Gold-nanoparticle-assisted random lasing from powdered GaN

Anderson Localization Enabled Spectrally Stable Deep-Ultraviolet Laser Based on Metallic Nanoparticle Decorated AlGaN Multiple Quantum Wells

Random lasers exhibit many exotic properties, including chaotic behavior, light localization, broad angular emission, and cost-effective fabrication, which enable them to attract both scientific and industrial interests. However, before the realization of their potential applications, several challenges still remain including the underlying mechanism and controllability due to their inherent multidirectional and chaotic fluctuations. Through more than two decades of collaborative efforts, the discovery of Anderson localization in random lasers provides a plausible route to resolve the difficulties, which enables one to tailor the number of lasing modes and stabilize the emission spectra. However, the related studies are rather rare and only restricted to limited wavelengths. In this study, based on enhanced Anderson localization assisted by surface plasmon resonance, spectrally stable deep-ultraviolet lasing action in AlGaN multiple quantum wells (MQWs) is demonstrated. Our work serves as firm evidence to demonstrate the underlying mechanism of stabilized deep-ultraviolet random laser action that multiple scattering of a light beam in a disordered medium can induce Anderson localization similar to electron behavior. This feature covers the whole spectral range, and it is a universal phenomenon of an electromagnetic wave. Notably, stabilized deep-ultraviolet random laser action has not been demonstrated in all previous studies, even though it has great academic interest and potential application in many areas from environmental protection to biomedical engineering.

A RGB random laser on an optical fiber facet

A red-green-blue random laser is fabricated on an optical fiber facet by the dip-coating method.

Random Lasing with Systematic Threshold Behavior in Films of CdSe/CdS Core/Thick-Shell Colloidal Quantum Dots

While over the past years the syntheses of colloidal quantum dots (CQDs) with core/shell structures were continuously improved to obtain highly efficient emission, it has remained a challenge to use them as active materials in laser devices. Here, we report random lasing at room temperature in films of CdSe/CdS CQDs with different core/shell band alignments and extra thick shells. Even though the lasing process is based on random scattering, we find systematic dependencies of the laser thresholds on morphology and laser spot size. To minimize laser thresholds, optimizing the film-forming properties of the CQDs, proven by small-angle X-ray scattering, was found to be more important than the optical parameters of the CQDs, such as biexciton lifetime and binding energy or fluorescence decay time. Furthermore, the observed systematic behavior turned out to be highly reproducible after storing the samples in air for more than 1 year. These highly reproducible systematic dependencies suggest that random lasing experiments are a valuable tool for testing nanocrystal materials, providing a direct and simple feedback for further development of colloidal gain materials toward lasing in continuous wave operation.

Ultraviolet and visible random lasers assisted by diatom frustules

Random laser actions in ultraviolet and visible regions have been demonstrated based on the composites consisting of bio-inspired diatom frustules. Owing to the low optical loss derived from porous network of diatom structures, we report wide spectrum range random lasers arising from GaN film and Rh6G dye via using biological diatoms as scattering centers. Interestingly, both ultraviolet and visible-range random laser actions with very sharp peaks can be easily obtained, with the average length of optics cavity closed to the average size of diatom frustules in both cases, indicating the excellent optical confinement of diatom frustules. It is expected that the first proof of concept shown here can pave an avenue toward future broad-range random lasers and eco-friendly biophotonics devices with high performance and wide spectrum response.

Surface plasmon-enhanced lasing in dye-doped cholesteric liquid crystals

This study shows the results of a photonic band-edge laser using dye-doped cholesteric liquid crystals (CLCs) combined with silver (Ag) nanoparticles. When the Ag nanoparticle surface plasmon resonance wavelength matched the excitation source wavelength, the large optical fields provided by surface plasmons increased the fluorescence of dye molecules by enhancing the molecular excitation rate, achieving a low lasing threshold and high pumping efficiency.