Abstract

Recently integrated cw lasers and traveling wave amplifiers have been reported in rare earth doped LiNbO₃, an electro-optically active guided wave medium.^1,2,3 Efforts to optimize rare earth doped LiNbO₃ devices have focused on waveguide and cavity fabrication. Materials engineering of the gain media itself has not been addressed. This is, in part, due to the fact that rare earth doped LiNbO₃ is so inhomogeneously broadened that it is not possible to optically characterize the system using standard site-selective spectroscopy alone.⁴ Er:LiNbO₃ lasers display upconversion and, when pumped at 1479 nm in the π polarization can have simultaneous lasing at 1563 and 1576 nm, in the σ and π polarizations, respectively.³ The upconverted light arises from two possible processes, excited state absorption and/or non-radiative energy transfer. Excited state absorption is a fundamental aspect of a given system and must be accepted. Conversely, upconversion due to non-radiative energy transfer between coupled Er ions is produced by Er cluster sites and can be enhanced or suppressed by changing the concentration of these sites. The simultaneous lasing at two wavelengths is not yet understood.³

© 1994 Optical Society of America