Integrated optics have been stuck in two-dimensional(2D)topologies for decades until the femtosecond laser direct writing(FLDW)technique enables direct lithography of three-dimensional(3D)geometries and nanoscale stru...Integrated optics have been stuck in two-dimensional(2D)topologies for decades until the femtosecond laser direct writing(FLDW)technique enables direct lithography of three-dimensional(3D)geometries and nanoscale structures with rapid prototyping and large-scale manufacturing capabilities in a variety of transparent substrates.The 3D capability of FLDW makes diverse lightwave remapping geometries possible,thereby realizing efficient interconnection of optical systems at different spatial scales,offering a 3D integrated-optics footprint capable of scaling a benchtop optical system down to a 3D glass chip.This work summarizes the history and important milestones in developing FLDW waveguides.Basically,all revolutionary improvements in waveguide key performance,including low propagation loss and small bending radius,were accompanied by the discovery and development of new mechanisms for laser-induced refractive index modification.At the same time,advanced laser beam-shaping methods for tightly focused spatiotemporal fields have been technically grafted onto the fine control of laser–matter interaction in FLDW,notably achieving variable cross-section,arbitrary refractive index and mode-field distribution,thus providing new degrees of freedom beyond the limitations of traditional 2D planar waveguides for more complex photonics circuit design.In this work,we present a comprehensive review of the field,encompassing fundamental mechanisms(such as refractive index modification)as well as key technological advances that enable true 3D integration.On the basis of this,we summarize the basic integrated waveguide components fabricated by FLDW and point out the prospective challenges and future research directions.Tentative routes towards large-area,ultra-broadband,hybrid,multifunctional,all-optical system integration in 3D glass chips are also suggested.展开更多
Three-dimensional(3D)glass chips are promising waveguide platforms for building hybrid 3D photonic circuits due to their 3D topological capabilities,large transparent windows,and low coupling dispersion.At present,the...Three-dimensional(3D)glass chips are promising waveguide platforms for building hybrid 3D photonic circuits due to their 3D topological capabilities,large transparent windows,and low coupling dispersion.At present,the key challenge in scaling down a benchtop optical system to a glass chip is the lack of precise methods for controlling the mode field and optical coupling of 3D waveguide circuits.Here,we propose an overlap-controlled multi-scan(OCMS)method based on laser-direct lithography that allows customizing the refractive index profile of 3D waveguides with high spatial precision in a variety of glasses.On the basis of this method,we achieve variable mode-field distribution,robust and broadband coupling,and thereby demonstrate dispersionless LP21-mode conversion of supercontinuum pulses with the largest deviation of<0.1 dB in coupling ratios on 210 nm broadband.This approach provides a route to achieve ultra-broadband and low-dispersion coupling in 3D photonic circuits,with overwhelming advantages over conventional planar waveguide-optic platforms for on-chip transmission and manipulation of ultrashort laser pulses and broadband supercontinuum.展开更多
基金National Natural Science Foundation of China(Nos.52432001,12404367)Natural Science Foundation of Zhejiang Province(No.LDG25F050001)+1 种基金National Key Research and Development Program of China(No.2024YFB4607403)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(No.2023C03089).
文摘Integrated optics have been stuck in two-dimensional(2D)topologies for decades until the femtosecond laser direct writing(FLDW)technique enables direct lithography of three-dimensional(3D)geometries and nanoscale structures with rapid prototyping and large-scale manufacturing capabilities in a variety of transparent substrates.The 3D capability of FLDW makes diverse lightwave remapping geometries possible,thereby realizing efficient interconnection of optical systems at different spatial scales,offering a 3D integrated-optics footprint capable of scaling a benchtop optical system down to a 3D glass chip.This work summarizes the history and important milestones in developing FLDW waveguides.Basically,all revolutionary improvements in waveguide key performance,including low propagation loss and small bending radius,were accompanied by the discovery and development of new mechanisms for laser-induced refractive index modification.At the same time,advanced laser beam-shaping methods for tightly focused spatiotemporal fields have been technically grafted onto the fine control of laser–matter interaction in FLDW,notably achieving variable cross-section,arbitrary refractive index and mode-field distribution,thus providing new degrees of freedom beyond the limitations of traditional 2D planar waveguides for more complex photonics circuit design.In this work,we present a comprehensive review of the field,encompassing fundamental mechanisms(such as refractive index modification)as well as key technological advances that enable true 3D integration.On the basis of this,we summarize the basic integrated waveguide components fabricated by FLDW and point out the prospective challenges and future research directions.Tentative routes towards large-area,ultra-broadband,hybrid,multifunctional,all-optical system integration in 3D glass chips are also suggested.
基金supported by the National Key R&D Program of China (No.2021YFB2802000)National Natural Science Foundation of China (Nos.U20A20211,62275233,62005164,62375246,and 62105297)+1 种基金“Pioneer”and“Leading Goose”R&D Program of Zhejiang (2023C03089)Zhejiang Provincial Natural Science Foundation (Nos.LZ23F050002 and LQ22F050022).
文摘Three-dimensional(3D)glass chips are promising waveguide platforms for building hybrid 3D photonic circuits due to their 3D topological capabilities,large transparent windows,and low coupling dispersion.At present,the key challenge in scaling down a benchtop optical system to a glass chip is the lack of precise methods for controlling the mode field and optical coupling of 3D waveguide circuits.Here,we propose an overlap-controlled multi-scan(OCMS)method based on laser-direct lithography that allows customizing the refractive index profile of 3D waveguides with high spatial precision in a variety of glasses.On the basis of this method,we achieve variable mode-field distribution,robust and broadband coupling,and thereby demonstrate dispersionless LP21-mode conversion of supercontinuum pulses with the largest deviation of<0.1 dB in coupling ratios on 210 nm broadband.This approach provides a route to achieve ultra-broadband and low-dispersion coupling in 3D photonic circuits,with overwhelming advantages over conventional planar waveguide-optic platforms for on-chip transmission and manipulation of ultrashort laser pulses and broadband supercontinuum.
