KEYWORDS: Optical amplifiers, High power lasers, Fiber amplifiers, Prototyping, Solid state lasers, Mirrors, Laser development, Near field, Integrated optics, Fusion energy
We are currently developing a large aperture neodymium-glass based high-power solid state laser, Shenguang-III
(SG-III), which will be used to provide extreme conditions for high-energy-density physical experiments in China. As a
baseline design, SG-III will be composed of 48 beams arranged in 6 bundles with each beam aperture of 40cm×40cm. A
prototype of SG-III (TIL-Technical Integration experimental Line) was developed from 2000, and completed in 2007.
TIL is composed of 8 beams (four in vertical and two in horizontal), with each square aperture of 30cm×30cm. After
frequency tripling, TIL has delivered about 10kJ in 0.351 μm at 1 ns pulsewidth. As an operational laser facility, TIL has
a beam divergence of 70 μrad (focus length of 2.2m, i.e., 30DL) and pointing accuracy of 30 μm (RMS), and meets the
requirements of physical experiments.
For laser detonator application, high-peak power pulsed Nd:YAG laser is transmitted through all-silica optical fiber. The
transmission properties of step-index fibers are investigated, using a high-peak power pulsed Nd: YAG rod laser with
beyond 1MW power and Q-switch mode. The fibers are step-index multimode fibers with 400 or 600 μm core diameters,
440 or 660 μm cladding diameters. The power delivery characteristics were studied by theory and experiments. The
results show that the fiber core diameter, NA, length and so on affect the transmission efficiency for high power laser.
When the laser power is beyond a certain threshold, the SRS and SBS will be serious; the quantity of fiber end-face
limits to the raising of laser power passing through fibers; the zero-probability damage threshold is calculated according
to ISO/DIS standard 11254-1.2, which is 58.6J/cm2. Energy distribution of output beam from fibers will be uniform.
Even the fiber end-face was partly damaged, laser power is still deliverable, and the transmission efficiency is related to
the fiber damage grade.
The geometry of ytterbium-doped active media in diode-pumped lasers can be calculated with the help of numerical
modeling for the optimization of high-energy and repetitively pulse amplifiers. In the first step the optimum thickness
of the longitudinally pumped gain medium of Yb:YAG is obtained with a theory of quasi-three level laser ions. For the
parameters of the amplifier which will deliver a 100 J, 10 Hz, 10 ns pulse, the optimum thicknesses is 5.5mm with a
doping concentration of 3.92*1020 cm-3 taking the amplified spontaneous emission (ASE) into account. In the second
step, we analyze the laser performance of the amplifiers by using various cooling configurations. The cooling
configurations investigated here include those both by forced convection cooling in a narrow passage. In every case
we determine the temperature rise, the longitudinal and radial temperature gradient, and the resulting energy storage
and extraction efficiency. The simulation results show that, with a pumping intensity of 20 kW/cm2 at 10 Hz and a
doping concentration of 3.92*1020 cm-3 at a thickness of 5.5 mm thick piece Yb:YAG, for a laser injection fluence of
0.2 J/cm2 (10 ns) ,the output laser fluence and optical-to-optical efficiency are expected to be 7.2 J/cm2 and 35%,
respectively, at a heat exchange coefficient of 1 W/cm2/K of water and 250 W/m2/K of gas.
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.
We are now constructing a technical integration experiment line (TIL) at CAEP, which is the prototype facility of Shenguang III laser fusion driver. Currently, many important results have been obtained on the first integrated beam line, which established a sound foundation for Shenguang III engineering design.
KEYWORDS: Interferometers, CCD cameras, Materials processing, Imaging systems, Digital cameras, Image enhancement, Digital Light Processing, Mechanics, Data acquisition, Data conversion
We have designed a new detecting system, which consists of Nomarski polarized light interferometer and a digital camera, to investigate the damage of optical materials. The interferometer has an advantage of measuring the transient and residual strain/stress in the optical materials.
A novel equivalent optical path polarized light interference microscopy has been designed which provides two attractive properties of the perfect bright-field background techniques. This microscopy is suitable for detecting the phase objects and microdamage spots or inclusions in the transparent optical materials.
Investigation of damage to glass surfaces by high power laser beams is presented in this paper. Surface damage thresholds for K8 glass induced by 200 ps laser pulse at near normal incidence are measured. The reason for the difference between the entrance and exit damage thresholds is briefly explained.
The cavitation and cavity are produced near the focus when high power laser is focused into the liquid, and Raman seed source is generated in this cavity, which will give a backward and forward Raman light pulse due to amplification.
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