Search

Quasi-2D layers of transition metal dichalcogenides are promising candidates for creating saturable absorbers for pulsed lasers. However, the peculiarities of intense electromagnetic radiation’s influence on such structures have not been thoroughly studied. This paper explores the dynamics of photoexcited carriers in WSe2 flakes through experimental studies. These studies found that WSe2 flakes significantly change their optical properties under the influence of a high-power optical pump, allowed estimating the thermalization time of these structures (about 2 ps), and found that full relaxation takes more than 10 ps. The concentration of carriers in the semiconductor surface layer was estimated to be about 1028 m–3. It was found that standard description models of the optical response based on exciton resonances and absorption by free carriers could not adequately describe the experiments’ results. Thus, for an accurate description of the optical response, it was necessary to consider the effects associated with Coulomb screening that are caused by the high concentration of photo-excited carriers of the optical pumping densities used in this experiment.

To study the influence of thermal annealing on the charge generation and transport in PM6-based non-fullerene solar cells. Morphology, optical and electrochemical properties of active layers as well as electrical properties of polymer solar cells were studied. Furthermore, the photoelectric conversion processes of annealed and unannealed devices were also examined by means of time resolved spectroscopy. The results showed that thermal annealing had a weak influence on the dynamics of exciton states. Besides, annealed device is found to suppress bimolecular recombination owing to its higher charge carrier mobility in ordered donor and acceptor aggregation phases, which led to higher photocurrent and power conversion efficiency than unannealed photovoltaic device.

This paper introduces some applications of time-of-flight or time-resolved spectroscopy to cellulosic materials like wood. Time-of-flight or time-resolved spectroscopy uses short pulses of light illumination where a portion of the light is scattered but most of the light propagates through the sample. By using such technique, we could know that the light scattering contribution to near infrared spectra in wood is significant because it is a complex and highly scattering medium due to its cellulosic structure.

Harvesting solar energy for catalytic conversion of CO2 into valuable chemical fuels/feedstocks is an attractive yet challenging strategy to realize a sustainable carbon-cycle utilization. Homogene...

In this study, ultrafast dynamics of photoexcited carriers in an intrinsic CdTe film are investigated deeply and systematically as a function of carrier density and excess energy using femtosecond-resolved pump-probe transient differential transmission spectroscopy. A dynamic model is developed based on an interband transition absorption model in direct bandgap semiconductors by introducing the dynamics of thermalization, cooling and recombination of photoexcited carriers into the interband transition absorption model. Then, the model is used to best fit the measured ultrafast dynamics to retrieve the initial temperature of thermalized electrons and time constants of the thermalization, cooling and recombination dynamic processes as a function of carrier density and excess energy. The increase with carrier density and the decrease with excess energy of thermalization time constant reveal that thermalization process of photoexcited carriers is dominated by carrier-phonon scatterings. We find for the first time that cooling of thermalized carriers depend strongly on carrier density and excess energy, and cooling time constant varies in a wide range from 0.2 to 5 ps. It is also found that carrier recombination in the intrinsic CdTe film is dominated by the radiative recombination of electron-hole pairs, rather than Auger recombination as reported in doped CdTe films. These new results are very important to understanding of microscopic mechanism of relaxation processes of photoexcited carriers and applications of CdTe-based optoelectronic devices.

We proposed a complex method based on a combination of shadow photography and time-resolved Raman spectroscopy to observe the non-stationary laser-induced supercritical state in molecular media. Shadow photography is applied for retrieving pressure values, while Raman spectroscopy with molecular dynamics for temperature estimation. Time resolution of 0.25 ns is achieved by varying the delay between the pump (creating an extreme energy delivery) and the probe laser pulses by the self-made digital delay electronic circuit . The proposed method was employed in liquid carbon dioxide and water. Under nanosecond laser pulse impact, the estimated temperatures and pressures (∼700 K and ∼0.5 GPa) achieved in media are higher than the critical parameters of the samples.

