Ultralow-loss electro-absorption modulator based on bound-state-in-continuum waveguides

Abstract

Electrically controlled information encoding plays an indispensable role in modern optical communications networks. Electro-absorption modulator, one of the extensively studied elements, generally inevitably suffers from a remarkable insertion loss. Here, we elaborately design an electro-absorption modulator with an ultralow insertion loss down to 0.00593 dB/μm, through engineering the photonic waveguide decoupling from the slab continuum modes. Meanwhile, by leveraging the epsilon-near-zero effect of indium tin oxide (ITO), the modulator achieves an extinction ratio of 1.015 dB/μm in the optimized framework. The simulations indicate that the extinction mainly originates from the enhanced absorption of ITO at the epsilon-near-zero state, and only about 11.66 % is from the damaged bound state due to voltage-induced refractivity change. Moreover, the modulator features a broad working bandwidth of hundreds of nanometers, and the extinction ratio can be further improved in the short-wavelength region. Therefore, our results provide a novel strategy to reduce the propagation loss in optoelectronics and lay the foundation for the design of high-performance integrated telecommunication circuits.