Abstract

Upconversion, a process in which two low-energy excitations combine to yield one excitation at the sum energy, occurs in most solid-state laser materials. The effect is particularly strong when the doping concentrations are high and when the excited-state level populations are high. In the search for more efficient lasers and for new wavelengths we usually encounter these conditions. Examples incluse the Cr-sensitized Nd laser and the Tm-sensitized Ho laser. In both of these, upconversion results in the potential loss of efficiency. Another example is the Er 2.8μm laser, where upconversion is necessary and should ideally yield a quantum efficiency of 2 when pumped by 800 nm diode lasers. Even though the upconversion phenomenon has been known for a long time, there is little reliable information on the parameters governing the process. This talk will summarize what is known about upconversion, how it affects various laser schemes, and what we need to know to profitably live with upconversion.

© 1990 Optical Society of America