MODIFICATION OF STRUCTURAL AND OPTICAL-PROPERTIES OF IRON-DOPED LITHIUM-NIOBATE BY PULSED EXCIMER-LASER IRRADIATION

Pulsed excimer laser induced effects (lambda = 308 nm, tau = 10 ns, E = 100 mJ/pulse, N = 50 and 150 pulses/spot, repetition rate 10 Hz) in Fe-57:LiNbO3 have been studied by optical absorption measurements, Mos sbauer spectroscopy, scanning electron microscopy (SEM), and Raman mic roanalysis. The laser-induced growth in the optical absorption of the crystal over the 450-800 nm wavelength range was found to depend on th e number of applied laser pulses. Compared to the as-grown state, a 1% increase in the Fe2+ vs Fe3+ concentration resulted as an effect of t he laser treatment performed. SEM examinations of the laser-exposed su rfaces revealed the presence of alternating recrystallized and laser a blated regions. Additional crystalline phases, such as Li7NbO6 and Nb2 O5 were identified by Raman microanalysis, depending upon the location of the irradiated areas relative to the center of the laser impact zo ne. The effects of excimer laser induced rec:ystalszation, ablation, r eduction, and increased optical absorbance in Fe-57:LiNbO3 were eviden ced and found relevant to laser processing.