Nanolaser Array Research Articles

Optical injection effects in electrically pumped semiconductor nano-laser arrays

A theoretical analysis is performed on the response of electrically pumped nano-laser arrays to external optical injection. The response to both continuous wave and modulated optical injection is explored. Continuous wave injection is shown to excite several varieties of dynamical behaviour in the array elements including regular dynamics and quasi-periodic behaviour. The strength of the optical injection, the frequency detuning between the injected light and the target laser, and the magnitude of the Purcell spontaneous emission enhancement factor are shown to markedly affect the dynamics. When subject to modulated optical injection, the effects of frequency detuning and optical injection strength are the focus of attention. It is shown that the elements of the array subject to modulated optical injection exhibit oscillatory behaviour over broad regimes determined by the optical injection strength and the frequency detuning.

Reconfigurable coherent nanolaser array based on twisted systems

Reconfigurable coherent nanolaser array based on twisted systems

Tailoring the Direct Current Modulation Response of Electrically Pumped Semiconductor Nano-Laser Arrays

Semiconductor nano-lasers have been a topic of interest from the perspective of advancing the capabilities of photonic integration. Nano-lasers are perceived as the means to achieve improved functionality in photonic integrated circuits. The properties and performance of nano-lasers have been examined by means of simulations and laboratory measurements. Nano-lasers lend themselves to integration to form dense arrays in both one and two dimensions. In a recent work, a theoretical treatment was presented for the dynamic behaviour of stand-alone electrically pumped nano-laser arrays. In this work, the response of nano-laser arrays to direct current modulation is examined. As in previous works, attention is given to two prototype array geometries: a linear three-element linear array and an equilateral triangular array. Large one-dimensional arrays can be built by repeating this elementary linear array. Two-dimensional photonic integrated circuits can incorporate the triangular arrays studied here. Such prototypical configurations offer opportunities to tailor the modulation response of the nano-laser arrays. The principal factors which provide that capability are the coupling strengths between lasers in the arrays and the direct modulation parameters. The former are fixed at the design and manufacture stage of the array whilst the latter can be chosen. In addition, the enhancement of the spontaneous emission rate via the so-called Purcell effect in nano-lasers offers a device-specific means for accessing a range of modulation responses. Two-dimensional portraits of the regimes of differing modulation responses offer a convenient means for determining the dynamics that may be accessed by varying the laser drive current. It is shown by these means that a rich variety of modulation responses can be accessed in both linear and triangular arrays.

Reconfigurable moiré nanolaser arrays with phase synchronization.

Miniaturized lasers play a central role in the infrastructure of modern information society. The breakthrough in laser miniaturization beyond the wavelength scale has opened up new opportunities for a wide range of applications1-4, as well as for investigating light-matter interactions in extreme-optical-field localization and lasing-mode engineering5-19. An ultimate objective of microscale laser research is to develop reconfigurable coherent nanolaser arrays that can simultaneously enhance information capacity and functionality. However, the absence of a suitable physical mechanism for reconfiguring nanolaser cavities hinders the demonstration of nanolasers in either a single cavity or a fixed array. Here we propose and demonstrate moiré nanolaser arrays based on optical flatbands in twisted photonic graphene lattices, in which coherent nanolasing is realized from a single nanocavity to reconfigurable arrays of nanocavities. We observe synchronized nanolaser arrays exhibiting high spatial and spectral coherence, across a range of distinct patterns, including P, K and U shapes and the Chinese characters '' and '' ('China' in Chinese). Moreover, we obtain nanolaser arrays that emit with spatially varying relative phases, allowing us to manipulate emission directions. Our work lays the foundation for the development of reconfigurable active devices that have potential applications in communication, LiDAR (light detection and ranging), optical computing and imaging.

Dynamics of Electrically Pumped Semiconductor Nano-Laser Arrays

Semiconductor nano-lasers have been actively investigated both theoretically and experimentally with to the aim of providing a highly compact laser amenable to photonic integration. Such devices are naturally suited for assembly in close-packed one- and two-dimensional arrays. In such arrangements, optical coupling between elements of the array opens opportunities to generate a range of dynamical behaviours. In this paper, we present the first theoretical treatment of the dynamics of electrically pumped nano-laser arrays. Two specific forms of such arrays are analysed in detail: a three-element linear array, and triangular arrays. The former is the basis for extensive one-dimensional arrays, whilst the latter is a building block of many possible geometric configurations of two-dimensional nanolaser arrays. Using these prototypical configurations enables the identification of novel dynamical behaviours, which may be accessed using nano-laser arrays. A distinguishing physical feature of nano-lasers is the enhancement of the spontaneous emission rate via the so-called Purcell effect. Allowing for a range of Purcell enhancement factors, the analysis focusses on the effects of experimentally controllable parameters such as the laser drive current. It is shown that the Purcell enhancement factor is critical to the availability of a range of dynamical behaviours which arise simply due to inter-element optical coupling. Two-dimensional portraits of the regimes of differing dynamics offer a convenient means for determining the dynamics which may be accessed by varying the laser drive current.

