Nanowire Lasers Research Articles

Lasing up to 380 K in a sublimated GaN nanowire

We report on GaN nanowire lasers fabricated by selective-area sublimation, and we show that sublimated GaN nanowires can exhibit ultraviolet lasing action under optical pumping beyond room temperature, up to 380 K. We study by microphotoluminescence the temperature-dependent behavior of single nanowire lasers between 7 K and 380 K and extract a characteristic temperature of T = 126 K. We finally present a statistical study of the maximum lasing temperature in individual sublimated GaN nanowires and use it to assess the performance of the selective-area sublimation method for nanowire-based lasing applications.

Light-Emitting Nanophotonic Designs Enabled by Ultrafast Laser Processing of Halide Perovskites.

Nanophotonics based on resonant nanostructures and metasurfaces made of halide perovskites have become a prospective direction for efficient light manipulation at the subwavelength scale in advanced photonic designs. One of the main challenges in this field is the lack of large-scale low-cost technique for subwavelength perovskite structures fabrication preserving highly efficient luminescence. Here, unique properties of halide perovskites addressed to their extremely low thermal conductivity (lower than that of silica glass) and high defect tolerance to apply projection femtosecond laser lithography for nanofabrication with precise spatial control in all three dimensions preserving the material luminescence efficiency are employed. Namely, with CH3 NH3 PbI3 perovskite highly ordered nanoholes and nanostripes of width as small as 250 nm, metasurfaces with periods less than 400 nm, and nanowire lasers as thin as 500 nm, corresponding to the state-of-the-art in multistage expensive lithographical methods are created. Remarkable performance of the developed approach allows to demonstrate a number of advanced optical applications, including morphology-controlled photoluminescence yield, structural coloring, optical- information encryption, and lasing.

Optical property and lasing of GaAs-based nanowires

GaAs-based nanowire (NW) lasers working in the infrared region is critical in integrated optoelectronics. In the past few decades, the field of NW lasers has developed rapidly. Compared with materials working in the ultraviolet and visible ranges, GaAs-based infrared NW lasers, however, are more difficult to achieve because of their specific properties. In this review, we focus on the recent developments of GaAs-based NWs, more especially, the optical property and lasing of GaAs-based NWs. The growth mechanism of GaAs NWs is introduced in detail, including the crystal phase control and the growth of complex structures. Subsequently, the influence and improvement of the optical properties of GaAs-based NWs are introduced and discussed. Finally, the design and latest progress of GaAs-based NW lasers are put forward.

Miniaturized GaAs Nanowire Laser with a Metal Grating Reflector.

This work proposed a miniaturized nanowire laser with high end-facet reflection. The high end-facet reflection was realized by integrating an Ag grating between the nanowire and the substrate. Its propagation and reflection properties were calculated using the finite elements method. The simulation results show that the reflectivity can be as high as 77.6% for a nanowire diameter of 200 nm and a period of 20, which is nearly three times larger than that of the nanowire without a metal grating reflector. For an equal length of nanowire with/without the metal grating reflector, the corresponding threshold gain is approximately a quarter of that of the nanowire without the metal grating reflector. Owing to the high reflection, the length of the nanowire can be reduced to 0.9 μm for the period of 5, resulting in a genuine nanolaser, composed of nanowire, with three dimensions smaller than 1 μm (the diameter is 200 nm). The proposed nanowire laser with a lowered threshold and reduced dimensions would be of great significance in on-chip information systems and networks.

Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing

Continuous room temperature nanowire lasing from silicon-integrated optoelectronic elements requires careful optimisation of both the lasing cavity Q-factor and population inversion conditions. We apply time-gated optical interferometry to the lasing emission from high-quality GaAsP/GaAs quantum well nanowire laser structures, revealing high Q-factors of 1250 ± 90 corresponding to end-facet reflectivities of R = 0.73 ± 0.02. By using optimised direct–indirect band alignment in the active region, we demonstrate a well-refilling mechanism providing a quasi-four-level system leading to multi-nanosecond lasing and record low room temperature lasing thresholds (~6 μJ cm−2 pulse−1) for III–V nanowire lasers. Our findings demonstrate a highly promising new route towards continuously operating silicon-integrated nanolaser elements.

Characterization, Selection, and Microassembly of Nanowire Laser Systems.

