Fig. 5: Curvature realization of the flexible and rollable HMM device.

The emission spectra of random lasing action for the HMM2 device on the concave glass substrates under the curvature radius of a 20 mm and b 50 mm with the corresponding insets. c, d The emission spectra on the convex glass substrates under the curvature radius of 20 and 50 mm, respectively. The insets are the corresponding photo images. e The enhancement factors of concave and convex substrates as compared with the planar substrate. f The threshold variations with the curvature radius for the flexible and rollable HMM structure on concave and convex substrates. Error bars are the standard deviation of spectra fluctuation of random laser action from 15 datasets. All the measurements were performed under the same pumping energy density of 0.24, 0.20, and 0.13 kW cm⁻². All the scale bars are 1 cm.