Saturated Raman scattering for sub-diffraction-limited imaging

Würthwein, Thomas; Irwin, Niels; Fallnich, Carsten

doi:10.1063/1.5128874

Cited by 15 publications

(17 citation statements)

References 41 publications

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“…[ 12‐15 ] Especially, artifacts due to XPM distort the line shape of the stimulated Raman signal and become more relevant for high pulse energies and ultra‐short pulse durations as used in a number of experiments. [ 16‐20 ]…”

Section: Introductionmentioning

confidence: 99%

“…One example in the current research, where pulse energies in the order of hundreds of nano‐joules and pulses with a duration in the femtosecond regime are needed, is the field of spatial resolution enhancement in CRS, [ 18,20‐25 ] to overcome the diffraction limit given by Abbe. [ 26 ] All these methods are based on depleting one of the three scattering resources: the pump photons, the Stokes photons, or the molecules in the ground state.…”

Section: Introductionmentioning

confidence: 99%

“…[ 26 ] All these methods are based on depleting one of the three scattering resources: the pump photons, the Stokes photons, or the molecules in the ground state. Although the depletion of one of the resources for the Raman process shows a high potential for super‐resolution microscopy, there are a few drawbacks: Besides, a complex setup with three different beams included, high pulse energies in the order of 200–300 nJ are needed, [ 17‐20,22 ] which besides damaging the sample introduce unwanted effects, like XPM, disturbing the measurable spectrum.…”

Section: Introductionmentioning

confidence: 99%

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Mitigating cross‐phase modulation artifacts in femtosecond stimulated Raman scattering

Würthwein

Lüpken

Irwin

et al. 2020

J Raman Spectroscopy

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In contrast to spontaneous Raman scattering, coherent Raman scattering techniques, such as femtosecond stimulated Raman scattering (FSRS), show advantages for many applications. Besides an enhanced signal strength, FSRS is free of a nonresonant background but is affected by cross‐phase modulation (XPM). The resulting artifacts in FSRS become relevant for high pulse intensities (GW/cm2‐regime) and ultrashort pulses (<2 ps), both necessary for super‐resolution experiments. As the pulse duration is a crucial parameter for XPM as well as for FSRS, we present a setup in which we adjust the pulse duration across the relevant range (0.5–3 ps), in order to investigate the XPM influence on the spectra. Furthermore, we vary the peak intensity, the temporal overlap between the interacting pulses, and the nonlinear refractive index coefficient n2 of the sample, showing that a trade‐off between all these quantities enables the measurement of unaffected FSRS spectra

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mitigating cross‐phase modulation artifacts in femtosecond stimulated Raman scattering

Würthwein

Lüpken

Irwin

et al. 2020

J Raman Spectroscopy

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“…[18,19] To avoid the use of fluorophores, label-free superresolution techniques have been the focus of significant research efforts. [4,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Techniques based on Raman spectroscopy have drawn interest due to the fact that it probes vibrational modes that are inherent in a given molecule. Even if an analyte of interest has a Raman spectrum that makes it difficult to isolate in a matrix containing similar vibrations, a very small vibrational tag can be used to provide contrast.…”

Section: Introductionmentioning

confidence: 99%

Stimulated Raman imaging below the diffraction limit with a MHz laser

Graefe

Punihaole

Lynch

et al. 2020

J Raman Spectroscopy

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Super‐resolution techniques based on Raman spectroscopy could be implemented as label‐free alternatives to fluorescence‐based techniques due to their chemically specific signal and multiplexing potential. In previous work, we developed a stimulated Raman‐based imaging technique that surpassed the diffraction limit using a toroidally shaped pulse to deplete the signal in a spatially defined area. The photophysical principles of depletion and improved spatial resolution were demonstrated using a 1‐kHz laser with high peak power that were able to efficiently drive depletion. However, this laser was not well suited for soft matter samples, which degraded under the intense beams. To improve the biological capabilities of our setup, we have adapted our technique for a 2.04‐MHz laser system. The increased repetition rate produces far more spectra per second, allowing us to decrease the pulse powers while maintaining reasonable acquisition times. Using the 2.04‐MHz laser, we are able to demonstrate strong signal depletion of 62% and resolution enhancements of 52%, which is comparable with the metrics obtained with the 1‐kHz laser. However, further improvements in resolution were not achieved despite increases in the depletion beam energy relative to the other beams. Frequency‐resolved optical gating analysis of the fundamental output of the 2.04 MHz laser indicated an inconsistent pulse phase and duration. We expect that the inconsistent depletion was a result of this pulse profile and conclude that efficient depletion depends on highly reproducible and stable laser pulses.

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“…Achieving vibrational subdiffraction imaging is an ongoing quest, − interest in which has been motivated by the successful implementation of fluorescence techniques like stimulated emission depletion (STED), structured-illumination microscopy, stochastic optical reconstruction microscopy (STORM), and photoactivated localization microscopy (PALM) . These methods have made it possible to probe samples with features that are sub-10 nm on a routine basis.…”

Section: Introductionmentioning

confidence: 99%

Spectral Narrowing Accompanies Enhanced Spatial Resolution in Saturated Coherent Anti-Stokes Raman Scattering (CARS): Comparisons of Experiment and Theory

et al. 2020

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We demonstrate theoretically and confirm experimentally the mechanism by which spectral narrowing accompanies enhanced spatial resolution in a saturated coherent anti-Stokes Raman scattering (CARS) signal that is demodulated at the third harmonic (3f) of the pump modulation frequency (f). Under these modulation conditions, theory predicts a narrowing of the full width at half-maximum (FWHM) of the CARS spectrum by a factor of 2.0 with respect to that of the spectrum obtained by demodulation at the fundamental frequency. Theory also predicts an improvement of spatial resolution by a factor of 1.7. Experimentally, narrowing of the FWHM of the CARS spectrum of 1,4-bis((E)-2-methylstyryl) benzene (MSB) crystals by a factor of 2.5 is observed upon saturation. Further experimental confirmation is provided from investigating diamond particles, for which spectral narrowing was enhanced by a factor of 2.8 and spatial resolution was enhanced by a factor of 2. Details of the mechanism and execution of the saturated CARS experiment are elucidated and limits to its applicability are suggested, one of which is the conclusion that the saturation approach is not suitable for extraction of harmonics beyond 3f. In this work, we have developed a more comprehensive understanding of the correlation between the observed experimental results and experimental factors than has been previously reported. Disciplines Disciplines Physical Chemistry Comments Comments

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Saturated Raman scattering for sub-diffraction-limited imaging

Abstract: High-order harmonic generation using quasi-phase matching and two-color pump in the plasmas containing molecular and alloyed metal sulfide quantum dots

Cited by 15 publications

References 41 publications

Mitigating cross‐phase modulation artifacts in femtosecond stimulated Raman scattering

Mitigating cross‐phase modulation artifacts in femtosecond stimulated Raman scattering

Stimulated Raman imaging below the diffraction limit with a MHz laser

Spectral Narrowing Accompanies Enhanced Spatial Resolution in Saturated Coherent Anti-Stokes Raman Scattering (CARS): Comparisons of Experiment and Theory

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