Semiconductor nanowire (NW) lasers are a promising technology for the realization of coherent optical sources with ultrasmall footprint. To fully realize their potential in on-chip photonic systems, scalable methods are required for dealing with large populations of inhomogeneous devices that are typically randomly distributed on host substrates. In this work two complementary, high-throughput techniques are combined: the characterization of nanowire laser populations using automated optical microscopy, and a high-accuracy transfer-printing process with automatic device spatial registration and transfer. Here, a population of NW lasers is characterized, binned by threshold energy density, and subsequently printed in arrays onto a secondary substrate. Statistical analysis of the transferred and control devices shows that the transfer process does not incur measurable laser damage, and the threshold binning can be maintained. Analysis on the threshold and mode spectra of the device populations proves the potential for using NW lasers for integrated systems fabrication.

Ultrafast plasmonic lasing from a metal/semiconductor interface.

To date, plasmonic nanowire lasers mostly adopt hybrid plasmonic waveguides, while there is a lack of study in terms of the confinement effect and the corresponding ultrafast dynamics of non-hybridized plasmonic lasers. Here, we report ultrafast plasmonic nanowire lasers composed of a single CH3NH3PbBr3 nanowire on a silver film without any insulating layer at room temperature. The non-hybridized plasmonic nanowire lasers exhibit ultrafast lasing dynamics with around 1.9 ps decay rate and 1 ps peak response time. Such values are among the best ones ever reported. Interestingly, the threshold of the non-hybridized plasmonic nanowire lasers is in the same order as that of their hybrid counterparts. The low threshold is due to the ultra-flat single-crystal silver films and high-quality single-crystal perovskite nanowires. The non-hybridized plasmonic lasing in CH3NH3PbBr3 nanowires originates from the stimulated emission of an electron-hole plasma based on our experiments. This work deepens the understanding of non-hybridized plasmonic lasers and paves the way to design electric pump plasmonic lasers by getting rid of insulating layers.

III–V nanowire array telecom lasers on (001) silicon-on-insulator photonic platforms

III–V nanowires have recently gained attention as a promising approach to enable monolithic integration of ultracompact lasers on silicon. However, III–V nanowires typically grow only along ⟨111⟩ directions, and thus, it is challenging to integrate nanowire lasers on standard silicon photonic platforms that utilize (001) silicon-on-insulator (SOI) substrates. Here, we propose III–V nanowire lasers on (001) silicon photonic platforms, which are enabled by forming one-dimensional nanowire arrays on (111) sidewalls. The one-dimensional photonic crystal laser cavity has a high Q factor >70 000 with a small footprint of ∼7.2 × 1.0 μm2, and the lasing wavelengths can be tuned to cover the entire telecom bands by adjusting the nanowire geometry. These nanowire lasers can be coupled to SOI waveguides with a coupling efficiency > 40% while maintaining a sufficiently high Q factor ∼18 000, which will be beneficial for low-threshold and energy-efficient operations. Therefore, the proposed nanowire lasers could be a stepping stone for ultracompact lasers compatible with standard silicon photonic platforms.

Mid-Infrared Lasing of Single Wurtzite InAs Nanowire.

Mid-infrared (MIR) photonics is a developing technology for sensing materials by their characteristic MIR absorptions. Since silicon (Si) is a low-loss material in most of the MIR region, Si photonic structures have been fabricated to guide and confine MIR light, and they allow us to achieve sensitive and integrated sensing devices. However, since the implementation of MIR light sources on Si is still challenging, we propose a thick indium arsenide (InAs) nanowire as an MIR laser that can couple to Si photonic structures with material manipulation. In this study, thick InAs nanowires are grown on an indium phosphide substrate with a self-catalyst vapor-liquid-solid method and transferred to gold-deposited SiO2/Si substrates. Low-temperature microphotoluminescence (PL) spectroscopy shows that InAs nanowires exhibit broad PL peaking at a wavelength of around 2.6 μm (3850 cm-1 in frequency), which corresponds to the bandgap energy of wurtzite InAs. At high optical pump fluences, single InAs nanowire exhibits sharp emission peaks, while their integrated intensity and polarization degree increase abruptly at the threshold pump fluence. These nonlinear behaviors indicate that the MIR lasing action takes place in the InAs nanowire in its cavity mode. Our demonstration of the MIR nanowire laser expands the wavelength coverage and potential application of semiconductor nanowires.

