Modulating Spatial Light by Grating Slot Waveguides With Transparent Conducting Oxides

Transparent conducting oxides (TCOs) are emerging active materials for light modulating due to their special epsilon-near-zero effect. A novel spatial light modulating technique based on the guided mode resonance effect in a slot waveguide with TCOs is proposed, where both transmission and reflection can be manipulated by injecting or depleting carriers into the TCO layer. Temporal coupled mode theory and finite element method are used to analyze the light coupling and filtering. A modulation depth at 1550 nm as high as 0.85 is obtained due to the dramatic variations of modal properties in a TCO layer embedded slot waveguide. The wavelength bandwidth with a modulation depth above 0.5 is 8.6 nm. In addition, the resonant wavelength is sensitive to the bias on the TCO layer, which makes the device a tunable transmissive/reflective filter with a tuning range of 40 nm.