Research Of Supercontinuum And Frequency Comb Generation In Hybrid Silicon-based Waveguide

Supercontinuum(SC)is widely used in many basic and applied sciences because of its wide spectrum,high brightness and good coherence.In mid-infrared region(MIR),highly coherent octave-spanning SC has always attracted the interest of researchers.With the development of laser and new material technology,the study on SC has become more and more in-depth.Meanwhile,some new applications of SC also put forward higher requirements for the performance of supercontinuum spectrum.Group IV photonics,such as silicon(Si),germanium(Ge)and their derivatives,are favored because of their great potential in the non-linear applications of near-infrared and mid-infrared.The transparent window of Si is in the mid-infrared region of 2.2?m to 8.5?m,while the transparent window of Ge is from 1.5?m to 14.3?m.Chalcogenides,such as arsenic sulfide(As2S3)and arsenic selenide(As2Se3),are also known for their high nonlinear and ultra-wide transparent windows.Optical frequency comb is a spectrum consisting of a series of uniformly spaced and phase-coherent frequency components,which has been widely used in astronomy,physics,chemistry and communication because of its excellent stability.There are many ways to produce frequency comb,in which the SC-based OFC is a major one now.In this paper,Ge and As2Se3 are used as core of waveguides to study highly coherent octave-spanning SC and SC-based OFCs.The research contents and innovative results are as follows:1.The important role of supercontinuum and optical frequency comb in modern optics is introduced.The general descriptive equation for the propagation and evolution of pulse in waveguides is derived,and the effects of dispersion and nonlinearity on the supercontinuum generation are analyzed.2.A germanium T-shaped waveguide is designed to analyze how dimensions of waveguide can effect its dispersion and nonlinear characteristc.The effects of peak power,pulse width and noise on the SC are studied with center wavelength of 3000 nm(normal dispersion region)after the flat dispersion in the MIR is obtained.The simulation results show that when the pulse width of 120 fs and the peak power of 800 W is pumped into a 4 mm waveguide,the highly coherent supercontinuum with more than two octaves(1.6 ?m to 6.8?m)at-60 dB can be obtained.3.T-shaped and L-shaped waveguides based on As2Se3 are designed.The effects of waveguide structure and dimension on the dispersion and nonlinearity of waveguides are analyzed.The simulation results show that the dispersion curves of L-shaped waveguide exhibit the characteristcs of flatness and multiple zero dispersion wavelengths(ZDWs).When pumping at the wavelength of 3000 nm(anomalous dispersion region),the influence of pulse peak power on supercontinuum is studied.The results show that when the pulse width of 120 fs and the peak power of 800 W is pumped into 5 mm waveguide,the supercontinuum of more than three octaves(1.3 to 12.9 ?m)at-60 dB can be obtained.Futhermore,the influence of weak continuous wave(CW)on the coherence of the supercontinuum is studied.4.The frequency comb based on highly coherent octave-spanning SC is alse studied.The simulation results show that after the initial pulse sequence propagates 5 mm in Ge and As2Se3 waveguide,the MIR frequency combs from 1.6 ?m to 6.8 ?m and 1.3 ?m to 15.0 ?m can respectively be obtained.In summary,waveguide structures based on Ge and As2Se3 are designed and used to study the highly coherent and octave-sapnnig supercontinnum and frequency comb generation.The related research results can actively promote the research and development of MIR non-linear photonics.