Optimizing Wavelength for Enhanced Cycling Durability of Laser-Induced Phase Change in Sb₂S₃ Films: A Survey on Optical Transmission Phase Shift

The advancement of nonvolatile reconfigurable photonic elements has led to the development of Sb₂S₃ as a desirable phase change material for optical phase modulation in visible and near-infrared wavebands. However, achieving long-lasting cycling durability of the phase change remains a formidable challenge. Traditional characterization methods like transmittance or reflectance measurement fail to provide a quantitative assessment of the degree of phase change. To address this, the study focuses on enhancing the cycling durability of complete phase change in Sb₂S₃ films by manipulating the wavelength of a femtosecond laser for amorphization. To accurately measure optical transmission phase shifts during phase change experiments, a novel liquid-crystal retardance matching technique based on the Mach–Zehnder interferometer is developed. This approach allows for a direct and quantitative assessment of the degree of phase change without relying on an optical model. The findings reveal that longer wavelengths and multi-pulse irradiation with increasing pulse energy significantly enhance the cycling durability of the phase change. Additionally, the cost-effective customization of nonvolatile photonic elements is demonstrated using laser direct writing, eliminating the need for lithography. It is anticipated that this work will drive advancements in Sb₂S₃-based reconfigurable devices and contribute to the broader field of nonvolatile reconfigurable photonic elements.