Doctoral Defense

Lithium Niobate Nanophotonics: From Passive to Active

Mingxiao Li

Supervised by Professor Qiang Lin

Monday, November 29, 2021
2 p.m.

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For decades, lithium niobate (LN), a human-made dielectric material is dominant in the electro-optic modulation market, benefited by its relatively large electro-optic (EO) factor, wide intrinsic bandwidth and large transparent window. Moreover, it exhibits outstanding material characteristics with great potential for applications in various areas, including nonlinear optics, quantum photonics and optical communication system. However, the large scale of existing LN products not only limits its performance, but also makes it bulky, pricey and high power consumed. With brilliant materials property and the high integration capacity, the emergence of thin-film single crystalline LN breaks that bottleneck and appears to be a promising platform for future optical processing systems. On the other hand, enhancing light-matter interaction in the nanoscopic scale would result in intriguing device characteristics which enables application in nonlinear optics and quantum photonics, in addition, revealing new physical phenomena resulting in novel functionalities inaccessible by conventional means. In this presentation, first of all, I will demonstrate one of those approaches by using photonic crystal (PhC) nano-cavities. The high optical quality (Q) together with the tiny effective mode volume supports extremely strong nonlinear optical interactions, which results in many first time in on-chip LN nanophotonic devices. Moreover, this tiny scale allowing us to achieve a femtofarad EO device, resulting in a demanded low power consuming modulator. Additionally, open up a great avenue for the exploration of nonlinear and quantum optics. Finally, by incorporating with gain materials, we demonstrate an integrated III/V LN laser with narrow linewidth and high speed tunability, together with a multicolor lasing potential. This found enables the path to fully integration of LN devices for future applications and industrial manufactures.