Plasmonic Saturable Absorbers

Abstract

Plasmonic materials are able to spatially confine light to a nanometer scale far smaller than the diffraction limit, resulting in drastically enhanced electrical field strength and stimulating applications in nonlinear optics, energy and biomedicine. Resonant excitation of plasmonic nanostructures by ultrafast pulses could result in a sub-picosecond scale transient photo-bleaching originated from the thermalization and cooling of hot carriers, which manifests strong optical nonlinearity that has been leveraged for optical modulation and switching. Here, we discuss recent advances in the use of noble and non-noble metal based plasmonic materials as saturable absorbers (SAs) in both solid-state and fiber lasers for the generation of Q-switched and mode-locked pulses. Starting with a brief introduction on the operation mechanisms of pulsed lasers and photo-physics of plasmonics, we focus our discussion on the nonlinear optical properties as well as the recent developments of pulsed lasers driven by these plasmonic SAs. We further analyze the pros and cons of using different plasmonic materials for SAs in terms of their material properties and Accepted Article This article is protected by copyright. All rights reserved linear/nonlinear optical responses. Along with a short summary of the current progress of plasmonic SAs, we finally highlight future challenges in the development of plasmonic SAs for practical laser systems.