|
Recent developments in blue and green light generation by optical frequency doubling in nonlinear optical materials will be reviewed. Inorganic waveguiding materials such as KNbO3, LiNbO3, LiTaO3, and KTiOPO4 have been shown to be good candidates for high efficiency optical frequency doubling of laser diode radiation into the blue-green spectral range for applications on high density optical storage. Relatively new phase matching concepts such as Cerenkov type doubling and periodically poled materials have been developed. We will compare the results obtained by these techniques employing several of the above mentioned materials. It will be shown that 15 mW of blue light can be generated from 100 mW input power using He+ ion implanted KNbO3 channel waveguides. In recent years organic materials with extended, delocalized 7c-electron systems and functional groups acting as electron donors and -acceptors have been shown to have nonlinear optical effects which can be more than one order of magnitude larger than in any other material. Nonlinear optical bulk single crystals and crystalline thin films, crystal cored optical fibers, Langmuir-Blodgett films as well as poled polymers have been prepared. The nonlinear optical effects observed in these materials will be described and compared with the effects observed in inorganic compounds. The relationship between the molecular arrangement and the functional properties outlined and the main materials requirements for optoelectronic and photonic applications will be given.
|
