Digital holography for second harmonic microscopy

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Non-ablative femtosecond laser processing of transparent substrates involves cumulative, multi-timescale dynamics that hinder precise control of induced structural modifications. Here, we demonstrate a feedback-compatible diagnostic based on mid-infrared transmission monitoring using a continuous-wave QCL emitting at 4.46 µm. This approach enables in situ observation of structural dynamics induced by femtosecond laser irradiation at repetition rates up to 250 kHz. The technique shows sensitivity to key tran

The electrostatic potential of lipid membranes is an important metric to gain insight into the physiological state of cells. Second harmonic (SH) imaging has emerged as a powerful tool to perform in-situ and in-vivo electrostatic potential measurements, either using targeted probes, or label-free by using water as a probe. In this work we compare both modalities, by performing SH imaging on freestanding lipid membranes (FLMs) in aqueous solutions. Correlating the SH intensity to an applied external potentia

Wavelength‐tunable pulsed lasers have garnered significant research interest due to their critical role in applications requiring precise spectral matching, such as wavelength‐division multiplexing and spectroscopic analysis. Although recent hybrid architectures integrating saturable absorbers with wavelength‐selective components have enabled notable progress, these systems remain constrained by two fundamental challenges: excessive coupling losses and complex alignment procedures. Here, a compact wavelengt

This study explores the ferroelectric domain structure and mechanical properties of PbTiO3‐based membranes, which develop a well‐ordered and crystallographic‐oriented ripple pattern upon release from their growth substrate. The ferrolectric domain structure of the PbTiO3 layer is examined at various length scales using optical second harmonic generation, piezoresponse force microscopy, and scanning transmission electron microscopy. These methods reveal the presence of purely in‐plane domains organized into

A dielectric multilayer platform sustaining Bloch surface waves is investigated for planar integrated optics. We study the optical properties of high refractive index material (TiO2) and obtain propagation lengths in the range of millimeters.

Purpose – Since pulsed lasers are mainly used in selective laser sintering (SLS) – contrarily to selective laser melting (SLM) – only the exterior of the powder particles is molten while their core stays solid. The purpose of this paper is to investigate the binding mechanism between two particles of titanium powder. Design/methodology/approach – A dedicated experimental setup is used to isolate the particles. They are then irradiated by the laser. SEM micrographs are taken at each step and image analysis i

We report on the experimental and numerical demonstration of immersed submicron-size hollow focused spots, generated by structuring the polarization state of an incident light beam impinging on a micro-size solid immersion lens (μ-SIL) made of SiO2. Such structured focal spots are characterized by a doughnut-shaped intensity distribution, whose central dark region is of great interest for optical trapping of nano-size particles, super-resolution microscopy and lithography. In this work, we have used a high-

Nanoparticles are interesting for biomedical imaging as novel non- fluorescent non-bleaching labels. We present the characterization of freely diffusing nanoparticles using third harmonic generation correlation spectroscopy by illumination with a focussed pulsed femtosecond laser. We present the optical system as well as first spectroscopic results on nanoparticles.

Many biological objects are mainly transparent and weakly scattering, thus a promising (and already widely used) way of imaging them consists in considering optical refractive index variations. The method proposed here permits 3D imaging of the refractive index distribution with a tomographic approach. Usually, the classical Radon transform does not sufficiently take into account the physical interaction between light and biological cells, therefore diffraction has to be considered.

We experimentally demonstrate significantly enhanced second harmonic generation using nanoengineered plasmonic nanocavities of core-shell structures (BaTiO3/Au). An enhancement factor of over 500 is measured in the second harmonic scattering efficiency compared to the bare core. (C) 2009 Optical Society of America

Digital holographic microscopy (DHM) is a technique that allows obtaining, from a single recorded hologram, quantitative phase image of living cell with interferometric accuracy. Specifically, the optical phase shift induced by the specimen on the transmitted wave front can be regarded as a powerful endogenous contrast agent, depending on both the thickness and the refractive index of the sample. We discuss some approaches allowing to directly obtain separate measurements of the thickness and the refractive

We report direct absorption spectroscopic detection of ozone at ambient pressure with a pulsed, DFB quantum-cascade laser (QCL) tuned within 1044-1050 cm(-1) by temperature scanning. Wavelength calibration curves were derived from FTIR and CO2 spectra and interpreted with respect to the heat transfer from the heterostructure to the sink. The laser linewidth (similar to0.13 cm(-1) FWHM) was found to decrease with temperature, probably as a result of operation at constant current. Spurious spectral features d

A 3D imager is presented capable of computing the depth map as well as the intensity scale of a given scene. The heart of the system is a two-dimensional array of single photon avalanche diodes fabricated in standard CMOS technology. The diodes exhibit low noise equivalent power, high dynamic range and superior linearity. The 3D imager achieves sub-millimetric precision at depth-of-field of a few meters. It operates using a standard LASER source pulsed at 50MHz with 40mW peak power and requires no mechanica

