Up‐conversion Luminescence in Dye‐Doped Crystals of Potassium Hydrogen Phthalate

Abstract

Optically nonlinear single crystals of potassium hydrogen phthalate were grown in the presence of a variety of laser dyes. Up‐conversion fluorescence (as shown in the Figure) in the visible part of the spectrum was observed as a result of two excitation mechanisms involving trapped, oriented luminophores: two‐photon absorption in general orientations, and absorption of the second harmonic of the fundamental beam at 800 nm, when aligned with the phase‐matching direction.