#  Nonlinear Optics and Frequency Combs 

 



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As a material that contains both large \\(\\chi^{(2)}\\) and \\(\\chi^{(3)}\\), lithium niobate has lead to variaty investigation and application on nonlinear optics. Recent development on the thin-film lithium niobate allows micro-structure lithium niobate device, which can enhance the nonlinear effect to a new regime.

Our group works on investigating the novel nonlinear optics phenomena on thin-film lithiumniobate, including periodic-poled lithium niobate (PPLN) for efficient frequency conversion, electro-optic frequency comb, Kerr frequency comb, etc

**EO frequency comb:**

- **Single-resonator EO comb \[Mian Zhang, et al. Nature 568, 373 (2019)\]:** We demonstrate the generation of broadband electro-optic frequency combs with a record-high bandwidth (one orders of magnitude higher than previous EO comb).

   ![frequency comb](/sites/g/files/omnuum6446/files/styles/hwp_1_1__960x960_scale/public/nano-optics/files/comb_1.jpg?itok=RI7g0q6y) 

 

- **Coupled-resonator EO comb \[Yaowen Hu, et al. Nature Photonics 16, 679 (2022)\]:** We further demosntrate high-efficiency and broadband electro-optic frequency combs, featuring a 100-times higher conversion efficiency and a 2.2-times broader bandwidth compared to previous our state-of-the-art EO comb \[Zhang, et al. Nature 568, 373 (2019)\]. We also demonstrate the device is an on-chip femtosecond pulse source with pulse duration of 336 fs.

   ![HPEO](/sites/g/files/omnuum6446/files/styles/hwp_1_1__720x720_scale/public/nano-optics/files/cover_version_1_ya_suo__0.jpg?itok=n5E1STFz) 

 

- **Femtosecond pulse source using time-lens \[Mengjie Yu, et al. arXiv 2112.09204 (2021)\]:** We demonstrate femtosecond pulse source with pulse duration of 520 fs using time-lens system.

   ![tl](/sites/g/files/omnuum6446/files/styles/hwp_1_1__720x720_scale/public/nano-optics/files/333333333333333333.png?itok=ljUmibkl)