Determination And Locking Of Relative Phase Of Laser’s Multiple Transverse Modes

This article presents the word template for Doctor’s(Master’s)At present,laser has become an important tool of modern optics applied to scientific research,industry and military fields.The traditional application mostly uses the basic mode of laser.With the development of science and technology,the high-order mode of laser has some advantages in some specific fields,such as optical imaging,precise displacement detection,atom capture and quantum information transmission,because of its special spatial structure and orthogonal characteristics.There are two common high-order modes of laser: Hermite mode and Laguerre Gauss mode.In the field of space quantum precise measurement,these two modes correspond to different measurement physical quantities,Hermite Gauss mode corresponds to laser lateral displacement and angle measurement,Laguerre Gauss mode corresponds to space angle and orbit angular momentum measurement.In this kind of space precise measurement,the coupling or separation of two or more beams with different modes is often involved,and a certain relative phase is required between them.Different from the coupling between the traditional fundamental modes or the same order modes,the relative phase between different modes is not only related to the propagation phase,but also related to the Gouy phase of the higher order mode.And because the Gouy phase is related to the propagation position,it increases the difficulty of relative phase determination and locking.In order to solve the above problems,this paper focuses on the generation of the mode with high order and the determination and locking of the relative phase between the transverse modes.1.The generation principle and mode of Hermite Gaussian beam are analyzed theoretically.The proportion of higher-order mode excited by different translation is obtained,and the theoretical curve is drawn.In order to facilitate the preparation of Hermite high-order modes with lower order,mode cleaner is generally used as mode conversion cavity to prepare high-order modes.This method is simple and commonly used in the experiment.For higher order modes,spatial light modulator is used to prepare high-order modes,but the loss of optical power in this way is large.Therefore,in the experiment,we need to choose the appropriate method to prepare the high-order modes according to the situation.2.Through the way of sampling the part of the spot to obtain the interference curve of the interference intensity changing with the phase,the numerical calculation is carried out and the phase determination and locking method between different higher-order modes are simulated.In the experiment,4f system is used to compensate the Gouy phase difference in the process of beam propagation,and the method of phase determination and locking between different high-order Hermite Gaussian beams is verified.3.This paper introduces the application of multi-mode relative phase locking in quantum precise measurement,and the principle and scheme of using multi-mode squeezed state to improve the measurement accuracy of displacement and dip angle,which provides theoretical support and technical support for future quantum precise measurement experiments.