Dual-comb spectroscopy (DCS) is a powerful spectroscopic technique, which is developing for the detection of transient species in reaction kinetics on a short time scale. Conventionally, the simultaneous determination of multiple species is limited to the requirement of broadband spectral measurement at the cost of the measurement speed and spectral resolution owing to the inherent trade-off among these characteristics in DCS. In this study, a high-speed multi-molecular sensing is demonstrated and achieved through using a programmable spectrum-encoded DCS technique, where multiple narrow encoding spectral bands are reserved selectively and other comb lines are filtered out. As a dual-comb spectrometer with a repetition rate of 108 MHz is encoded spectrally over a spectral coverage range of 1520 to 1580 nm, the measurement speed is increased 6.15 times and single-shot absorption spectra of multiple molecules (C2H2, HCN, CO, CO2) at a time scale of 208 µs are obtained. Compared to conventional single-shot dual-comb spectra, encoded dual-comb spectra have improved short-term signal-to-noise ratios (SNRs) by factors of 3.65 with four encoding bands and 5.68 with two encoding bands. Furthermore, a fiber-Bragg-grating-based encoded DCS is demonstrated, which reaches 17.1 times higher average SNR than that of the unencoded DCS. This spectrum-encoded technique can largely improve the DCS measurement speed, and thus is promising for use in studies on multi-species reaction kinetics.

International audience; Spin Crossover (SCO) is a promising switching phenomenon when implemented in electronic devices as molecules, thin films or nanoparticles. Among the properties modulated along this phenomenon, optically induced mechanical changes are of tremendous importance as they can work as fast light-induced mechanical switches or allow to investigate and control microstructural strains and fatigability. The development of characterization techniques probing 2 nanoscopic behaviour with high spatio-temporal resolution allows to trigger and visualize such mechanical changes of individual nanoscopic objects. Here we use Ultrafast Transmission Electron Microscopy (UTEM) to precisely probe the length changes of individual switchable nanoparticles induced thermally by nanosecond laser pulses. This allows us to reveal the mechanisms of spin switching, leading to the macroscopic expansion of SCO materials. This study was conducted on individual pure SCO nanoparticles and SCO nanoparticles encapsulating gold nanorods that serve for plasmonic heating under laser pulses. Length changes are compared with time-resolved optical measurements performed on an assembly of these particles.

Time-resolved near-infrared absorption spectroscopy of single non-repeatable transient events is performed at high spectral resolution with a dual-comb interferometer using a continuous-wave laser followed by a single electro-optic amplitude modulator. By sharing high-speed electrical/optical components, our spectrometer greatly simplifies the implementation of dual-comb spectroscopy and it offers a high mutual coherence time, measured up to 50-s, without any active stabilization system and/or data processing. The time resolution, which can be reconfigured a posteriori, is as short 100 microseconds in our experimental demonstration. For a span of 36 GHz, the mean signal-to-noise ratio of 80, at 100-MHz spectral resolution and 100-microsecond measurement time, enables the precise determination of the parameters of rovibrational lines, including intensity or concentration., Comment: 8 pages, 4 figures

Intralipid is a material widely employed for the preparation of phantoms for optical imaging and biophotonics applications in medical field. The development of new optical diagnostic equipment in these fields requires the use of well-designed phantoms with optical properties (including scattering and absorption) mimicking those of biological tissues in all the pre-clinical stages of investigations. For this reason, great research effort has been devoted to optically characterize Intralipid and at preparing optimal phantoms. In this short review, we summarize the principal physico-chemical characteristics of Intralipid and the main contributions in the assessment of its scattering and absorption properties. In addition, the most largely used Intralipid-based homogeneous and non-homogeneous phantoms are discussed. Even though other materials are available for the preparation of phantoms, the use of Intralipid still offers an inexpensive and easy-to-use method for preparing phantoms with finely tuned optical properties.

A 512 $\times $ 16 single photon avalanche diode (SPAD)-based line sensor is designed in a 0.13- $\mu \text{m}$ CMOS image sensor technology for time-resolved multispectral beam scanned imaging. The sensor has 23.78- $\mu \text{m}$ pixel pitch and incorporates one SPAD array with 49.31% fill factor optimized for detection in the blue–green spectral region, and a second array at 15.75% fill factor optimized for the red-near-infrared response spectral region. Each pixel contains a 32-bin histogramming time-to-digital converter (TDC) with a mean time resolution of 51.20 ps. Histogram bin resolutions are adjustable from 51.20 ps to 6.55 ns per bin. The line sensor can operate in single photon counting (SPC) mode (102.1 giga-events/s), time-correlated SPC (TCSPC) mode (192.4 million-events/s) or on-chip histogramming mode (16.5 giga-events/s), increasing the count rate up to 85 times compared to TCSPC mode. Sensor capability is demonstrated through spectral fluorescence lifetime imaging, resolving three fluorophore populations with distinct fluorophore lifetimes.

