OPTICAL-DETECTION OF FIR GENERATED MONOCHROMATIC PHONONS IN CR3+ DOPED BORATE GLASS

Anti-Stokes emission following optical excitation within the inhomogeneously broadened R lines (2E double-line arrow pointing left and right 4A2) of Cr3+ doped borate glass has previously been used as a detector of high frequency non-equilibrium acoustic phonons. We report the optical detection by anti-Stokes emission of similar phonon populations generated by the absorption of far infra-red radiation (FIR) at 43 cm-1 in this same material at 1.8 and 8.5 K. This technique for the generation of phonons is similar to that of defect-induced one phonon absorption (DIOPA) as previously used in crystalline materials. Here, the disordered structure eliminates the necessity of a defect to activate the FIR absorption. These results are discussed in relation to the general properties of phonons in glassy materials.