Room-Temperature Excitonic Nanolaser Array with Directly Grown Monolayer WS2

Two-dimensional (2D) transition-metal chalcogenides (TMDCs) with strong excitonic emission are ideal candidates for small-volume gain materials in nanolasers, which can be realized by integrating 2D TMDCs with optical microcavities. However, at present, the integration is usually realized by the transfer method, which is not suitable for large-scale production, and the quality factor of the microcavity usually drops sharply in the process of transfer. Therefore, scalable fabrication of nanolasers remains an urgent issue to be solved. In this paper, by embedding continuous monolayer WS2 between silicon nitride (Si3N4) microdisks and Al2O3, we demonstrated the room-temperature transfer-free excitonic nanolaser array. Lasing at room temperature is achieved with the help of the high-quality-factor Si3N4 microdisks and the physical vapor deposition method for growing 2D gain material directly. This work provides a practical solution for large-scale and low-cost TMDC-based nanolaser arrays in the integrated optical communication systems.

Three-dimensional programming of nanolaser arrays through a single optical microfiber

Efficient programming of integrated small optical sources is a key component of photonic technologies. However, as the density of laser arrays increases, the miniaturization and scalability of laser control using an electric drive are pushed to the limit. This study presents an all-optical drive scheme for complete programming of nanolaser arrays through a single waveguide port. Three photonic crystal nanolasers, printed three-dimensionally on the sides of a 2-µm-diameter fiber with an 18 µm laser spacing, were entirely controlled by modal interference, adjusted by the polarization and pulse width of the pump beam through the same fiber. Our approach is applicable to various small optical sources coupled to a single waveguide, and it will lay the foundation for applications in high-density optical integrated circuits, biosensing, and quantum network technologies.

Quantum Density Matrix Theory for a Laser Without Adiabatic Elimination of the Population Inversion: Transition to Lasing in the Class‐B Limit

AbstractDespite the enormous technological interest in micro and nanolasers, surprisingly, no class‐B quantum density‐matrix model is available to date, capable of accurately describing coherence and photon correlations within a unified theory. In class‐B lasers—applicable for most solid‐state lasers at room temperature—, the macroscopic polarization decay rate is larger than the cavity damping rate which, in turn, exceeds the upper level population decay rate. Here, a density‐matrix theoretical approach for generic class‐B lasers is carried out, and closed equations are provided for the photonic and atomic reduced density matrix in the Fock basis of photons. Such a relatively simple model can be numerically integrated in a straightforward way, and exhibits all the expected phenomena, from one‐atom photon antibunching, to the well‐known S‐shaped input–output laser emission and super‐Poissonian autocorrelation for many atoms (), and from few photons (large spontaneous emission factors, ) to the thermodynamic limit ( and ). Based on the analysis of , it is concluded that super‐Poissonian fluctuations are clearly related to relaxation oscillations in the photon number. A strong damping of relaxation oscillations with an atom number as small as is predicted. This model enables the study of few‐photon bifurcations and nonclassical photon correlations in class‐B laser devices, also leveraging quantum descriptions of coherently coupled nanolaser arrays.

Binary image classification using collective optical modes of an array of nanolasers

Recent advancements in nanolaser design and manufacturing open up unprecedented perspectives in terms of high integration densities and ultra-low power consumption, making these devices ideal for high-performance optical computing systems. In this work, we exploit the symmetry properties of the collective modes of a nanolaser array for a simple binary classification task of small digit images. The implementation is based on a 8 × 8 nanolaser array and relies on the activation of a collective optical mode of the array—the so-called “zero-mode”—under spatially modulated pump patterns.

Experimental demonstration of mode selection in bridge-coupled metallo-dielectric nanolasers.

