Phase transition modulated fiber-shaped random lasers

A flexible random laser with switchable modes and directional emission will advance the application of random lasers in high-quality light sources and photonic integration. In this paper, a fiber-shaped random laser based on phase transition hydrogel is proposed. The change of phase states in hydrogel affects the light scattering and optical feedback path, enabling the reversible switching of lasing mode between incoherent and coherent random lasing. The switching mechanism of random lasing modes has been explained by analyzing the appearance of changes in molecular structure and calculating the cavity lengths using PFT analysis. Additionally, due to the fiber-shaped geometry, the emission angular of random lasing is confined to a small range of about 20 degrees by restricting light propagation. The proposed random lasers will inspire the design and application of novel random lasers in multi-function laser light sources, information security, and ultrasensitive sensors.