Characterization of LiNbO3 optical-waveguide film grown on sapphire by ArF excimer laser ablation

Heteroepitaxial growth of LiNbO3 film is expected to provide a novel hybrid integration of optical and electronic components and devices. In this paper, are present! for the first time, to our knowledge, characterization of LiNbO3 optical-waveguide film grown on c-cut sapphire by ArF excimer laser ablation. Almost droplet-free LiNbO3 film was deposited only by increasing the target-to-substrate distance d to 40 mm, where Li-rich LiNbO3 ceramics with the Li/Nb ratio of 2.1 was used as the target. The deposited LiNbO3 film also exhibited a strong (006) peak in the X-ray diffraction spectrum, showing good orientation along the c axis. Optical properties were characterized based on excitation of guided modes in the film with a prism coupler. The propagation loss of the TM(0) mode was lowered to be 5 dB/cm at lambda = 0.633 mu m. The film indices were exactly determined, followed by evaluation of the chemical composition of the film from the measured index n(e) of the extraordinary wave. Lack of Li2O in the film became more significant as the distance d increased. A Bragg light deflector was then fabricated to evaluate the electrooptic coefficient tau(33) in the film deposited under the condition that d=40 mm. tau(33) was found to be as large as 4.9 pm/V, which was nearly one-sixth of the single-crystal value, irrespective of nonstoichiometry of the film.