We report on the enhancement effect of metal nanotriangles (NTs) on the photoluminescence and its time-resolved dynamics of tris(8-quinolinolato) aluminum (Alq3). Regularly arranged Al NTs arrays were fabricated on the quartz substrate by means of nanosphere lithography. The absorption peaks corresponded to the localized surface plasmon (LSP) resonance of Al NTs were observed within a visible light region, and it was significantly shifted towards longer wavelength as increasing refractive index of the covering medium. The typical resonance wavelength of LSP of Alq3/Al NTs fabricated with 350 nm-PSt beads was 600 nm. From the PL measurement 2.6-fold PL enhancement was observed in Alq3 with Al NTs at room temperature, whereas the 4.4-fold PL enhancement was observed for Ag NTs with same size. According to the time-resolved PL data, the coupling of LSP with the excitation light field mainly contribute to the observed emission enhancement for the Al NTs, whereas the emission enhancement by Ag NTs can be originated from the direct coupling of LSP and emission which was suggested from the large contribution of short lifetime component.

Laser pulses with a duration of one femtosecond or shorter can be generated both in the visible-infrared (Vis-IR) and in the extreme UV, but the deep UV is a spectral region where such extremely short pulses have not yet been demonstrated. Here, a method for the synthesis of ultrashort pulses in the deep UV is demonstrated, which utilizes the temporal and spatial harmonics that are generated by two noncollinear Vis-IR pulses in a thin MgF2 plate. By controlling the groove-envelope phase of the Vis-IR pulses, spatial harmonics are concatenated to form deep UV waveforms with a duration of 1.5 fs.

Femtosecond time-resolved spectroscopy and frequency-comb spectroscopy have been individually developed to achieve better time and frequency resolutions, respectively. The two spectroscopic techniques have been developed for different systems, even though they use mode-locked laser in common. Recently, there was an interesting merge of the two techniques into a dual frequency-comb (DFC) spectroscopy, resulting in a new femtosecond spectroscopy with simple instrumentation and high data acquisition speed compared to conventional femtosecond spectroscopic techniques. By slightly detuning the repetition rates of two phase-locked frequency-comb lasers, both automatic time-delay scanning and parallel data recording with single point detectors are possible. Thus, we anticipate that the DFC spectroscopy would allow one to expand the application limits of the conventional femtosecond spectroscopic methods. In this Perspective article, we provide reviews of linear and nonlinear DFC spectroscopy theory and applications with a perspective on the development of coherent multidimensional frequency-comb spectroscopy.

Surpassing the Shockley–Queisser limit, which places an upper bound on solar conversion efficiency for a single p–n junction solar cell at slightly more than 30%, is one of the grand challenges in the field of solar-energy research. Singlet fission (SF) in molecular acenes, the molecular analog of multiple exciton generation (MEG), has the potential to initiate a game-changing advance in solar-energy conversion. SF allows singlet-excited states (S1) to be down-converted into twice as many triplet-excited states (T1).

The results of spectral–temporal studies of the filament plasma emission in air with a time resolution of 2 ps were presented. The filament was created by laser radiation with pulse duration of 60 fs and wavelength of 940 nm. It was shown that a spectral composition of the filament plasma depended on the numerical aperture (NA). At NA > 0.035, the atomic and ion lines of oxygen and nitrogen dominate in the spectrum on the background of an intense continuous continuum in the visible region. Molecular lines of the second positive system of nitrogen and the first negative system of molecular ions appear in the spectrum for NA 0.03. In case of NA 0.01, the spectrum consists of only the molecular and ion lines of N 2 and N 2 + . The emission intensity maxima of these lines delay relative to the laser pulse. The atomic lines begin to glow per (80–100) ps after the laser pulse. The characteristic time of the luminescent lines decay at 1/e level for ions is 18 ps, for molecules is 27 ps, and for atomic lines is 20 ns. Rapid decrease in the intensity of molecular lines emission is due to the deactivation of the particles upper states by electrons. The formation of N 2 + ( B 2 Σ u + ) excited states is most likely through their N 2 + ( X 2 Σ g + ) ground state in the process of multiphoton absorption of pumping radiation by nitrogen molecules and subsequent their excitation by electron impact.

