Femtosecond and Attosecond Light Sources and Techniques for Spectroscopy

Gallmann, L.; Keller, U.

doi:10.1002/9780470749593.hrs086

Cited by 5 publications

(3 citation statements)

References 75 publications

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“…(242) Encyclopedia Emerging trends in laser technology, leading to shorter pulses at the timescales of subfemtosecond (valence electron motion) to attosecond (core electron motion), may expedite our understanding of bulk electron dynamics in the solid and gas phase. (243) In particular, they have enabled several interesting studies in solid-state physics, such as advancing our understanding of the timescales of carrier-carrier interactions and switching from insulator to metallic state. (244) Furthermore, these shorter pulses can also advance our understanding of intramolecular charge transfer in molecular systems.…”

Section: Summary and Perspectivesmentioning

confidence: 99%

Time‐Resolved Spectroscopy: Instrumentation and Applications

Ariese

Roy

Venkatraman

et al. 2017

Encyclopedia of Analytical Chemistry

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Light–matter interaction may lead to three fundamental phenomena, viz. (i) absorption, (ii) emission, and (iii) scattering. Spectroscopic techniques based on these phenomena are used to characterize the materials of interest, not only stable compounds but also short‐lived species during molecular transformations. Determining the electronic and molecular structure of the transient species is crucial in order to understand various photochemical, physical, and biological processes of fundamental and technological importance. Identifying various redox species during photosynthesis, understanding the photoinduced charge transfer process in solar cells, unraveling the photochemistry of vision that involves photoisomerization of retinal, etc. require spectroscopic techniques that can resolve various transient species in time and were practically impossible until the advent of pulsed lasers. The absorption of a photon by a molecule may initiate a cascade of dynamic molecular events, namely vibrational relaxation (VR), solvation dynamics, internal conversion (IC), intersystem crossing (ISC), electron transfer, isomerization reactions, etc., which can occur at femtosecond (fs) to picosecond (ps) timescales. Bimolecular reaction dynamics in liquids, such as H‐atom abstraction reaction, are typically diffusion controlled and therefore can be observed at nanosecond (ns) timescales. Therefore, time‐dependent (time‐resolved) spectroscopy has been an exquisite tool to follow the molecular dynamics after an initial phototrigger. Apart from studying molecular dynamics, time resolution can also be used to distinguish conformers, isomers or enantiomers, or distinguish identical compounds in different environments. It can also be applied to suppress unwanted signals occurring at different timescales, for instance fluorescence suppression in Raman experiments, or selectively detect compounds deeper inside a sample. In this article, we first give an introduction to the fundamentals of time‐resolved electronic absorption, spontaneous excited‐state resonance Raman, and coherent Raman scattering and emission techniques, spanning the range from femtosecond to microsecond timescales. Important technical aspects of time‐resolved spectroscopic equipment are also discussed. We then present some examples of cis–trans isomerization, thermal equilibrium of the two lowest triplet states, H‐atom abstraction reactions, etc. and demonstrate the molecular dynamic events after an initial phototrigger by a comprehensive kinetic analysis of the peak position, width and intensity of the marker bands in the time‐resolved electronic absorption, and Raman and emission spectra.

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Section: Summary and Perspectivesmentioning

confidence: 99%

Time‐Resolved Spectroscopy: Instrumentation and Applications

Ariese

Roy

Venkatraman

et al. 2017

Encyclopedia of Analytical Chemistry

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“…The invention of the self-referenced frequency comb laser (Holzwarth et al 2000, Jones et al 2000, Udem et al 2002 has caused a revolution in precision frequency metrology and attosecond laser science (Corkum and Krausz 2007, Baltuska et al 2003, Gallmann and Keller 2011. Indeed, the high precision obtained in, e.g., the aforementioned 1S-2S hydrogen experiment is partly due to the use of a frequency comb.…”

