Mid‐infrared materials antireflection is in high demand for high‐powered or ultra‐broadband coherent light sources, where conventional antireflection coatings cannot be reliably applied. This work provides a critical review of the recent advances in microstructure fabrication technology for mid‐infrared antireflection applications. Several techniques are reviewed, including direct imprinting, wet and reactive ion etching using conventional photoresist masking, novel colloid crystal masks, and maskless etching, laser‐induced periodic structure formation, and multiple laser ablation method modifications, including femtosecond laser direct writing, direct laser interference ablation, and single pulse ablation. The advantages and drawbacks of the different approaches are discussed in detail to highlight the most promising techniques for the fabrication of antireflection microstructures capable of achieving 99% transmittance in the 2–16 μm range.

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GaSe crystals are promising as nonlinear optical converters in the mid- and far-IR ranges. However, it is challenging to increase the GaSe surface transmittance of 77% with conventional antireflection coatings because of poor surface quality, leading to coating adhesion problems. Antireflection microstructures (ARMs) offer an alternative way of increasing surface transmittance. In this work, ARMs were fabricated on the surface of a GaSe plate by single-pulse femtosecond laser ablation. An average GaSe surface transmittance of 94% in the 7–11 µm range and a maximum transmittance of 97.8% at 8.5 µm were obtained. The proposed method can be used to increase the efficiency of GaSe-based nonlinear converters.

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