Nanolasers: Current status of the trailblazer of synergetics

The laser is a prototypical non-equilibrium and self-organizing system that led to the birth of synergetics, and thus considered the trailblazer of synergetics by Prof. Haken. The field of laser science and technology today is as active and exciting as it has ever been since the invention of lasers in 1960’s and the trailblazing days in late 1970s. One of the constant themes of research in semiconductor lasers has been size miniaturization, which has led to the invention of many ever smaller lasers. But miniaturization using pure dielectric cavities encountered significant barriers due to the constraint of wavelength or the diffraction limit. To reduce the size of semiconductor lasers further into the nanoscale or deep sub-wavelength scale, metallic and surface-plasmon-polariton (SPP) waveguides were proposed and demonstrated experimentally in the last few years. Since then, such nanolasers have attracted a great deal of attention. Rapid progress has been made in various aspects of nanoscale lasers. After some brief introduction and personal reminiscences, this paper will discuss recent progress in experimental and theoretical studies of semiconductor nanolasers. We will first discuss various mechanisms of wave confinement at nanoscale. Major progress will be reviewed including the first experimental demonstration of continuous wave operation of sub-wavelength cavity lasers at room temperature. Future prospects of the further size reduction and remaining challenges will be discussed.