Research On On-Chip Supercontinuum Light Source Based On Chalcogenide Optical Waveguides

With the rapid development of Internet technology and the continuous growth of information flow,silicon photonic functional devices with ultra-high speed,low delay and large bandwidth at the chip level have attracted increasing attention.However,silicon is a semiconductor material with indirect band gap,thus its band gap is narrow and there are many non-radiative recombination mechanisms,which leads to low luminous efficiency and brings great challenges to the development and application of on-chip light sources.Chalcogenide materials have the characteristics of ultra-wide transmission spectrum,high nonlinearity,low absorption and rich material components,expecting to break the limited development of on-chip light sources and then become an international research hotspot.The on-chip sensor developed on this basis greatly enriches the biochemical detection means,improves the detection accuracy and efficiency,and greatly promotes the development of miniaturized on-chip sensing detection and on-chip spectrometer.At present,on-chip light source based on chalcogenide materials is mainly realized by pumping chalcogenide optical waveguide with ultrashort pulse to produce supercontinuum spectrum.The research schemes mainly include As₂S₃ and Ge_11.5As₂₄Se_64.5,but there are still the following problems:(1)As₂S₃ glass film is prone to produce photodarkening effect after laser illumination;(2)The prepared glass film containing Se has poor resistance to laser damage.Therefore,how to obtain high-quality chalcogenide glass films with stable optical properties and high laser damage threshold,which is a key scientific and technical problem to be solved.The research work in this dissertation focuses on the above key scientific and technical problems faced by chalcogenide on-chip supercontinuum light source.Chalcogenide glass films and waveguides have been prepared,and the optical properties have been characterized.On-chip supercontinuum light source based on chalcogenide optical waveguides has been proposed,designed and realized,and the reusability of the waveguides and the stability of the output spectrum are also studied.On this basis,on-chip spectrum detection with on-chip supercontinuum light source is realized,providing technical support for further realizing high-performance biochemical sensing detection.The main research work and innovative achievements are summarized as follows:1.The transmission characteristic equation of rectangular optical waveguide based on the nonlinear transmission theory are derived and numerically analysed.Then,the propagation equation and numerical analysis method of ultrashort pulse in rectangular optical waveguide are derived,where the physical meaning of each parameter,window setting,step selection and noise model are analyzed in detail.The effects of dispersion and nonlinear effects on supercontinuum are also discussed.The effects of the zero-dispersion wavelength and pump wavelength on the spectrum broadening mechanism with femtosecond pulse laser are numerically simulated,which lays a theoretical foundation for the experimental study of on-chip supercontinuum light source.2.Aiming at the optical stability of multicomponent chalcogenide films,the preparation and characterization methods of chalcogenide glass films and waveguides are studied.The preparation process of multicomponent chalcogenide films is studied by vacuum thermal evaporation.The deposition process is controlled by double hole tantalum boat,which solves the stability of the films under non-equilibrium conditions,and realizes the preparation of chalcogenide films with high compactness,good adhesion,uniform and smooth.The characterizations and principles of optical properties of chalcogenide films and glasses are studied.The characterization results are used as the basis for improving the preparation process,which provides an inspection standard for obtaining high-quality chalcogenide films.The processing technology of chalcogenide waveguide is studied and optimized,and the preparation of low loss chalcogenide waveguide is realized.The spatial coupling system and nonlinear transmission platform of chalcogenide optical waveguide are designed and built,which lays a good experimental foundation for realizing a stable supercontinuum light source based on chalcogenide optical waveguide.3.In order to improve the laser damage resistance of chalcogenide films,an on-chip supercontinuum light source based on Ge_11.5As₂₄S_64.5 planar optical waveguide is proposed by doping Ge into As₂S₃.The Ge_11.5As₂₄S_64.5 films are demonstrated to be consistent with the structure of bulk glass and show high resistance to laser damage by nonlinear optical characterization.The structural parameters of chalcogenide waveguide are designed and optimized by finite element method,and the dispersion engineering is realized.Supercontinuum spectrum is experimentally demonstrated covering the range of 0.9-2.0?m.4.As the system containing As is easy to oxidize and not conducive to environmental protection,an on-chip supercontinuum light source based on environment-friendly chalcogenide glass component Ge₂₅Sb₁₀S₆₅ planar optical waveguide is proposed by replacing As with Sb,and on-chip detection of?-phenylethylamine solution is realized.The compositions,structures and optical properties of Ge-Sb-S glass are studied.The films of Ge₂₅Sb₁₀S₆₅ component with the optical properties highly consistent with that of bulk glasses are obtained,where the laser damage threshold is measured to be 817.6 GW/cm².The waveguide dispersions with two thicknesses are engineered leading to the optical communication wavelength lies in the anomalous dispersion region and in the vicinity of zero-dispersion wavelength.On-chip supercontinuum light sources are demonstrated experimentally based on both of waveguides,respectively.For the waveguides with a thickness of900 nm,the coverage of the output spectrum is obtained with the range of 850-2150nm.And the spectral range of the waveguides with thickness of 1.4?m is extended to the range of 870-2480 nm,where the long wavelength edge is near 2.5?m.The detections of?-phenylethylamine solution with different concentrations are also demonstrated with the sensitivity of 1.92 d B/(mol/L).