Optic Properties And Application Of Ge And Al Co-doped SiO₂Films

Because bulk Si and Ge is indirect-gap semiconductor and their lighe emissionmust depend on phonos acting,the efficiency of light emission is very low.To breakthrough limitation of their light emission,people have fabricated many kinds ofsemiconductor quantun dots materials.These semiconductor quantun dots confined bymatrix intensely exhibit unique light emission and optical nonlinear feature,whichhod people’s considerable interests and provide important theory for integratedoptoelectronic devices on the Si substrates. the semiconductor quantun dots filmshave broad applications prospects in optical emission, display, information storage,transmission, processing, photoelectric detection, high-speed optical switches and soon.The Ge-SiO₂and Ge/Al-SiO₂films are prepared by RF magnetroncosputtering,then nanocrystal Ge and GeO₂are induced in the films by subsequentthermal anneal.The films’ composition and structure are tested by XRD,FTIR,XPSand UV-VIS technologied.The experiments show that Nc-Ge and Nc-GeO₂appearinthe films through post-annealing treatment,and the average size of Nc-GeO₂becomesbigger first but smaller subsequently with annealing temperature increasement.The photoluminescence spectra （PL） excited by260nm ultra-violet of xenon lampof films are measured at room temperature.The experiments suggest that doped Al notimproves luminescence efficiency of GeNOV and SiNOV defects centres but is ofadvantage to the defect centres fabrication. The new defects centres are made bydoped Al which affects fabrication of Nc-Ge and Nc-GeOx, and also make the494nmphotoluminescence.The third-order nonlinear optical properties of the Ge/Al-SiO₂films areinvestigated by single beam Z-scan technique with a picoseconds laser pulse atλ=532nm andλ=1064nm. The measured third-order optical nonlinear susceptibilityis x³2.7510^-8（e su）. The larger value of third-order optical nonlinearsusceptibility is mainly attributed to the enhancement of quantum confinement and two photons absorption of the film,and the doped Al is also good for the nonlinearsusceptibility.The Ge-SiO₂and Ge/Al-SiO₂films are inserted as saturable absorber into theresonator of LD pumped Nd:YVO₄laser. The passive Q-switched operation of1064nm laser is achieved and the laser pulses is12.47ns. Through the experimentsphenomenon and the nonlinear optical properties of the films, the formationmechanism of the Q-switched pulse is discussed. Stable passive mode-lockingoperation of1064nm is also realized in a flashlamp pumped Nd:YAG laser,and theaverage laser pulses is about40ps.