First results and analysis of second harmonic generation with a Nd:YAG laser working in the long pulse, free running mode are presented in this paper. Second harmonic generation conversion efficiencies of up to 17.5% and pulse powers of 162W have been generated with a free running Nd:YAG laser and a KTP non-linear crystal. The conversion efficiency is limited by a saturation effect and optical damage occurring at similar to50 times lower peak intensities than in the Q-switch mode. The saturation and damage

The formation of sub-micron sized particulates has been studied in a low pressure (0.1 mbar) radio-frequency (13.56 MHz) capacitively coupled plasma discharge. Particles are studied in situ by infrared absorption spectroscopy, laser illumination and Cavity Ring Down Absorption Spectroscopy. Transmission Electron Microscopy was applied ex situ for particulates collected during the plasma. We propose that two principal mechanisms may be involved in the formation of these particulates: formation and trapping o

The TCV tokamak (R = 0.88 in, a < 0.25 in, BT < 1.54 T) is equipped with six 0.5 MW gyrotron sources operating at 82.7 GHz for second harmonic X mode ECH. By distributing the ECCD current sources over the discharge cross section, fully driven stationary plasmas with I-p = 210 kA, n(e0) = 2 x 10(19) m(-3), T-e0 approximate to 4 keV, were obtained for the full discharge duration of 2 s. Highly peaked electron temperature profiles with T-e0 up to 12 keV were obtained in central counter-current drive scenarios

The absorption spectrum of C60 embedded in Ne matrixes in the 410-360 nm region is revisited. A complete assignment of the absorption lines therein is proposed in terms of transition to the ungerade states 1 1G1u, 1 1T1u and 2 1T1u states, with progression of Jahn-Teller hg modes and of the totally sym. ag modes. The authors also identify a new progression at l ? 375 nm, which the authors attribute to the transition to the 2 1T2u state and its hg and gg Jahn-Teller modes. Its pure electronic origin is at .a

We present a tunable interference filter for infrared and visible light that scans the desired part of the optical spectrum within milliseconds. A single pixel detector measures serially the intensity at selected wavelengths. This concept avoids expensive linear detectors as used for grating spectrometers. The tunable optical interference filter is fabricated by a new porous silicon batch technology using only two photolithography steps. The refractive index of this filter microplate is gradually modulated

Chalcogenide glass optical fibers were fabricated into functional apertured probes for near field scanning infrared microscopy. Probe fiber tips were chemically etched and aluminum coated for the purpose of simultaneously collecting near field shear force and optical signals. Surface topography and infrared optical reflectivity data were obtained using the tips in a scanning near field microscope while illuminating an integrated microcircuit with the output from a free electron laser operating at a lambda o

For future divertor studies on TCV measurements of electron temperature and density and their spatial gradients along open flux surfaces will be of major interest. A Thomson scattering system is proposed for this purpose, which takes advantage of the good access via horizontal ports on three vertical levels. The modular design of the existing Thomson scattering diagnostic on TCV offers the possibility to modify it for simultaneous measurements in the main plasma and in the divertor region using the same las

Digital holography for second harmonic microscopy

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Laser-based in situ monitoring of femtosecond-laser in-bulk processing of glass

Second harmonic imaging of membrane potentials: comparing water and chromophores as probes

Wavelength Tunable Pulsed Lasers Enabled by a Versatile Metafiber Functioning as Both Saturable Absorber and Filter

Curvature‐Controlled Polarization in Adaptive Ferroelectric Membranes

Bloch Surface Waves Based Platform for Integrated Optics

Study of the inter-particle necks in selective laser sintering

Submicron hollow spot generation by solid immersion lens and structured illumination

Characterization of Nanoparticles Using Non-linear Correlation Spectroscopy

Diffraction tomography for biological cells imaging using digital holographic microscopy

Enhanced Second Harmonic Generation in Plasmonic Nanocavities

Analysis of cellular structure and dynamics with digital holographic microscopy

Ozone detection by differential absorption spectroscopy at ambient pressure with a 9.6 mu m pulsed quantum-cascade laser

Toward a 3-D Camera Based on Single Photon Avalanche Diodes

Second harmonic generation with free running Nd : YAG laser

Etude de l'origine et de la croissance de particules submicrométriques dans les plasmas radiofréquence réactifs

Overview of TCV results

Assignment of the near-UV absorption spectrum of C60

Microspectrometer based on a tunable optical filter of porous silicon

Scanning near field infrared microscopy using chalcogenide fiber tips

A Thomson scattering diagnostic for measurements in the divertor region of TCV