Fluorescence Excitation by the Absorption of Two Consecutive Photons

Abstract

Fluorescence radiation from polycrystalline La: PrCl/sub 3/ was observed using two separate excitation sources. This fluorescence cannot be attributed to either source alone. The scheme is similar to N. Blocmbergen's proposal for a solid-state infrared quantum counter (Phys. Rev. Letters Porter, Jr., J. Appl. Phys. 32, 825(1961)). (L.N.N.)