Low-loss strong index modulated ultra-thermally stable optical phase-change material for broadband nonvolatile photonics

Optical phase change materials (O-PCMs) have attracted increasing attention and provide promising solutions for non-volatile reconfigurable photonics due to their large index contrast and non-volatile switching characteristics. In this work, we have explored the optical phase change properties of a dozen different O-PCMs and established the corresponding gene bank. Among these O-PCMs, Ge1Sb2Se3Te1 (G1S2S3T1) films exhibit unprecedented low-loss, strong light modulation capability, and ultra-thermal stability capability, which are prepared by pulsed laser deposition. Meanwhile, we investigate the phase transition kinetic mechanism of G1S2S3T1 films by transmission electron microscope, temperature dependent transmission spectroscopy, and temperature dependent Raman spectroscopy. It is found that the wide bandgap (1.09 eV) in the amorphous state, the large bandgap variation (0.51 eV) between amorphous and crystalline states, the needle-like configuration of its crystalline state, and the special phase change process contribute to strong refractive index modulation. Moreover, we find that their ultra-thermal stability is from a strong Sb-Se bond. Through the simulation, we found that G1S2S3T1 can be applied to prepare ultra-low loss waveguide devices. The present work represents a significant step in the development of broadband nonvolatile photonics derived from O-PCMs.