Ultralow-energy electro-absorption modulator consisting of InGaAsP-embedded photonic-crystal waveguide

Abstract

Towards realizing highly integrable low-energy optical modulators, the small device capacitance (C) as well as the low driving voltage (Vpp) is demanded for suppressing the charging energy during the dynamic operation. Although an electro-absorption modulator (EAM) has great potential in reducing them, the additional energy associated with the photocurrent flow will limit the lower-bound of the consumption energy. In this work, a broadband EAM based on an InGaAsP-embedded photonic crystal waveguide is demonstrated, revealing a high modulation bit rate of up to 56 Gbit/s. The air-bridge structure and a device length of 100 μm or less result in a small C ≤ 13 fF while operating with Vpp < 1 V. Particularly, the operation in low reverse voltage for a p-i-n junction, that is, −0.2 V as the minimum value in this study, works effective for the reduction of energy involving the photocurrent. This results in the total electrical energy consumption of <2 fJ/bit, which is lower than that of any waveguide EAMs.