Broadband optical modulation in a zinc-oxide-based heterojunction via optical lifting

Abstract

Broadband electro-absorptive optical modulation in a zinc-oxide (ZnO)-based heterojunction is demonstrated. The presence of high-density two-dimensional electron gas (2DEG) at the bottom of conduction band offset in a MgZnO-CdZnO heterojunction is shown to exhibit electrically tunable optical absorption in the regions well below the material bandgap. Electrons confined near the heterojunction are lifted across the potential barrier on optical excitation. Optical modulation with an extinction ratio of 8 dB is reported at an operating wavelength of 527 nm. The extinction ratio remains around 7–8 dB over a wide bandwidth of 115 nm, providing an excellent opportunity to explore ZnO-based heterojunctions to realize a broadband optical modulator for applications in optical communication and interconnects.