Ho 3+ ions exhibit an up-conversion luminescence mechanism, where the material can emit ultraviolet, visible, or high-energy photons at higher frequencies when excited by light of longer wavelength and lower frequency. This unique property is particularly valuable for medical imaging technologies, such as computed tomography. Additionally, it can be utilized as a photon-counting detector, representing cutting-edge technology in the field of medical computed tomography . The photoluminescence spectrum of Ho 3+ predominantly shows multiple emission lines in visible range at blue area ~ 480 nm ( 5 F3 → 5 I8), green area ~ 540 nm