Near-infrared imaging via upconversion in Er:CaF crystal with dual wavelength excitation.

We propose a system for imaging 1510 nm near-infrared (NIR) wavelength via upconversion (UC) luminescence in an Er-doped CaF crystal. Er ions are excited from the ground to the excited state levels by an 800-nm pre-excitation wavelength, followed by the promotion of these ions to a higher energy level by the NIR excitation wavelength. Relaxation of these excited ions gives rise to 540 nm UC luminescence in the visible region, enabling the detection of the 1510 nm NIR wavelength.

Mid-infrared imaging through up-conversion luminescence in trivalent lanthanide ion-doped self-organizing optical fiber array crystal.

We propose a scheme for imaging mid-infrared (MIR) wavelengths via pre-excitation-assisted up-conversion luminescence in lanthanide ion ()-doped Self-organizing Optical FIber Array (SOFIA) crystal. First, near-infrared pre-excitation wavelength excites an electron from the ground state to an excited state of . Next, the MIR wavelength to be imaged promotes this excited electron to a higher-lying energy state.