We experimentally demonstrate bridge-coupled metallo-dielectric nanolasers that can operate in the in-phase or out-of-phase locking modes at room temperature. By varying the length of the bridge, we show that the coupling coefficients can be realized in support of the stable operation of any of these two modes. Both coupled nanolaser designs have been fabricated and characterized for experimental validation. Their lasing behavior has been confirmed by the spectral evolution, light-in light-out characterizations, and emission linewidth narrowing. The operating mode is identified from the near-field and far-field emission pattern measurements. To the best of our knowledge, this is the first demonstration of mode selection in bridge-coupled metallo-dielectric nanolasers, which can serve as building blocks in nanolaser arrays for applications in imaging, virtual reality devices, and lidars.

Polarized Stimulated Emission of 2D Ensembles of Plasmonic Nanolasers

Plasmonic nanolasers produce coherent light with wavelengths on a scale similar to their own or larger. In the past decade they have attracted intense interest, particularly from the emerging areas of integrated photonic circuits and biomedicine. Despite these capabilities, plasmonic nanolasers are still not completely understood, and this lack of understanding leads to confusing them with spasers and random lasers. Herein, the operation of pure spaser‐based plasmonic nanolaser arrays is presented. For this, a monolayer of silver nanoparticles (NPs) affixed to a dielectric surface and covered with a fluorescent polymethyl methacrylate (PMMA)–coumarin solid composite is investigated. The input–output characteristic measured for the composites on a bare substrate (without Ag NPs) reveals that the emission at pump pulse energies above 2.4 mJ (at 355 nm excitation wavelength) stops growing, and instead is inhibited by saturation. In contrast, in such structures with Ag NPs an additional emission band pops up over a fluorescence background. It has a spectral width order of units of nanometers and its intensity grows faster than at lower pump pulse energies, revealing a nonlinear dependence of the input–output characteristic. The spaser‐based lasing observed is completely linearly polarized and clearly directed as 45° from the substrate.

Nanolaser arrays: toward application-driven dense integration

AbstractThe 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.

Multipoint Nanolaser Array in an Individual Core–Shell CdS Branched Nanostructure

AbstractNanoscale laser arrays are attractive for their potential applications in highly integrated nanodevices, which are always obtained by nanowire arrays with complicated fabrication techniques. Here, a quite different nanolaser array is successfully realized based on a highly ordered core–shell CdS branched nanostructure with implanted Sn nanoparticles in junctions that split the individual multichannel nanostructures to various microcavities with effective light confinement and oscillation, thus to achieve a multipoint nanolaser array. Under the excitation of an ultraviolet laser, the strong band‐edge emission can be well reflected between Sn nanoparticles at junctions and effectively scattered into branch segments due to Sn nanoparticles existence in junctions, furthermore oscillating in various microcavities along trunks or branches to form multipoint lasing from Fabry‐Pérot (F‐P) mode with a quality factor up to 990 and the low threshold at around 3.78 MW cm−2. The corresponding fluorescent microscope images further demonstrate the formation of multipoint F‐P lasing at various segments. The theoretical simulation indicates that implanted Sn nanoparticles work as hot point to enhance the confinement of light around the Sn centers. The existence of surface plasmon from the Sn metal particles is further confirmed by the polarization dependent photoluminescence measurement. The results provide a new way to realize nanolaser arrays.

Near-Infrared Organic Single-Crystal Nanolaser Arrays Activated by Excited-State Intramolecular Proton Transfer

<h2>Summary</h2> Near-infrared (NIR) solid-state lasers (SSLs) have advanced telecommunication, spectroscopy, and medical diagnosis. However, the development of organic NIR SSLs still faces severe challenges due to the low stimulated emission of narrow-band-gap molecules and the lack of the effective four-level energy system for population inversion. Here, we fabricated organic single-crystal nanowire arrays based on an excited-state intramolecular proton transfer (ESIPT)-active organic small molecule. The dynamic intramolecular proton transfer within ∼2.5 ps verified the establishment of the four-level energy system. Consequently, room-temperature single-mode 775-nm lasing with a low lasing threshold <i>P</i>_th of 9.9 μJ cm⁻² is achieved from the nanowire arrays with the length of <i>L</i> = 10 μm. Our work gives the unambiguous demonstration of the mechanism of ESIPT lasers and the first realization of organic nanolaser arrays over 760 nm, which will boost the practical application of integrated organic coherent light sources at near-infrared wavelength.

Control of molecular packing toward a lateral microresonator for microlaser array

We demonstrated a facile method to prepare uniform nanolaser arrays based on a transverse lateral Fabry–Pérot (FP) microresonator built within single-crystalline organic microribbons of 1,4-bis((E)-2,4-dimethylstyryl)-2,5-dimethylbenzene (6M-DSB).

