Very narrow-bandwidth tunable infrared difference frequency generation with injection-locked dye lasers

Two flashlamp pumped dye lasers of very high spectral quality are mixed in a LiIO3 crystal to generate a tunable infrared beam through the difference frequency mixing. Thanks to the injection-locking process of the pulsed dye lasers leading to a linewidth of 6 MHz with peak powers of about 10 kW, we obtain an IR beam tunable from 3.5 to 5.9 μm with a peak power of 40 W and a linewidth of 9 MHz. As an application we present a spectrum of N2O obtained by differential absorption near 1880 cm−1. The lines of thisQ-branch are Doppler limited at the working pressure (102 Pa).

Flashlamp-pumped Nd:KGW laser at repetition rates up to 50 Hz

:YAG passive element. Energies up to 1.1 J and 550 mJ, respectively, are obtained with a total efficiency close to 3%.

CW and Q-switched diode end-pumped Nd:YAP laser at 1.34 µm. Influence of Nd doping level

A multi watt CW 1.34 µm diode end-pumped Nd:YAP laser is described. Acoustooptic device is tested to obtain Q-switched operation. The influence of the Nd3+ doping level in YAP crystal on the laser efficiency, in CW and in Q-switched mode, is presented.

Aspects physico-chimiques du nettoyage de surface par laser : critères de choix de la longueur d'onde

Le procede de decapage de surface par faisceau laser impulsionnel est actuellement envisage comme une technique de substitution a des procedes de nettoyage chimique afin de reduire les risques sur l'environnement ou a des procedes mecaniques afin de reduire dans ce cas les risques d'endommagement du substrat a nettoyer. Si les sources lasers choisies peuvent etre regroupees dans le domaine des lasers impulsionnels (temps d'interaction de l'ordre de la nanoseconde), le choix de la longueur d'onde est rarement justifie a partir d'une etude physico-chimique de l'interphase substrat-contaminant a expulser. Differents exemples sont presentes illustrant le besoin de developper des bases de donnee…

Comparative laser study of Nd:KGW and Nd:YAG near 1.3 μm

A comparative study of Nd:KGW and Nd:YAG laser crystals pumped by flashlamp has been conducted near 1.3 μm with output energy up to 1 J and at a repetition rate up to 50 Hz. An average power of 23 W for KGW in free-running mode was achieved with a total efficiency better than 2.8 % for the Nd:KGW and 1.8 % for the Nd:YAG.

Photochemically induced, graded cerebral infarction in the mouse by laser irradiation evolution of brain edema

Cerebral infarction was produced in mice by intravenous injection of a photosensitive dye, rose bengal (10 mg/kg), and by focal illumination of the intact skull surface for 3 min with a laser source, operating at 570 nm with power levels of 2, 5, 10, and 20 mW. Location of infarction was made using 2,3,5-triphenyltetrazolium chloride and the time course of edema in the irradiated cerebral hemisphere was evaluated by measuring water, sodium, and potassium content 4, 24, and 72 hr after irradiation. With power levels of 2 and 5 mW, the infarct was restricted to the cortex, whereas with power levels of 10 and 20 mW, it extended to subcortical regions. Increases in water and sodium and decrease…

Surface acceleration during dry laser cleaning of silicon

We report on measurements of the surface acceleration for the application of dry laser cleaning. For that purpose, industrial silicon samples were irradiated by a frequency-doubled Q-switched Nd:YAG laser. The surface displacement was measured by a heterodyne interferometer and recorded by a digital storage oscilloscope. Several hundreds of shots were averaged to give smooth displacement curves which could be derived numerically. The experiments show that the highest accelerations, which are thought to be responsible for the cleaning, occur on the time scale of the laser pulse. Simple theoretical models are in good agreement with the experimental data. The maximal displacement depends only …

50 mJ/30 ns FTIR Q-switched diode-pumped Er:Yb:glass 1.54 μm laser

Abstract 50 mJ Q-switched output at 30 ns pulse duration was demonstrated with a transversely diode-pumped bulk Er 3+ :Yb 3+ :glass 1.54 μm laser system of uncomplicated and compact design, using a piezoelectrically driven FTIR shutter. In long-pulse operation, 360 mJ output was obtained for 2.65 J incident optical pump energy. Maximum optical slope efficiencies of 20.5% and 5.4% were measured in long-pulse and Q-switched operation, respectively. Optimum Q-switch timing was studied taking into account the Yb 3+ →Er 3+ energy transfer process and was correlated with free-running delay parameters.

