Two-beam coupling measurements of an avalanche upconversion transition in concentrated Tm:LiYF <sub>4</sub> confirm that, despite the resonant nature of the excited-state optical interaction, the induced response is strongly dispersive. This surprising characteristic is shown to be a general feature of avalanche polarization, with an off-resonant process dominating the resonant response.
© 1997 Optical Society of America
Q. Shu, H. Ni, and S. C. Rand, "Nonlinear dispersion of avalanche upconversion," Opt. Lett. 22, 123-125 (1997)