Transition metal dichalcogenides integrated waveguide modulator and attenuator in silicon nitride platform

Embedding transition metal dichalcogenides (TMDs) into optical devices enhance the light-matter interaction, which holds a great promise for designing compact integrated photonic components. The chemical composition and thickness of TMDs affect their electronic and optical properties. The optical properties demonstrate stable and strong gate tunable optical response near the excitonic transitions. These materials are, therefore, promising candidates for designing electro-optic modulators and attenuators. Here, an electro-absorption modulator is investigated based on integrating different TMD monolayers on silicon nitride waveguides near the excitonic binding energy. A comparison of absorption changes due to electrostatically induced charges in MoS₂, MoSe₂, WS₂, WSe_2, and graphene has been presented for modulator design. The results show that with the confinement factor of about 0.10% in the monolayer TMDs, the modulation strength is 10x higher in WS₂ as compared to the graphene-based modulator design. The WS₂ based modulator shows the highest modulation strength with an improvement by a factor of 5 as compared to Mo based designs. Further, the change in the spectral response of these materials with thickness and chemical composition has been exploited for the design of attenuator. A micro-opto-mechanical system technology with TMD integrated supersubstrate above a Si₃N₄ waveguide affecting the optical response is investigated. By replacing the TMD in the supersubstrate with Se atom instead of S in the MX₂ and WX₂ compound, the attenuation is shifted from visible to near-infrared range allowing tuning from 620 to 750 nm. The tuning of the attenuation wavelength will help the designer choose the best material for visible light photonic applications.