宽带脉冲压缩光栅研制：金属—介质膜光栅与后镀膜光栅
发布时间：2019-01-22 18:07
【摘要】：啁啾脉冲放大技术是产生高能脉冲激光的重要手段,脉冲压缩光栅是啁啾脉冲放大系统的核心器件。针对更短脉冲的放大需求,本论文研究金属-介质膜光栅和后镀膜光栅。金属-介质膜光栅指浮雕光栅结构刻蚀在金属-介质膜系表面形成的光栅,后镀膜光栅指在浮雕光栅表面镀金属层和介质膜层形成的光栅。金属-介质膜光栅的研制过程中,我们首先分析上海光机所提供的光栅设计槽形对应的工艺容差范围,在此基础上开始光栅制作工艺实验。首先,制作光刻胶掩模,并用氧气等离子体灰化手段对其槽深与占宽比进行修正;通过实验确定了金属-介质膜光栅占宽比与掩模占宽比的关系,掩模占宽比控制范围为0.14至0.18,刻蚀后可得到占宽比为0.15至0.21的金属-介质膜光栅。然后,我们通过实验确定了金属-介质膜光栅槽形在离子束刻蚀过程中的演化规律,建立对掩模槽深、占宽比变化不敏感的刻蚀监测模型,实现对金属-介质膜光栅刻蚀槽深的实时在线监测。根据实验结果,这一监测方法对槽深的控制范围为310nm至320nm,精度为10nm。我们制作完成的金属-介质膜光栅中衍射效率超过90%的最大带宽为169nm(705-874nm),带宽内平均效率93.71%,峰值是95.1%,位于810nm波长处。后镀膜光栅研制的探索性更强,我们通过实验确定了合适的基底材料与刻蚀工艺,并制作出了不同槽形参数的裸光栅基底。之后,实验对比了不同镀膜工艺的成膜质量,确定了合适的镀膜方案,即利用电子束蒸发工艺镀金膜,用离子束溅射镀膜工艺镀多层介质膜。我们制作完成的裸光栅槽深分布范围为170nm至370nm,占宽比范围是0.40-0.71。根据扫描电镜图片,分析这些裸光栅镀膜后的槽形演变规律,建立唯象的槽形演变模型。基于建立的光栅槽形演变模型,对后镀膜光栅参数进行优化设计,并对其工艺容差作理论分析。优化设计后的后镀膜光栅效率大于90%的带宽为100nm(755nm-855nm),峰值效率为95.70%(785nm波长处),755nm-845nm波长区间的平均效率为93.21%。优化设计与容差分析结果表明,在现有工艺条件下,优化得到的后镀膜光栅能够满足脉冲压缩光栅的效率指标要求,并具有较好的可加工性。
[Abstract]:Chirped pulse amplification is an important means to produce high energy pulse laser. Pulse compression grating is the core device of chirped pulse amplification system. In this paper, metal-dielectric film grating and post-coating grating are studied in order to amplify the shorter pulse. The metal-dielectric film grating refers to the gratings etched on the surface of the metal-dielectric film system by the structure of the relief grating, and the post-coated grating refers to the grating formed by the plating of metal layer and the dielectric film layer on the surface of the relief grating. In the development of metal-dielectric film gratings, we first analyze the corresponding technological tolerance range of grating design grooves provided by Shanghai Optical Machine, and on this basis begin the fabrication experiments of gratings. Firstly, the photolithographic mask is made and the depth and duty cycle of the cell are modified by oxygen plasma ashing. The relationship between the duty cycle ratio of the metal-dielectric film grating and the width ratio of the mask is determined by experiments. The control range of the mask duty ratio is from 0.14 to 0.18. After etching, the metal-dielectric film grating with the duty ratio of 0.15 to 0.21 can be obtained. Then, we determine the evolution rule of metal-dielectric film grating grooves in the process of ion beam etching through experiments, and establish a etching monitoring model which is not sensitive to the change of mask groove depth and width ratio. The real-time on-line monitoring of the etched groove depth of metal-dielectric film grating is realized. According to the experimental results, the control range of the groove depth is from 310nm to 320nm, and the precision is 10nm. The maximum bandwidth of diffraction efficiency over 90% in the fabricated metal-dielectric film grating is 169nm (705-874nm). The average bandwidth efficiency is 93.71 and the peak value is 95.1, which is located at the wavelength of 810nm. The experimental results show that the substrate material and etching process are suitable and the bare grating substrate with different grooves has been fabricated. After that, the film quality of different coating processes was compared, and the suitable coating scheme was determined, that is, using electron beam evaporation process to deposit gold film and ion beam sputtering process to deposit multilayer dielectric film. The groove depth distribution ranges from 170nm to 370 nm, and the ratio of width to width is 0.40-0.71. Based on scanning electron microscope (SEM) images, the evolution law of the grooves after these bare gratings were analyzed, and the phenomenological grooves evolution model was established. Based on the evolution model of grating grooves, the parameters of post-coating gratings are optimized and their technological tolerances are analyzed theoretically. After optimized design, 100nm (755nm-855nm), 95.70% peak efficiency (785nm wavelength) and 93.21% average efficiency of 755nm-845nm wavelength range can be obtained when the efficiency of post-coating grating is more than 90%. The results of optimum design and tolerance analysis show that the optimized post-coated grating can meet the efficiency requirements of pulse compression grating under the existing technological conditions and has good processability.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN25
