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Plasmonic nanolasers are a new class of coherent emitters where surface plasmons are amplified by stimulated emission in a plasmonic nanocavity. In contrast to lasers, the physical size and mode volume of plasmonic nanolasers can shrink beyond the optical diffraction limit, and can be operated with faster speed and lower power consumption. It was initially proposed by Bergman and Stockman in 2003, and first experimentally demonstrated in 2009. Here we summarize our studies on the fundamental properties and applications of plasmonic nanolasers in recent years, including dark emission characterization, scaling laws, quantum efficiency, quantum threshold, gain and loss optimization, low loss plasmonic materials, sensing, and eigenmode engineering.

The past two decades have seen widespread efforts being directed toward the development of nanoscale lasers. A plethora of studies on single such emitters have helped demonstrate their advantageous characteristics such as ultrasmall footprints, low power consumption, and room-temperature operation. Leveraging knowledge about single nanolasers, the next phase of nanolaser technology will be geared toward scaling up design to form arrays for important applications. In this review, we discuss recent progress on the development of such array architectures of nanolasers. We focus on valuable attributes and phenomena realized due to unique array designs that may help enable real-world, practical applications. Arrays consisting of exactly two nanolasers are first introduced since they can serve as a building block toward comprehending the behavior of larger lattices. These larger-sized lattices can be distinguished depending on whether or not their constituent elements are coupled to one another in some form. While uncoupled arrays are suitable for applications such as imaging, biosensing, and even cryptography, coupling in arrays allows control over many aspects of the emission behavior such as beam directionality, mode switching, and orbital angular momentum. We conclude by discussing some important future directions involving nanolaser arrays.

The local integration of III–Vs on Si is relevant for a wide range of applications in electronics and photonics, since it combines a mature and established materials platform with desired physical properties such as a direct and tuneable bandgap and high mobility. The large thermal expansion coefficient and lattice mismatch, however, pose a challenge for the direct growth of III–Vs on Si. In this paper we will review fabrication concepts to overcome this mismatch for the local integration of III–Vs on Si. In particular, we will briefly discuss processing methods based on aspect ratio trapping, nanowire growth, and template-assisted selective epitaxy (TASE). The focus of this review will be on the latter, where we will provide an overview of the different possibilities and embodiments of TASE and their promise for locally integrated active photonic devices.

Micro- and nanolasers are emerging optoelectronic components with many properties still to be explored and understood. On the one hand, they make it possible to address fundamental physical questions in the border area between classical physics and quantum physics, on the other hand, they open up new application perspectives in many areas of photonics. This progress report provides an overview of the exciting developments from conventional semiconductor lasers toward nanoscale lasers, whose function relies on increased light–matter interaction in low-mode-volume resonators and unconventional gain concepts. The latest advances in the physical understanding of light emission from high-β lasers, in which a large part of the spontaneous emission is coupled into the laser mode, are highlighted. In the limit of β = 1, this leads to thresholdless lasing and it is shown that quantum optical characterization is required to fully explore the underlying emission processes. In addition, emerging nanolaser concepts based on Fano resonators, topological photonics, and 2D materials are presented. Open questions, future prospects, and application scenarios of high-β lasers in integrated photonics, quantum nanophotonics, and neuromorphic computing are discussed.

We systematically studied the characteristics of hybrid perovskite-based surface plasmon nanolasers. If one changes the anion composition of perovskites, the emission wavelength can be easily tuned. We conducted in full-spectrum modeling that featured hybrid perovskite nanowires placed on different SiO2-coated metallic (Au, Ag, and Al) plates. The proposed nanocavities that supported plasmonic gap modes exhibited distinguished properties of nanolasers, such as low-transparency threshold-gain and low lasing threshold. The corresponding experimental results for the MAPbBr3 nanolaser on Ag revealed the low-threshold operation. These superior features were attributed to enhanced light-matter interaction with strong coupling. Therefore, the proposed scheme, integrated with hybrid perovskite as gain material, provides an excellent platform for nanoscale plasmon lasing in the visible to near-infrared spectra.

The quest for subwavelength coherent light sources has recently led to the exploration of dark-mode based surface lasers, which allow for independent adjustment of the lasing state and its coherent radiation output. To understand how this unique design performs in real experiments, we need to consider systems of finite size and quantify finite-size effects not present in the infinite dark-mode surface laser model. Here we find that, depending on the size of the system, distinct and even counterintuitive behavior of the lasing state is possible, determined by a balanced competition between multiple loss channels, including dissipation, intentional out-coupling of coherent radiation, and leakage from the edges of the finite system. The conclusions are crucial for the design of future experiments that will enable the realization of ultrathin coherent light sources.

