A5058556821- Spectroscopy Techniques in Biomedical and Chemical Research
- Advanced Fiber Laser Technologies
- Perovskite Materials and Applications
- Optical Coherence Tomography Applications
- Photonic and Optical Devices
- Photoreceptor and optogenetics research
- Advanced Fluorescence Microscopy Techniques
- 2D Materials and Applications
- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Spectroscopy and Quantum Chemical Studies
- Photosynthetic Processes and Mechanisms
- Laser-Matter Interactions and Applications
- Plasmonic and Surface Plasmon Research
- Carbon Nanotubes in Composites
- Molecular spectroscopy and chirality
- Graphene research and applications
- Mechanical and Optical Resonators
- Spectroscopy and Laser Applications
- Advanced Optical Sensing Technologies
- Isotope Analysis in Ecology
- Photonic Crystals and Applications
- Light effects on plants
- Electrochemical Analysis and Applications
- Hemoglobin structure and function
Politecnico di Milano
2013-2021
Istituto di Fotonica e Nanotecnologie
2017
National Research Council
2014
Abstract Graphene nanoribbons display extraordinary optical properties due to one-dimensional quantum-confinement, such as width-dependent bandgap and strong electron–hole interactions, responsible for the formation of excitons with extremely high binding energies. Here we use femtosecond transient absorption spectroscopy explore ultrafast ultranarrow, structurally well-defined graphene a function excitation fluence, impact enhanced Coulomb interaction on their excited states dynamics. We...
The 2D semiconductor MoS 2 in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show strong photovoltaic effect work active material high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy sub‐ps ms time scales used study photoexcitation dynamics . results suggest that...
Significance Chloroplasts are particularly prone to photooxidative damage, and carotenoids play a key role in photoprotection. Under excess light conditions, plants accumulate carotenoid, zeaxanthin, involved multiple photoprotection events. Although the function of zeaxanthin photosystem II (PSII) has been investigated thoroughly, its I (PSI) had not identified. In this work we report zeaxanthin-dependent regulation PSI functional antenna size Arabidopsis thaliana . We identified quenching...
The enhancement of nonlinear optical effects via nanoscale engineering is a hot topic research. Optical nanoantennas increase light-matter interaction and provide, simultaneously, high throughput the generated harmonics in scattered light. However, optics has dealt so far with static or quasi-static configurations, whereas advanced applications would strongly benefit from high-speed reconfigurable nanophotonic devices. Here we propose experimentally demonstrate ultrafast all-optical...
We introduce a scheme for the generation of tunable few-optical-cycle UV pulses based on sum-frequency between broadband visible pulse and narrowband ranging from to near-IR. This configuration generates 0.3 0.4 μm, with energy up 1.5 μJ. By exploiting nonlinear phase transfer, transform-limited durations are achieved. Full characterization spectral is obtained by two-dimensional shearing interferometry, which here extended range. demonstrate clean 8.4 fs pulses.
We show the ultrafast photodoping and plasmon dynamics of near-infrared (NIR) localized surface resonance (LSPR) fluorine-indium codoped cadmium oxide (FICO) nanocrystals (NCs). The combination high temporal resolution broad spectral coverage allowed us to model transient absorption (TA) spectra in terms Drude model, verifying increase carrier density upon photodoping. Our analysis also suggests that a change effective mass takes place LSPR excitation as result nonparabolic conduction band...
Abstract We report the first demonstration of a solution processable, optically switchable 1D photonic crystal which incorporates phototunable doped metal oxide nanocrystals. The resulting device structure shows dual optical response with bandgap covering visible spectral range and plasmon resonance near infrared. By means facile photodoping process, we tuned plasmonic switched effectively properties crystal, translating effect from infrared to visible. ultrafast pumping induces signal...
Stimulated Raman scattering spectroscopy is a powerful technique for label-free molecular identification, but its broadband implementation technically challenging.We introduce and experimentally demonstrate novel approach based on photonic time stretch.The femtosecond Stokes pulse, after interacting with the sample, stretched by telecom fiber to ≈15ns, mapping spectrum in time.The signal sampled through fast analog-to-digital converter, providing single-shot spectra at 80-kHz rate.We ≈10 -5...
We introduce a broadband single-pixel spectro-temporal fluorescence detector, combining time-correlated single photon counting (TCSPC) with Fourier transform (FT) spectroscopy. A birefringent common-path interferometer (CPI) generates two time-delayed replicas of the sample's fluorescence. Via FT their interference signal at we obtain two-dimensional map as function detection wavelength and emission time, high temporal spectral resolution. Our instrument is remarkably simple, it only...
