Status and prospects for metallic and plasmonic nano-lasers

A remarkable miniaturization of lasers has occurred in just the past few years by employing metals to form the laser resonator. From having minimum laser dimensions being at least several wavelengths of the light emitted, many devices have been shown where the laser size is of a wavelength or less. Additionally some devices show lasing in structures significantly smaller than the wavelength of light in several dimensions, and the optical mode is far smaller than allowed by the diffraction limit. In this article we review what has been achieved then look forward to what some of the directions development could take and where possible applications could lie. In particular we show that there are devices with an optical size slightly larger or near the diffraction limit which could soon be employed in many applications requiring coherent light sources. Application of devices with dimensions far below the diffraction limit is also on the horizon, but may take more tim