Research On Properties Of Quasi-phase Matched Crystal-based Wavelength Converter

Application of quasi-phase matching for wavelength conversion technology wasstudied in this paper, focusing on the influence of non-uniform quasi-phase matching(QPM) structure on wavelength converter characteristics. The phase-dismatching amonginteracting light waves can be efficiently compensated by use of the QPM technology,i.e., using nonlinear polarizability cycle to realize nonlinear optical frequency conversionefficiency enhancement. Thus it is used in many areas. In this dissertation, the gratingstructure is investigated theoretically and numerically, a reasonable set of structuralparameters to extend the wavelength conversion bandwidth, and remain with highwavelength conversion efficiency while limiting efficiency volatility curve.First, the paper describes the basic principles of QPM technology applications inoptical communication systems, an important role and the status of the development ofdomestic and international research progresses, Introduces the characteristics ofperiodically poled crystals and the application in terms of wavelength conversion.Secondly, analysis based on the principle of QPM wavelength conversion technology,provides a theoretical basis for the study of future all-optical wavelength conversion.Thirdly, the use of the ladder segmented QPM structure is based on a singlepass/double-pass cascaded harmonic+difference(SHG+DFG) wavelength conversionprocess conducted a theoretical study of the effect when the crystal length unchanged,increased by the number of ladder sections, rational design the initial parameters of thepolarization cycle segment the change amount of step between adjacent segments, whilethe high flatness, a large bandwidth and high conversion efficiency can be obtained;analysis the impact of the wavelength conversion characteristic according to the designedstructure parameters. Finally, analysis the effect of uniform segmented QPM structurebased on single-pass/double-pass cascaded sum+difference frequency (SFG+DFG)wavelength converter characteristics, increasing segmentation the number and rationaldesign of structural parameters can be greatly expand the bandwidth of the signal light toensure obtained a high conversion efficiency; addition, the influence of the crystal lengthto the converter bandwidth, efficiency and gain characteristic of the flatness. Above all,the study provides a theoretical guidance for developing QPM wavelength convertion.