The present study focuses on controlling the antireflective (AR) characteristics of one-dimensional moth eye structures on a high-resistivity silicon substrate by adjusting the profile (i.e., refractive index distribution) of its micro-tapers using femtosecond laser processing. Moth eye structures that comprise periodically arranged tapers with varying sizes and profiles (triangle, parabola, stair, and triangle–stair) were fabricated using femtosecond laser ablation via a fine adjustment of the processing pattern. The AR characteristics of these samples were experimentally evaluated by a standard terahertz (THz) time-domain spectroscopy and modeled by employing the method of Finite-difference time-domain (FDTD). The measurement data agreed well with the simulation results, and the power reflectance of these structures was induced from approximately 30% (bare silicon substrate) to a very low value (less than 5%) for a broad THz band. Furthermore, the profiled structures showed a varying power reflectance distribution with respect to the frequency in the THz region, especially for the low reflection one (<5%) approximately from 0.5 to 1.0 THz. Three samples with different aspect ratios (approximately 1–3) but having the similar refractive index distribution were also fabricated by using an industrial high-power femtosecond laser (40 W) to demonstrate the relationship between the AR characteristics and the aspect ratio of the moth-eye structures, as well as the processing efficiency. The structures displayed a very good AR performance for a broadband THz region. Besides the broad AR band and low reflectance, this adjustability for the profile of laser-fabricated tapers could improve the flexibility of anti-reflection for THz devices, such as THz wave emitters, receivers, and filters, and the antireflective frequencies less than 1 THz suggest that this technology can be used in the next generation of mobile communication.

本研究的重点是通过使用飞秒激光处理调节微锥的轮廓（即折射率分布）来控制高电阻率硅基板上的一维蛾眼结构的抗反射（AR）特性。通过飞秒激光烧蚀，通过精细调整加工图案，制成了具有周期性变化的锥度的蛾眼结构，这些锥度具有不同的大小和轮廓（三角形，抛物线形，阶梯和三角形阶梯）。这些样品的AR特性通过标准太赫兹（THz）时域光谱进行实验评估，并采用有限差分时域（FDTD）方法进行建模。测量数据与模拟结果吻合得很好，对于宽的THz频段，这些结构的功率反射率从大约30％（裸硅衬底）感应到非常低的值（小于5％）。此外，异型结构相对于THz区域中的频率表现出变化的功率反射率分布，特别是对于低反射率（<5％）大约在0.5至1.0 THz的情况。还通过使用工业高功率飞秒激光（40 W）制作了三个具有不同长宽比（大约1-3）但具有相似折射率分布的样品，以证明AR特性与蛾的长宽比之间的关系。眼结构以及加工效率。这些结构在宽带THz区域显示出非常好的AR性能。除了宽广的AR波段和低反射率之外，