Kaifeng Lin （林凯风）
I am a PhD candidate at Peking University, advised by Prof. Kaihui Liu. My research focuses on nonlinear and quantum optics in two-dimensional materials. I study how the structure of these materials shapes their interaction with light and how their optical properties can be used to generate and control light in integrated photonic devices.
Selected publications
First author
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We stacked rhombohedral boron nitride (rBN) flakes on a fibre tip and used the twist angles to control the phase of the nonlinear response. By choosing the angles to compensate for phase shifts during propagation, we made the contributions from successive flakes add coherently. We used this design to demonstrate frequency doubling and photon-pair generation in fibre-integrated devices. We also built a graphene/rBN heterostructure for an all-fibre ring laser, using graphene for saturable absorption to mode-lock the laser and rBN for intracavity frequency doubling.
Co-first author
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We used the two ends of a crack in a dome-shaped WS₂ monolayer to guide the growth of left- and right-handed stacks. Each stack repeats the same twist from one layer to the next and has low residual strain. Comparing these mirror-image structures let us test how the direction of twist shapes circular dichroism in both transmission and second-harmonic generation.
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We placed graphene inside a nanocavity made from MoS₂ and boron nitride layers on a fibre tip. Adjusting the boron nitride thickness let us tune the optical field at the graphene and thereby control its saturable absorption. The resulting absorber suppressed competing pulses during laser start-up, allowing a single soliton to form and remain stable.
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We used short infrared pulses to heat the electrons in graphene so that some could escape into vacuum while the lattice stayed relatively cool. Mounting graphene directly on a single-mode fibre tip let the guided light define the excitation spot, giving us a compact source that could emit ultrafast electron pulses stably over long periods.