Controlling and generating coherent light fields in the nanoscale is critical for reducing the size of photonic circuitry. There are several demonstrations of zero-, one-, two-, and three-dimensional nanolaser architectures. Here we experimentally demonstrate a one-dimensional plasmonic laser, which consists of a periodic chain of aluminum nanoparticles and organic gain media. Lasing is observed at visible wavelengths, with clear thresholds and line widths down to 0.11 nm. Lasing occurs in a dark mode that extends over the whole structure, even outside the pumped area. The single lithography step fabrication and one-dimensional character allow for easy integration of these laser sources with other plasmonic structures.

A new approach for analytically solving quantum nonlinear Langevin equations is proposed and applied to calculations of spectra of superradiant lasers where collective effects play an important role. We calculate lasing spectra for arbitrary pump rates and recover well-known results such as the pump dependence of the laser linewidth across the threshold region. We predict new sideband peaks in the spectrum of superradiant lasers with large relaxation oscillations as well as new nonlinear structures in the lasing spectra for weak pump rates. Our approach sheds new light on the importance of population fluctuations in the narrowing of the laser linewidth, in the structure of the lasing spectrum, and in the transition to coherent operation., Comment: 19 pages, 10 figures

Nanoscale light sources are being intensively investigated for their potential to enable low-energy, high-density optical communication and sensing systems. Both nano-light-emitting diodes (nanoLEDs) and nanolasers have been considered, based on advanced nanophotonic concepts such as photonic crystals and plasmonic structures, with dimensions well into the sub-micrometer domain. With decreasing dimensions, light-matter interaction becomes stronger, potentially leading to efficient and ultrafast radiative emission, both in the spontaneous and stimulated regime. These features have created wide expectations for the practical prospects of such nanoscale light sources, in particular for optical interconnects. In this article we examine the limits to the downscaling of LEDs and lasers, and ask ourselves which type of source is most suited to ultralow-power optical communications. Based on simple physical considerations on the scaling of spontaneous and stimulated emission rates for semiconductor active regions at room temperature, we analyze the speed and energy limits for nanoLEDs and nanolasers as a function of their size. The role of spontaneous emission enhancement (Purcell effect) in practical nanophotonic sources is also revisited. The main conclusion is that nanoLEDs reach a fundamental energy/speed limit for data rates exceeding a few Gb/s, whereas nanolasers with active dimensions in the range of few 100s nm may enable direct modulation rates larger than 40 Gb/s at power levels adequate for short-distance and low-energy optical interconnects., 13 pages, 8 figures

Here we experimentally characterize photonic crystal nanolasers where the first endhole of the mirror has been systamatically shifted. FDTD simulations of similar passive cavities are done in order to find the expected evolution of the quality factor. We find that the predicted increase in the quality factor of the equivalent passive cavities leads to a decrease in the threshold power of the active nanolasers as expected. The maximum output power for varying endhole shifts has also been investigated and shifting the holes to optimize quality factor leads to lower maximum output power, when measuring from the top. The mirror of the photonic crystal cavity is further investigated as the mirror phase and penetration depth into the mirror are determined as a function of the endhole shift.

11 pags., 5 figs., Nearly half a century ago, the German physicist Hermann Haken proved that the laser dynamics could be described, under certain conditions, by the Lorenz equations, the paradigm of deterministic chaos. Unfortunately, its experimental realization has remained elusive for conventional laser materials and cavities mostly due to the extreme pumping conditions and the low cavity quality factors (“bad-cavity condition”) required to achieve Lorenz–Haken (L-H) self-pulsing dynamics upon continuous wave excitation. In this paper, it is theoretically proved that dielectric and plasmonic nanolasers, that can naturally fulfill the bad-cavity condition, may overcome the limitations of macroscopic cavities and make the observation of L-H instabilities in visible-IR solid-state materials become a reality. Remarkably, the adequate choice of active material and cavity design enables the generation of trains of ultrashort pulses in the sub-ps regime and with MHz–GHz repetition rates without the need of resorting to neither mode-locking nor Q-switching techniques. Thus, the results reported in this manuscript unveil a new paradigm in the generation of ultrashort pulses at the nanoscale.

Nanoscale laser sources based on single metallic nanoparticles (spasers) have attracted significant interest for their fundamental implications and technological potential. Here we theoretically investigate the spatio-temporal dynamics of lasing action in core–shell metallic nanoparticles that include optically pumped four-level gain media. By using detailed semiclassical simulations based on a time-domain generalization of the finite-element method, we study the evolution of the lasing dynamics when going from a spherical case to an elongated nanorod configuration. Our calculations show that there exists an optimal nanoparticle elongation that exhibits significantly improved lasing threshold and slope efficiency over those obtained for its spherical counterpart. These results are accounted for in terms of a coupled-mode theory analysis of the variation with elongation of the light confinement properties of localized surface plasmons. This work could be of importance for further development of nanoscale light sources based on localized surface plasmon resonances.

