紫外飞秒脉冲光刻全光开关光纤光栅的实验研究

This project intends to use the nonlinear frequency conversion technology, transfer of ultrashort pulse infrared wavelengths to get uv ultraviolet band femtosecond laser pulses, and the micro-nano optical fiber, optical fiber Bragg grating, and the ultraviolet pulse laser lithography micro processing technology, the combination of all three developing high performance based on micro-nano optical fiber Bragg grating, fiber optical switch and the beam splitter. Have reported splitting grating based on the type of surface relief, mostly because of the incident light in a air and grating substrate interface reflection, there is a disadvantage of low diffraction efficiency, thus the project intends to carry out the following specific research (1) study how to adopt the ultraviolet frequency doubling crystal KBBF will titanium sapphire laser double frequency to 200 nm uv light directly frequency band, and get a single pulse energy is as high as mJ level, suitable for 5 um optical fiber core lithography uv ultrashort pulse; (2) experimental study ultraviolet femtosecond laser point compose the production process, fiber grating to realize a variety of size and the structure of the beam splitter grating fabrication; (3) to improve the diffraction efficiency of optical fiber grating splitter, research based on broadband multilayer grating structure basic theory and key technology of high efficient beam splitter, instead of surface relief through the structure type, improve the broadband characteristic of grating. The project in high-speed optical communication system and integration of optical field has extensive application value.

拟利用非线性频率转换将红外波段超短脉冲转换到UV波段获得紫外飞秒激光脉冲，并将光纤布拉格光栅、微纳光纤与紫外脉冲激光光刻微加工技术三者相结合，研制基于微纳光纤布拉格光栅的高性能全光纤光开关及其分束器。已报道的分束光栅大多基于表面浮雕型，由于入射光在光栅一空气和光栅一基底界面反射，存在着衍射效率低的缺点，因而本项目拟开展如下具体研究(1)如何釆用紫外倍频晶体KBBF将钛宝石激光器的二倍频光直接进行频率上转到200 nm紫外波段，并获得单脉冲能量高达0.1mJ，适用于5um光纤纤芯光刻的紫外超短脉冲；(2)实验研究紫外飞秒激光逐点刻写光纤光栅的制作工艺，实现多种光栅尺寸和分束器结构的制作；(3)为提高光纤光栅分束器的衍射效率，研究基于多层光栅结构的宽带高效率分束器的基础理论和关键技术，通过该结构代替表面浮雕型，提高光栅的宽带特性。此项目的研究在高速光通信系统和集成光学领域具有广泛的应用。

本项目在项目开展四年中，成功实现利用非线性频率转换将红外波段超短脉冲转换到UV波段获得紫外飞秒激光脉冲，并将光纤布拉格光栅、微纳光纤与紫外脉冲激光光刻微加工技术三者相结合，研制得到基于微纳光纤布拉格光栅的高性能全光纤光开关及其分束器，具体的研究目标依期实现，包括有：产生了267nm的单脉冲能量达到0.83mJ，实现了紫外激光在光纤的纤芯光刻；实验上利用以上紫外飞秒激光的高重复频率特性所搭建的飞秒激光微加工系统，结合所编写得到的程序精密控制三维移动平台移动路径和高速快门，在加工功率为365mＷ、移动速率为１ｍｍ/s时，利用直写技术在无胶铬版上得到了微米量级的任意形状的平面衍射光栅；其中工业相机对光栅制备过程进行实时监视，保证了光栅的加工质量；制备的光栅在显微镜下观察，条纹边缘清晰、线纹粗细均匀，使用氦氖激光照射加工的光栅，可以获得清晰、稳定、与理论符合很好的夫琅和费衍射图样，显示了所加工的光栅具有良好的光学性能，实验结果也表明了紫外飞秒激光在光栅制作过程中所具备的良好的加工性能；结合光电图像处理的对准技术而完成的紫外飞秒激光逐点刻写光纤光栅制作工艺，实现多种光栅尺寸和分束器结构的制作；提高了光纤光栅分束器的衍射效率，解决了多层光栅结构的宽带高效率分束器的基础理论和关键技术，提高了光栅的宽带特性。相应的研究成果报道见报于高速光通信系统领域，实现在集成光学领域的应用。