Ultra-wideband multi-level optical modulation in a Ge2Sb2Te5-based waveguide with low power consumption and small footprint

Abstract

A Ge2Sb2Te5 (GST)-based four-level pulse amplitude optical modulator is proposed and its optical and electrical properties are studied. The four-level pulse amplitude modulation (PAM4) scheme is used as a solution to overcome the inherent speed limitation of the phase-change based optical modulators. The modulator is formed by implementing two GST-based active waveguide sections in a silicon ridge waveguide where the propagation loss of each active waveguide section can be varied by changing the GST phase. Optical simulation results show that the four different output states of the modulator are separated by more than 2.5dB in the ultra-wide wavelength range of 1.4μm<λ<1.7μm, while the small overall footprint of 3.28μm2, results in low insertion loss of 1.19dB. Electrical and thermal properties of the structure are also investigated which reveal the very small energy consumption of 11.97pJ/bit and high modulation speed of 0.428Gbit/sec for the proposed PAM4 modulator. These calculations show substantial improvement in the performance parameters of the proposed structure compared to the previously reported phase-change material (PCM)-based optical modulators in terms of modulation speed and energy consumption.