光束偏振态斯托克斯参量的实时测量

【作者】 史萌；

【导师】 吴福全；

【作者基本信息】 曲阜师范大学 ， 光学， 2006， 硕士

【摘要】 伴随着信息时代的来临,人们越来越注重对信息载体的拓展。偏振作为光的本质属性之一,不仅其地位与光的其他主要属性如振幅、频率、位相是等同的,更重要的是它也可以作为信息调制的载体:物体发射或反射光束的偏振态携带有物体本身丰富的信息;使用偏振光与待测物体发生相互作用的过程就是将物体的信息加载到光束偏振态上的过程,对偏振态的测量和分析相当于对加载信息的解调过程,由此可以获取待测物体的信息。 描述光束偏振态最普遍最全面的方法,是用一组物理量纲完全相同的参量——斯托克斯参量来描述的。而将描述器件性质的米勒矩阵与斯托克斯参量相结合,能够解决几乎所有的偏振光传播问题。 查阅文献资料得知,目前国内对斯托克斯参量的测量基本上还是停留在单光路测量,采集数据。其方法是使入射光束经过一系列的光学元件,通过机械转动或连续的周期性调制改变元件状态来改变光束的偏振态,先后四次测量光强,最后计算出斯托克斯参量的四个分量。这种测量的弊端在于费时麻烦,不能测量出某个确定时刻光束的偏振态,因此不能适用于脉冲激光及偏振态迅速变化的光束。而在光纤通信,尤其是相干光通信中,在环境比较恶劣的情况下,光纤中偏振态的变化速率小于10ms;在光纤传感中,对实时性的要求也很高,要求在变化超出允许范围时及时发出警告。所有这些都要求能够实时测量光的偏振态,这也是我们设计实施光束斯托克斯参量实时测量系统的初衷。 我们搭建的系统在光路的设计中引入分振幅方法,将单光路拓展为四光路,由四个统一定标的光电探测器来接收探测光强。我们在器件的选取、光路的设计、程序的编制、误差分析等方面做了一些具体的工作,研制出了一套集光、机、电、算一体化的斯托克斯参量测量系统。针对所做的主要工作,本论文主要从以下几个方面进行了论述: 第一章主要介绍了斯托克斯参量的发展历史及现状,指出对其进行实时测量的意义,并简要概括自己的工作重点。在第二章中,主要介绍了描述光束偏振态的几种典型方法,以及它们之间的相互关系,突出强调了斯托克斯参量表示法的普遍性和通用性。更多还原

【Abstract】 With the arrival of information age, people pay more and more attention to the expansion of information carrier. Polarization , regarded as one of the essential attributes of light, not only its position is equivalent to light’s other main attributes such as amplitude , frequency , location looks, more importantly, it can also be used as information modulation carriers: the polarization states of the light beam that the object launches or reflects carry abundant information of the object;the course of using polarized light interacted with the to-be measured object happens to be that of loading the information of the object to the polarized states of light beam, the measurement and analysis of the polarization states is equivalent to the course the demodulation of the loaded information, therefore we can obtain the information of the to-be-measured object.The most general and the most overall method of describing the polarization state of light beam is to use a group of parameters with all the same physical dimension - -Stokes parameter. And the combination of matrix of Muller which describes properties of devices with Stokes parameter can solve almost all problems of the propagate of the polarized lights.Consulting the documents and materials, we know at present he domestic measurement of Stokes parameter basically stays on the single way, gathering the data. Its method is to make incidence light beam go through a series of optical components, through machinery rotating or continuous periodic modulation to change component state in order to change the polarization state of light beam, measure the light intensity four times successively, and finally calculate four pieces of weight of Stokes parameter. This kind of measurement is time-consuming, and it can’t measure the polarization state of light beam at a certain moment. Therefore it is not suitable for pulse laser and the light beam with fast-moving polarization state. Among fiber optic communication, especially relevant photo-communication, in abominable environment, the change speed of the polarization state in the optic fibre is less than 10ms;In the optic fibre sensing,it requires real time character strictly, and it requires immediate warning while the change goes beyond the allowed range. All these require real-time measurement of polarization state, which is also the original intention of our designing and implementing the real-time measuring system of Stokes parameter of light beam.The system that we build introduces the method of dividing the amplitude method in the design of the light way, expands single light way into four ways, and uses four photodiode with standard made in unison to receive and survey the light intensity. We have done some concrete work in such aspects as the choosing of the device , design of light way, establishment of the procedures, error analysis, and develop a system of Stokes parameter measurement, which integrates light, machine , electricity and calculation. To the groundwork done, this thesis mainly discusses from the following aspects:Chapter one mainly introduces the history of Stokes parameter development and its current situation , points out the significance of its real-time measurement, and briefly summarizes the focal point of work .In chapter two, it mainly introduces several typical methods of measuring the polarization state of light beam, and the interrelationship between them, and stress the universality and commonability of the expression method of Stokes parameter.Chapter three lays particular emphasis on the deriving of systematic theory and principle. It leads out and the condition of the systematic optimization, introduces the treatment method of the key problems in the course of finalizing the bid detailedly, and finally designs the mathematics method which describes the polarization state differences.Chapter four describes the design and making of the key device of the system -the polarization-independent beam splitter. Under the guidance of system optimization theory in chapter three, the method that we adopt is to coat the single layer of mediums film on the incidence terminal surface of the beamsplitter, through choosing the reflecting index and thickness of film, as well as the design of the prism structure, concerned the light beam with a consulting wavelength X and a certain incidence $, it can make the beam splitter realize the polarization-independent beam splitting over a broad spectra including the consulting wavelength.In chapter five, firstly ,we provide the experiment apparatus used in the experiment, and introduce the adjustment and test steps of light path. Secondly, we use the mathematics tool to analyze the systematic principle , draw the general conclusion and carry on error analysis.The innovation of this thesis liese in chapters 3,4,and 5, which involves the systematic optimization theory, the promotion of the hardware performance and setting-up of error analysis standard.更多还原