Lithium Niobate (LN) crystal has high spontaneous polarization (0.70 C/m² at room temperature) and is a ferroelectric crystal with the highest Curie temperature (1210 ℃) found so far. LN crystal has two characteristics that attract special attention. First, it has many super photoelectric effects, including piezoelectric effect, electro-optic effect, nonlinear optical effect, photorefractive effect, photovoltaic effect, photoelastic effect, acoustooptic effect and other photoelectric properties. Second, the performance of LN crystal is highly adjustable, which is caused by the lattice structure and abundant defect structure of LN crystal. Many properties of LN crystal can be greatly regulated by crystal composition, element doping, valence state control and so on. In addition, the LN crystal is rich in raw materials, which means high-quality and large-size single crystal is relatively easy to prepare.

The LN crystal has stable physical and chemical properties, easy to process, wide light transmission range (0.3 ~5μm), and has a large birefringence (about 0.8 @ 633 nm) , and easy to made into high-quality optical waveguide. Therefore, the LN-based optoelectronic devices, e.g. surface acoustic wave filter, light modulator, phase modulator, optical isolator, electro-optic Q-switch (www.wisoptic.com), are widely studied and applied to the following fields: electronic technology, optical communication technology, laser technology. Recently, with the breakthroughs in the application of 5G, micro/nano photonics, integrated photonics and quantum optics, LN crystals have attracted wide attention again. In 2017, Burrows of Harvard University even proposed that the era of “lithium niobate valley” is now coming.

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