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Photonics
Special Issues
Ultrafast Spectroscopy: Fundamentals and Applications
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Ultrafast Spectroscopy: Fundamentals and Applications

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Lasers, Light Sources and Sensors".

Deadline for manuscript submissions: closed (10 January 2023) | Viewed by 9725

Special Issue Editor

Dr. Andrea Lapini

E-Mail Website
Guest Editor
INRIM (Istituto Nazionale di Scienza Metrologica), Strada delle Cacce 91, 10135 Torino, Italy
Interests: time-resolved spectroscopy; multidimensional spectroscopy; non-linear microscopy; ultrafast spectroscopy; infrared spectroscopy

Special Issue Information

Dear Colleagues,

Ultra-fast optical spectroscopy comprises a set of experimental techniques that use ultrashort light pulses (with durations from femto to attoseconds) to study dynamic processes in atoms, molecules, biological systems and nanostructures. The advancement of technology in the generation of stable ultrashort pulses, on the one hand, and the development of complex spectroscopic techniques on the other have contributed to the growth of this field of research.

In the area of ultrafast sources, the systematic improvement in the generation of high harmonics has allowed the time resolution to be pushed up to 100 attoseconds, extending the coherent spectroscopy experiment’s spectral range from far infrared or terahertz to hard X-rays. On the other hand, the progress in the stability of the pulses generated by free-electron lasers has made it possible to carry out ultra-fast coherent spectroscopy experiments with pulses below 50 fs in the extended ultraviolet and soft X-ray spectral region.

Having stable primary sources of ultrashort pulses available has allowed for the development of new types of non-linear experiments, such as two-dimensional (2D) spectroscopy, in a range from far-infrared to X-ray wavelengths, and that in itself has become a key method for studying the coupling between electronic and/or vibrational excitations and for elucidating interactions between molecules and their fluctuating environment in condensed phases.

This Special Issue is dedicated to ultrafast spectroscopy, both its fundamental aspects and in its applications. As regards the fundamental aspects, we want to give space to works dedicated to the advancement of ultrafast spectroscopic techniques ranging from the THz to the X-ray spectral range, and new types of pulsed sources. Concerning the applications of ultrafast spectroscopy, this Special Issue will give space to works that address the study of photophysical and photochemical processes at the molecular level in organic molecules, biological chromophores and light harvesting systems; to the study of the structural dynamics of molecular systems in their electronic ground state; to the study of ultrafast structural dynamics, mapped by time-resolved X-ray methods and electron diffraction.

Dr. Andrea Lapini
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ultrafast spectroscopy
  • 2D infrared and electronic spectroscopy
  • ultrafast structural dynamics
  • pump–probe spectroscopy
  • coherent Raman spectroscopy
  • surface sum-frequency generation spectroscopy
  • photophysical properties and photochemical reactions
  • energy and coherence transfer
  • non-linear spectroscopy
  • ultrafast electron x-ray methods

Published Papers (4 papers)