High-power, few-cycle lasers are viable tools, e.g. in time-resolved spectroscopy [1] and nanoscale imaging [2] . No laser emits such pulses directly due to its limited gain bandwidth and, hence, either nonlinear pulse compression in fibers [3] or optical parametric amplification [4] are commonly applied to generate few-cycle pulses.

Reaction centers (RCs) are the pivotal component of natural photosystems, converting solar energy into the potential difference between separated electrons and holes that is used to power much of biology. RCs from anoxygenic purple photosynthetic bacteria such as Rhodobacter sphaeroides only weakly absorb much of the visible region of the solar spectrum, which limits their overall light-harvesting capacity. For in vitro applications such as biohybrid photodevices, this deficiency can be addressed by effectively coupling RCs with synthetic light-harvesting materials. Here, we studied the time scale and efficiency of Forster resonance energy transfer (FRET) in a nanoconjugate assembled from a synthetic quantum dot (QD) antenna and a tailored RC engineered to be fluorescent. Time-correlated single-photon counting spectroscopy of biohybrid conjugates enabled the direct determination of FRET from QDs to attached RCs on a time scale of 26.6 ± 0.1 ns and with a high efficiency of 0.75 ± 0.01.

Lead halide perovskites are emerging as extremely interesting active materials for a wide variety of optoelectronic and photonic devices. A deep understanding of their photophysics is thus fundamental in order to properly understand the origins of the materials active properties and to provide strategies for improving them. In this work, we exploit the local morphological variations in a drop-cast thin CsPbBr3 nanocrystal film to show that the aggregation of NCs has strong effects on the peak wavelengths of PL spectra, the linewidth, and the intensity of dependence on temperature. An analysis based on models that are frequently used in the literature led to completely different conclusions about the intrinsic NC emission properties extracted from spectra measured in points with different contribution of the PL from the aggregates. Our results demonstrate that extreme care has to be used in order to correctly correlate the spectral PL features with the intrinsic emission properties of lead halide perovskite NC films.

Dual-comb spectroscopy (DCS) is an emerging and promising spectrometric technique with high resolution, high sensitivity, broad spectral range, and fast acquisition speed. For the recovery of the information encoded on comb modes without resolution loss, two continuous wave lasers are commonly utilized as optical intermedia to track the real-time jitter of dual-comb interferograms. This paper presents a simplified error correction method based on single optical intermedium for quasi-free-running fiber DCS. This method combines the strengths of conventional optical referencing and self-referencing error correction. We acquired whole P branch H13C14N transmittance spectra in the near infrared as a demonstration. In contrast to that of conventional dual intermedium error correction, the standard deviation of our method was merely 0.01 over the 4 THz spectral range. Our method provides a balanced and practical postprocessing routine for high-performance mode-resolved DCS applications.

We will demonstrate the performance of a spectrometer-microscope assembly for characterization and analysis of samples in terms of lifetime, spectral and spatial resolution. This combined approach provides access to further information, which are not available when using only lifetime or steady-state experiments. The combination of both techniques in one setup can help to understand biochemical or physical processes by detecting changes in local environment such as pH, temperature, or ion concentration, and to identify molecular interactions or conformation changes via Forster Resonance Energy Transfer (FRET).

