The CANARY on-sky MOAO demonstrator is being integrated in the laboratory and a status update about its
various components is presented here. We also discuss the alignment and calibration procedures used to improve
system performance and overall stability. CANARY will be commissioned at the William Herschel Telescope at
the end of September 2010.
EAGLE is an instrument for the European Extremely Large Telescope (E-ELT). EAGLE will be installed at the Gravity
Invariant Focal Station of the E-ELT, covering a field of view of 50 square arcminutes. Its main scientific drivers are the
physics and evolution of high-redshift galaxies, the detection and characterization of first-light objects and the physics of
galaxy evolution from stellar archaeology. These key science programs, generic to all ELT projects and highly
complementary to JWST, require 3D spectroscopy on a limited (~20) number of targets, full near IR coverage up to 2.4
micron and an image quality significantly sharper than the atmospheric seeing. The EAGLE design achieves these
requirements with innovative, yet simple, solutions and technologies already available or under the final stages of
development. EAGLE relies on Multi-Object Adaptive Optics (MOAO) which is being demonstrated in the laboratory
and on sky. This paper provides a summary of the phase A study instrument design.
Laser-Induced Breakdown Spectroscopy (LIBS) technique combined with Laser-Induced Fluorescence (LIF) is known
to be a high sensitivity and high selectivity analytical technique. Although sub-ppm limits of detection (LoD) have
already been demonstrated, there is still a constant and urgent need to reach lower LoDs. Here, we report results obtained
for the detection of lead trace in brass samples. The plasma was produced by a Q-switched Nd:YAG laser at 1064 nm
and then re-excited by a nanosecond optical parametric oscillator (OPO) laser tuned at 283.31 nm. Emission from Pb
atoms was then observed at 405.78 nm. The experiments were performed in air at atmospheric pressure. We found out
that the optimal conditions were obtained for an ablation fluence of 2-3 J/cm2 and inter-pulse delay of 8-10 μs. Also,
excitation energy of about 200 μJ was required to maximize the Pb(I) 405.78 nm emission. Using the LIBS-LIFS
technique, the LoD was estimated to be about 180 ppb over 100 laser shots, which corresponds to an improvement of
about two orders of magnitude with that obtained using conventional LIBS.
A promising way of improving the sensitivity of the LIBS (Laser-Induced Breakdown Spectroscopy) technique consists in using basically two successive laser pulses instead of only one as in conventional LIBS: the first pulse generates the plasma and the second pulse selectively excites a specific quantum level of a given trace atomic species inside the plasma. The effect of this second laser pulse is to increase the emission of the atomic species of interest and therefore enhance the signal-to-noise ratio, leading to an improved detection. As a first step toward the detection of Pb in various materials, we present in this work a study of the resonant excitation and decay paths of Pb atoms in a laser-produced plasma. The ablation was performed using a Nd:YAG laser and the 2nd pulse provided by an Optical Parametric Oscillator (OPO) laser was launched several μs afterwards.
Ultrashort laser pulses are very promising tools for performing accurate dissection in the eye, especially in the corneal stroma. The development of eye femtosurgery requires basic knowledge about laser-tissue interaction. One of the most significant parameters is the ablation threshold, the minimal laser energy per unit surface required for ablation. We present here measurements of the femtosecond laser ablation threshold as a function of the pulse duration for two cornea layers (epithelium and stroma) using optical damage diagnosis. Experiments have been realized with the INRS Ti:Sapphire laser (60 fs-5000 fs, 800 nm, 10 Hz). Our experimental results are fitted with a model for laser-matter interaction in order to determine some intrinsic physical parameters
In 1985, the discovery of chirped-pulse amplification (CPA) by G. Mourou and D. Strickland led to ultrashort and high energy pulse lasers. Since energy deposition of ultrashort pulses occurs with limited heat transfer and damages, potential applications of femtosecond lasers to corneal surgery are very promising. By focusing a femtosecond laser on a solid surface, matter is ablated and this process is strongly laser parameter dependent. The goal of the experiment presented here was to measure the femtosecond laser ablation thresholds for different corneal layers and hydrogels. Experiments have been realized with the INRS Ti:Sapphire laser (60fs-400ps, 800nm, 10Hz) and they constitute an initial step toward the development of a new type of high precision surgical tool for corneal microsurgery. Results will be compared to theoretical calculation for light-tissue interaction and propagation using the hydrodynamic code developed at INRS. Grant Identification: NSERC, FRSQ Research in Vision Network and China Scholarship 22836034.
This paper presents result form a systematic study of the feasibility of triggering lightning in a controlled fashion, using ultrashort pulse lasers. We show the importance of producing a plasma with local gradients of electron density by focusing the laser beam in order to trigger streamers, which are the first condition required for the initiation of large-scale spark discharges. We present evidence of the ability of laser filaments to guide streamer discharges, which are akin to the final jump phase of a lightning discharge. We also demonstrate that the leader propagation can be considerably modified by the presence of a laser- produced plasma channel, in a rod-plane electrode geometry. Finally, we have developed numerical models for the ultrashort pulse laser beam propagation through air, plasma production and streamer inception.