We investigate an observed lack of excitation symmetry of discrete diffraction patterns in periodic arrays of waveguides written by ultrafast laser inscription (ULI) in gallium lanthanum sulfide glasses. We found experimentally that successive waveguides written with identical parameters are detuned from the previous one by Δβ ∼ 0.2–0.5 mm−1. We show that by varying the writing speed of successive waveguides, we increase the symmetry of the array and reduce the detuning by a factor of 2. After careful analysis of possible physical causes, observations suggest that the density of the laser irradiated material is affected by long range stresses induced by ULI.

中文翻译：

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应力对硫化镓镧中相邻激光写入波导的影响

我们调查了在由超快激光刻字 (ULI) 写入镓镧硫化物玻璃的周期性波导阵列中观察到的离散衍射图案的激发对称性缺乏。我们通过实验发现，用相同参数写入的连续波导与前一个波导失谐了 Δβ ∼ 0.2-0.5 mm-1。我们表明，通过改变连续波导的写入速度，我们增加了阵列的对称性并将失谐降低了 2 倍。经过仔细分析可能的物理原因后，观察表明激光照射材料的密度受ULI 引起的长程应力。