Three-dimensional microphotonic optical systems

本研究的目的是：1)研究超短激光脉冲诱导光折变晶体和掺锗硅玻璃的折射率变化机理；2)制作和评价玻璃内部的微结构，如波导、分压器、耦合器和小布拉格反射器。在研究期间获得的结果如下。1)利用自捕获光丝诱导折射率变化我们利用飞秒激光脉冲（800 nm）聚焦到硅玻璃上形成的光丝诱导折射率变化。折射率变化区域的直径约为2μm，长度为几十~几百mm，最大折射率变化为0.01.2)双折射微光子元件的制备通过对超短激光脉冲形成的灯丝进行机械平移，制备了损耗可忽略的光波导（芯径2μm，长度2 mm）。我们进一步发现这些波导具有双折射特性，并利用这些波导制作光栅来评估其双折射特性。3)孔洞的光学捕获与形成利用高na物镜聚焦超短激光脉冲，在玻璃内部形成孔洞。利用扫描电子束显微镜对玻璃内部形成空隙进行了切割和观察。我们认为这些空洞是玻璃内部的空洞。我们通过重复超短激光脉冲的照射和聚焦透镜的平移，成功地使空洞沿光轴移动了约5μm。我们还成功地将两个空间合二为一。不幸的是，这些结果并没有导致对机制的直接阐明。然而，它们为解释二氧化硅玻璃折射率变化的机理提供了强有力的线索。这项工作的一部分已经发表在《光学快报》上，正在准备出版。在日本科学技术公司的帮助下，正在申请两项与空洞的运动和合并以及双折射光波导的形成有关的专利。技术杂志《激光聚焦世界》（2001年第37卷第2期）收录了空洞运动和合并的结果。少

The purpose of this research was 1) the investigation of the mechanism of refractive index changes in photorefractive crystal and Ge-doped silica glass that are induced by ultrashort laser pulses and and 2) fabrication and evaluation of microstructures inside glass such as the waveguides, dividers, couplers and small Bragg reflectors. The results obtained in the research term are listed below.1) Induction of refractive index change by self-trapped filamentsWe induced the refractive index change by using the filaments formed by femtosecond laser pulses (800 nm) focused into the silica glass. The diameter of the area of refractive index change was approximately 2μm and the length was several ten to several hundred mm. The maximum refractive index change was 0.01.2) Fabrication of birefringent microphotonic elementsBy mechanically translating the filament formed by the ultrashort laser pulses, we fabricated optical waveguides with negligible loss (core diameter ; 2μm, length ; 2 mm). We f … More ound that the waveguides had birefringence and evaluated the birefringence by making a grating with these waveguides.3) Optical seizing and mering of voidsWe focused the ultrashort laser pulses by high-NA objectives and formed voids inside glass. We cleaved the glass inside which voids are formed and observed the void by scanning electron-beam microscope. We identified the voids as the vacancies inside the glass. We succeeded in moving the void by approximately 5μm along the optical axis by repeating the irradiation of the ultrashort laser pulse and translation of the focusing lens. We also succeeded in merging the two voids into one.These results do not unfortunately lead to the direct elucidation of the mechanism. However, they provide strong clues to the interpretation of the mechanism of refractive index change in silica glass.A part of this work has been published in Optics Letters and is under preparation for publication. Two patents related to the movement and merger of voids and formation of birefringent optical waveguides are under application by the help of Japan Science and Technology Corporation. The results of movement and merger of voids are picked up by the technical magazine, Laser Focus World (Vol.37, Issue 2, 2001). Less