Beam Polarization State Of The Real-time Measurement Of The Stokes Parameters

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.