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-mu m 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 similar to 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-20 (dB), 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.