New approach to enhance the up-conversion efficiency in the Ho³⁺-Yb³⁺ co-doped system

We investigate the up-conversion luminescence spectra of Ho³⁺-Yb³⁺ co-doped materials excited with two types of laser. It is found that the efficiency of green emission (⁵S₂－⁵I₈) can be enhanced by restraining the transition of ⁵S₂－⁵I₇ since the two types of radiation both start on the ⁵S₂ level. We propose an important approach to enhance an expected up-conversion emission.