Plasmonic Nanolasers: Pursuing Extreme Lasing Conditions on Nanoscale

Abstract

and techniques have been proposed and/ or developed. Here we focus on a newly emerging area-plasmonic nanolaser that pursuing extremely smaller cavity size in one or more dimensions, and consequently extreme lasing conditions, by using a plasmonic cavity with feature size possibly far below the diffraction limit of light.The miniaturization of a laser can be traced back to the early age of the laser, when compact semiconductor structures were introduced. In particular, the introduction of semiconductors as the gain media in 1962, [11,12] followed by a series of elaborately engineered structures from heterostructure, [13] quantum well, [14] vertical-cavity surface-emitting laser (VCSEL), [15,16] microdisk, [17][18][19] photonic crystal, [20][21][22] quantum dot [23,24] to nanowire (NW) [25][26][27] have made great success in shrinking a laser from bulk scale to wavelength level using reduced cavity sizes. [28] For example, to date, typical commercial edgeemitting quantum well laser diodes have dimensions of several micrometers in width and hundreds of micrometers in length, and a single quantum dot can lase in a photonic crystal cavity with overall dimension of merely 0.7(λ/n) 3 , where λ is the vacuum wavelength and n the refractive index of the dielectric. [29] With optimized geometry and material for cavity design, lower structural dimension is expected. However, in a dielectric cavity with limited refractive index n, the cavity size is intrinsically restricted by optical diffraction limit that sets an ultimate limit λ/2n for both cavity length and mode size in all three dimensions.An effective step to shrink a cavity beyond the diffraction limit is converting light into surface plasmon polaritons (SPPs) in nanostructuralized metals, which is a kind of collective oscillation of quasi free electrons on the interface of a metal and a dielectric. [30] While SPP is featured with ultrahigh optical confinement and ultrafast relaxation process as shown in Figure 1a, [31] it is inevitably accompanied by ultrahigh energy dissipation (i.e., Ohmic loss), leading to a mutual balance between the mode size and the optical loss in either a nanowaveguide or a nanocavity as shown in Figure 1b. [32] For example, the transverse mode area of SPP mode on an Ag nanowire with diameter of 100 nm can be as small as 0.01 µm 2 but also exhibits a propagation loss larger than 200 dB mm −1 . Despite of the high loss coefficient of plasmonic resonance at optical frequency, a properly designed nanoplasmonic cavity coupled with a gain medium is possible to lase with miniature cavity length.Owing to their ultrahigh optical confinement, plasmonic nanolasers with cavity sizes beyond the diffraction limit of light, are attracting increasing attention for pursuing extreme lasing conditions on nanoscale including ultracompact cavity mode, ultrafast lasing modulation, significantly enhanced light-matter interaction, and Purcell effect. In this review, the recent progress on plasmonic nanolasers from both theoretical and experimental aspects is intro...

Polarized Stimulated Emission of 2D Ensembles of Plasmonic Nanolasers

“…The plasmon‐based sources overcome the diffraction limit, have faster (up to THz) switching capabilities in comparison to semiconductor counterparts, exploiting stimulated recombination, [ 13 ] and are limited to switching rates of the order of GHz. The spaser‐based nanolaser is the smallest, biocompatible, and nontoxic tool, and can be incorporated in living tissues for a large number of biomedical in vivo and in vitro applications.…”

Active Nanophotonics

“…Since the invention of plasmonic nanolasers, different approaches and geometries have been explored, including metallic-nanoparticle lasers [238], [312], plasmonic nanowire lasers [51], [61], coaxial nanolasers [182], metal-insulator-metal gap-mode nanolasers [311], plasmonic crystal nanolasers [313], Tamm plasmon laser [148] to name just a few. We address the interested readers to the review papers discussing the various nanolaser geometries [57], [314]. Below in this section, we discuss the problem of lasing threshold definition, various laser geometries and new active materials (2D TMDCs, perovskites, MOFs), perspective for nanolaser realizations.…”

Plasmon–Exciton Interactions: Spontaneous Emission and Strong Coupling

“…In nanogaps of nearby metal nanostructures, the enhancement is extremely prominent. [1][2][3] The field enhancement effect has been used for enhancing various optical processes, such as Raman scattering, [4] fluorescence, [5][6][7] optical forces, [8,9] lasing, [10,11] and various nonlinear processes. [12][13][14] The SP resonance frequencies can be finely tuned by controlling the nanostructure geometries, and are very sensitive to the dielectric environment.…”