Photoexcitation spectroscopy and material alteration with free-electron laser

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Mid-infrared spectroscopy offers unparalleled opportunities in sensing through chemically specific detection of molecular absorption fingerprints. Yet its practical applications are limited by weak light-matter interaction and complex and relatively slow instrumentation relying on scanning components. Here, we develop a rapid imaging-based mid-IR spectroscopy platform that combines broadband resonance gradient metasurfaces and radiofrequency-modulated quantum cascade laser generating broad (250 cm-1

X-ray free-electron lasers (FELs) are powerful photon sources offering a wide wavelength range, subfemtosecond pulse duration, and high brightness. Most x-ray FELs are based on self-amplified spontaneous emission (SASE). SASE-FEL radiation has excellent transverse but only limited longitudinal coherence, with power and spectral profiles consisting of multiple randomly distributed spikes. In this Letter, we present the first experimental demonstration of mode-locked SASE, which generates periodic trains of p

Laser Powder Bed Fusion (LPBF) is a promising metal additive manufacturing (AM) technology that enables high-precision fabrication of high-performance parts with unprecedented design flexibility. However, its widespread adoption remains hindered by the occurrence of various defects, which significantly degrade the mechanical properties and reproducibility of fabricated parts. These defects are inherently linked to the complex and dynamic nature of melt pool behavior, governed by a combination of laser-mater

Transition metal dichalcogenides (TMDs) are semiconductor Van der Waals materials that can be obtained as stable monolayers (ML), characterized by bandgap values from visible to near infrared range. With decreasing thickness from bulk to MLs, TMDs show a transition from indirect to direct bandgap, which combined to strong exciton binding energies makes them propitious for optoelectronic applications. Their atomically flat, dangling bond free surfaces and weak interlayer van der Waals bonding enable stable e

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In this paper, we report recent results on the efficient generation of SWIR sources exploiting broadband wavelength conversion in silica fibers. Optimized cavity-less designs of fiber parametric amplifiers (FOPA) associated with Thulium amplification capable of high CW powers, wide tunability and modulation will be presented. We also present how parametric conversion can be extended deeper in the Mid-IR by engineering of non-silica mixing platforms.

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is similar to 150 K. This observation suggests that, despite the significant translational heating by radio-fre

We report on transverse mode discrimination in long-wavelength wafer-fused vertical-cavity surface-emitting lasers (VCSELs) incorporating ring-shaped air gap patterns at the fused interface between the active region and the top distributed Bragg reflector (DBR). These 60-nm deep patterns were implemented with the aim of favoring the fundamental mode while preserving high output power. The VCSELs under consideration emit in the 1310-nm band and incorporate an AlGaInAs-based quantum well active region, a regr

We report coupled VCSEL arrays, emitting at 1.3μm wavelength, in which both the optical gain/loss and refractive index distributions were defined on different vertical layers. The arrays were electrically pumped through a patterned tunnel junction, whereas the array pixels were realized by intra-cavity patterning using sub-wavelength air gaps. Stable oscillations in coupled modes were evidenced for 2x2 array structures, from threshold current up to thermal roll-over, using spectrally resolved field pattern

This communication presents a review of the developments carried out towards the electromagnetic modeling, design and practical implementation of the basic building block of a planar antenna for the reception of Ku-band satellite broadcasting services from user terminals on board automotive platforms. The antenna is conceived as a low profile phased array with fully electronic beam steering and polarization tracking capabilities. This phased array is intended to address the market of low cost consumer appli

We report the fabrication and the performance of phase-locked VCSEL arrays emitting near 1310 nm wavelength. The arrays were fabricated using double wafer fusion by patterning a tunnel junction layer, which serves to define the individual single mode array elements. Phase-locking in both one-dimensional and two-dimensional array configurations was confirmed by means of far field and spectral measurements as well as theoretical modeling. CW output powers of more than 12 mW were achieved. (C) 2009 Optical Soc

We calculate the transverse and the longitudinal infrared absorption spectra of the hydrated silicon surface using a first-principles approach. The absorption spectra are computed for two different configurations of water molecules dissociatively chemisorbed on the Si(100)-(2 X 1) surface at full coverage. Our calculations compare favorably with the experimental spectra for both the frequency and the intensity of the absorption peaks. Our results suggest the possibility of combining infrared spectroscopy an

