Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on var...Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on various material platforms,realizing complete comb functionality on photonic chips requires the co-integration of highspeed modulators and efficient frequency doublers,features that are available in a monolithic form on X-cut thin-film lithium niobate(TFLN).However,the pronounced Raman nonlinearity associated with extraordinary light in this platform has so far precluded soliton microcomb generation.Here,we report the generation of transverse-electric-polarized soliton microcombs with a 25 GHz repetition rate in high-Q microresonators on X-cut TFLN chips.By precisely orienting the racetrack microresonator relative to the optical axis,we mitigate Raman nonlinearity and enable soliton formation under continuous-wave laser pumping.Moreover,the soliton microcomb spectra are extended to 350 nm with pulsed laser pumping.This work expands the capabilities of TFLN photonics and paves the way for the monolithic integration of fast-tunable,self-referenced microcombs.展开更多
基金supported by Beijing Natural Science Foundation(Z210004)National Key R&D Plan of China(Grant No.2021ZD0301500)+2 种基金National Natural Science Foundation of China(92150108,12293050,12304412)the highperformance computing Platform of Peking Universitythe Advanced Photonic Integrated Center(APIC)of State Key Laboratory of Advanced Optical Communication System and Networks.
文摘Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on various material platforms,realizing complete comb functionality on photonic chips requires the co-integration of highspeed modulators and efficient frequency doublers,features that are available in a monolithic form on X-cut thin-film lithium niobate(TFLN).However,the pronounced Raman nonlinearity associated with extraordinary light in this platform has so far precluded soliton microcomb generation.Here,we report the generation of transverse-electric-polarized soliton microcombs with a 25 GHz repetition rate in high-Q microresonators on X-cut TFLN chips.By precisely orienting the racetrack microresonator relative to the optical axis,we mitigate Raman nonlinearity and enable soliton formation under continuous-wave laser pumping.Moreover,the soliton microcomb spectra are extended to 350 nm with pulsed laser pumping.This work expands the capabilities of TFLN photonics and paves the way for the monolithic integration of fast-tunable,self-referenced microcombs.
