Abstract

We study the possibility of application of direct laser writing technique for the fabrication of large-size uniform phase structures in the bulk of the borosilicate glass N-BK7. The morphology and the type of modifications induced by the sub-picosecond (500 fs) pulses are studied depending on the energy dose of irradiation. We show that with moderate focusing and at pulse energies below the threshold of self-focusing effects, it is possible to choose writing regimes (the scanning speed, the repetition rate of pulses) which allow the fabrication of extended structures with flat modification of the glass refractive index in the layer-by-layer scanning mode. At higher peak intensities of the laser, the Kerr nonlinearities affect the pulse propagation and the dynamics of the relaxation processes, and the resulting structures are essentially inhomogeneous with the alternating sign of refractive index change. To validate the approach, a buried phase structure with large dimensions was fabricated showing a rather uniform refractive index change over the entire processed range.

中文翻译：

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使用超短激光脉冲在N-BK7玻璃的整体中制造均匀的相结构

摘要

我们研究了应用直接激光写入技术在硼硅玻璃N-BK7的整体中制造大尺寸均匀相结构的可能性。根据辐射的能量剂量，研究了亚皮秒（500 fs）脉冲引起的形貌和修饰类型。我们表明，在适度聚焦和脉冲能量低于自聚焦效应阈值的情况下，可以选择写入方式（扫描速度，脉冲重复率），该方式允许对玻璃进行平面修饰来制造扩展结构逐层扫描模式下的折射率。在较高的激光峰值强度下，克尔非线性会影响脉冲传播和弛豫过程的动力学，并且所得的结构基本上与折射率变化的交替符号不均匀。为了验证该方法，制造了具有大尺寸的掩埋相结构，其在整个加工范围内显示出相当均匀的折射率变化。