We report on the realization of adiabatic light transfer in lithium niobate (LiNbO₃) waveguides. This peculiar adiabatic tunneling scheme was implemented in a three-waveguide coupling configuration with the intermediate waveguide being inclined with respect to the outer waveguides to facilitate the adiabatic passage process. We have investigated and determined the adiabatic conditions of the LiNbO₃ device in terms of the structure configuration of the waveguide system and found optimal structure parameters by both simulation and experimental approaches. Broadband adiabatic couplings of bandwidth ~456 and 185 nm and peak coupling efficiencies of >0.96 have been obtained with a 2-cm long device for TE- and TM-polarized fundamental modes, respectively. Longer (5 cm) devices were also studied and found to be useful in increasing the adiabaticity of the device, especially for the TM-polarized mode.

We report the first experimentally demonstrated active Šolc-type optical wavelength filters based on Ti:PPLN waveguides. A peak spectral transmittance of ~99% at a bandwidth of ~2.6 nm in telecom bands was obtained in this device.

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We report the first experimental demonstration of active narrowband multiple wavelength filters in aperiodically poled lithium niobate (APLN) crystals. Simultaneous transmission of >90% (~100% in design) of 8 telecom wavelengths was achieved in this device.