Study On Diffraction Characteristics Of Reflection Echelon Grating

With the rapid development of optical communications and the dense wave division multiplexing,the increasingly complex network topology for reliable and flexible network management requirements are higher and higher.Optical cross-connext(OXC) technology is one of the key technologies.Optical switches are key components in OXC.especially the all-optical cross-connect devices without photoelectric and electro-optical conversion directly determines the optical communication network's performance.The low loss,low-cost,highreliability,ease of mass production of optical switches,particularly suitable for wavelength division multiplexing optical switch is an urgent need.This paper binding optical switches'development at home and abroad,withemphasis on the key components of reflection gratings micro-optical switch array,making further study on the reflection echelon grating diffraction characteristics.Reflection echelon grating is one of the binary optical elements,it has some advantages such as miniaturization,can be copied,integration,low cost,which make it having broad application prospects.As a dispersion element,it has broad application spectrum area,high resolution,high diffraction efficiency,these are research hotspots of reflection echelon grating.This paper makes further study of diffraction characteristics of the reflection echelon grating.For binary optical elements,diffraction efficiency is one of the important performance index. With the development of the grating theory,there are lots of methods to solve grating diffraction's problems.These methods can be divided into two main categories: the scalar diffraction theory and the vector diffraction theory. This paper completes the following work:①It reviews the development history and mainstream technology of gratings and Binary optical elements.②This paper is focus on the reflection echelon grating. Based on the scalar diffraction theory, the geometric method is used to calculate the distribution of optical path difference of the beam in the edge of steps under the light beam's oblique incidence. According to the multi-slit Fraunhofer diffraction,we derive the reflection echelon grating's diffraction intensity expression . On the basis of that,we discuss the number of the reflection echelon grating's steps'change. On the two limiting cases: the number is 2 and the number tends to infinity , how the light intensity formula of the reflection echelon grating changes.③Based on the basis of the reflection echelon grating's light intensity formula, we gain a diffraction efficiency formula model under the normal incidence of the light diffraction.Based on the formula model,we deduce the expression of diffraction efficiency which is different from that of other articles.We discuss in details about the impacts of the reflection echelon grating's step number and the ratio of the grating's etching depth and the light's wavelength on the maxmum diffraction efficiency and the blazed order.The diffraction efficiency formula is a periodic function about H /λ.Through the changes of H /λin the first half cycle ,in the later half cycle and outside of the cycle,we calculate the maximum diffraction efficiency under the three cases.According to the maximum diffraction efficiency's diffraction order,we obtain the formula model's blazed conditions. Through a number of experimental data,we confirm that the formula model's blazed conditions is also the reflection echelon grating's blazed congditions under the light's normal incidence.We also confirm that H /λis the key factor ,which impacts the maximum diffraction efficiency's distribution of the reflection echelon grating.④When the incident light oblique incidence,the maximum diffraction efficiency is distributed in a diffraction order as the incidence angle changes with a certain range.This diffraction is still determined by H /λ. As the incident angle increases, the maximum diffraction efficiency changes from one diffraction order to another .The changing direction is from big to small.⑤Through the analysis of reflection echelon grating diffraction efficiency,we gain the corresponding systems theory and research methods,and provide a new way for optical switches'design.