Taming the randomness of random lasers with reconfigurable active particle assemblies

This proposed research program aims to develop a novel random laser system with enhanced lasing performance using reconfigurable particle assemblies. A random laser relies on light scattering in an amplifying optical medium to generate lasing emission. Compared to traditional lasers, the random laser has unique features such as low cost in device fabrication and low spatial coherence for speckle-free imaging. However, currently the random laser is still hindered by limited means to “tame the randomness” in its lasing properties (e.g., uncontrolled emission direction, polarization, modal profile etc.), limiting its impact on photonic applications. The goal of the proposed research is to overcome these limitations by developing a reconfigurable random lasing platform with dynamically tunable gain and scattering landscapes for controlling the lasing characteristics, such as threshold, output power, emission directionality and polarization. The proposed method leverages reconfigurable, electric field directed particle assembly to control particle locations and orientations. Spatiotemporal programming of the electric field (e.g., tuning the field gradient, shape, and frequency) coupled with the versatile choice of particle functionalities (e.g., gain, scattering, anisotropy), provides unprecedented capability to control the collective lasing response of particle populations. Three Research Objectives are proposed: (1) Understand and control random lasing in assemblies of scattering particles suspended in dye solution, including control of emission directionality and polarization; (2) Understand and control random lasing in assemblies where both gain and scattering are provided by particles, including one type of particles serving both roles (e.g., ZnO) or different particles combined to serve as gain/scattering and scattering-only components (e.g., ZnO+TiO2); (3) Demonstrate feedback controlled, smart random lasing that can learn to achieve desired lasing properties. The research program will provide cross-disciplinary, team-based training for student researchers to help prepare them as future leaders. It will be integrated with a sustainability-focused Green Lab effort and education activities aimed at training future scientists and engineers. The education plan will provide opportunities for a broad range of students including K-12 students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.