Department of Engineering Science, University of Oxford, Oxford, United Kingdom.
Opt Lett. 2012 Feb 15;37(4):470-2. doi: 10.1364/OL.37.000470.
We demonstrate an improved method for fabricating optical waveguides in bulk materials by means of femtosecond laser writing. We use an LC spatial light modulator (SLM) to shape the beam focus by generating adaptive slit illumination in the pupil of the objective lens. A diffraction grating is applied in a strip across the SLM to simulate a slit, with the first diffracted order mapped onto the pupil plane of the objective lens while the zeroth order is blocked. This technique enables real-time control of the beam-shaping parameters during writing, facilitating the fabrication of more complicated structures than is possible using nonadaptive methods. Waveguides are demonstrated in fused silica with a coupling loss to single-mode fibers in the range of 0.2 to 0.5 dB and propagation loss <0.4 dB/cm.
我们展示了一种通过飞秒激光写入在体材料中制造光波导的改进方法。我们使用 LC 空间光调制器 (SLM) 通过在物镜的光瞳中产生自适应狭缝照明来改变光束焦点的形状。衍射光栅以条状形式应用于 SLM 上，以模拟狭缝，第一级衍射光被映射到物镜的光瞳平面上，而零级光则被阻挡。这种技术能够在写入过程中实时控制光束整形参数，从而能够制造出比使用非自适应方法更复杂的结构。我们在熔融石英中演示了波导，其与单模光纤的耦合损耗在 0.2 到 0.5 dB 之间，传播损耗<0.4 dB/cm。
