Fast scintillators are necessary for electron microscopes, as well as in many other application fields like medical diagnostics and therapy and fundamental science. InGaN/GaN multiple quantum well structures (QW) are perspective candidates due to strong exciton binding energy, high quantum efficiency, short decay time in order of ns and good radiation resistance. The aim of our work is to prepare scintillator structure with fast luminescence response and high intensity of light.
InGaN/GaN multiple QW structures described here were prepared by metal-organic vapour phase epitaxy and characterized by high resolution X-ray diffraction measurements. We demonstrate structure suitability for scintillator application including a unique measurement of wavelength-resolved scintillation response under nanosecond pulse soft X-ray source in extended dynamical and time scales. The photo-, radio- and cathodo-luminescence (PL, RL, CL) were measured. We observed double peak luminescence governed by different recombination mechanisms: i) exciton in QW and ii) related to defects. We have shown that for obtaining fast and intensive luminescence response proper structure design is required. The radioluminescence decay time of QW exciton maximum decreased 4 times from 16 ns to 4 ns when the QW thickness was decreased from 2.4 nm to 2 nm. We have proved suitability of InGaN/GaN structures for fast scintillator application for electron or other particle radiation detection. For x-ray detection the fast scintillation response would be hard to achieve due to the dominant slow defect luminescence maximum.
About 20 μm thick Ce-doped Lu3Al5O12 thin films grown by Liquid Phase Epitaxy and thin plates of similar thickness
prepared by mechanical cutting and polishing from Czochralski grown crystals are used in 2D-imaging experiment down
to μm 2D-resolution. Their scintillation response is also measured under α-particle excitation and performance of film
and bulk material is mutually compared. Furthermore, scintillation and thermoluminescence characteristics of UV
emitting Sc-doped LuAG grown by Czochralski method are presented since this system is a candidate material for UV
emission-based 2D sensors with improved diffraction limit with respect to the presently used Ce-doped aluminum
Laser efficiency of diode pumped active Nd:YAG material with and without undoped ends was compared. From the physical and computer experiments follow that the laser with the multi-pieces rod gives better results.
Thinking about the pumping and generated power of the longitudinally diode-pumped solid-state laser enhancement, the question of an active material cooling should be solved. One of the possible solutions is the active material cooling surface enlargement. Besides the cylindrical surface of the crystal, the laser rod front surfaces could be cooled through undoped ends. The temperature gradient effect in three various samples was investigated in a computer experiment, and the differences in generated output power were measured experimentally. The samples were three Nd:YAG rods - one conventional, one with one undoped end, and one with two undoped ends. The crystal samples were placed in sequence into a resonator 6 cm long and longitudinally diode-pumped. The dependencies of the generated power on the absorbed pump power have shown that with the two undoped ends the output power is more than twice as high as against the conventional Nd:YAG sample. The results were explained by a computer experiment based on the heat transfer equation solution where the changes of the temperature gradient were least for the Nd:YAG rod with two undoped ends.
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 %.