Stoichiometric dependent optical limiting in PLD SiOx thin films
Advanced Materials Letters,
2017, Volume 8, Issue 4, Pages 331-335
In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiOx) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O2 pressure in the range of 5×10 -5 to 0.5 mbar. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O2 pressure. Raman spectra of SiOx films depicted the presence of micron sized clusters composed of nanocrystalline Silicon embedded in uniform matrix of oxidized amorphous Silicon. The open Z-scan of the thin films, under cw He-Ne laser irradiation, showed strong reverse saturation absorption (RSA) features and non linear absorption (NLA) coefficient, β, was found to be decreasing from 23.5 cm/W to 1.64 cm/W, with increase in O2 pressure from 5×10 -5 to 10 -1 mbar, respectively. Also, the SiOx films except that with maximum oxygen content showed optical limiting, where limiting threshold increases with increasing transparency controlled by oxygen content. The key feature of the present work is the tunability in linear absorption, nonlinear RSA and optical limiting in the SiOx films which can be used as novel material for optical switching application.
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