Section: Frequency Comb Lasersmentioning

confidence: 99%

Precision Laser Spectroscopy in the Extreme Ultraviolet

Eikema

Ubachs

2011

Handbook of High‐resolution Spectroscopy

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Techniques for the production of short wavelengths in the extreme ultraviolet wavelength range are described, spanning low‐order harmonic generation in the perturbative regime for narrow bandwidth XUV production to the plateau‐regime with the three‐step collisional model for the generation of high harmonics with broadband ultrafast pulses. In addition, the intermediate regime is discussed for pulses of 300 ps duration, as well as the regime of harmonic conversion based on continuous wave lasers aiming at the production of coherent Lyman‐α radiation. Applications of XUV sources in the frequency domain typically rely on the production of XUV‐light from narrowband Fourier‐transform‐limited pulses for recording high‐resolution spectra. Alternatively, harmonically upconverted pulses of ultrashort duration (with inter‐pulse coherence) can be used for spectroscopic studies in the time and frequency domain (such as direct frequency comb spectroscopy techniques). Examples of both approaches for atomic and molecular spectroscopy are discussed at some length. For precision metrology on atomic systems, a focus is put on the Lamb shift determination in the He ground state. In the realm of molecular spectroscopy, predissociation phenomena in the nitrogen molecule are highlighted, with relevance for dissociation processes occurring in the upper layers of the Earth atmosphere. Similar predissociation phenomena in carbon monoxide are also treated in some detail, in this case with relevance for the chemistry in interstellar clouds. Precision XUV spectroscopy of molecular hydrogen is discussed as well, as it relates to the possibility of detecting a variation of the proton–electron mass ratio on a cosmological time scale. In the last section, applications of direct frequency comb spectroscopic techniques at short wavelengths are explained and prospects are given for using these techniques at extreme ultraviolet wavelengths.

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“…Recently, similar broadband high-brightness mid-infrared radiation have also been generated using high-power femtosecond lasers [9][10][11] at outstanding wavelength and power stability [12]. More intriguingly, the femtosecond nature of such output, especially when in the form of a stabilized frequency comb, opens the way to a multitude of time-and frequency-domain techniques [13][14][15] that can reveal ultrafast dynamics and drastically improve the speed, dynamic range, and many other aspects of spectroscopic measurements [16][17][18][19][20]. Solid-state lasers based on Cr 2+ -doped II-VI material, often called the Ti:Sapphire of the mid-infrared, are reliable sources for directly generating ultrashort femtosecond pulses in the 2-3 μm spectral range [21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Directly diode-pumped, Kerr-lens mode-locked, few-cycle Cr:ZnSe oscillator

et al. 2019

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Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX Lasers based on Cr 2+ -doped II-VI material, often known as the Ti:Sapphire of the mid-infrared, can directly provide few-cycle pulses with super-octave-spanning spectra, and serve as efficient drivers for generating broadband midinfrared radiation. It is expected that the wider adoption of this technology benefits from more compact and costeffective embodiments. Here, we report the first directly diode-pumped, Kerr-lens mode-locked Cr 2+ -doped II-VI oscillator pumped by a single InP diode, providing average powers of over 500 mW and pulse durations of 45 fsshorter than six optical cycles at 2.4 µm. These correspond to a sixty-fold increase in peak power compared to the previous diode-pumped record, and are at similar levels with respect to more mature fiber-pumped oscillators. The diode-pumped femtosecond oscillator presented here constitutes a key step towards a more accessible alternative to synchrotron-like infrared radiation, and is expected to accelerate research in laser spectroscopy and ultrafast infrared optics.

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Femtosecond and Attosecond Light Sources and Techniques for Spectroscopy

Abstract: Handbook of High-resolution Spectroscopy. Edited by Martin Quack and Frédéric Merkt.

Cited by 5 publications

References 75 publications

Time‐Resolved Spectroscopy: Instrumentation and Applications

Time‐Resolved Spectroscopy: Instrumentation and Applications

Precision Laser Spectroscopy in the Extreme Ultraviolet

Directly diode-pumped, Kerr-lens mode-locked, few-cycle Cr:ZnSe oscillator

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