Abstract

Upconversion pumping of rare earth doped materials has been extensively studied over the two past decades. Most of mechanisms for converting infrared radiation to short wavelength output are quite well known and relative strengths of these processes have already been reported in bulk materials [1]. However, due to length of interaction of laser ligth with luminescent centers in a fiber, Excited State Absorption (E.S.A.) can dominate the Addition of Photons by Energy Transfer (so-called A.P.T.E.). This is mainly true because of low doping of fibers. Such low concentration is required to prevent from clustering or agregation which causes losses along the fiber.

© 1993 Optical Society of America