Study On Splitting Performance Of Diffraction Grating Under A Littrow Mounting

With the rapid development of the modern optoelectronic industry,a variety of precision optical devices have appeared in the industry,and such devices have extremely high requirements for integration.Diffraction gratings,which are based on highly integrated and high-precision structures,are widely used in various optical devices or systems to meet these industrial needs.With the diversification of high-precision devices,the industry has put forward higher requirements for the structure and performance of the diffractive devices.Nowadays,some of the diffractive devices on the market have not met the demand and are being slowly eliminated.For such an excellent device with high diffraction efficiency,research should be accelerated on its diverse structure and efficiency.Therefore,It is necessary to meet industrial needs that research on various new structures and properties of micro-nano gratings.This paper is based on the rigorous coupled wave analysis and modal methods to study the different structures and different properties of multilayer micro-nano gratings:1.This paper presents a single-port high-efficient metal dielectric grating with a wide spectrum and angular bandwidth under a Littrow mounting.In a three-layer grating ridge structure,transverse electric(TE)polarization and transverse magnetic(TM)polarization,the efficiency of-1st order can reach 97.3% and 96.0%,respectively.For TE and TM polarization,the diffraction efficiency exceeds 95% over a wavelength band of 150 nm and an angle of incidence of 8.6°.In the structure of a single-layer grating ridge with cover layer and a connection layer,it has high manufacturing tolerances.When the groove depth is between 1.75 μm and 1.87 μm and the duty ratio is 0.63-0.67,the-1st order efficiency of TE and TM are over 95%.It has great significance.The incident wavelength is1527-1581 nm and the incident angle is 19.1°-21.5°,the-1st order efficiency of TE and TM will reach over 90%.In the design of single-channel high efficiency grating,the simple field mode method is used to pre-estimate the grating parameters,and an approximate range of parameters is obtained.Based on the obtained range,the exact coupling wave method is used to obtain accurate parameters.2.This paper presents a three-layer polarization-selective dielectric grating with a wideangular bandwidth under Littrow mounting.TE polarization is equivalent to a high efficiency grating.The TM polarization is equivalent to a two-port beam splitter.At the same time,this grating device exhibits a certain angular bandwidth advantage,that is to say,the incident angle is not limited to a certain angle.This device combines the advantages of high-efficiency and split-beam gratings,and its contribution to integration is extremely significant.3.This paper presents a two-port beam splitting grating with uniform beam splitting and wide angular bandwidth under a Littrow mounting.The splitting performance of the two structures is discussed.The first one is a single-layered grating structure with a connecting layer,and the second is a single-layered grating structure with a covering layer.They can be divided into two stages of TE or TM polarization with good uniformity.In the first structure,for TE polarization,the efficiency of 49.50% and 49.53% can occur in-1st order and 0th order under optimized grating parameters,respectively.for TM polarization,the efficiencies of 49.32% and 49.62% appear on the-1st order and 0th order under optimized grating parameters,respectively.Improved efficiency compared to simple grating beam splitters.In the second structure,the TE polarization achieves an efficiency of more than 45% for both stages in the wavelength range of 750 nm to 843 nm and the angle range of 23.7° to 36.8°.The TM polarization achieves an efficiency greater of more than 45% for both stage in the wavelength range of 775 nm to 827 nm and the angle range of 21.1° to 37.1°.