Submicron-thick thin-film lithium niobate(TFLN)has emerged as a promising platform for nonlinear integrated photonics.In this work,we demonstrate the efficient simultaneous generation of broadband 2nd–8th harmonics i...Submicron-thick thin-film lithium niobate(TFLN)has emerged as a promising platform for nonlinear integrated photonics.In this work,we demonstrate the efficient simultaneous generation of broadband 2nd–8th harmonics in chirped periodically poled(CPP)TFLN.This is achieved through the synergistic effects of cascadedχ^((2))nonlinear up-conversion andχ^((3))self-phase modulation,driven by near-infrared femtosecond pulses with a central wavelength of 2100 nm and a pulse energy of 1.2μJ.Remarkably,the 7th and 8th harmonics extend into the deep ultraviolet(DUV)region,reaching wavelengths as short as 250 nm.The 3rd–8th harmonic spectra seamlessly connect,forming a broadband supercontinuum spanning from the DUV to the visible range(250–800 nm,-25 d B),with an on-chip conversion efficiency of 19%(0.23μJ).This achievement is attributed to the CPP-TFLN providing multiple broadband reciprocal lattice vector bands,enabling quasi-phase matching for a series ofχ^((2))nonlinear processes,including second harmonic generation(SHG),cascaded SHG,and third harmonic generation.Furthermore,we demonstrated the significant role of cascadedχ^((2))phase-mismatched nonlinear processes in high-harmonic generation(HHG).Our work unveils the intricate and diverse nonlinear optical interactions in TFLN,offering a clear path toward efficient on-chip HHG and compact coherent white-light sources extending into the DUV.展开更多
基金National Natural Science Foundation of China(12434016,11974119)Science and Technology Project of Guangdong(2020B010190001)National Funded Postdoctoral Researcher Program(GZB20240785)。
文摘Submicron-thick thin-film lithium niobate(TFLN)has emerged as a promising platform for nonlinear integrated photonics.In this work,we demonstrate the efficient simultaneous generation of broadband 2nd–8th harmonics in chirped periodically poled(CPP)TFLN.This is achieved through the synergistic effects of cascadedχ^((2))nonlinear up-conversion andχ^((3))self-phase modulation,driven by near-infrared femtosecond pulses with a central wavelength of 2100 nm and a pulse energy of 1.2μJ.Remarkably,the 7th and 8th harmonics extend into the deep ultraviolet(DUV)region,reaching wavelengths as short as 250 nm.The 3rd–8th harmonic spectra seamlessly connect,forming a broadband supercontinuum spanning from the DUV to the visible range(250–800 nm,-25 d B),with an on-chip conversion efficiency of 19%(0.23μJ).This achievement is attributed to the CPP-TFLN providing multiple broadband reciprocal lattice vector bands,enabling quasi-phase matching for a series ofχ^((2))nonlinear processes,including second harmonic generation(SHG),cascaded SHG,and third harmonic generation.Furthermore,we demonstrated the significant role of cascadedχ^((2))phase-mismatched nonlinear processes in high-harmonic generation(HHG).Our work unveils the intricate and diverse nonlinear optical interactions in TFLN,offering a clear path toward efficient on-chip HHG and compact coherent white-light sources extending into the DUV.