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Research

27 pages, 5428 KiB  
Article
Theoretical Study on the Ultrafast Selective Excitation of Surface-Enhanced Coherent Anti-Stokes Raman Scattering Based on Fano Resonance of Disk-Ring Nanostructures by Shaped Femtosecond Laser Pulses
by Yingjie Xia, Kaiqiang Cao, Hua Zhao, Shian Zhang, Donghai Feng, Zhenrong Sun, Jinping Li and Tianqing Jia
Photonics 2022, 9(5), 338; https://doi.org/10.3390/photonics9050338 - 12 May 2022
Viewed by 2137
Abstract
The enhancement and selective excitation of coherent anti-Stokes Raman scattering (CARS) and the suppression of background noise are very important problems for real-time detection at the single-molecule level. Optimizing the plasmonic substrate to ensure that all the hot spots of the pump, probe, [...] Read more.
The enhancement and selective excitation of coherent anti-Stokes Raman scattering (CARS) and the suppression of background noise are very important problems for real-time detection at the single-molecule level. Optimizing the plasmonic substrate to ensure that all the hot spots of the pump, probe, Stokes, and anti-Stokes light are at the same position is the key to increasing the CARS signal to reach the level of single-molecule detection. The selective excitation of the target CARS peak and the suppression of the other peaks are the key to improving the signal-to-noise ratio. In this paper, we present a theoretical study to control the selective excitation and enhancement of any one of the three CARS peaks using the Fano resonance of a disk-ring structure. By optimizing the modulation of the pump, Stokes, and probe pulse, one CARS peak is maximized, while the other two are suppressed to zero. Fano resonance is applied to simultaneously enhance the four surface plasmon modes of the pump, probe, Stokes, and anti-Stokes light and to ensure that all the hot spots are located at the same position by adjusting the size of the disk-ring structure. The hot spots of the four pulses are concentrated in the disk-ring gap with a deviation distance of less than 2 nm, and the intensity of the CARS is enhanced by 1.43 × 1012 times, which is much higher than the requirement of single-molecule detection. The time, frequency, and phase distribution of the input and the response of the four pulses are studied in detail. It was found that the selective excitation and the spectra of CARS are both well preserved. Full article
(This article belongs to the Special Issue Ultrafast Spectroscopy: Fundamentals and Applications)
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12 pages, 928 KiB  
Article
Multiphoton Resonance in Attosecond Transient Absorption
by Jinxing Xue, Meng Wang, Cangtao Zhou and Shuangchen Ruan
Photonics 2022, 9(4), 257; https://doi.org/10.3390/photonics9040257 - 12 Apr 2022
Viewed by 1875
Abstract
We present the theory and simulation of attosecond transient absorption in helium atoms under the single-active-electron approximation. This study investigates the attosecond dynamics of intrinsic atomic states that interact with a field comprising vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) fields. The absorption [...] Read more.
We present the theory and simulation of attosecond transient absorption in helium atoms under the single-active-electron approximation. This study investigates the attosecond dynamics of intrinsic atomic states that interact with a field comprising vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) fields. The absorption spectrum of the helium atom is obtained from the response function, which is constructed by numerically solving the three-dimensional time-dependent Schrödinger equation. We observe a fine structure near the intrinsic atomic level, which is modulated with a 0.2 fs period. Based on high-order time-dependent perturbation theory, the frequency-dependent phase of the dipole response induced by the VUV and XUV fields is analytically obtained, and the fine structure is well explained by the phase difference. In addition, the absorption fringes are dependent on the chirp of the VUV field. This study investigates the features of the attosecond transient absorption in the VUV region, which may have valuable applications in the study of ultrafast phenomena in atoms, molecules, and solids. Full article
(This article belongs to the Special Issue Ultrafast Spectroscopy: Fundamentals and Applications)
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7 pages, 2582 KiB  
Communication
High-Transmittance Femtosecond Optical Kerr Gate with Double Gate Pulses Based on Birefringence Effect
by Zhenqiang Huang, Wenjiang Tan, Jinhai Si, Shijia Zeng, Zhen Kang and Xun Hou
Photonics 2022, 9(2), 71; https://doi.org/10.3390/photonics9020071 - 27 Jan 2022
Cited by 1 | Viewed by 2232
Abstract
An optical Kerr gate (OKG) is an ultrafast optical switch based on the optical Kerr effect. The performance of a conventional OKG depends mainly on Kerr materials. Traditional Kerr materials do not demonstrate both large optical nonlinearity and an ultrafast response time. Therefore, [...] Read more.
An optical Kerr gate (OKG) is an ultrafast optical switch based on the optical Kerr effect. The performance of a conventional OKG depends mainly on Kerr materials. Traditional Kerr materials do not demonstrate both large optical nonlinearity and an ultrafast response time. Therefore, the performance of a conventional OKG is limited by an inherent trade-off between high signal transmittance and fast switching time, which limits its application in many fields. We propose an improved femtosecond OKG with double gate pulses, based on the use of a birefringent crystal to realize an ultrashort switching time, even with a slow-response optical Kerr medium. We assessed the dependence of the double gate pulsed OKG (D-OKG)’s performance on the intensity ratio of the double gate pulses. A transmittance of 50% and a switching time of 142 fs were achieved. The D-OKG is convenient to construct, and its integrated performance is superior to that of a conventional OKG. Full article
(This article belongs to the Special Issue Ultrafast Spectroscopy: Fundamentals and Applications)
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8 pages, 2960 KiB  
Communication
Generation of Ultrabroad and Intense Supercontinuum in Mixed Multiple Thin Plates
by Jing Li, Wenjiang Tan, Jinhai Si, Zhen Kang and Xun Hou
Photonics 2021, 8(8), 311; https://doi.org/10.3390/photonics8080311 - 3 Aug 2021
Cited by 4 | Viewed by 2314
Abstract
Supercontinuum (SC) generation using multiple thin plates is demonstrated with a femtosecond laser pulse. We propose an improved technique to obtain larger spectrum broadening and higher spectral intensity by employing mixed multiple thin plates with different thicknesses and materials. Furthermore, the spectrum has [...] Read more.
Supercontinuum (SC) generation using multiple thin plates is demonstrated with a femtosecond laser pulse. We propose an improved technique to obtain larger spectrum broadening and higher spectral intensity by employing mixed multiple thin plates with different thicknesses and materials. Furthermore, the spectrum has good stability, which is superior to that of the spectrum induced by the traditional single filament in bulk material. Our approach offers a route towards simple and stable SC generation for potential applications. Full article
(This article belongs to the Special Issue Ultrafast Spectroscopy: Fundamentals and Applications)
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