Room temperature III–V nanolasers with distributed Bragg reflectors epitaxially grown on (001) silicon-on-insulators

Efficient, scalable, bufferless, and compact III–V lasers directly grown on (001)-oriented silicon-on-insulators (SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of III–V telecom nanolaser arrays with integrated distributed Bragg reflectors (DBRs) epitaxially grown on industry-standard (001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around 1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale III–V light emitters on Si-photonics standard (001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.

Random Organic Nanolaser Arrays for Cryptographic Primitives.

Next-generation high-security cryptography and communication call for nondeterministic generation and efficient authentication of unclonable bit sequences. Physical unclonable functions using inherent randomness in material and device fabrication process have emerged as promising candidates for realizing one-way cryptographic systems that avoid duplication and attacks. However, previous approaches suffer from the tradeoffs between low-efficiency fabrication and complicated authentication. Here, all-photonic cryptographic primitives by solution printing of organic nanolaser arrays with size-dependent dual lasing emission are reported. The stochastic distribution of organic solution into discrete capillary bridges, triggered by high-rate solvent evaporation, on a periodic topographical template yields organic single crystals with regulated position, alignment, and random size, which ensures high entropy. Stimulated emission from different vibrational sublevels and the intrinsic self-absorption effect permit size-dependent dual-wavelength lasing emission at wavelengths of 660 and/or 720 nm, which can be efficiently encoded into quaternary cryptographic keys with high reliability. High entropy, solution-processed programming and all-photonic authentication of random organic nanolaser arrays facilitate their cryptographic implementation in secure communication with high throughput, efficiency, and low cost.

Top-down fabrication of GaN nano-laser arrays by displacement Talbot lithography and selective area sublimation

We show that a 4 μm thick GaN layer grown by metal-organic vapour phase epitaxy can be transformed into a well-organized array of GaN nanowires (NWs) using displacement Talbot lithography and selective area sublimation. The optical quality of the GaN NWs obtained by this method is attested by their room temperature photoluminescence and the observation of lasing under optical pumping with a minimum excitation power density threshold of 2.4 MW cm−2.

Telecom InP/InGaAs nanolaser array directly grown on (001) silicon-on-insulator.

A compact, efficient, and monolithically grown III-V laser source provides an attractive alternative to bonding off-chip lasers for Si photonics research. Although recent demonstrations of microlasers on (001) Si wafers using thick metamorphic buffers are encouraging, scaling down the laser footprint to nanoscale and operating the nanolasers at telecom wavelengths remain significant challenges. Here, we report a monolithically integrated in-plane InP/InGaAs nanolaser array on (001) silicon-on-insulator (SOI) platforms with emission wavelengths covering the entire C band (1.55μm). Multiple InGaAs quantum wells are embedded in high-quality InP nanoridges by selective-area growth on patterned (001) SOI. Combined with air-cladded InP/Si optical cavities, room-temperature operation at multiple telecom bands is obtained by defining different cavity lengths with lithography. The demonstration of telecom-wavelength monolithic nanolasers on (001) SOI platforms presents an important step towards fully integrated Si photonics circuits.

Room-temperature InP/InGaAs nano-ridge lasers grown on Si and emitting at telecom bands

Semiconductor nano-lasers grown on silicon and emitting at the telecom bands are advantageous ultra-compact coherent light sources for potential Si-based photonic integrated circuit applications. However, realizing room-temperature lasing inside nano-cavities at telecom bands is challenging and has only been demonstrated up to the E band. Here, we report on InP/InGaAs nano-ridge lasers with emission wavelengths ranging from the O, E, and S bands to the C band operating at room temperature with ultra-low lasing thresholds. Using a cycled growth procedure, ridge InGaAs quantum wells inside InP nano-ridges grown on patterned (001) Si substrates are designed as active gain materials. Room-temperature lasing at the telecom bands is achieved by transferring the InP/InGaAs nano-ridges onto a SiO2/Si substrate for optical excitation. We also show that the operation wavelength of InP/InGaAs nano-lasers can be adjusted by altering the excitation power density and the length of the nano-ridges formed in a single growth run. These results indicate the excellent optical properties of the InP/InGaAs nano-ridges grown on (001) Si substrates and pave the way towards telecom InP/InGaAs nano-laser arrays on CMOS standard Si or silicon-on-insulator substrates.