Tunable photonic band gaps in Lithium Niobate slab waveguide through Lamb waves

Abstract

Tunable photonic band gap generation in Y–Z Lithium Niobate slab through Lamb wave is theoretically studied and presented. The applied 5.5 GHz frequency of Lamb wave able to provide a periodic sinusoidal variation of refractive index through photo-elastic effect in considered 600 nm thick Lithium Niobate slab with period 615 nm. The achieved maximum and minimum change in refractive index along z axis is 0.026 with respect to unperturbed refractive index 2.2 of considered Lithium Niobate slab. The induced photonic band gap in optically modified structure is calculated using Bloch’s theorem and the transmittance of the structure is obtained by transfer matrix method. The obtained photonic band gap at 5.5 GHz Lamb wave frequency is 7.8 THz with central angular frequency is 695.9 THz. Since, the unit cell dimension and central frequency of photonic band gap are highly depend on the applied Lamb wave frequency therefore the possible application of the proposed structure is a tunable photonic crystal.