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Femtosecond laser irradiation has various noticeable effects on fused silica. It can locally increase the index of refraction and modify the material chemical selectivity. Regions that have been exposed to the laser are etched hundred fold faster than unexposed regions. These effects are of practical importance from an application point-of-view and open new opportunities for the development of integrated photonics devices that combine structural and optical functions. Various observations reported in the li

This thesis reports on results of three different experiments of photo-induced structural dynamics in the condensed phase, investigated by time-resolved pump-probe spectroscopy with femtosecond time-resolution. In the first part, we address the ultrafast dynamics of a quantum solid : crystalline hydrogen. This is accomplished by optical excitation of a dopant molecule, Nitric Oxide (NO), to a large orbital Rydberg state, which leads to a bubble-like expansion of the species surrounding the impurity. The dyn

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Single crystals of self-synthesized mordenite−Na were used for incorporation of the cationic dye molecule thionin blue (C12H10N3S+). The planar organic molecule (7.5 × 15 Å), which fits into the large 12-membered ring channel of mordenite, was incorporated by ion-exchange replacing extraframework Na+ cations. Deep blue thionin-exchanged mordenite crystals were chemically analyzed by electron microprobe yielding the composition Na5.5Thionin0.4Si42.02Al5.88O96 × nH2O indicating that the large 12-membered ring

We have employed femtosecond laser writing in order to induce refractive-index changes and waveguides in Ti3+-doped sapphire. Doping the sapphire crystal with an appropriate ion significantly reduces the threshold for creating structural changes, thus enabling the writing of waveguide structures. Passive and active buried channel waveguiding is demonstrated and images of the guided modes, propagation-loss values, fluorescence spectra, and output efficiencies are presented. The guiding area is located around

Broadband synchrotron X-rays with limited coherence can be used for high resolution phase contrast radiology. Our experimental results confirm the prediction that the extreme spatial coherence of third-generation synchrotron sources although helpful but not strictly necessary for refraction-based or diffraction-based edge enhancement. Source with rather limited lateral coherence can produce Fresnel diffraction fringes. The direct observation of the same fringes using broadband synchrotron lights demonstrate

We report on the fabrication of Ti:sapphire channel waveguides. Such channel waveguides are of interest, e.g., as low-threshold tunable lasers. We investigated several structuring methods including ion beam implantation followed by wet chemical etching strip loading by polyimide spin coating and subsequent laser micro-machining, direct laser ablation or reactive ion etching through laser-structured polyimide contact masks. The later two methods result in ribs having different widths and heights up to simila

Photoexcitation spectroscopy and material alteration with free-electron laser

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Metasurface-enhanced mid-infrared imaging spectroscopy with broadband quantum cascade lasers

Demonstration of Mode-locked Frequency Comb for an X-ray Free-electron Laser

Uncovering melt pool dynamics and laser absorption mechanisms in laser powder bed fusion through in-situ experiments and high-fidelity multiphysics simulations

Engineering GaAs nanostructures for heterointegration with 2D transition metal dichalcogenides

MATHICSE Technical Report : Using separable non-negative matrix factorization techniques for the analysis of time-resolved Raman spectra

Efficient broadband parametric conversion: reaching for the Mid IR

Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions

Improved single-mode emission characteristics of long-wavelength wafer-fused vertical-cavity surface-emitting lasers by intra-cavity patterning

Intra-cavity patterning for mode control in 1.3μm coupled VCSEL arrays

Design review of a compact and low cost elementary radiating cell for satellite broadcasting automotive receiving arrays

1.3µm-wavelength phase-locked VCSEL arrays incorporating patterned tunnel junction

First-principles theory of infrared absorption spectra at surfaces and interfaces: Application to the Si(100): H2O surface

Time-resolved imaging and spatially-resolved spectroscopy of Electrical Discharge Machining Plasmas

Investigation of Femtosecond Laser Irradiation on Fused Silica

Ultrafast structural dynamics in electronically excited many-body systems

White beam x-ray waveguide optics

Cationic Thionin Blue in the Channels of Zeolite Mordenite: A Single-Crystal X-ray Study

Femtosecond-irradiation-induced refractive-index changes and channel waveguiding in bulk Ti3+: Sapphire

Edge-enhanced radiology with broadband synchrotron X-rays

Laser-assisted microstructuring for Ti : sapphire channel-waveguide fabrication