Theory of Laser ML in Coloured Alkali Halide Crystals and II-VI Semiconductors

摘要

When a coloured alkali halide crystal is exposed to a laser pulse, it will produce strain then the rate of interaction of F-centres with dislocations In the expansion region of dislocations, the average energy E_i of F-centre interactiong with dislocations will be lie between the normal ground state of F-centres and dislocation band. When the dislocation containing electrons are moving in a crystal, then the electrons may recombine with the defect centers containing holes also with the deep trap present in the crystals. The retrapping of dislocation electrons in the negative ion vacancies my also take place. The decay time will be controlled by pinning time of dislocations. When a II-VI semiconductor exposed to laser pulse they will produce a shock-wave in the crystal and consequently the deformation of crystal takes place. Similarly we obtain the rate of generation of electron in the shallow traps and number of electrons in the shallow trap finally we obtain the maximum intensity and corresponding time The decay time of ML well be equal to the life time of electrons in the shallow traps. The ratio I_(m2)/I_(m1) depend on the probability of transfer of electrons from the conduction band to shallow traps and on the ratio of pinning time of dislocation and life time of electrons in the shallow traps.