[Abstract]:Chirped pulse amplification is an important means to produce high energy pulse laser. Pulse compression grating is the core device of chirped pulse amplification system. In this paper, metal-dielectric film grating and post-coating grating are studied in order to amplify the shorter pulse. The metal-dielectric film grating refers to the gratings etched on the surface of the metal-dielectric film system by the structure of the relief grating, and the post-coated grating refers to the grating formed by the plating of metal layer and the dielectric film layer on the surface of the relief grating. In the development of metal-dielectric film gratings, we first analyze the corresponding technological tolerance range of grating design grooves provided by Shanghai Optical Machine, and on this basis begin the fabrication experiments of gratings. Firstly, the photolithographic mask is made and the depth and duty cycle of the cell are modified by oxygen plasma ashing. The relationship between the duty cycle ratio of the metal-dielectric film grating and the width ratio of the mask is determined by experiments. The control range of the mask duty ratio is from 0.14 to 0.18. After etching, the metal-dielectric film grating with the duty ratio of 0.15 to 0.21 can be obtained. Then, we determine the evolution rule of metal-dielectric film grating grooves in the process of ion beam etching through experiments, and establish a etching monitoring model which is not sensitive to the change of mask groove depth and width ratio. The real-time on-line monitoring of the etched groove depth of metal-dielectric film grating is realized. According to the experimental results, the control range of the groove depth is from 310nm to 320nm, and the precision is 10nm. The maximum bandwidth of diffraction efficiency over 90% in the fabricated metal-dielectric film grating is 169nm (705-874nm). The average bandwidth efficiency is 93.71 and the peak value is 95.1, which is located at the wavelength of 810nm. The experimental results show that the substrate material and etching process are suitable and the bare grating substrate with different grooves has been fabricated. After that, the film quality of different coating processes was compared, and the suitable coating scheme was determined, that is, using electron beam evaporation process to deposit gold film and ion beam sputtering process to deposit multilayer dielectric film. The groove depth distribution ranges from 170nm to 370 nm, and the ratio of width to width is 0.40-0.71. Based on scanning electron microscope (SEM) images, the evolution law of the grooves after these bare gratings were analyzed, and the phenomenological grooves evolution model was established. Based on the evolution model of grating grooves, the parameters of post-coating gratings are optimized and their technological tolerances are analyzed theoretically. After optimized design, 100nm (755nm-855nm), 95.70% peak efficiency (785nm wavelength) and 93.21% average efficiency of 755nm-845nm wavelength range can be obtained when the efficiency of post-coating grating is more than 90%. The results of optimum design and tolerance analysis show that the optimized post-coated grating can meet the efficiency requirements of pulse compression grating under the existing technological conditions and has good processability.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN25
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