Research Of Pulse Compression And Supercontinuum Generation In Silicon Waveguide

On-chip high quality and high degree pulse compression is desirable in the realization of integrated ultrashort pulse sources,which are important for nonlinear photonics and spectroscopy.Optical pulse compression technique is important for many applications,including optical communication,nonlinear microscopy,supercontinuum and frequency comb generations.There are still some disadvantages on several proposed nonlinear pulse compression schemes.In anomalous dispersion region,the breathing of higher-order solitons can be used to compress the pulse without grating pairs,but significant pedestal will accompany the compressed pulse,and the compression factor is not high.Adiabatic soliton compression in a dispersion decreasing fiber can provide a high compression factor without generating significant pedestal,however,the long fiber length is required,which is undesirable in most systems because of compactness and cost.Compared with the adiabatic compression,self-similar pulse compression can achieve large compression factor without pedestal generation in much shorter nonlinear media.Previous works on self-similar pulse compression are mainly focused on the pulse compression at telecommunication wavelength in photonic crystal fibers(PCFs)and chalcogenide waveguide.There is few works on self-similar pulse compression at the mid-infrared wavelength.In this paper,aiming at the shortcomings of the self-similar pulse compression in PCFs and chalcogenide waveguide,a simple tapered silicon waveguide is used to study the self-similar pulse compression in the mid-infrared spectral region.The influence factors on the pulse compression process are deeply studied.Moreover,highly coherent and octave spanning supercontinuum(SC)is generated by using the compressed pulse.The main contents and achievements of this paper are as follows1.The optical properties of silicon waveguides and several optical pulse compression techniques based on nonlinear fiber optics are introduced.The introduced pulse compression techniques are analyzed and compared.We also introduce the research status of the SC.2.The generalized nonlinear Schrodinger equation(GNLSE),which is needed to obey when pulse propagates in the nonlinear media,is derived,and two commonly used numerical solution method of GNLSE are introduced.The effects of nonlinear and dispersion effects on the pulse propagation are analyzed.3.A simple inversely tapered silicon ridge waveguide with exponentially decreasing dispersion profile along the propagation direction is designed,and self-similar pulse compression of the fundamental soliton for the ideal and non-ideal cases in the mid-infrared spectral region is numerically investigated.When higher-order dispersion(HOD),higher-order nonlinearity(HON),losses(a),and variation of the Kerr nonlinear coefficient ?(z)are considered,a 1 ps input pulse at wavelength 2490 nm is successfully compressed to 57.29 fs in only 5.1-cm propagation,along with a compression factor F,of 17.46.We demonstrated that the impacts of HOD and HON are minor on the pulse compression process,compared with that of a and variation of ?(z).We also study the 2-soliton breather pulse compression in the designed waveguide taper.A 1 ps input pulse at wavelength 2490 nm is compressed to 72.58 fs in 2.09-cm propagation.4.The SC generation is one of the important applications of ultrashort pulses generated by the pulse compression.In this paper,simple silicon straight waveguide is designed for the SC generation.At wavelength 2490 nm,a 57.29 fs input pulse with peak power of 100 W generates a highly coherent and octave spanning SC with the width at-40 dB level of 1851 nm in a 2.06-mm propagation.We also investigate the influence factors on the SC generation.In this paper,the self-similar pulse compression of the fundamental soliton and its application in SC generation are investigated by using the good optical characteristics of silicon waveguide.The research results provide a promising solution for the realization of on-chip ultrashort pulse sources for nonlinear photonics and spectroscopy in the mid-infrared spectral region.