Visible to Near-infrared Chip-integrated Tunable Optical Modulators Based on Niobium Plasmonic Nano-antenna and Nano-circuit Metasurface Arrays

Abstract

We report on the numerical and experimental demonstration of novel chip-integrated tunable optical modulators operating at visible to near-infrared telecommunication bands. Our integrated photonic devices are based on plasmonic nano-antenna and nano-circuit metasurface arrays fabricated on the facet of niobium (Nb) thin metallic films. We engineer the photoresponse of our Nb nano-antenna based modulator devices and observe optical modulation properties with a modulation depth $\mathrm{MD} \cong 60$% at $\lambda=716 \mathrm{~nm}$, and a maximum extinction $A(\lambda)=1-R(\lambda) \cong 95$% at $\lambda=650 \mathrm{~nm}$, at room temperature. Moreover, with a similar photoresponse engineering technique, we observe a maximum extinction $A(\lambda) \cong 88$% at $\lambda=1380 \mathrm{~nm}$ in our near-infrared nano-circuit array-based modulators. Our optical modulators are polarizationsensitive, and their photoresponse can be controlled by altering the geometrical parameters of their subwavelength elements and unit cells. Our ultracompact Nb modulators, with their tunable and controllable photoresponse, empower new types of optical links and photonic interconnects interfacing quantum circuits and fibre optic telecommunication systems for applications in quantum technologies.