In this talk, we discuss our recent experiments on the spectral response under applied strain of quantum emitters based on structural defects in hBN. We also report on photoluminescence excitation experiments that allow to identify the vibronic excited states associated to their characteristic energy level structure.
We derive an expression for electric-field intensity enhancement due to the epsilon-near-zero modes in ultra-thin conducting layers. We show that absorptance and field enhancement in aluminum-doped zinc oxide nanolayers grown by atomic layer deposition are controlled by nanolayer thickness and optical losses.