Fluorescence lifetime imaging (FLI) plays an important role in detection of different fluorescence substances. However, when background light is strong and image noise is high, FLI is hard to discriminate substances with approximate fluorescence lifetime. An enhanced time-resolved fluorescence imaging method is proposed. In the method, a dual-gated intensity-correlation enhancement algorithm is developed. Compared with traditional rapid fluorescence lifetime determination imaging method, the method focuses on improve image contrast and can effectively remove background noise. It utilizes two fluorescence intensity images at different delay times, and adaptively chooses the filter threshold and the up threshold to remove noise and enhance contrast. The thresholds are determined by the distribution of image variance. In proof experiments, three brands of highlighters with the same color have close fluorescence lifetime, and the proposed method shows their fine fluorescence difference. The simulation and experimental results prove that the method can improve the ability of time-resolved fluorescence imaging.

Understanding and controlling the nonlinear optical properties and coherent quantum evolution of complex multilevel systems out of equilibrium is essential for the new semiconductor device generation. In this work, we investigate the nonlinear system properties of an unbiased quantum cascade structure by performing two-dimensional THz spectroscopy. We study the time-resolved coherent quantum evolution after it is driven far from equilibrium by strong THz pulses and demonstrate the existence of multiple nonlinear signals originating from the engineered subbands and find the lifetimes of those states to be in the order of 4–8 ps. Moreover, we observe a coherent population exchange among the first four intersubband levels during the relaxation, which have been confirmed with our simulation. We model the experimental results with a time-resolved density matrix based on the master equation in Lindblad form, including both coherent and incoherent transitions between all density matrix elements. This allows us to replicate qualitatively the experimental observations and provides access to their microscopic origin., Nanophotonics, 10 (1), ISSN:2192-8614

Fluorescence lifetime imaging was used during open craniotomy procedures to detect differences between healthy and tumor-infiltrated brain. Optical parameters validated against histopathological biomarkers demonstrate that brain regions with infiltrative glioblastoma multiforme are characterized by longer lifetime values relative to the adjacent healthy tissues.

A multimodal nonlinear microscope using single source and detector was developed. With the microscope we successfully acquired two-photon excited fluorescence (TPEF), second-harmonic generation (SHG), coherent anti-Stokes Raman scattering (CARS) and back reflection images of biological samples.

Colloidal quantum dots (QDs) have unique optical and electrical properties with promising applications in next‐generation semiconductor technologies, including displays, lighting, solar cells, photodetectors, and image sensors. Advanced analytical tools to probe the optical, morphological, structural, compositional, and electrical properties of QDs and their ensemble solid films are of paramount importance for the understanding of their device performance. In this review, comprehensive studies on the state‐of‐the‐art metrology approaches used in QD research are introduced, with particular focus on time‐resolved (TR) and spatially resolved (SR) spectroscopy and microscopy. Through discussing these analysis techniques in different QD system, such as various compositions, sizes, and shell structures, the critical roles of these TR‐spectroscopic and SR‐microscopic techniques are highlighted, which provide the structural, morphological, compositional, optical, and electrical information to precisely design QDs and QD solid films. The employment of TR and SR analysis in integrated QD device systems is also discussed, which can offer detailed microstructural information for achieving high performance in specific applications. In the end, the current limitations of these analytical tools are discussed, and the future development of the possibility of interdisciplinary research in both QD fundamental and applied fields is prospected.

Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes. We demonstrate that the change in fluorescence intensity of carboxyfluorescein with pH in this &ldquo, high-density&rdquo, regime is opposite to that normally observed, with complex variations in fluorescent lifetime across the emission spectra of coupled fluorophores. Improved understanding of such highly loaded sensor beads is important because it leads to large increases in photostability and will aid the development of compact fibre probes, suitable for clinical applications. The time-resolved spectral measurement techniques presented here can be further applied to similar studies of other optodes.

The singlet oxygen quantum yield (ΦΔ) was monitored in real time through time resolved spectroscopy measurement, using gadolinium labeled hematoporphyrin monomethyl ether (Gd-HMME) as photosensitizer. According to the kinetics equations of singlet oxygen generation and reaction, ΦΔ was related to phosphorescence lifetime (τp). Through measuring τp of Gd-HMME in different oxygen conditions, the radiation transition property of first exited triplet state (T1) was monitored; combined with the triplet state quantum yield (ΦT) determined by linear fitting the ΦΔ, which was measured in different oxygen content using a relative measurement, ΦΔ can be determined in real time. The identification of anoxia during the treatment of photodynamic therapy (PDT) by this method is also presented.

