Measurement of the Transient Spatial Profiles of Refractive Index and Lattice Temperature during Femtosecond Pulse Inscription in Fused Silica

自1996年飞秒~（fs）激光诱导各种透明材料的折射率变化实验发明以来，人们对其越来越感兴趣。铭文过程中涉及的物理过程尚未完全了解，铭文技术有待改进并变得更加可重复，重要的是，进一步发展表征和理解过程的测量技术。该计划旨在开发技术，以测量折射率和晶格温度的瞬态空间分布在飞秒光脉冲刻录过程中的平面硅器件。这项研究将导致刻字过程的改进和在线监测工具，可以提供飞秒激光刻字系统的可重复性和控制方面的重大改进。我们打算开发的两种特殊技术是nomarsky差分干涉对比（DIC）显微镜，用于在微米尺度上提供折射率变化的定性测量，以及使用Yb$^{3+}$掺杂玻璃的泵浦/探针实验，以测量空间瞬态晶格温度分布-据我们所知，以前没有观察到注入二氧化硅的情况。该项目的主要费用是资助访问研究员oleksandr Turchyn的4次访问（相当于他两年时间中的一年），他在对该项目重要的固态材料进行光学测量方面具有丰富的经验。需要一些额外的资源，如额外的组件，使我们能够构建必要的实验设备来执行拟议的测量。

Since its experimental invention in 1996 femtosecond~(fs) laserinduced modification of refractive index in variety of transparentmaterials has been of growing interest. The physical processesinvolved in the inscription processes are not fully understood and ifinscription techniques are to improve and become more repeatable it isimportant that measurement techniques to characterise and understandthe processes be further developed.This program seeks to develop techniques to measure the transientspatial profiles of refractive index and lattice temperature duringthe femtosecond optical pulse inscription process in planar silicadevices. This investigation will lead to improvements in theinscription process and to on-line monitoring tools whichcould offer significant improvements in the repeatability and controlof femtosecond laser inscription systems.Two particular techniques which we intend to develop are NomarskyDifferential Interference Contrast (DIC) microscopy to provide aqualitative measurement of refractive index variation on a micrometerscale and pump/probe experiments using Yb$^{3+}$ doped glass tomeasure the spatial transient lattice temperature profile - somethingwhich to the best of our knowledge has not previously been observed infused silica. The major cost of this project is to fund 4 visits (amounting to a oneyear of his time spread over two years in total) by visiting fellowOleksandr Turchyn who has significant experience in performing opticalmeasurements on solid state materials important for this project. Someadditional resources are required in terms of additional components toenable us to construct the experimental equipment necessary to performthe proposed measurements.