Thin-film lithium niobate(LN)has emerged as an ideal platform for efficient nonlinear wave-mixing processes due to its strong quadratic nonlinearity and high optical confinement.We demonstrate unprecedentedly efficien...Thin-film lithium niobate(LN)has emerged as an ideal platform for efficient nonlinear wave-mixing processes due to its strong quadratic nonlinearity and high optical confinement.We demonstrate unprecedentedly efficient second-harmonic generation(SHG)in a double-layer thin-film LN waveguide.The modal overlap between fundamental and second-harmonic waves is significantly enhanced by the polarization-reversed double layers,leading to a normalized conversion efficiency higher than 10,000%W-1 cm-2 in theory.Under the low-and high-power pumping conditions,the measured normalized and absolute conversion efficiencies are 9600%W-1 cm-2 and 85%,respectively,substantially higher than state-of-the-art values among the reported SHGs in thin-film LN waveguides.Our results hold great promise for the development of efficient and scalable nonlinear photonic devices,with applications including metrology and quantum information processing.展开更多
Due to its strong piezoelectric effect and photo-elastic property, lithium niobate is widely used for acousto-optical applications. However, conventional bulk lithium niobate waveguide devices exhibit a large footprin...Due to its strong piezoelectric effect and photo-elastic property, lithium niobate is widely used for acousto-optical applications. However, conventional bulk lithium niobate waveguide devices exhibit a large footprint and limited light–sound interaction resulting from the weak guiding of light. Here, we report the first acousto-optical modulators with surface acoustic wave generation, phononic cavity, and low-loss photonic waveguide devices monolithically integrated on a 500 nm thick film of lithium niobate on an insulator. Modulation efficiency was optimized by properly arranging the propagation directions of surface acoustic waves and optical guided modes.The effective photo-elastic coefficient extracted by comparing the first and third harmonic modulation signals from an on-chip Mach–Zehnder interferometer indicates the excellent acousto-optical properties of lithium niobate are preserved in the thin film implementation. Such material property finding is of crucial importance in designing various types of acousto-optical devices. Much stronger amplitude modulation was achieved in a high Q(>300,000) optical resonator due to the higher optical sensitivity. Our results pave the path for developing novel acousto-optical devices using thin film lithium niobate.展开更多
Silicon carbide has recently emerged as a promising photonics material due to its unique properties, including possessing strong second-and third-order nonlinear coefficients and hosting various color centers that can...Silicon carbide has recently emerged as a promising photonics material due to its unique properties, including possessing strong second-and third-order nonlinear coefficients and hosting various color centers that can be utilized for a wealth of quantum applications. Here, we report the design and demonstration of octave-spanning microcombs in a 4H-silicon-carbide-on-insulator platform for the first time, to our knowledge. Such broadband operation is enabled by optimized nanofabrication achieving >1 million intrinsic quality factors in a 36-μm-radius microring resonator, and careful dispersion engineering by investigating the dispersion properties of different mode families. For example, for the fundamental transverse-electric mode whose dispersion can be tailored by simply varying the microring waveguide width, we realized a microcomb spectrum covering the wavelength range from 1100 nm to 2400 nm with an on-chip power near 120 mW. While the observed comb state is verified to be chaotic and not soliton, attaining such a large bandwidth is a crucial step towards realizing f-2f self-referencing.In addition, we also observed a coherent soliton-crystal state for the fundamental transverse-magnetic mode,which exhibits stronger dispersion than the fundamental transverse-electric mode and hence a narrower bandwidth.展开更多
基金support from the Advanced Integrated Optoelectronics Facility at Tianjin University.
文摘Thin-film lithium niobate(LN)has emerged as an ideal platform for efficient nonlinear wave-mixing processes due to its strong quadratic nonlinearity and high optical confinement.We demonstrate unprecedentedly efficient second-harmonic generation(SHG)in a double-layer thin-film LN waveguide.The modal overlap between fundamental and second-harmonic waves is significantly enhanced by the polarization-reversed double layers,leading to a normalized conversion efficiency higher than 10,000%W-1 cm-2 in theory.Under the low-and high-power pumping conditions,the measured normalized and absolute conversion efficiencies are 9600%W-1 cm-2 and 85%,respectively,substantially higher than state-of-the-art values among the reported SHGs in thin-film LN waveguides.Our results hold great promise for the development of efficient and scalable nonlinear photonic devices,with applications including metrology and quantum information processing.
基金Defense Advanced Research Projects Agency(DARPA)(N66001-16-1-4025)
文摘Due to its strong piezoelectric effect and photo-elastic property, lithium niobate is widely used for acousto-optical applications. However, conventional bulk lithium niobate waveguide devices exhibit a large footprint and limited light–sound interaction resulting from the weak guiding of light. Here, we report the first acousto-optical modulators with surface acoustic wave generation, phononic cavity, and low-loss photonic waveguide devices monolithically integrated on a 500 nm thick film of lithium niobate on an insulator. Modulation efficiency was optimized by properly arranging the propagation directions of surface acoustic waves and optical guided modes.The effective photo-elastic coefficient extracted by comparing the first and third harmonic modulation signals from an on-chip Mach–Zehnder interferometer indicates the excellent acousto-optical properties of lithium niobate are preserved in the thin film implementation. Such material property finding is of crucial importance in designing various types of acousto-optical devices. Much stronger amplitude modulation was achieved in a high Q(>300,000) optical resonator due to the higher optical sensitivity. Our results pave the path for developing novel acousto-optical devices using thin film lithium niobate.
基金Division of Electrical,Communications and Cyber Systems(2127499)Defense Advanced Research Projects Agency(D19AP00033).
文摘Silicon carbide has recently emerged as a promising photonics material due to its unique properties, including possessing strong second-and third-order nonlinear coefficients and hosting various color centers that can be utilized for a wealth of quantum applications. Here, we report the design and demonstration of octave-spanning microcombs in a 4H-silicon-carbide-on-insulator platform for the first time, to our knowledge. Such broadband operation is enabled by optimized nanofabrication achieving >1 million intrinsic quality factors in a 36-μm-radius microring resonator, and careful dispersion engineering by investigating the dispersion properties of different mode families. For example, for the fundamental transverse-electric mode whose dispersion can be tailored by simply varying the microring waveguide width, we realized a microcomb spectrum covering the wavelength range from 1100 nm to 2400 nm with an on-chip power near 120 mW. While the observed comb state is verified to be chaotic and not soliton, attaining such a large bandwidth is a crucial step towards realizing f-2f self-referencing.In addition, we also observed a coherent soliton-crystal state for the fundamental transverse-magnetic mode,which exhibits stronger dispersion than the fundamental transverse-electric mode and hence a narrower bandwidth.