Strong light-matter coupling in the terahertz (THz) region has strong potential for a new generation of THz devices based on polariton devices. In this work we investigate intersubband polaritons by time domain spectroscopy and characterize the coupled light-matter states at low k-vector for potential THz laser structures. A range of THz devices are studied to control the light-matter interaction and compared with the simulated polariton dispersion. The potential and investigations of THz stimulated emission via optical pumping at the so called “magic angle” for conservation of momentum and energy are presented.

In femtosecond stimulated Raman microscopy, two laser pulses (Raman pump and probe) interact at the focus of a scanning microscope. To retrieve the Raman signature of the sample, an amplitude modulation of the pump pulses is necessary. Here, different methods to achieve this modulation are presented and compared.

Aspects of laser spectroscopy applied to the biomedical fields are reviewed with examples illustrating the techniques taken mostly from the author’s research experience. Basic principles of quantum-mechanical background are described, and powerful implementations in the biophotonics field are discussed.

As one of the successful approaches to GaAs surface passivation, wet-chemical nitridation is applied here to relate the effect of surface passivation to carrier recombination processes in bulk GaAs. By combining time-resolved photoluminescence and optical pump-THz probe measurements, we found that surface hole trapping dominates the decay of photoluminescence, while photoconductivity dynamics is limited by surface electron trapping. Compared to untreated sample dynamics, the optimized nitridation reduces hole- and electron-trapping rate by at least 2.6 and 3 times, respectively. Our results indicate that under ambient conditions, recovery of the fast hole trapping due to the oxide regrowth at the deoxidized GaAs surface takes tens of hours, while it is effectively inhibited by surface nitridation. Our study demonstrates that surface nitridation stabilizes the GaAs surface via reduction of both electron- and hole-trapping rates, which results in chemical and electronical passivation of the bulk GaAs surface.

The present work has been carried out with the aim to design and develop an efficient light harvesting inorganic-organic hybrid nanoscale material by employing a less toxic, environment friendly inorganic substance and also to understand the mechanism of inter-particle electronic interaction between the inorganic and organic components of the nanomaterial. Specifically, the inorganic-organic hybrid associate has been made by integrating water soluble semiconductor (zinc-silver-indium-sulfide (ZAIS)) QDs and organic J-aggregates of a cyanine dye (S2165). The fabrication of the present nano-hybrid system has been achieved via electrostatically driven self-assembly of organic dyes over ZAIS QDs. The interaction between QD and J-aggregates has been investigated by using steady state and time resolved fluorescence measurements. Zeta potential measurements have also been performed to understand the role of electrostatic interaction and thermodynamic feasibility of the association process. The investigations have revealed that the energy transfer (ET) process between QD and J-aggregates was mediated through a dipole-dipole mechanism. Interestingly, data analysis based on Forster theory has further revealed that the ET from QD to J-aggregates is very high, indicating efficient electronic coupling between the inorganic QD and the organic J-aggregates. Zeta potential measurements and thermodynamic calculations have demonstrated that the interaction between QD and organic dye is electrostatically driven and the association of organic dyes over QDs is thermodynamically feasible. The outcome of the present study is expected to be helpful in designing efficient nanoscale light harvesting devices. Additionally, fluorescence microscopy and toxicity studies on the QDs have also shown their suitability for biological applications.

The optical design of a soft X-ray spectrometer that utilizes Wolter mirrors to enable imaging-mode spectroscopy with a beam-size independent spatial resolution in, for example, tandem catalysts in reaction is presented. When such a spectrometer is used in pump–probe experiments to study the transient electron dynamics, the imaging capability of the Wolter mirrors can offer femtosecond time delay between the pump and probe beams with non-collinear wavefronts., The optical design of a Hettrick–Underwood-style soft X-ray spectrometer with Wolter type 1 mirrors is presented. The spectrometer with a nominal length of 3.1 m can achieve a high resolving power (resolving power higher than 10000) in the soft X-ray regime when a small source beam (

Material and functional stability remains a major issues in field of perovskite photovoltaics. To achieve a long device lifetime, it is crucial that we understand and optimize the lifetime of the material itself. One-step antisolvent processing is a facile method to enhance stability. Herein, we report that changes in the degradation process of perovskite films is modified by the antisolvent treatment in comparison to the conventional film without the process which we measure by monitoring the emission. Perovskite films prepared with anti-solvent processing have improved film morphology and reduced evolution of surface metallic lead, which correlated with improved film lifetimes.

