Speckle-Free, Angle-Free, Cavity-Free White Laser with a High Color Rendering Index.

The freedom from efficiency droop motivates monochromatic lasers to progress in general lighting applications due to the demand for more efficient and sustainable light sources. Still, a white light based on monochromatic lasers with high lighting quality, such as a high color rendering ability, an angle-independent output, and a speckle-free illumination, has not yet been fabricated nor demonstrated. Random lasers, with the special mechanism caused by multiple scattering, the angle-free emission, and the uncomplicated fabrication processes, inspire us to investigate the feasibility of utilizing them in general lighting. In this work, a white random laser with a high color rendering index (CRI) value, regardless of pumping energy and observing direction, was performed and discussed. We also investigated the stability of white RL as its CIE chromaticity coordinates exhibit negligible differences with increasing pump energy density, retaining its high-CRI measurement. Also, it exhibits angle-independent emission while having a high color rendering ability. After passing through a scattering film, it generated no speckles compared to the conventional laser. We demonstrated the advances in white laser illumination, showing that a white random laser is promising to be applied for high-brightness illumination, biological-friendly lighting, accurate color selections, and medical sensing.

Multifunctional Random-Laser Smart Inks.

With the superiority of laser-level intensity, narrow spectral line width, and broad-angular emission, random lasers (RLs) have drawn considerable research interests for their potential to carry out a variety of applications. In this work, the applications associated with optical-encoded technologies, including security printing, military friend or foe identification (FFI), and anticounterfeiting of documents are highlighted, and the concept of a transient RL "smart ink" has been proposed. The proof-of-concept was demonstrated as invisible signatures, which encoded the messages through the spectral difference of spontaneous emission and RL under specified conditions. Next, the possibility of encoding the data with multibit signals was further confirmed by exploiting the threshold tunability of RLs. Moreover, the transient characteristic of this smart ink and its capability to be attached on freeform surfaces of different materials were also shown. With the advantages of a facile manufacturing process and multiple purposes, it is expected that this ink can soon be carried out in a variety of practical utilities.

Self-Healing Nanophotonics: Robust and Soft Random Lasers.

Self-healing technology promises a generation of innovation in cross-cutting subjects ranging from electronic skins, to wearable electronics, to point-of-care biomedical sensing modules. Recently, scientists have successfully pulled off significant advances in self-healing components including sensors, energy devices, transistors, and even integrated circuits. Lasers, one of the most important light sources, integrated with autonomous self-healability should be endowed with more functionalities and opportunities; however, the study of self-healing lasers is absent in all published reports. Here, the soft and self-healable random laser (SSRL) is presented. The SSRL can not only endure extreme external strain but also withstand several cutting/healing test cycles. Particularly, the damaged SSRL enables its functionality to be restored within just few minutes without the need of additional energy, chemical/electrical agents, or other healing stimuli, truly exhibiting a supple yet robust laser prototype. It is believed that SSRL can serve as a vital building block for next-generation laser technology as well as follow-on self-healing optoelectronics.