Microlasers as a platform to study fluctuations in non-Hermitian dynamical systems

Princeton University, Princeton NJ

Investigators

Abstract

NONTECHNICAL SUMMARY The Division of Materials Research and the Division of Electrical, Communications, and Cyber Systems contribute funds to this award, which supports theoretical research and education towards advancing the understanding of the properties and the design of novel laser systems that are key components of communication and sensing systems. Enormous progress in nanofabrication technologies has allowed the fabrication of compact chip-based structures that enable confinement of light and tunable laser emission. However, and while allowing the design of complex laser systems with improved functionality, the high level of control over fabrication and the many available design parameters present a substantial challenge for laser theory. The objective of the research is to develop conceptual foundations and computational tools to investigate the properties of complex on-chip laser systems. The concepts, methods, and computational tools developed in the course of the proposed research will be instrumental in the design of novel applications such as on-chip coherent light sources for spectroscopy and electrically controllable optical switches. In addition to mentoring and training graduate students on modern analytical and computational techniques of laser physics, the proposed research will forge interdisciplinary collaborations between engineers and physicists, and has the potential to accelerate the translation of basic science to applications such as optical spectroscopy. TECHNICAL SUMMARY The Division of Materials Research and the Division of Electrical, Communications, and Cyber Systems contribute funds to this award, which supports theoretical research and education towards advancing the understanding of the dynamics and noise properties of novel laser systems that feature complex resonator geometries and spatially modulated gain and loss. The manipulation of the real part of the index of refraction of optical systems is the cornerstone of modern photonics and quantum optics. Selective pumping of complex laser systems, which is at the core of this project, represents a new design space that relates to the simultaneous electrical tuning of the imaginary along with the real part of the index of refraction (non-Hermitian engineering), with potentially transformative implications for laser physics. A key property of these laser systems is that their fluctuations are governed by non-Hermitian evolution operators, which are of current interest across several fields ranging from mathematics to biology, chemistry, and physics. One objective of the research is to theoretically investigate fluctuation properties and dynamics governed by non-Hermitian operators using microlasers as a physical system, where the parameters of such operators can be continuously tuned. The PI's earlier work has demonstrated that judicious spatial modulation of gain and loss through spatially tailored pump injection can provide novel functionalities and significantly boost the out-coupled optical power of microlasers. Instrumental in that earlier work was the Steady-state Ab Initio Laser Theory (SALT) that the PI had developed to access laser characteristics in the presence of optical leakage and spatial hole-burning interactions. These earlier studies have exclusively addressed steady-state operation. One of the primary goals of the proposed research is to develop a theoretical and computational framework to study the nonequilibrium dynamics and noise properties of complex laser systems beyond their steady state behavior, which is not accessible by SALT. The research will focus on interesting dynamical regimes where the fluctuation dynamics display spectral degeneracies or instabilities towards self-pulsing. The proposed research will integrate state-of-the-art techniques and concepts from a multitude of fields, such as stochastic evolution techniques of quantum optics, spectral theory of non-Hermitian operators, and laser theory. Close contact to experiments will be maintained through existing collaborations of the PI. The concepts, methods, and computational tools developed for the research will be instrumental in the design of novel coherent light sources for optical sensing and frequency-comb-based spectroscopy. In addition to mentoring and training graduate students on modern analytical and computational techniques of laser physics, the proposed research will forge interdisciplinary collaborations between engineers and physicists, and has the potential to accelerate the translation of basic science to applications such as optical spectroscopy.