A hybrid graphene–insulator–metal (GIM) platform is proposed with a supported surface plasmon polariton (SPP) wave that can be manipulated by breaking Lorentz reciprocity. The ZnO SPP nanowire lasers on the GIM platforms are demonstrated up to room temperature to be actively modulated by applying external current to graphene, which transforms the cavity mode from the standing to propagation wave pattern. With applying 100 mA external current, the laser threshold increases by ≈100% and a 1.2 nm Doppler shift is observed due to the nonreciprocal propagation characteristic. The nanolaser performance also depends on the orientation of the nanowire with respect to the current flow direction. The GIM platform can be a promising platform for integrated plasmonic system functioning laser generation, modulation, and detection., Plasmonic nanolasers are incorporated into the hybrid graphene–insulator–metal platform that can break the Lorentz reciprocity by applying external current to graphene in order to actively modulate the laser threshold. Room temperature laser modulation demonstrates that the laser threshold increases by ≈100% with applying 140 mA external current.

The ongoing miniaturization of semiconductor lasers has enabled ultra‐low threshold devices and even provided a path to approach thresholdless lasing with linear input-output characteristics. Such nanoscale lasers have initiated a discourse on the origin of the physical mechanisms involved and their boundaries, such as the required photon number, the importance of optimized light confinement in a resonator, and mode‐density enhancement. Here, high‐β metal‐clad coaxial nanolasers, which facilitate thresholdless lasing are investigated. Both the conventional lasing characteristics, as well as the photon statistics of the emitted light at 10 K under continuous wave excitation are experimentally and theoretically investigated. While the former lacks adequate information to determine the threshold to coherent radiation, the latter reveals a finite threshold pump power. The work confirms an important aspect of high‐β lasers, namely that a thresholdless laser does have a finite threshold pump power and must not be confused with a hypothetical zero‐threshold laser. Moreover, the results reveal an excitation power dependent β‐factor which needs to be taken into account to correctly describe the experimental data.

The latest breakthroughs on the frontiers of semiconductor laser capabilities are presented. Achievements including the impressive advances in high-speed lasers with low pJ/bit energy consumption, high-power vertical external cavity surface emitting lasers (VECSELs), advances in Ill-nitrides, record-high temperature operation quantum dot lasers, the longest wavelength Type-I quantum well lasers to date, and the fascinating field of nanolasers with ultralow volume and threshold are all discussed.

Recent progress in the field of semiconductor nanolasers is discussed. New designs have emerged that eliminate the need for a conventional Fabry-Perot cavity, bringing down the physical dimensions of the lasers below the diffraction limit. Semiconductor nanolasers are critical components for nanophotonics and offer possible integration with Si nanoelectronics.

Recent progress on nanoscale lasers, especially metal-cavity nanolasers, is highlighted. In spite of the metal loss, metal cavities of subwavelength scales have been used successfully for semiconductor lasers by optical or electrical pumping from low to room temperature. We focus on the demonstration of a substrate-free metal-cavity surface emitting microlaser operating continuous wave at room temperature with electrical injection.

Following a similar trend in the scaling of electronic integrated circuits (ICs), the downscaling of optical sources promises revenues such as higher energy efficiency and faster operation speed in photonic ICs. With the rapid development of advanced fabrication techniques and optical cavity designs, light confinement and manipulation at the nanoscale, far below the diffraction limit of light, have been achieved. However, downscaling can lead to problems such as large threshold current and excessive self-heating for nanolasers. In addition, the modulation bandwidth of a laser is ultimately limited by the large damping at high injection current levels due to gain compression. Recently, nanoLEDs that utilize the Purcell effect were proposed as fast and efficient nanoscale light sources to address the limitations of nanolasers. In this review, we summarize recent advances and several important figures of merit of nanoLEDs. To illustrate their practicalities, we use a specific nano-emitter design example to calculate and predict the dynamic response as well as energy consumption of the device with a rate-equation analysis. This short review is intended to offer new perspectives to the design and application of nanoscale light sources in high-speed on-chip optical communication systems.

The Purcell effect strongly affects the emission in laser nanocavities. We investigate its role in the gain and spontaneous emission rate of nanopillar lasers over a wide range of cavity dimensions and emitter/cavity relative linewidths enabling the modeling of either nano-, meso-or macro-scale lasers.