Chinese Scientists Develop Ultra-thin, Energy-efficient Optical Crystal

Optical crystal can realize frequency conversion, parametric amplification, signal modulation and other functions, is the "heart" of laser technology. After years of research, the Peking University team creatively put forward a new optical crystal theory, and the application of light element material boron nitride for the first time to prepare...
Optical crystal can realize frequency conversion, parametric amplification, signal modulation and other functions, is the "heart" of laser technology. After years of research, the Peking University team creatively put forward a new optical crystal theory, and applied the light element material boron nitride to prepare an ultra-thin, high-efficiency optical crystal "corner rhombic boron nitride" (TBN for short) for the first time, which lays the theoretical and material foundation for a new generation of laser technology. The results have been published in Physical Review Letters, a leading physics journal.
Academician of the Chinese Academy of Sciences and professor at Peking University's School of Physics, Wang Engo, said in an exclusive interview with Xinhua News Agency that this achievement is not only an original breakthrough in China's theory of optical crystals, which opens up a new field of preparing optical crystals by using two-dimensional thin-film materials with light elements, but also prepares TBN with a thickness of only micrometers, which is the world's thinnest optical crystal known to date, and its energy efficiency is 100 to 10,000 million times higher compared to that of a conventional crystal with the same thickness. Its energy efficiency is 100 to 10,000 times higher than that of conventional crystals of the same thickness.
Phase is a metric that describes the change in the waveform of a light wave. When the light waves in a crystal are phase-matched and in step, a laser with ideal efficiency and power can be output. In recent years, due to the limitations of traditional theoretical models and material systems, existing crystals have been difficult to meet the development needs of miniaturization, high integration and functionalization of lasers.
To this end, Professor Liu Kaihui, Director of the Institute of Condensed Matter Physics and Materials Physics at the School of Physics, Peking University, and Deputy Director of the Light Element Quantum Materials Cross-Platform at the Huairou Comprehensive National Science Center in Beijing, together with Wang Engo, led a team of researchers to propose a new "corner phase matching theory". The team found that by stacking boron nitride materials like "building blocks" and then "rotating" them to a special angle, the phases of different light waves can be converged to form a high-efficiency optical crystal, TBN.
"If the laser generated in the crystal is regarded as a team, the use of 'cornering' method can make all the members of the direction and pace of highly coordinated, you can enhance the energy conversion efficiency of the laser." Liu Kaihui said the TBN is only 1 to 10 microns thick, equivalent to one-thirtieth of the thickness of an ordinary A4 paper, while the thickness of current optical crystals is mostly on the order of millimeters or even centimeters.
"Optical crystals are the cornerstone of laser technology development." With its ultra-thin size, excellent integrability and brand-new functions, TBN is expected to realize new application breakthroughs in the future in fields such as quantum light sources, photonic chips and artificial intelligence, Wang Engo said.