Dual-Depletion-Region Electroabsorption Modulator With Evanescently Coupled Waveguide for High-Speed (${>}$ 40 GHz) and Low Driving-Voltage Performance

We demonstrate a novel structure of a electroabsorption modulator (EAM) at a 1.55-mum wavelength. By incorporating the epilayer structure of dual-depletion-region EAM with an evanescently coupled optical waveguide, the demonstrated device can achieve low electrical return loss (-20 dB at ~60 GHz), wide 3-dB bandwidth (60 GHz) of electrical transmission loss, wide electrical-to-optical bandwidth (45 GHz), and low 20-dB static driving voltage (V
_20dB
, 1.65 V) with extremely small polarization dependency. This new structure can not only achieve excellent figures-of-merit but release the burden imposed on downscaling the core width or length of high-speed/low driving-voltage EAM without using epitaxial regrowth or ion-implantation techniques to isolate the active and passive regions