Diode-pumped bulk Er:Yb:Glass 1.54μm pulsed laser with 1.2J output and 25% optical efficiency

We report a pulsed transversely diode-pumped compact Er:Yb:Glass laser of uncomplicated design, delivering output energy of approx. 1.2J in free-running operation and 25% optical slope efficiency.

High resolution CARS spectrum and analysis of the v1bandQ-branch of carbon dioxide

High resolution coherent anti-Stokes Raman spectroscopy (CARS) has been applied to the study of the Q-branch of the fundamental vibrational v 1 band of CO2 in the Fermi resonance region near 1285·5 cm-1. Thanks to the use of high spectral quality (linewidth = 6 MHz) injection-locked flashlamp-pumped dye lasers, it was possible to resolve this band for the first time. The spectrum was recorded at a pressure of 5 kPa (37·5 Torr) at room temperature. We measured the line positions and collisional widths for the transitions with J values from 8 to 38. Our experimental line positions are in excellent agreement with those derived from molecular constants given on the literature. The observed line…

Lasing characteristics of a new DCM derivative under flashlamp pumping

Abstract A new DCM derivative (4-dicyanomethylene-2-methyl-6-p-diethanolamino-styryl 4H-pyran or DCM-OH), was tested under flashlamp pumping. This dye lased in the 600–700 nm range with efficiency up to 0.4% at maximum. Lasing performances of DCM-OH in methanol and water-methanol mixture are reported and compared to normal DCM.

Flashlamp-pumped Ti:Sapphire laser with different rods grown by Czochralski and Verneuil methods

The design and the development of a flashlamp-pumped Ti:Sapphire laser is described. Design criteria are discussed and performance improvements using different types of fluorescent UV converters or filters, such as organic dyes or doped glass are presented. We have tested different laser rods at various Ti-concentrations obtained by Verneuil or Czochralski growth techniques. The maximum laser output energy of 540 mJ with a differential efficiency up to 1% was achieved by using only a pyrex filter surrounding the laser rod.

Optical rotary power at the resonance of the Terbium 7F6→5D4 line in Terbium Gallium Garnet

Abstract The Tb 3+ absorption line 7 F 6 → 5 D 4 of the Terbium Gallium Garnet crystal is excited with an Argon ion laser. The Verdet's constant has been determined and reported against 1/ λ 2 , showing no significant resonant behaviour at absorption resonance. The utility and the constraints of the crystal at this particular resonant wavelength are pointed out.

Flashlamp-Pumped Nd:KGW Laser at 1.06 and 1.35 μm in Free-Running and Q-Switched Mode Results in MOPA Configuration

Flashlamp-pumped Ti:Sapphire laser: Influence of the rod figure of merit and Ti3+ concentration

A flashlamp-pumped Ti:Sapphire laser is tested with rods of various Figures of Merit (FOM from 100 to 800) and Ti3+ concentrations (0.1 and 0.15% by weight) and we measured the laser energy dependence as a function of these parameters. Output energies above 2 J are obtained without dye converter, leading to a 1.8% overall efficiency and a 2.2% slope efficiency. The effects of pump pulse duration by variation of the discharge capacitance are also monitored.

Phase-conjugate emission of a two-mirror solid state laser

We show that phase conjugation strongly contributes to the emission of a solid state laser in a two-mirror (Fabry-Perot) resonator , enabling dynamic correction of thermal lensing . Full correction of thermal effects is reached by vector phase conjugation .

