A transparent alkali-phosphate glass composite containing SrAl2O4:Eu2+, Dy3+ particles was elaborated and a constitutive law for the mechano-optical coupling will be presented, based on a DFT analysis and mechanical testing under various loading modes. Then, the mechanoluminescence observed in an oxynitride glass-ceramic will be discussed. In this latter case, the glass was synthesized by conventional melting, quenching and annealing stages at temperatures ranging from 1500 to 1700 °C, in controlled atmosphere, and the active crystalline phase is the Ba4Si6O16 phase (space group P21/c). In both cases, the activecrystalline particles fill up with trapped electrons when exposed to UV light, and emit light when submitted to a mechanical loading. A major finding of the present study is that the elasto-mechanoluminescence (EML) intensity scales with the mechanical power. The mechanoluminescence behavior of Ba4Si6O16:Eu2+, Ho3+ differs from the one of SrAl2O4:Eu2+, Dy3+ in that the luminescence intensity drops rapidly upon unloading. In the case ofSrAl2O4:Eu2+, Dy3+ , a mechanism for the mechanoluminescence based on the existence of three discreet trap levels in the crystal structure was proposed and sustained by experiments conducted in hydrostatic pressure, compression and shear and by Density Function Theory (DFT) calculations and the increase of the EML intensity showing up on unloading is governed by the deviatoric part of the applied stress (no effect under hydrostatic pressure).