Raman investigation of the nonlinear optical phenomenon of polarization rotation in Ti:LiNbO3 channel waveguides

The nonlinear phenomenon of polarization rotation in Ti:LiNbO3 optical channel waveguides was investigated using Raman microprobe microscopy. Polarization sensitive Raman selection rules permitted the identification of polarization rotation of the propagating transverse electric or transverse magnetic waveguide mode. From an analysis of the Raman scattered light collected orthogonal to the waveguide surface the threshold power necessary to initiate the process of mode conversion could be determined. In addition, the Raman microprobe was used to determine waveguide loss coefficients by collecting inelastically scattered light. The values obtained by this method were compared to those measured by collecting the elastically scattered light. A value for the asymmetric component, β15, of the photovoltaic tensor was calculated to be 7.8×10−13 A/W for the X-cut, Y-propagating and 3.8×10−14 A/W and 1.2×10−14 A/W for the rapid thermally annealed Z-cut, Y-propagating channel waveguides, respectively.