In this paper, we report the measurements of the specific heat, the density and the thermal diffusivity at room and cryogenic temperatures of Ytterbium doped cubic sesquioxides (Sc2O3, Y2O3, Lu2O3) ceramics and of Ytterbium doped crystals (YAG, CaF2). These materials appear to have very interesting properties for setting up high average power laser chains useful for plasma physics and for inertial fusion energy drivers.
Measurements of the key thermo-optical properties of Yb3+ in sesquioxides ceramics Y2O3, Sc2O3 and Lu2O3 are done at room and cryogenic temperatures. We show that laser performances are improved at low temperatures. We obtain a maximum output energy of 570 mJ, corresponding to a slope efficiency of nearly 40%, in free running regime at 1 Hz with a 10 at. % Yb:Y2O3 ceramic at 77 K. Temperature effects on the emitted wavelength are also investigated. Room temperature measurements, using both "laser flash" and "hot disk" methods, lead to thermal conductivity values of
ytterbium doped Y2O3 ceramics of 6.3 W/m.K and 5.3 W/m.K respectively. We also show that the thermal expansion
coefficients of a 10 at. % Yb:Y2O3 and a 20 at. % Yb:YAG are divided by a factor two between 293 K and 130 K.
This work relates to combining a phase corrected array of tapered laser diodes, emitting at λ = 975 nm, coherently
using the Talbot effect. Diffractive coupling of semiconductor lasers by use of the Talbot effect provides a means for
coherent beam addition of multiple elements in laser diode arrays and makes possible a very compact external
cavity. We have used, in this work, fully index guided tapered laser diodes. They contain a
ridge waveguide, which acts as a
modal filter, and a tapered section of increasing width, which provides high power. We have realized arrays of
several emitters (N=10), which are not optically coupled to each other. First, to improve the beam quality of the array, a phase correcting micro system, achieving collimation in the fast
axis, correction of the wave front tilts in both directions and also a slow axis collimation, was added. The FWHM
divergences of the array were reduced from 34 ° to 0.17 ° in the fast-axis and from 3.5 ° to 0.7 ° in the slow-axis at
6A, 3.7 W. Then, to be close to diffraction limit, we have combined this corrected array coherently using the Talbot effect. We
have obtained quasi-monolobe slow axis far field profile for the in phase mode with a central peak divergence of
only 0.27 ° at 1.5 A, 315 mW under CW operation and of only 0.20 ° at 2.5 A, 787 mW under pulsed operation.
This work relates to combining a phase corrected array of tapered laser diodes, emitting at λ = 975 nm, coherently
using the Talbot effect. Diffractive coupling of semiconductor lasers by use of the Talbot effect provides a means for
coherent beam addition of multiple elements in laser diode arrays and makes possible a very compact external
cavity. We have used, in this work, fully index guided tapered laser diodes. They contain a
ridge waveguide, which acts as a
modal filter, and a tapered section of increasing width, which provides high power. We have realized arrays of
several emitters (N=10), which are not optically coupled to each other. First, to improve the beam quality of the array, a phase correcting micro system, achieving collimation in the fast
axis, correction of the wave front tilts in both directions and also a slow axis collimation, was added. The FWHM
divergences of the array were reduced from 34° to 0.17° in the fast-axis and from 3.5° to 0.7° in the slow-axis at
6A, 3.7 W. Then, to be close to diffraction limit, we have combined this corrected array coherently using the Talbot effect. We
have obtained quasi-monolobe slow axis far field profile for the in phase mode with a central peak divergence of
only 0.27° at 1.5 A, 315 mW under CW operation and of only 0.20° at 2.5 A, 787 mW under pulsed operation.
We present in this paper the actual status of the LUCIA project, a high average power diode-pumped solid-state laser chain capable to deliver 100 J in nanosecond regime at 10 Hz. In a first step, we deal with the choice of the amplifier medium and the pump and extraction architecture. We present after the thermal management and the cooling architecture. Then, we investigate the damage threshold required. We present last the performances already obtained and the improvements we are working out.
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.
A diode-pumped Yb:YAG laser has been demonstrated. A V-shape unstable resonator with a Super Gaussian coupling mirror was chosen. We describe the model that permits to choose the parameters of the cavity and predict the laser performances. A diode pumping architecture is used in which 941 nm radiation is homogenously delivered to the laser crystal. We present here the Pumping Delivery Optics and the laser performances.
