Near-infrared imaging via upconversion in Er3+:CaF2 crystal with dual wavelength excitation.

We propose a system for imaging 1510 nm near-infrared (NIR) wavelength via upconversion (UC) luminescence in an Er3+-doped CaF2 crystal. Er3+ 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. Using this UC scheme, 1510 nm was successfully imaged. Our system enables imaging of NIR wavelengths using low-cost optics and readily available Si-based detectors that are sensitive only to visible wavelengths, opening new possibilities for detection and imaging of NIR wavelengths.

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 (Ln3+)-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 Ln3+. Next, the MIR wavelength to be imaged promotes this excited electron to a higher-lying energy state. Finally, relaxation of the electron from the higher-lying energy state to the ground state emits the up-conversion luminescence in the visible region, completing the MIR-to-visible wavelength conversion. An analysis of the 4f to 4f intra-configurational energy level transitions in Ln3+, together with an appropriate selection of the pre-excitation wavelength and the visible luminescence constrained within the 500-700 nm wavelength range, reveals that trivalent erbium (Er3+), thulium (Tm3+), holmium (Ho3+), and neodymium (Nd3+) can be used to image MIR wavelengths. Our proposed scheme, called MIR imAging through up-Conversion LuminEscence in a SOFIA crystal, will enable the imaging of MIR wavelengths using low-cost optics and readily available silicon-based detectors in the visible spectral region and will open up new possibilities for MIR wavelength detection and imaging.