利用飞秒激光在熔融石英雕塑中加工结构色

Objective Color serves as a vital artistic language in creative practices. For centuries, artists have relied on surface-applied pigments to manifest chromatic expressions in artworks. Structural color emerges as an alternative technical approach for color representation, garnering extensive research attention in recent years. Owing to the distinctive advantages of femtosecond laser processing —including low thermal effects, sub-diffraction-limit precision, and three-dimensional material modification capabilities —this study employs femtosecond lasers to fabricate high-precision periodic gratings within transparent fused silica substrates. By leveraging the grating diffraction mechanism, we achieve structural color presentation at designated observation angles. This methodology enables three-dimensional chromatic processing within bulk materials, thereby unlocking new creative dimensions for sculpture design. Methods We have established a femtosecond laser processing system capable of achieving 15 µm resolution and 5 cm-scale fabrication within fused silica through the implementation of a long working distance, low numerical aperture objective lens (Fig.2). Utilizing this system, we successfully fabricated periodic grating structures inside fused silica (Fig.3), demonstrating their structural color effects. We created a heart-shaped national flag pattern exhibiting dynamic chromatic variations when viewed from different angles (Fig.4). Furthermore, we integrated this patriotic heart motif into the cardiac region of a medical practitioner sculpture (Fig.6), exemplifying the system's capacity for simultaneous processing of both surface and internal structures in sculptural applications. Results and Discussions We conducted a detailed analysis of the fundamental mechanisms underlying structural color generation through periodic gratings. Gratings with different periodicities selectively diffract specific wavelengths (colors) from the visible spectrum to fixed observation angles through diffraction effects. The resultant structural colors emerge from the additive combination of these diffracted wavelengths. Based on this principle, we engineered the stars in the heart-shaped flag pattern with a 4.5 µm period to exhibit yellow hues, while configuring the background with a 5.5 µm period to produce red coloration. This design achieves complete flag visualization at designated viewing angles. When integrated into the cardiac region of a medical practitioner sculpture, the pattern demonstrates discernible chromatic effects. However, surface irregularities on the sculpture cause light refraction during white light transmission, compromising color fidelity. Future sculpture designs should incorporate dedicated light-entry windows and optimized observation portals to enhance the perceptual quality of internal chromatic features. Conclusions This study investigates structural coloration in fused silica through femtosecond laser processing, theoretically analyzing the diffraction-based mechanisms of periodic gratings and demonstrating their applications in artistic patterns and sculptures. The principal findings are summarized as follows: 1) By utilizing femtosecond laser processing to fabricate micrometer-scale high-precision gratings, structural colors can be observed at specific viewing angles. Leveraging this characteristic, we have achieved chromatic display of processed structures and patterns inside transparent materials. 2) To simplify fabrication, this study adopts the diffraction mechanism of gratings to demonstrate structural colors. These colors exhibit viewing angle selectivity, producing different visual effects at various observation angles. However, due to the uneven surface of the sculpture, the structural color observation effect within the sculpted area remains suboptimal. Future sculpture designs could incorporate observation window features to facilitate the viewing of more refined structural colors. 3) Novel structural color mechanisms, such as optical metamaterials, hold promise for enabling structural color displays across broader viewing angle ranges, thereby addressing the current limitation of single-angle observation dependency. These findings demonstrate that femtosecond lasers can create chromatic 3D architectures inside transparent materials, establishing a novel paradigm for sculptural design. The technology expands artistic possibilities by integrating internal color engineering with volumetric fabrication, offering unprecedented spatial and chromatic control in sculptural applications.