With the goal to set up a high average power Diode Pumped Solid State Laser (100 Joules/10 Hz/10 ns), the Laboratory for Use of Intense Laser (LULI) is now studying various solutions concerning the amplifier medium, the cooling, the pumping and the extraction architectures. In this paper, we present the last states of these developments and the solutions already chosen.
The classical radio technique used for FM detection, the frequency discriminator can also be used in optical frequency detection. In this sense, Chanin et al [2] proposed a lidar system that measures atmospheric wind fields by detecting Doppler-shift in the return signal in a differential way by using two Fabry-Perot interferometers or any other high resolution optical filters as frequency discriminators. This technique was also studied and used by Korb et al. They named it "edge-technique." The UPC lidar group is developing a wind lidar based on the "edge-technique." The first prototype of the wind lidar is a continuous-wave system that is able to measure the surface displacement velocity of solid targets. The transmitting laser is the seeder of a Spectra Physics GCR-190 laser, which will be used for the final wind measurements. It includes a Fairy-Perot interferometer, two APD-based optical receivers, and several auxiliary optics, electro-optic and electronic elements. Among them, there is a servo-loop, based on two acousto-optic frequency-shifters and a lock-in amplifier, which is responsible of the proper tuning between the laser and the Fabry-Perot interferometer. To our knowledge, this servo-loop has not been used before for wind lidars based on the edge-technique. The aim of this first prototype is to test the performance of the edge-technique to measure velocities and to assess the role of the servo-loop in the precision of the measurements. The study and design of the prototype, with emphasis in the servo-loop will be presented.
Phase coupling of medium power high beam quality lasers are of great interest for achieving high power diffraction limited beam with high gain lasers. This make it possible to set up compact and efficient sources. In this paper, we review the work performed in our laboratory concerning the coherent array of CO2 waveguide lasers. We report the various techniques used for phase coupling like Talbot effect, intra-cavity spatial filtering and anti-guiding effect and we give the relevant performances in terms of beam quality and efficiency. After, we discuss the advantages and drawbacks brought by each one. The far field diffraction pattern supplied by a series of coherent independent lasers is made of several asymmetric lobes. We then present lossless techniques making it possible to convert this multilobe asymmetric far field diffraction patterns into a single lobe symmetric beam. Last, we discuss the capability of slab CO2 laser with a graded-phase mirror cavity for generating large stable mode and, then, improving the energy extraction efficiency.
In this paper, we present the experimental results obtained with Tm:YVO4 and Tm,Ho:YLF active medium pumped in an active mirror configuration. Optical to optical efficiency, beam quality and spectral characteristics obtained for both crystals are compared. Extensive research is being devoted to the development of solid state lasers emitting in the eye safe spectral range with the possibility of efficient diode-pumped sources. There is a promising range of applications foreseen for such devices including LIDAR, metrology and medical applications. The microchip concept, where the mirrors are coated directly on the crystal faces polished parallel, allows to set up in very compact sources with high spatial quality beams. Resulting from the compactness of the cavity, these lasers are very stable. We present in this paper the results obtained in our laboratory for both Tm:YVO4 and Tm,Ho:YLF microchip lasers.
In this paper, we present theoretical and experimental results on the effects of binary phase plates on the far field diffraction pattern of in phase and out of phase coupled linear array of square waveguide lasers. Different configurations of Talbot cavity are compared in terms of power contained in the main lobe.
In this paper we describe a new technique for controlling the shape and frequency of a single mode solid state laser. This technique is based on the injection of a single frequency powerful CW laser in a high power pulsed laser through a phase conjugate mirror. We will expose the principle of this experiment and give the first experimental results obtained up to date.
The main characteristics of a compact phase conjugate resonator TEA CO2 laser as a function of the cw pump power are reported. Nonlinear dependence of the output peak-power has been measured, and the existence of an optimum pump power value has been demonstrated. Output peak-powers in excess of 40 kW have been reproducibly obtained for 5 W cw pump power. Heterodyne measurements have shown that a Fourier-limited high-power pulse can be generated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.