Tunable control of electromagnetically induced transparency effect in a double slot terahertz waveguide

In this paper, we investigate double slot waveguide configuration to explore the actively tunable electromagnetically induced transparency (EIT) effect in terahertz regime. One of the slot structures is filled with a dielectric material of certain refractive index which causes a slight shift in its resonance frequency as compared to the unfilled slot. The two frequencies say, ω₁ and ω₂ from the unfilled and filled slots, respectively act as the bright resonators. The EIT effect is observed due to the destructive interference of these two modes. The electric field profiles clearly indicate the emergence of the EIT effect. We observe that the transparency effect can be tuned by varying the refractive index of the dielectric material, which promises an active and tunable control of the effect without changing the physical dimensions. We have employed an analytical model based upon the coupled harmonic oscillators to understand the coupling mechanism between the two resonators resulting in EIT effect and validate numerical findings. The proposed study could be significant in the construction of tunable terahertz components such as slow light systems, buffers, etc. where an active control of optical properties is desirable.