Frequency combs have revolutionized time and frequency metrology. Their application to spectroscopy over broad spectral bandwidths attracts an ever-increasing number of scientists for its intriguing potential for high accuracy, resolution and recording speed.

A highly sensitive method for measuring time-resolved reflection in extreme ultraviolet region was developed. We observed optical modulation ΔR/R~1×10-4 by boxcar integration and lock-in detection, and the data acquisition takes four minutes.

We show that tabletop high-harmonic extreme ultraviolet transient absorption spectroscopy measures transitions from the Br 3d core to the valence and conduction band of CH3NH3PbBr3 perovskite, enabling us to observe carrier specific dynamics.

Applied Sciences 10(8), 2728 (2020). doi:10.3390/app10082728, X-ray pump/X-ray probe applications are made possible at X-ray Free Electron Laser (XFEL) facilities by generating two X-ray pulses with different wavelengths and controllable temporal delay. In order to enable this capability at the European XFEL, an upgrade project to equip the soft X-ray SASE3 beamline with a magnetic chicane is underway. In the present paper we describe the status of the project, its scientific focus and expected performance, including start-to-end simulations of the photon beam transport up to the sample, as well as recent experimental results demonstrating two-color lasing at photon energies of 805 eV + 835 eV and 910 eV + 950 eV. Additionally, we discuss methods to analyze the spectral properties and the intensity of the generated radiation to provide on-line diagnostics for future user experiments., Published by MDPI, Basel

We present an all-fiber coherent dual-comb system suitable to perform time-resolved spectroscopy measurements in the long-wave infrared.

We demonstrated the time-resolved luminescence spectroscopy during femtosecond laser ablation with a streak camera. We observed the luminescence dynamics of the plasma and found relationships between the plasma temperature dynamics and ablated morphology.

An ultra-short pulsed, ultra-broadband (~13nm-~13pm) light-source has been developed to drive atto- to femto- second time-resolved studies on EUV photo-resist materials. The same source will also be used to investigate EUV driven nano-lithography.

Dual-comb spectrometers based on QCLs offer a unique tool for environmental sensing. We present high-resolution absorption and dispersion spectra covering 55 cm-' of methane and time-resolved spectroscopy of combustion diagnostics, stopped-flow reaction monitoring and photochemistiy.

Purpose One of the major problems in breast cancer surgery is defining surgical margins and establishing complete tumor excision within a single surgical procedure. The goal of this work is to establish instrumentation that can differentiate between tumor and normal breast tissue with the potential to be implemented in vivo during a surgical procedure. Methods A time-resolved fluorescence and reflectance spectroscopy (tr-FRS) system is used to measure fluorescence intensity and lifetime as well as collect diffuse reflectance (DR) of breast tissue, which can subsequently be used to extract optical properties (absorption and reduced scatter coefficient) of the tissue. The tr-FRS data obtained from patients with Invasive Ductal Carcinoma (IDC) whom have undergone lumpectomy and mastectomy surgeries is presented. A preliminary study was conducted to determine the validity of using banked pre-frozen breast tissue samples to study the fluorescence response and optical properties. Once the validity was established, the tr-FRS system was used on a data-set of 40 pre-frozen matched pair cases to differentiate between tumor and normal breast tissue. All measurements have been conducted on excised normal and tumor breast samples post surgery. Results Our results showed the process of freezing and thawing did not cause any significant differences between fresh and pre-frozen normal or tumor breast tissue. The tr-FRS optical data obtained from 40 banked matched pairs showed significant differences between normal and tumor breast tissue. Conclusion The work detailed in the main study showed the tr-FRS system has the potential to differentiate malignant from normal breast tissue in women undergoing surgery for known invasive ductal carcinoma. With further work, this successful outcome may result in the development of an accurate intraoperative real-time margin assessment system. Lasers Surg. Med. 50:236-245, 2018. © 2018 Wiley Periodicals, Inc.