Gilbert L. Bourdet

Absolute distance measurements by CO 2 laser multiwavelength interferometry

This paper describes a CO(2) laser interferometer allowing absolute distance measurements using a set of CO(2) lines. The method relies on the so-called fractional fringe technique. First, we introduce some theoretical topics related to this application of CO(2) spectroscopy. The second part of the paper is a description of the instrument.

High-efficiency diode-pumped femtosecond Yb:YAG ceramic laser

A highly efficient diode-end-pumped femtosecond Yb:yttrium aluminum garnet (YAG) ceramic laser was demonstrated. Pumped by a 968 nm fiber-coupled diode laser, 1.9 W mode-locked output power at a repetition rate of 64.27 MHz was obtained with 3.5 W absorbed pump power, corresponding to a slope efficiency of 76%. Our measurement showed that the pulse duration was 418 fs with the central wavelength of 1048 nm.

Comparison of pulse amplification performances in longitudinally pumped Ytterbium doped materials

Using a theoretical model, the amplification of laser pulse performances achievable with various Ytterbium doped longitudinally pumped materials is compared. The investigated materials have been separated into two categories: some of them seem to be well suited for diode pumping as they allow good extraction efficiency when pumped by low pump intensity and long pulses. For the others, high pump intensity even with short pulses is required for achieving good extraction efficiency and they can be efficient when pumped by laser. It appears that the classification of these host materials is different from the one set for CW or pulsed lasers.

Time and Spectrum Resolved Model for Quasi-Three-Level Gain-Switched Lasers

We derive and compute a model to describe the spectral dynamic behavior of quasi-three-level laser resonators operated in gain-switched conditions. This model, based on rate equations, predicts both intensity and spectrum evolutions of the laser output. It is specifically applied to a Yb:YAG laser resonator, and the effects of intracavity losses on the emitted wavelength are also investigated. The phenomena forecasted by our model are in very good agreement with our experiments

Theoretical modelling and design of a Tm:YVO4 microchip laser

Abstract We present theoretical investigations concerning the output power and mode size of a Tm:YVO 4 microchip laser in which the crystal is uniformly cooled on the rear face and the cavity has the capability to store the pump light in order to increase pump intensity inside the amplifier medium. Good agreement with experimental results has been found.

Experimental investigations and theoretical modeling of a Tm:YVO4 microchip laser

We present experimental results on a Tm:YVO4 microchip laser pumped by a Ti:Sa laser. These results are compared with a theoretical model which is based on the thermal guiding of the emitted laser mode and a rate equation model which includes the pump beam parameters. The efficiency of the laser does not depend on the pump beam waist if its location is adapted.

Overview of the Lucia laser program: toward 100-Joules, nanosecond-pulse, kW averaged power based on ytterbium diode-pumped solid state laser

We present the current status of the Lucia laser being built at the LULI laboratory, the national civil facility for intense laser matter interaction in France. This diode pumped laser will deliver a 100 Joules, 10 ns, 10 Hz pulse train from Yb:YAG using 4400 power diode laser bars. We first focus on the amplifier stage by describing the reasons for selecting our extraction architecture. Thermal issues and solutions for both laser and pumping heads are then described. Finally, we emphasize more specifically the need for long-lifetime high-laser-damage-threshold coatings and optics.

High-power, low-divergence, linear array of quasi-diffraction-limited beams supplied by tapered diodes

We describe for the first time to our knowledge the performance for a linear array of tapered laser diodes with both fast- and slow-axis collimation using a microlens for fast-axis collimation and a laser-written phase plate for slow-axis collimation and correction of the residual fast-axis errors from lens aberrations, thermal lensing, astigmatism, pointing errors, and other wavefront distortions. The phase plate leads to M(2) factor reductions of 1.5 for the lensed array following the fast axis and 2.6 for the whole bar following the slow axis.

Phase coupling of a linear array of 9 square CO2 cw wave guide lasers by intra-cavity spatial filtering

An experimental study of phase coupling of a linear array of 9 CO2 waveguide lasers by an intra-cavity spatial filter is presented. First the results obtained in a simple two-mirror cavity are shown. Both, theoretically and experimentally, the ability to improve the coupling efficiency by using a three-mirror cavity is shown.

New evaluation of ytterbium-doped materials for CW laser applications

In this paper, it is proposed a new evaluation of ytterbium-doped laser crystals valid for CW laser applications. Starting from a theoretical model that makes possible to express analytically the output characteristics of a CW Yb-doped laser, a graphic technique allowing the computation of the global efficiency for the optimum amplifier length and the coupling mirror reflectivity is proposed. This technique is applied for evaluating the efficiency corresponding to various ytterbium-doped crystals. We find that the performances depend on the pump intensity. By comparing this evaluation to the classical one based on the respective values of the emission cross-section and the pump intensity need for getting crystal transparency at laser wavelength and we find that, in CW regime, more parameters must be taken into account.