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LiNbO3 Crystal and the Application

LiNbO3 crystal integrates various optoelectronic properties and can meet practical performance requirements, making it very rare in optoelectronic materials. With the development and improvement of the core technologies such as the theory, preparation and application of integrated photonics chips of LiNbO3 crystals, it has become the “optical silicon” materials in the photonic era, providing basic support for the development of integrated photonics.

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About LiNbO3 Crystal:

LiNbO3 crystal is a compound of niobium, lithium, and oxygen, LiNbO3 crystal has two characteristics that are particularly noteworthy. Firstly, LiNbO3 crystal has many photoelectric effects, including piezoelectric effect, electro-optic effect, nonlinear optical effect, photorefractive effect, photovoltaic effect, photoelastic effect, acoustooptic effect, and other photoelectric properties; Secondly, the performance of LiNbO3 crystals is highly controllable, which is caused by the lattice structure and rich defect structure of LiNbO3 crystals. Many properties of LiNbO3 crystals can be greatly regulated through crystal composition, element doping, valence state control, etc.

In addition, the physical and chemical properties of LiNbO3 crystals are quite stable, easy to process, have a wide range of light transmission, have large birefringence, and are easy to prepare high-quality optical waveguides. Therefore, light modulators based on LiNbO3 crystals have unparalleled advantages in long-distance communication – not only have very small chirp effect, high modulation bandwidth, good extinction ratio, but also have excellent stability, making them outstanding in high-speed devices, Therefore, it is widely used in long-distance communication with high speed and high bandwidth.

The Main Application of LiNbO3 Crystal:

1. Piezoelectric Applications

LiNbO3 crystal has high Curie temperature, low temperature coefficient of piezoelectric effect, high electromechanical coupling coefficient, low dielectric loss, stable physical and chemical properties, good processing performance, and is easy to prepare large-sized high-quality crystals. It is an excellent piezoelectric crystal material.
Compared with commonly used piezoelectric crystal quartz, LiNbO3 crystal has a higher sound speed and can be used to prepare high-frequency devices. Therefore, LiNbO3 crystal can be used for resonators, transducers, delay lines, filters, etc. It is applied in civil fields such as mobile communication, satellite communication, digital signal processing, television, broadcasting, radar, remote sensing and telemetry, as well as military fields such as electronic countermeasures, fuses, and guidance, The most widely used among them is the Surface Acoustic Wave Filter (SAWF).

2. Optical Applications

In addition to the piezoelectric effect, LiNbO3 crystals have a rich range of photoelectric effects, among which the electro-optic effect and nonlinear optical effect have outstanding performance and are also most widely used. Moreover, LiNbO3 crystals can be used to prepare high-quality optical waveguides through proton exchange or titanium diffusion, and can also be used to prepare periodically polarized crystals through polarization reversal, so they are widely used in electro-optic modulators, phase modulators, integrated optical switches, electro-optic Q-switching, electro-optic deflections, high voltage sensors, wavefront detection, Optical parametric oscillator, ferroelectric superlattice and other devices.
In addition, applications based on LiNbO3 crystals such as birefringent wedges, holographic optical devices, infrared pyroelectric detectors, and erbium-doped waveguide lasers have also been reported.

3. Dielectric Superlattice

In 1962, Armstrong et al first proposed the concept of Quasi-phase-matching (QPM), which uses the inverted lattice vector provided by superlattice to compensate for phase mismatch in the process of optical parameters. The polarization direction of ferroelectrics determines the nonlinear polarizability. The quasi phase matching technology can be realized by preparing ferroelectric domain structures with opposite periodic polarization directions in ferroelectrics, including LiNbO3, lithium tantalate, potassium titanate phosphate and other crystals, which can prepare periodically polarized crystals. Among them, LiNbO3 crystal is the earliest material to prepare and apply this technology and has the most extensive practical applications.
The initial application of periodically polarized LiNbO3 crystal is mainly considered to be applied to laser frequency conversion. In 2014, Jin et al. designed an optical superlattice integrated photonic chip based on a reconfigurable LiNbO3 waveguide optical path, and realized efficient generation of entangled photons on the chip and high-speed electro-optic modulation for the first time.
It can be said that the proposal and development of dielectric superlattice theory have pushed the application of LiNbO3 crystals and other ferroelectric crystals to a new height, and has important application prospects in all solid state lasers, optical frequency combs, laser pulse compression, beam shaping, and entanglement light sources in quantum communication.