Abstract

Efficient second and third-harmonic generation in Er³⁺-doped fibers pumped at 1.319 µm, has recently been reported [1, 2]. In this work, we report on the generation of visible light through harmonic generation and upconversion fluorescence in Pr³⁺-doped silica fibers pumped at 1.319 µm. The pump source was a Q-switched and modelocked Nd: Y AG laser operated at 1.319 µm. Figure 1 shows a typical power spectrum of radiation exiting a 50 cm length of Pr³⁺-doped fiber for an average pump power of 200 mW coupled into it. The spectrum shows two distinctives narrow lines at 440 nm and 660 nm corresponding to efficient third and second-harmonic generation processes, respectively. The broadband emission lines around 630 nm and 710 nm, correspond to fluorescence emission from the ³P₀ excited state level, to lower energy states as indicated in fig. 1. The pump mechanism utilized to populate the ³P₀ excited-state was accomplished by a first step strong one-photon transition connecting ³H₄ ground-state to ³F₄ excited state, followed by a two-photon excited state transition connecting ³F₄ to ³P₀ It is important to point out that the appearance of the second-harmonic signal light at 660 nm required a long-time preparation process as indicated in graph of fig. 2, and the third-harmonic generation process was instantaneous with pump light illumination.

© 1996 IEEE