A compact and portable laser-induced breakdown spectroscopy instrument for single and double pulse applications

Abstract We present LIBS experimental results that demonstrate the use of a newly developed, compact, versatile pulsed laser source in material analysis related to art and archaeological applications in view of research aiming at the development of portable LIBS instrumentation. LIBS qualitative analysis measurements were performed on various samples and objects, and the spectra were recorded in gated and non-gated modes. The latter is important because of advantages arising from size and cost reduction when using simple, compact spectrograph-CCD detection systems over the standard ICCD-based configurations. The new laser source exhibited a very reliable performance in terms of laser pulse …

INTEREST OF BEAM QUALITY IN MATERIALS TREATMENTS BY HIGH POWER LASER

The aim of the study is the increasing of performances of the YAG Lasers. For this, we use the principle established by Boquillon and Taisne : an X geometry of the resonator. In this case the number of emitted modes is lower than for the linear conception and the beam quality is greater. So, reached power density can be 7 times higher than for the classical cavity and consequently cutting speed can be about 2 times higher than for the linear one. Concerning welding, thick materials need a lot of energy and our system is not competitive. however it exists an interest for thin joining with an easely formed key hole and later a more important penetration.

Laser cleaning of oxide iron layer : efficiency enhancement due to electrochemical induced absorptivity change

Laser cleaning experiments exhibited a higher cleaning efficiency of the laser cleaning upon application of electrochemical potential on an oxidised iron surface. The objective of this study is to clarify the role of such an electrochemical control on cleaning efficiency. Therefore a study by optical spectrometry at normal incidence in the relevant conditions was performed. From these measurements the optical parameters n and k were deduced. While n is mainly not affected, k changes for a factor of 10 upon application of an electrochemical potential. These results explain the differences in laser cleaning efficiency due to the modified absorption length.

Pulse timing effects in bulk Er/Yb codoped diode-pumped eyesafe lasers

In this work, diode-pumping with appropriately modulated pulses is used to expose subtle input / output pulse-timing characteristics of Er3+ /Yb3+ systems, study their relation to laser efficiency and demonstrate some unique laser-pulse timing behavior. Er+3/Yb+3 codoped glass and YAG laser-host materials with similar concentrations (optimized for eyesafe emission in the 1.6-mum region) were studied in the same diode-pumped setup, in similar resonator configurations and analogous operating conditions.

Flashlamp-pumped Nd:KGW laser in MOPA configuration: comparative study of several rods

The laser performance of the Nd:KGW crystal has been studied in a master oscillator and power amplifier configuration (MOPA). Several crystals from two different producers were investigated for the oscillator and the amplifier. A maximum single-pass gain of 25 was observed in free-running and Q-switched mode. We obtained a maximum output amplified energy of 400 mJ at 30 Hz (with a pulse duration of 10 to 30 ns) with a divergence less than 3 mrad. We also studied the limitations of this configuration due to the very high gain of the Nd:KGW crystal.

Laser cleaning of oxidized iron samples: The influence of wavelength and environment

A phenomenological laser-cleaning study of pure oxidized iron samples has been performed in order to model the influence of wavelength in air and the role of environment in the IR domain. Two sets of experiments were performed: (i) cleaning of oxidized specimens at different laser spot sizes and pulse numbers at wavelengths of 1064 nm and 532 nm in air and (ii) cleaning in air with electrolytes at 1064 nm for low energy densities.

1.65-μm Er:Yb:YAG diode-pumped laser delivering 80-mJ pulse energy

We demonstrate efficient lasing of bulk diode-pumped Er 31 :Yb 31 :YAG at 1.645 mm. The material is transversely pumped using three quasi-cw 960-nm laser diode arrays in a simple arrangement. In the free-running mode of operation, an output pulse energy of 79 mJ is obtained at 4.7 J of incident optical pump energy. The lasing threshold lies in the range 1.0 to 1.9 J in long-pulse operation, depending on pumping conditions, and optical slope efficiencies of 2.2% to 3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7-mJ energy and 340-ns FWHM duration. As the reported laser setup also…

Application du laser impulsionnel à l’étude de l’adhérence et de la structure des dépôts

Nous decrivons le signal acoustique enregistre a l’epicentre lors d’une activation laser dans le cas d’un materiau bicouche (acier inoxydable revetu d’alumine d’epaisseur 1,2 µm, 30 µm et 230 µm respectivement). Les resultats obtenus sont analyses en fonction de l’energie incidente et de l’epaisseur du depot. On a constate que le signal est fortement affecte par la presence du depot et que chaque regime d’interaction laser/materiau (thermoelastique, cloquage, expulsion) est caracterise par une reponse acoustique differente. Ceci nous amene a discuter des diverses applications du laser dans la caracterisation du depot et de l’interface substrat/depot. Il s’agit, par exemple, d’evaluer la con…