All solid state mode-locked flashlamp pumped Nd:YAG laser system with selectable pulse duration was developed based on the oscillator where a single semiconductor structure containing a multiple-quantum-well was used as a saturable absorber for mode-locking, and energy limiter for passive negative feedback. Single pulse selection from various parts of extended 200 ns long Q-switched pulse train enables the changing of pulse duration before entering into three stages of laser amplifiers. Using of additional acousto-optic mode-locker, stability enhancement of the output pulses was obtained and the amplitude fluctuations were reduced below 5%. The exploitation of the solid state saturable absorber and limiter integrated in the single element improved significantly the long term characteristics of the laser system which can be therefore used for various applications as a satellite laser ranging, spectroscopy, or medicine.
Using of single semiconductor element containing multiple quantum well saturable absorber both for mode-locking and as passive negative feedback element in the resonator of flashlamp pumped Nd:YAG laser is reported. In the Q-switched and mode locked regime of generation, 40 ns long trains containing 5 pulses (at FWHM) were generated; the energy of the whole train was 1.5 mJ, single pulse duration was 50 ps. In the regime of passive negative feedback the pulse trains were stretched to 160-280 ns, and effective pulse shortening along the train from 50 ps to 25 ps was observed.
Flashlamp pumped oscillator - three amplifiers Nd:YAG picosecond laser system mode-locked with multiple quantum well (MQW) saturable absorber was developed and investigated. 80 ps long pulses with the energy of 120 mJ were generated.
Hana Turcicova, Jan Dostal, Gabriela Kocourkova, Jan Knyttl, Jiri Skala, Miroslav Pfeifer, Martin Divoky, Martin Smrz, Ondrej Novak, Petr Bohm, Andrej Dombrovsky, Walter Belardi, Petr Straka
SOFIE laboratory is conceived as a test laboratory for the PALS large scale facility. In both systems the principal resources are iodine photodissocation lasers (λ=1315 nm). At present the basic task of the SOFIA laser laboratory is the preparation of the OPCPA technique and a necessary know-how getting for a future implementation of OPCPA into PALS. The pumping beam is formed by the third harmonics (438 nm) of the iodine laser. A two-stage amplifying system is designed (LBO, KDP). The signal beam is produced by 10-fs Ti:sapphire laser stretched in time to 300 ps. A single diffraction grating and a telescope of Ofner type, retroreflector, form the stretcher.
We report on flashlamp pumped oscillator - three amplifiers Nd:YAG picosecond laser system in which the liquid saturable dye used for passive mode locking is replaced by semiconductor saturable absorber with multiple quantum well (MQW) structure. This element placed at Brewster angle inside a laser resonator had 100 layers of absorber and therefore it has high nonlinearity and is suitable for high power Q-switched and mode locked operation. The short pulse train from oscillator contained only 5-6 pulses with total energy of 3 mJ in single transversal mode, the pulse duration was 80 ps. After amplification, the maximum energy of the pulse train was 180 mJ. In the regime of the amplification of a single selected pulse the energy on the output of the third amplifier was 50 mJ. Operation of the oscillator in active-passive regime of mode locking using an additional acousto-optic mode-locker leads to improvement of reproducibility and stability of output parameters.
Operation of laser diode and flash lamp pumped Nd:YAG lasers mode locked with two different types of semiconductor saturable absorbers is reported. In the first type that is used mainly in diode pumped systems the absorber layers are integrated on highly reflective Bragg mirror. The second type is for use in transmission mode inside the resonator. Different design of semiconductor elements, pumping geometries and resonator configurations were investigated and characteristics of laser operation in mode-locked regime are presented.
We demonstrated that a simple flashlamp pumped Nd:YAG laser, with the insertion of solid state passive elements, can be made a source of trains of high power picosecond pulses with accurate pulse to pulse reproducibility. The combination of passive negative feedback using GaAs together with semiconductor quantum well saturable absorber in an actively mode-locked Nd:YAG laser led to generation of stretched 200 ns long trains with pulsewidth of 42 ps. Cavity dumping resulted in single pulses at energies of 500 (mu) J with a nearly Gaussian spatial profile at repetition rate of 5 Hz. Without passive negative feedback, stable 75 ns long trains of pulses with pulsewidth of 52 ps were generated.
We report on application of semiconductor quantum well saturable absorber as a passive mode-locker in flashlamp pumped Nd:YAP laser. In passive regime of modulation, reproducible single trains containg about 10 pulses were generated with probability higher than 90 %. The single pulse duration was ~ 50 ps with a nearly Gaussian spatial profile. Energy ofthe whole train was 3 mJ. In active passive-regime using an additional acousto-optic modulator the probability of generation of mode-locked trains increased to 98 %.
One of the most serious problems of the software market is to save programs from non- sanctioned copying. The purpose of this work is to create a device for computer games, which uses the information carrier, allowing simple editing by the manufacturer and the impossibility of copying and editing by other firms without expenditures for elaboration and putting into production.
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