232 / 2023-04-17 15:47:20

Micro-modulation of optical signals by optical waveguide structures on lithium niobate thin films

Lithium niobate,optical waveguide,thin film heterojunction,microring resonator

极端光下的基础物理学 > 基础物理-I

Lithium niobate, as an important nonlinear optical crystal, has excellent optical application values. The ultra-strong and ultra-short femtosecond laser was used to drive the lithium niobate crystal, and the phase mismatch caused by the refractive index difference was adjusted by tilting wavefront technology, meanwhile, the pump laser pulse width, spot shape and crystal cooling were optimized cooperatively. Finally, the ultra-strong terahertz radiation source with single pulse energy of 13.9mJ, conversion efficiency of 1.2% and peak field intensity of 7.5MV/cm was obtained. It is the highest value of terahertz source obtained by this method in the world. With the successful preparation of single-crystalline lithium niobate thin films with submicron thickness, the microscale modulation of optical signals by lithium niobate optical waveguide structures has become a research hotspot in integrated optics. As an optical component, lithium niobate optical waveguide structure has important applications in a variety of nonlinear optical devices. It is expected to play an important role in further improving the energy and conversion efficiency of terahertz light source driven by strong light. The preparation of single-crystalline lithium niobate thin films is achieved by a new film-fabrication technology, called “smart-cutting”. We applied this film fabrication method to more crystals with excellent optical properties, and prepared more single-crystalline thin films of optical crystals with complex lattice structures and poor conductivity, and further manufactured optical waveguide structures, such as microring resonators, on the prepared single-crystalline films by using micro-etching processing technology, to achieve microscopic control of optical signals. At present, through the continuous optimization of micro-etching process, low loss optical waveguide structure can be realized on single-crystalline lithium niobate thin films, and the optical transmission loss is less than 0.5dB/cm. Optical signal multiplexing modulation based on lithium niobate microring resonator can be achieved at both the visible and near infrared spectra, which has important application value in the field of optical communication.