A Wearable Thin-Film Hydrogel Laser for Functional Sensing on Skin

Angular dependence of random laser emission by using ZnO-CuO heterostructure as scatterer and its applications in biocompatible imaging

The angular dependence of random laser (RL) generation in a commercially available rhodamine 6G (Rh6G) dye has been demonstrated using ZnO-CuO heterostructure as passive scatterers. The grass-like superstructure formed at a 1M:1M molar ratio of ZnO-CuO significantly enhances scattering, resulting in RL spikes with a full width at half maximum (FWHM) of just a few nanometer and a noticeable reduction in the RL threshold. RL emission spectra were collected over an angular spread of 0-180 degrees, revealing a remarkable shift in RL emission from 566 nm to 580 nm. Additionally, we explored RL using a biological extract from Caesalpinia sappan L (Biancaeasappan L) and demonstrated speckle-free imaging with an affordable handheld microscope called the Foldscope. The biocompatibility of the wood extract shows significant potential for applications in speckle-free imaging. We had assessed the Pearson correlation coefficient between images captured under LED, RL, and conventional laser illumination. It is observed that the value of the coefficient becomes the lowest under RL illumination which confirms the formation of high-resolution and artifact-free images.