Nonlinear optical properties of Er3+/Yb3+-doped NaYF4 nanocrystals

Upconversion emission spectra of colloidal NaYF4 nanocrystals doped with 2% Er3+ 20% Yb3+ ions, and 2% Er3+ 40% Yb3+ ions, the spectra are recorded at room temperature with the excitation wavelength of 980 nm from the diode laser.