Research On Double Row Dislocation Laser Array Generation Based On Multi-step Phase Relief

Laser array generation is an optical element which is used to split the incident light beam into a laser beam array,and it is widely used in many optical fields such as accurate measurement,laser processing,machine vision guidance and so on.This thesis presents a double row dislocation laser array for the requirement of planet lander large area mapping with high efficiency.The laser array is different from output distribution of the traditional laser generation that is not 1×N or N×N.In the process of mapping in large area,the advantage is that it can increase the effective area,at the same time,it only have a fewer data volume and shorter processing time.The characteristics of double row dislocation array determine that the generation must have the characteristics of large divergence angle,high diffraction efficiency and good uniformity of the spots.The author developed a laser array generation based on multi-step phase relief which can generate the 9/8 double row dislocation array,to the study of high efficiency special fractional laser array generation with large divergence angle,the planet lander vision guidance and laser radar technology has greater role in promoting and application value.On the basis of the design principle and method of the laser array generation,we use the rigorous coupled wave method to analyze the structure.This thesis presents an improved method for the rigorous coupled wave analysis of multilayer relief structures,which realized the high calculation efficiency under the condition of numerical stability.We also discuss the principle of generating double row dislocation array of finite periodic discrete complex relief structure,design a four step 9/8 double row dislocation array laser generation,and conduct the simulation on it.According to the requirement of the manufacture precision of the resist mask and the existing condition of the laboratory,the preparation of the mask by the electron beam lithography is selected.For the alignment error on the resist mask surface precision in the preparation process of the multi-step relief structure in electron beam exposure process,we put forward the process of using a two-consecutive exposure to prepare multi-step relief structure on a resist layer.Exposure process and parameters of the preparation process is an important part of the preparation process.We use the variable acceleration voltage and variable dose exposure method with the same size and thickness of resist agent layer to discuss the impact of different acceleration voltage on exposure depth in detail,obtain the relationship between exposure limits of the depth value and the electron beam energy on different accelerating voltages with critical exposure dose,and determine the optimal parameters of process.At the same time,the problem of crack phenomenon in the resist layer after development is solved.We discuss the relationship of the radio-frequency power,working pressure,gas flow rate,substrate temperature,and O2,and the etching rate,the etching surface morphology and sidewall steepness,analyze the etching rate ratio of quartz substrate,Cr film and ZEP520,design the reactive ion etching process,which is with the multi-step subdivision variable frequency power and variable gas flow rate,realize the relatively independent etching process of the quartz substrate and Cr film masking layer.The process consists of 13 steps,which not only effectively ensures the accuracy of pattern transfer,but also produces a certain compensation for obtrapezoid resist layer in the electron beam lithography process.It lays a technical foundation for the good performance of the generation.Based to the above research,the 9/8 double row dislocation array laser generation is completed,and the test systems for spots quality and location are built.The test results show that,on the basis of meeting the requirements of spots position,the total diffraction efficiency of the generated 9/8 double row dislocation array is reach 80%,and the uniformity of the spot is more than 90%,which meets the design requirements.To sum up,the design parameters and the test results of the 9/8 double row dislocation laser array generation based on multi-step DOE can meet the design index requirement of the monocular vision navigation system for the star landing vehicle,verify the feasibility of relevant key technology solution,solve the development problem of the key device of monocular vision navigation laser array of the star landing vehicle.The key technology of this paper can also be applied in other fields such as laser range finder,intelligent transportation and so on.