The output window of a high-power laser system is vulnerable to damage, and this is the main limiting factor on the power scaling and structure integrity of the laser system. In endeavoring to obtain higher output powers from the laser system, the impact of the thermal and mechanical effects and the damage mechanism of the output window must be considered. In order to study these issues, a thermal model of the laser window is established based on the heat transfer and thermoelastic theories, and the expressions for the transient thermal and mechanical stress distributions of the output window are deduced in terms of the integral-transform method. Taking the infrared quartz window material as an example, the temperature and mechanical field distributions of a high-power all-solid-state 2-μm laser system window are simulated, and the laser-induced damage mechanism is deeply analyzed. The calculation results show that the laser window-induced damage is mainly caused by melting damage when the temperature exceeds the melting point of the material. The presented theoretical analysis and numerical simulation results are significant for the design and optimization of high-power laser windows.
The design, component selection, fabrication, testing, and evaluation of an optically-switched, binary, fiber optic
programmable delay line are discussed. The basic building blocks, including laser diode which is based on a rate
equation model, external modulated transmitter, transmission fiber and receiver, are explained. The system comprises
eight delay stages, has a maximum delay of 6.4μs with a 100ps step and operates over the 1-18 GHz band. This computer
controlled prototype used low-cost commercially available components in conjunction with graded-index, single-mode
fiber. Its overall performance is satisfied with the simulation result.
It is common to use Yb-doped double-clad fibers as gain medium of high power fiber lasers. These fibers are similar
to the so-called "un-doped" telecommunication fiber. Because of small core size, only from several microns to tens of
microns, there are easier causing self-pulsing affects in the fiber lasers. In the first part it is reported the several kinds of
self-pulsing according to the reported papers, like relaxed oscillation, saturated absorption effect, stimulated Brillouin
scattering and stimulated Raman scattering. Then it is presented the experimental study and the different self-pulsing
phenomena. The result shows that under the high power condition, although ytterbium ions without concentration effect,
but large core Yb-doped double-clad fiber are the same to three-level ion systems that self-pulsing behavior was the
result of relaxed oscillation. To Yb-doped fiber laser, saturated absorption effect, stimulated Brillouin scattering and
stimulated Raman scattering cannot be ignored.
In this paper cw (continuous wave) pumped self-started, widely tunable frequency-shifted feedback Yb-doped double-clad fiber laser is experimentally studied. We observed 1GHz repetition rate with an output power 56.3mW ps pulses. The laser was capable of generating as short as 5ps pulses in the range of 1078.7nm -1140.2nm (more than
60nm). The ps pulses were self-started without any other external trigger. We used 77MHz RF signal AOM and a grating which not only forms external cavity to provide feedback, but also make the laser linewidth narrower.
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