω 2 < ω 1 and ω 3 < ω 4 ). The optical field modes are all far detuned from the lowest electronic excited state |b〉. All modes, including the local oscillator, are treated in the same © 2011 American Physical Society * To whom all correspondence should be addressed. h.l.offerhaus@utwente.nl. , is the interference of these two processes that yields the resonant component of the CARS signal, and is associated with the imaginary component of χ (3) . This resonant dissipative term involves energy that is transferred from the optical fields into the molecule. In addition to this dissipative term there is a nonresonant parametric component S par that is equivalent to the real ...

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“…In particular, a strong, frequencyindependent non-resonant background interferes with the resonant signal of interest, reducing contrast and creating imaging and spectral artifacts that can be difficult to interpret. In order to remove, suppress, or extract this non-resonant background, a number of specialized methods have been developed that exploit polarization [9,13,14], spectral [15], time [16][17][18], and/or phase [19][20][21] dependencies of the CARS process. This last feature is of particular interest because it can be used to determine the full complex vibrational response of an arbitrary sample [22].…”

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Epi-detection of vibrational phase contrast coherent anti-Stokes Raman scattering

et al. 2014

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We demonstrate a system for the phase-resolved epi-detection of coherent anti-Stokes Raman scattering (CARS) signals in highly scattering and/or thick samples. With this setup, we measure the complex vibrational responses of multiple components in a thick, highly-scattering pharmaceutical tablet in real time and verify that the epi-and forward-detected information are in very good agreement. Coherent anti-Stokes Raman scattering (CARS) has matured in recent years into an imaging and spectroscopy technique that is finding applications in a range of disciplines including biology [1][2][3][4], remote sensing [5,6], and pharmaceutics [7,8]. The high spatial and spectral resolutions of CARS, combined with its capabilities for imaging in both transmission and reflection [9,10] at speeds up to video rate [11], have led to work specifically aimed at bringing down costs and complexity [12] to enable its use by non-specialists. However, this technique is not without problems. In particular, a strong, frequencyindependent non-resonant background interferes with the resonant signal of interest, reducing contrast and creating imaging and spectral artifacts that can be difficult to interpret. In order to remove, suppress, or extract this non-resonant background, a number of specialized methods have been developed that exploit polarization [9,13,14], spectral [15], time [16][17][18], and/or phase [19][20][21] dependencies of the CARS process. This last feature is of particular interest because it can be used to determine the full complex vibrational response of an arbitrary sample [22]. We previously introduced a method known as vibrational phase contrast CARS (VPC-CARS) to measure the pure vibrational phase of a sample [23], and used it to measure the full vibrational responses of multiple materials in both heterogeneous and homogeneous mixtures [24]. Heterodyne CARS measurements, in which an external local oscillator is interfered with the CARS emission, contain information about both the vibrational phase of the molecular oscillators and the relative local phases of the optical excitation fields. The local excitation phase is subject to disturbances from the variations in the relative phases of the pump, Stokes, and local oscillator beams, which can come from refractive index differences in the sample, interferometric instabilities, and field-of-view curvature resulting from dispersion in the focusing objective lens. To remove these effects a separate measurement is made in which only the local excitation phase is detected. The difference of the heterodyne and local excitation phases is the pure vibrational phase of the molecular oscillators. In previous experiments, heterodyne and local excitation phase measurements were performed in series on a pixel-by-pixel basis, with the local oscillator at nanowatt levels for the heterodyne process and at multi-millwatt powers for the local excitation phase detection. The exact power of the heterodyne local oscillator was a critical parameter for obtaining shot-noise-limited measurem...

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Exploring, tailoring, and traversing the solution landscape of a phase-shaped CARS process

Cited by 15 publications

References 38 publications

Communication: Comment on the effective temporal and spectral resolution of impulsive stimulated Raman signals

Communication: Comment on the effective temporal and spectral resolution of impulsive stimulated Raman signals

Background-free nonlinear microspectroscopy with vibrational molecular interferometry

Epi-detection of vibrational phase contrast coherent anti-Stokes Raman scattering

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