The X-HPD: Development of a large spherical hybrid photodetector

The X-HPD concept is a modern implementation of the Dumand and Lake Baikal approach to large area photon detectors, primarily aimed at water based Cherenkov detectors. Our prototype detector consists of an almost spherical vacuum tube of 8-inch diameter with a semi-transparent bialkali photocathode and a LYSO scintillation crystal mounted in the centre of the tube. The scintillation light produced after the impact of a photoelectron which was accelerated to about 20-30 keV energy is detected by a small standard PMT. In addition to the attractive characteristics already established with its historic predecessors, namely high gain, large collection efficiency and immunity to the earth magnetic field, the X-HPD concept leads to very high effective Q.E. values, an extended viewing angle and marginal transit time spread.We present recent results obtained with a prototype tube built at CERN and a second full tube under preparation in collaboration with the company Photonis

Three-dimensional writing inside silicon using a 2-µm picosecond fiber laser

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2 µm all-fiber dissipative soliton MOPA

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Octave-spanning coherent supercontinuum generation in a step-index tellurite fiber and towards few-cycle pulse compression at 2 μ m

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Generation of 35 kW peak power 80 fs pulses at 29 μm from a fully fusion-spliced fiber laser

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Supercontinuum-based Fourier transform infrared spectromicroscopy

International audienceFourier-transform infrared (FTIR) spectromicroscopy combines the spatial resolution of optical microscopy with the spectral selectivity of vibrational spectroscopy. Synchrotron sources can provide diffraction-limited beams in the infrared, and therefore synchrotron-based FTIR spectromicroscopy is nowadays an indispensable tool for biology and materials science studies where high spatial resolution is required. However, the increasing need for accurate and highly spatially resolved characterization is calling for alternative laboratory-based sources to complement synchrotron radiation. To date, the low brightness of thermal emitters or high temporal coherence and narrow bandwidth or tunability of laser sources have hindered the progress of bench-top FTIR spectromicroscopy. Here, we demonstrate that fiber-based supercontinuum sources in the mid-infrared enable fast spectral mapping of localized material properties with close to diffraction-limited resolution (3  μm×3  μm) and pave the way to table-top, on-demand, fast, and highly spatially resolved studies. We illustrate these capabilities by imaging thin sections of human liver samples and compare the results and performance with those obtained using a synchrotron source

Material processing with ultra-short pulse lasers working in 2μm wavelength range

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Competing Nonlinear Delocalization of Light for Laser Inscription Inside Silicon with a 2- µ m Picosecond Laser

International audienceThe metrology of laser-induced damage usually finds a single transition from 0% to 100% damage probability when progressively increasing the laser energy in experiments. We observe that picosecond pulses at 2-µm wavelength focused inside silicon provide a response that strongly deviates from this. Supported by nonlinear propagation simulations and energy flow analyses, we reveal an increased light delocalization for near critical power conditions. This leads to a nonmonotonic evolution of the peak delivered fluence as a function of the incoming pulse of the energy, a situation more complex than the clamping of the intensity until now observed in ultrafast regimes. Compared to femtosecond lasers, our measurements show that picosecond sources lead to reduced thresholds for three-dimensional (3D) writing inside silicon that is highly desirable. However, strong interplays between nonlinear effects persist and should not be ignored for the performance of future technological developments. We illustrate this aspect by carefully retrieving from the study the conditions for a demonstration of 3D data inscription inside a silicon wafer

Megawatt solitons generated above 2000 nm in Bragg fibers

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