KTN-based Lamb wave-stimulated tunable photonic band gaps

Based on potassium tantalate niobate (KTN) as a platform, a Lamb wave-generated tunable photonic structure is proposed. A half-micrometer-thick KTN film is perturbed by a GHz Lamb wave disturbance to produce alternate contraction and rarefaction. Considering the elasticity of the plate, the strength of the disturbance is optimized, and the induced strain is calculated. Following the photoelastic relations, the strain-modified optical properties of the medium along the film length are assessed. The spatial optical index distribution over a space of a few micrometers, as induced by elastic disturbance, may open forbidden electromagnetic band gaps. Utilizing the transfer matrix method, the dispersion curves and transmittance of electromagnetic waves are evaluated and analyzed. As a consequence of Lamb disturbance, a photonic band gap lying in the mid-wavelength infrared range is achieved from the KTN slab. To establish the band gap tunability, the effect of Lamb frequency on the range of photonic band gaps is analyzed. The accomplished acoustic-optical phenomenon on the KTN slab may be utilized for mid-wavelength infrared-ranged tunable optical applications.