Fiber-Integrated Reversibly Wavelength-Tunable Nanowire Laser Based on Nanocavity Mode Coupling.

As an ideal miniaturized light source, wavelength-tunable nanolasers capable of emitting a wide spectrum stimulate intense interests for on-chip optoelectronics, optical communications, and spectroscopy. However, realization of such devices remains a major challenge because of extreme difficulties in achieving continuously reversibly tunable gain media and high quality (Q)-factor resonators on the nanoscale simultaneously. Here, exploiting single bandgap-graded CdSSe NWs and a Fabry-Pérot/whispering gallery mode (FP/WGM) coupling cavity, a free-standing fiber-integrated reversibly wavelength-tunable nanolaser covering a 42 nm wide spectrum at room temperature with high stability and reproducibility is demonstrated. In addition, a 1.13 nm tuning spectral resolution is realized. The substrate-free device design enables integration in optical fiber communications and information. With reversible and wide, continuous tunability of emission color and precise control per step, our work demonstrates a general approach to nanocavity coupling affording high Q-factors, enabling an ideal miniaturized module for a broad range of applications in optics and optoelectronics, with optical fiber integration.

Fast Lasing Wavelength Tuning in Single Nanowires

AbstractNanowire lasers hold great potential as nanoscale coherent light sources. The rapid wavelength tuning of such light sources is one of the most important parameters for practical applications. Although significant efforts have been made in the past decades, the fast and reversible lasing wavelength tuning in nanowires or structures alike remains a challenge. Here, by incorporating temperature‐dependent Varshni shift of the bandgap with ultralow thermal inertia of a free‐standing cadmium sulfide (CdS) nanowire, a fast lasing wavelength tuning in single nanowires with excellent reversibility is demonstrated. Above room temperature, a Varshni shift rate (≈0.16 nm K−1) twice larger than that at low temperature (≈ 0.085 nm K−1) is observed, and the nanowire lasing peak is tuned from 514 to 549 nm with step down to 0.075 nm K−1. Using a beam of CO2 laser pulses to instantaneously modulate the temperature of a free‐standing lasing nanowire, a reversible wavelength tuning at a rate of ≈48 000 nm s−1, which is about three orders of magnitude faster than that reported previously is achieved. The results herein suggest a very promising route to fast wavelength tuning in lasing nanowires or other nanostructures, which may lead to fast tunable nanolasers for a variety of nanophotonic applications.

Optimized waveguide coupling of an integrated III-V nanowire laser on silicon

The recent integration of III-V semiconductor nanowire (NW) lasers on silicon waveguides marked a key step toward their usage as coherent light sources for future silicon photonics applications. However, the low index contrast between III-V semiconductors and silicon results in a weak modal reflectivity, calling for improved design structures that enable both low-threshold lasing and good in-coupling efficiency into waveguides. Here, we perform numerical simulations to explore how the alternating refractive index of a silicon waveguide with a thin SiO2 interlayer can be used to significantly improve the reflectivity at the III-V–silicon interface to values of up to 83%. We further investigate the frequency dependencies of the end-facet reflectivity and in-coupling efficiency as a function of the nanowire and waveguide dimensions. Our results are kept general by the normalization to the nanowire radius R and show for a waveguide width of 2.75⋅R a maximum coupling efficiency of 50%. Variations in waveguide height or SiO2 interlayer thickness by ±0.1⋅R increase the coupling efficiency by a factor of 2, with little effect on the end-facet reflectivity. Ultimately, a prototypical NW-laser structure consisting of a 1.3-μm emitting InGaAs MQW active region in a core-multishell structure was simulated, showing an optimized low-threshold gain of <500 cm−1 for a TE01 mode with a coupling efficiency of ∼13%. By simplified approximations, we illustrate that these analyses can be adapted to a variety of material systems and serve as guidelines in the construction of optimized nanowire lasers on silicon-on-insulator waveguides for future on-chip optical interconnects.

