Optically written displays based on up-conversion of near infrared light

A new type of display is reported based on up conversion of near infrared light to the visible. The display medium is a transparent polymer containing particles of crystals doped with Yb³⁺ and other rare earth ions. The Yb³⁺ ions absorb light from a commercially available diode laser emitting near 975 nm and transfer that energy to the other dopant ions. Using a fluoride crystal host, NaYF₄, co-doped with Tm³⁺ ions we obtain blue light at ∼480 nm, with Ho³⁺ or Er³⁺ ions we obtain green light at ∼550 nm and with Er³⁺ we obtain red light at ∼660 nm. The mechanisms that enable such display media are explained, a demonstration of a prototype display is shown, and concepts for full color, high brightness, high resolution, displays are presented.