Xueyang Li,Hao Liu,Xiaoyan Xu,Bing Yang,Hong Yuan,Jingwei Guo,Fengting Sang,Yuqi Jin
We describe herein a flexible and tunable random laser made from a flexible poly(dimethylsiloxane) substrate. The substrate is prepared by casting via soft lithography from a lotus leaf to produce a micropapilla surface structure similar to that of a lotus leaf. The micropapilla provides efficient multiple scattering for the photons generated in the gain medium, and random lasing emerges because photons undergo closed-loop paths by scattering from three equilaterally arranged micropapillae. Given the diverse distribution of microscale features on the soft substrate, the random laser spectrum can be tuned by as much as 26.0 nm by changing the pump position. Furthermore, the random laser can be easily tuned by about 14 nm by flexing it, which modifies the micropapilla density and thereby changes the reabsorption strength of the laser dye. The photostability of the random laser is ensured by sealing the gain medium (i.e., dye solution) in a closed system. The results provide a promising method to realize a variety of laser-based applications such as optical biosensors on chips, microscale structural alteration detectors, flexible wearable devices, and multicolor (even white) random lasers.
Jiatao Hu,Jiamin Yin,Yuxia Zhao,Yining Zhang,Hao Lv,Shuaiyi Zhang,Xia Wang
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.
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