Nanolasers generate coherent light at the nanoscale. In the past decade, they have attracted intense interest, because they are more compact, faster and more power-efficient than conventional lasers. Thanks to these capabilities, nanolasers are now an emergent tool for a variety of practical applications. In this Review, we explain the intrinsic merits of nanolasers and assess recent progress on their applications, particularly for optical interconnects, near-field spectroscopy and sensing, optical probing for biological systems and far-field beam synthesis through near-field eigenmode engineering. We highlight the scientific and engineering challenges that remain for forging nanolasers into powerful tools for nanoscience and nanotechnology.

Applications of nanolasers.

Ten years ago, three teams experimentally demonstrated the first spasers, or plasmonic nanolasers, after the spaser concept was first proposed theoretically in 2003. An overview of the significant progress achieved over the last 10 years is presented here, together with the original context of and motivations for this research. After a general introduction, we first summarize the fundamental properties of spasers and discuss the major motivations that led to the first demonstrations of spasers and nanolasers. This is followed by an overview of crucial technological progress, including lasing threshold reduction, dynamic modulation, room-temperature operation, electrical injection, the control and improvement of spasers, the array operation of spasers, and selected applications of single-particle spasers. Research prospects are presented in relation to several directions of development, including further miniaturization, the relationship with Bose-Einstein condensation, novel spaser-based interconnects, and other features of spasers and plasmonic lasers that have yet to be realized or challenges that are still to be overcome.

/pdf/ten-years-of-spasers-and-plasmonic-nanolasers-2ij6xn3hjw.pdf

Ten years of spasers and plasmonic nanolasers.

Manipulating the properties of the isofrequency contours (IFCs) of materials provides a powerful means of controlling the interaction between light and matter. Hyperbolic metamaterials (HMMs), an important class of artificial anisotropic materials with hyperbolic IFCs, have been intensively investigated. Because of their open dispersion curves, HMMs support propagating high-k modes and possess an enhanced photonic density of states. As a result, HMMs can be utilized to realize hyperlenses breaking the diffraction limit, metacavity lasers with subwavelength scale, high-sensitivity sensors, long-range energy transfer, and so on. Aimed at those who are about to enter this burgeoning and rapidly developing research field, this tutorial article not only introduces the basic physical properties of HMMs but also discusses dispersion manipulation in HMMs and HMM-based structures such as hypercrystals. Both theoretical methods and experimental platforms are detailed. Finally, some potential applications associated with hyperbolic dispersion are introduced.

Hyperbolic metamaterials: From dispersion manipulation to applications

Abstract Optical metamaterials have presented an innovative method of manipulating light. Hyperbolic metamaterials have an extremely high anisotropy with a hyperbolic dispersion relation. They are able to support high- k modes and exhibit a high density of states which produce distinctive properties that have been exploited in various applications, such as super-resolution imaging, negative refraction, and enhanced emission control. Here, state-of-the-art hyperbolic metamaterials are reviewed, starting from the fundamental principles to applications of artificially structured hyperbolic media to suggest ways to fuse natural two-dimensional hyperbolic materials. The review concludes by indicating the current challenges and our vision for future applications of hyperbolic metamaterials. 

/pdf/hyperbolic-metamaterials-fusing-artificial-structures-to-20kfjvuc.pdf

Hyperbolic metamaterials: fusing artificial structures to natural 2D materials

DOI: 10.1002/adom.201800554 and optoelectronics. Metasurfaces as 2D artificial photonic structures are composed of subwavelength resonators (often referred to as meta-atoms).[1–8] The optical responses/functionalities of metasurfaces can be tailored by choosing the proper geometrical parameters of these metaatoms.[9–14] They have been applied to realize ultrathin invisible cloaking,[15] metahologram,[16–20] surface plasmon launchers,[21–23] compact nonlinear devices,[24–28] nanolasers,[29–34] and many novel compact photonic devices.[11,35–57] Among all the promising applications of metasurfaces, planar metalenses with superior performance and functionalities over their conventional counterparts are definitely one of the most exciting and important research areas. This is because metasurface lenses (metalenses) can not only show better optical functionalities but also allow for much more compact device design than the conventional high-end objective lenses. In this article, we will review the progress in the development of metalenses. This article is organized into three major parts. First, the working mechanisms of chromatic and achromatic metalenses will be introduced. The design principle of integrated-resonant units for correcting chromatic aberration of a metalens will be discussed. Second, novel applications of metalenses mentioned in the first part for full color imaging, sensing, and spectroscopy will be reviewed. After the discussion of the passive metalenses, the emerging tunable metalenses and their applications will be surveyed, followed by concluding remarks on future prospects.

Metalenses: Advances and Applications

Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.

Chiieh Hsieh

Papers

Deep-Ultraviolet Hyperbolic Metacavity Laser.

Giant enhancement of emission efficiency and light directivity by using hyperbolic metacavity on deep-ultraviolet AlGaN emitter