Electro-optic long-period gratings on lithium niobate waveguides

This paper reviews the development of electro-optic (EO) long-period waveguide gratings (LPWG) on lithium niobate (LiNbO3). We first discuss the main difficulty of fabricating LPWGs on LiNbO3 and explain the principle and the method of forming a special LiNbO3 waveguide structure to overcome this difficulty. We then highlight the main findings from the study of EO LPWGs on LiNbO3, including the effects of using different cladding modes and waveguide parameters on the grating performance and the temperature sensitivity of the resonance wavelength. EO LPWG on LiNbO3 allows the grating strength and the resonance wavelength to be controlled effectively by the driving voltage and the temperature, respectively, and has the potential to be further developed into new dynamic optical filters and intensity modulators for high-speed applications. Our best sample demonstrated so far shows a grating strength of 25 dB at a driving voltage of 49 V and a thermally tunable resonance wavelength with a sensitivity of -1.0 nm/°C.