Incoherent and coherent random lasing in electrospun fiber-embedded glass microtube systems with different sizes

Random lasers (RLs), characterized by their utilization of disordered scattering media for optical feedback, offer unique benefits such as reduced spatial coherence and inherent speckle suppression. These attributes make them promising candidates for imaging and display technologies. However, the efficient achievement of coherence tunable RL in a restrained system remains a challenge in this field. In this study, we introduce a microtube-based RL system, which comprises gold nanoparticle (Au NP)-doped DCJTB dye embedded within electrospun fiber networks, and systematically examine the interaction between geometric constraints and lasing performance. The results reveal a marked dependence of the lasing threshold and coherence on microtube dimensions. A thick tube (1.3 mm diameter, 0.5 cm length) displayed incoherent emission with a high threshold of 355 μJ/Pulse, while a thin tube (1.0 mm diameter) generated coherent RL at a significantly lower threshold of 26 μJ/Pulse, which is only 7.3 % of the threshold of the thick tube. This notable disparity is attributed to the increased photon scattering efficiency and feedback mechanisms within the confined geometry of the thin tube, which optimize the effective cavity path length and amplify gain-to-loss ratios. Further investigations on thin-tube systems of varying lengths (0.5–1.5 cm) show a steady increase in threshold (26–37 μJ/Pulse) with the extension of tube length, directly linked to the reduced geometric confinement and weakened feedback effects. Furthermore, we confirm the practical application of the thin-tube RL as a compact, high-fidelity light source for speckle-free imaging, achieving speckle contrast values as low as 0.0665. These findings show the transformative potential of geometrically optimized microtube RL systems in advancing low-energy, high-resolution optical technologies for biomedical imaging and next-generation display applications.