Optical Modulation via Guided-Mode Resonance in an ITO-Loaded Distributed Bragg Reflector Topped With a Two-Dimensional Grating

Abstract

We are reporting the design procedure for a narrow-band ultra-low-power reflective optical modulator that operates at the critical coupling of an appropriately designed two-dimensional grating with the center frequency of a quarter wavelength distributed Bragg reflector (DBR). By sandwiching a three-layer stack of gated ITO/HfO2/ITO between the DBR and the grating, we can make the optical modulator operational, taking advantage of the tunable property of the ultrathin layer at the ITO/HfO2 interface accumulated by electrons under an ultra-low applied voltage (−0.1\xa0V). The corresponding energy consumption is ∼5.5 fJ/bit. Moreover, our simulations show that the capacitance limited modulation speed is more than 80 Mbps. Our numerical results also predict the influence of possible fabrication errors on the guided-mode resonance wavelength. This investigation shows that a ±3 nm deviation in the grating pitch affects the modulator performance profoundly. Furthermore, the numerical results demonstrate the modulation depth of ∼24 dB is achievable for an appropriately designed modulator with an acceptable insertion loss of ∼0.05 dB. This paper paves the way for developing next-generation optical modulators with high modulation depth, low insertion loss, and ultra-low energy consumption.