Abstract
We propose a free-space electro-optic transmission modulator based on multiple p-n-junction semiconductor subwavelength gratings. The proposed device operates with a high-Q guided-mode resonance undergoing electro-optic resonance shift due to direct electrical control. Using rigorous electrical and optical modeling methods, we theoretically demonstrate a modulation depth of 84%, on-state efficiency 85%, and on-off extinction ratio of 19 dB at 1,550 nm wavelength under electrical control signals within a favorably low bias voltage range from −4 V to +1 V. This functionality operates in the transmission mode and sustainable in the high-speed operation regime up to a 10-GHz-scale modulation bandwidth in principle. The theoretical performance prediction is remarkably advantageous over plasmonic tunable metasurfaces in the power-efficiency and absolute modulation-depth aspects. Therefore, further experimental study is of great interest for creating practical-level metasurface components in various application areas.
Highlights
ResultsFree-carrier-induced EO effect in multiple p-n junction layers. The EO effect of our interest in this paper is based on change in mobile electron and hole densities that we denote by Ne and Nh, respectively, in response to an applied bias voltage Va across the p-n junctions
Structure, and electrical connections, and a possible architecture for integrated modulator arrays are illustrated, respectively. This structure is designed such that a high-Q GMR is supported in the optical domain while in the electrical domain bias voltage across the multiple p-n junctions effectively control density of mobile electrons and holes, resulting in the associated tuning of the Drude-type optical dielectric constant[11]
The EO effect of our interest in this paper is based on change in mobile electron and hole densities that we denote by Ne and Nh, respectively, in response to an applied bias voltage Va across the p-n junctions
Summary
Free-carrier-induced EO effect in multiple p-n junction layers. The EO effect of our interest in this paper is based on change in mobile electron and hole densities that we denote by Ne and Nh, respectively, in response to an applied bias voltage Va across the p-n junctions. We note that Inoue et al.[19] recently demonstrated a high-Q GMR filter with a device footprint area reduced down to 10 × 10 μm[2] without significant degradation in the spectral performance characteristics by using graded-parametric design approach combined with integrated first-order Bragg reflection boundaries Introducing such miniaturization strategy to the proposed concept, Δfbias >Δfopt and the full resonance bandwidth should be available for the final optical signal-modulation bandwidth
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