超连续谱激光产生中的光谱调控机理研究

The supercontinuum(SC) laser has wide application prospects in fields of Information, Biomedicine and Industry, etc. Nowadays,how to control the output spectra of the supercontinuum has become one of the bottlenecks which restrict the improvement of its performance and applications. Therefore, it is of great significance to carry out the research on the mechanisms of the tunable broadband spectra both in scientific research and application fields. In the programme, special attention has been paid on the key factors which influence the supercontinuum’s tunable spectra, and corresponding research has been carried out. Starting from the generalized nonlinear Schrödinger equation, using the Split-Step Fourier Method, research has been done theoretically on the process of supercontinuum generation(SCG)in photonic crystal fiber(PCF). The major mechanisms for the partially spectra-enhancement and spectral tuning have been explored, based on the combination of the characteristics of the pump source and the parameters of the fiber; the main factors for the spectral flatting have been investigated, and the evaluation of the flatter spectra has been done; the theoretical model and corresponding software for the SC spectral tuning have been established, while the design for the control of broadband spectra has been proposed. The experimental setup for tunable, flatter SCG in PCF has been constructed. Compared with theoretical results, better parameters of the pump source and the fiber have been chosen, then the setup has been optimized, and finally SCs with flatter spectra, or tunable spectra have been obtained. The results can be used as the basis of the optimization for SCG’s performances.

超连续谱激光在信息、生物医学和工业等领域有着广泛的应用前景。目前，超连续谱光源的光谱可控性问题已成为制约其性能提升及应用的瓶颈之一，因此对超连续谱的光谱调控机理的研究具有重要的学术价值和应用价值。本项目针对影响超连续谱激光输出光谱可控性的关键问题展开研究：采用广义非线性薛定谔方程以及分步傅里叶变换法对光子晶体光纤(PCF)中超连续谱产生(SCG)过程进行理论研究，结合泵浦源特性和光纤特性参数，探索实现超连续谱局域波段增强与光谱调控的主要机制；研究影响输出光谱平滑化的主要因素，建立表征方法；研究建立超连续谱激光光谱调谐的理论模型与软件，提出实现超连续谱光谱调控的设计方案。搭建PCF中可调谐、平坦超连续谱激光产生的实验装置，结合理论研究结果，优选泵浦源参数和光纤微结构参数，优化和改进已有的实验装置，获得具有较好的光谱平滑化，光谱可调谐的超连续谱输出。研究结果将为超连续谱激光性能的优化奠定基础。

超连续谱光源的光谱可控性问题已成为制约其性能提升及应用的瓶颈之一，因此对超连续谱的光谱调控机理的研究具有重要的学术价值和应用价值。我们针对影响超连续谱激光输出光谱可控性的关键问题开展了理论和实验研究，取得以下成果：采用广义非线性薛定谔方程以及分步傅里叶变换法对光子晶体光纤(PCF)中超连续谱产生(SCG)过程进行了理论研究，结合泵浦源特性和光纤特性参数，分析了超连续谱局域波段增强与光谱调控的主要机制；提出了光谱平坦度参数(Spectral Flatness Measure，简称SFM)用于表征超连续谱(SC谱)激光的平坦性。研究了基于液芯的单芯PCF、多芯PCF微结构参数对SC谱输出平坦性的影响。着重针对给定结构的基于液芯的单芯PCF和多芯PCF，分析了泵浦光特性参数对输出的SC谱的平坦性和光谱的影响。研究了液体CS2填充的不同微结构PCF——仅有一个中心孔液芯阶跃型导光的光纤（LCOF）和两种PCF（三角形格子排布（TLCPCF）、正四边形格子排布（QLCPCF））中SC谱的局域调谐和局域增强的机理。分别搭建了纳秒脉冲泵浦PCF产生SC谱和皮秒脉冲泵浦PCF产生SC谱的实验装置，分析了泵浦参数以及光纤结构对产生SC谱的输出功率和输出光谱的影响。建立了超连续谱光谱控制模型与软件，系统分析了影响输出光谱局域谱特性、光谱平坦性以及光谱范围变化的关键因素和主要物理机制。研究结果将为超连续谱激光性能的优化奠定基础。