Theory predicts peculiar features for excited-state dynamics in one dimension (1D) that are difficult to be observed experimentally. Single-walled carbon nanotubes (SWNTs) an excellent approximation 1D quantum confinement, due their very high aspect ratio and low density of defects. Here we use ultrafast optical spectroscopy probe photogenerated charge-carriers (6,5) semiconducting SWNTs. We identify the transient energy shift highly polarizable S33 transition as a sensitive fingerprint By...
Nonlinear optical microscopy is a powerful label-free imaging technology, providing biochemical and structural information in living cells tissues. A possible drawback photodamage induced by high-power ultrashort laser pulses. Here we present an experimental study on thousands of HeLa cells, to characterize the damage focused femtosecond near-infrared pulses as function power, scanning speed exposure time, both wide-field point-scanning illumination configurations. Our data-driven approach...
With a power conversion efficiency (PCE) exceeding 22 %, perovskite solar cells (PSCs) have thrilled photovoltaic research. However, the interface behavior is still not understood and hot topic of research: different processes occur over hierarchy timescales, from femtoseconds to seconds, which makes physics intriguing. Herein, through femtosecond transient absorption spectroscopy with spectral coverage extending into crucial IR region, ultrafast interface-specific at standard newly...
We investigate the photogeneration of polaron pairs (PPs) in neat films semicrystalline donor-acceptor semiconducting copolymer PCPDTBT. Carefully selecting solution-processing procedures, we obtain with different amounts crystallinity and interchain aggregation. compare PPs between by monitoring their photoinduced absorption ultrafast pump-probe experiments, selectively exciting nonaggregated or aggregated polymer chains. The direct photoexcitation π-aggregates results prompt (<100 fs)...
We investigate the nature of S* excited state in carotenoids by performing a series pump-probe experiments with sub-20 fs time resolution on spirilloxanthin polymethyl-methacrylate matrix varying sample temperature. Following photoexcitation, we observe sub-200 internal conversion bright S2 into lower-lying S1 and states, which turn relax to ground picosecond scale. Upon cooling down 77 K, systematic decrease S*/S1 ratio. This result can be explained assuming two thermally populated isomers....
We use ultrafast transient absorption microscopy to map the effect of structural disorder on photophysical properties within a micrometer-sized crystal methylammonium lead iodide (CH3NH3PbI3) perovskite. reveal spatial inhomogeneity and behavior submicrometer scale induced by local distortion lattice, which affects electron–hole correlation over hundreds nanometers length scale.
We report on a Yb-pumped optical parametric oscillator (OPO) that delivers 30 fs pulses with spectral coverage from 680 to 910 nm and an average output power of up 1.1 W. The resulting peak is ∼0.5 MW, which is, the best our knowledge, highest ever demonstrated in femtosecond OPO. intensity noise remains at level 0.2% rms, rapid wavelength tuning obtained by simply scanning resonator length. performances OPO are promising for variety applications nonlinear microscopy ultrafast spectroscopy.
We study how the color and polarization of ultrashort pulses visible light can be used to control demagnetization processes antiferromagnetic insulator ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$. utilize time-resolved second harmonic generation (SHG) probe changes in magnetic structural state evolve time. show that varying pump photon-energy excite either localized transitions within Cr or charge transfer states leads markedly different dynamics. Through a full analysis SHG signal, symmetry...
We present a methodology that provides complete parametric description of the time evolution electronically and vibrationally excited states as detected by ultrafast transient absorption (TA). Differently from previous approaches, which started fitting data after ≈100 fs, no are left out in our methodology, “coherent artifact” instrument response function fully taken into account. In case studies, method is applied to solvents, dye Nile blue, all-trans β-carotene cyclohexane solution. The...
The absorption spectra of 2D semiconductors are dominated by excitons with binding energy several hundreds meV. Nevertheless, even single layers show an appreciable photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating some degree free charge carrier photogeneration. Here, we perform ultrafast transient spectroscopy on monolayer MoS2 a field-effect transistor configuration. We that moderate in-plane electric field few kV cm−1 can...
We demonstrate a wavelength-tunable graphene-synchronized all-fiber laser with Yb and Er cavities spanning 1040–1080 1535–1560 nm, corresponding to ~2750–3200 cm−1 frequency detuning. apply the coherent anti-Stokes Raman spectroscopy.