Arising from condensed-matter excitations, epsilon-near-zero (ENZ) modes are a new path for enhancing light-matter
interactions at nanoscale with their unique and interesting optical properties when probed at wavelengths
corresponding to their zero permittivity crossing points. In this work, a highly efficient tunable absorber can be achieved
by integrating an ultra-thin indium tin oxide (ITO) film into the periodically patterned metal-insulator-metal (MIM)
structure. Particularly strong absorption modulation could be achieved when the ITO is operated in the ENZ spectral
range. This work can make a significant contribution to direct application in a range of optoelectronic devices that
require active control over light absorption and energy conversion.