Infrared Laser Properties Of Erbium-doped Crystals

Lasers in the wavelength range of 2.7-3?m are of importance for fundamental studies and applications in surgery,air monitoring,radar guidance,remote sensing and many other fields.The transition between ~4I_11/2 and ~4I_13/2 energy states in erbium ions is suitable for light emission near 2.8?m wavelength.In addition,garnet crystals have excellent properties in structural symmetry,chemical stability,and thermal conduction,et al.Therefore,garnet crystals doped with erbium ion alone or erbium ion together with other ions become important media for developing laser sources around 2.8?m wavelength.Existing erbium-doped mid-infrared solid-state lasers usually use position-fixed mirror cavity.The natural competition between cavity modes often leads to lasing of multiple modes with poor spectral property.Meanwhile,the laser wavelength is not dynamically tunable.In order to further analyze infrared laser characteristics of erbium-doped crystals and to address the the problems of single-mode operation and wavelength tuning,this thesis studies lasing properties of Er:YSGG crystals,Er,Pr:GGG crystals,and Er,Cr,Tm:GGG crystals.In a grating cavity with Er:YSGG crystal,single mode lasing with tunable wavelength is demonstrated.The main research results obtained in this thesis are as follows:(1)Infrared lasing properties of Er:YSGG crystals,Er,Pr:GGG crystals and Er,Cr,Tm:GGG crystals are measured and analyzed by using a conventional spherical mirror concave cavity.Our experimental results show that laser emissions from these three crystals are multi-mode.Lasing wavelengths of Er:YSGG crystal are located at 2796.27nm,2796.96 nm and 2798.09 nm.Lasing emissions of Er,Pr:GGG crystal are located at2705 nm,2794 nm and 2824 nm,and lasing wavelengths of the Er,Cr,Tm:GGG crystal are near 2823 nm.The relationship between the laser output power of Er:YSGG crystal and the pump power is also measured.The maximum output power as obtained at 3.4 W pump power is 147 mW,and the laser threshold pump power is 0.37 W.(2)Single-mode laser with dynamically tunable wavelengths is demonstrated by using a grating cavity with YSGG crystal as the gain medium.Our measurements show that lasing emission of the Er:YSGG crystal is single mode.As the grating angle is rotated from 23.2°to 24.2°,the laser wavelength is tuned from 2796 nm to 2824 nm.Maximum output power at 2796 nm is measured to be 4.3 mW.These results suggest that grating cavity is a simple and effective method for obtaining single mode operation with tunable wavelengths in infrared solid-state lasers using rare earth doped crystals.