Tailoring Spectral and Temporal Properties of Semiconductor Nanowire Lasers

AbstractSemiconductor optoelectronics have contributed tremendously to various aspects of the technological progress in the past. Recently, they also stimulate research in nanophotonics seeking to overcome the inherent limitations of electronic integrated circuits and satisfy the growing demand for faster on‐chip communications. In particular, nanowire (NW) lasers generate coherent light at the nanoscale and meanwhile work consistently at room temperature covering a huge spectral range from the ultraviolet down to the mid‐infrared depending on the NW material. The underlying physics of their electronic and photonic systems are also studied very recently, thus NW lasers become relevant as an emergent tool for a variety of practical applications. In this review, the origins determining the emission wavelength of the device are explained, and approaches toward efficient improvement of the NW laser devices in terms of emission energy tunability are summarized. The optical mode field distribution strongly influences the emission dynamics of the nanolaser device; it will be highlighted how increasing the light–matter interaction in plasmonic type nanolasers causes a significant acceleration of their temporal emission dynamics. Both spectral and temporal tuning will help to solve scientific and engineering challenges forging semiconductor nanowire lasers into powerful tools for nanosensing, nanospectroscopy, and nanotechnology.

Design of ZnO Nanowire Laser Single Mode and Study Its Properties

Designing of single-mode ZnO nanowire laser has been achieved. Studying its properties has also been considered. Analysis of single-mode rate equations indicates that the laser has threshold current of 53 mA, the output power of 30 mW at bias current of 70 mA and the slope efficiency around 1.77 mW/mA for the output power from both mirrors. The critical diameter for nanowire has been calculated and it is found to be 128 nm. The number of nanowire rods through designed area of dimensions (21µm×21µm) has also been calculated. The cavity of nanowire laser is (F-P). The results are compared with some experimental work of ZnO nanowire lasers and good agreement is found.

Single nanowire defined emission properties of ZnO nanowire arrays

We report on stimulated emission from vertically aligned, vapor transport grown, ZnO nanowire arrays, and pumped by three-photon absorption in intense near-infrared femtosecond laser pulses. In respect to single nanowires, arrays have the advantage of a higher light absorption and emission rate. The intensity and bandwidth of the emitted ultraviolet radiation as a function of the pump intensity is compared for nanowire arrays with different wire lengths, diameters, and spacing. The measured lasing thresholds for all arrays can be well described by the geometry of individual nanowire lasers, showing that coupling effects between the individual emitters in the arrays are negligible, even for the smallest 100 nm diameter wires with an average distance of 200 nm.

Highly Strained III-V-V Coaxial Nanowire Quantum Wells with Strong Carrier Confinement.

Coaxial quantum wells (QWs) are ideal candidates for nanowire (NW) lasers, providing strong carrier confinement and allowing close matching of the cavity mode and gain medium. We report a detailed structural and optical study and the observation of lasing for a mixed group-V GaAsP NW with GaAs QWs. This system offers a number of potential advantages in comparison to previously studied common group-V structures (e.g., AlGaAs/GaAs) including highly strained binary GaAs QWs, the absence of a lower band gap core region, and deep carrier potential wells. Despite the large lattice mismatch (∼1.7%), it is possible to grow defect-free GaAs coaxial QWs with high optical quality. The large band gap difference results in strong carrier confinement, and the ability to apply a high degree of compressive strain to the GaAs QWs is also expected to be beneficial for laser performance. For a non-fully optimized structure containing three QWs, we achieve low-temperature lasing with a low external (internal) threshold of 20 (0.9) μJ/cm2/pulse. In addition, a very narrow lasing line width of ∼0.15 nm is observed. These results extend the NW laser structure to coaxial III–V–V QWs, which are highly suitable as the platform for NW emitters.

High-frequency dynamics of evanescently-coupled nanowire lasers

We analyse the dynamics and conditions for stability in an array of two laterally-coupled nanowire lasers in terms of their separation, difference in resonant frequencies and pumping rate under conditions of weak coupling. We find that the regions of stability are very small and are found close to zero frequency offset between the lasers. Outside these regions various forms of instability including periodic oscillation, chaos and complex dynamics are predicted. Importantly, the analysis of the frequency of periodic oscillations for realistic laser separations and pumping yields values of order 100 GHz thus underlining the significant potential of nanowire laser arrays for ultra-high frequency on-chip systems with very low foot-print and energy requirements.

High-Detectivity Perovskite Light Detectors Printed in Air from Benign Solvents

Summary Here, we propose a simple and low-temperature approach for the synthesis of methylammonium lead halide perovskite inks based on sub-micrometer-sized particles with tunable band gap. The particles allow the formulation of inks in benign solvents, such as propan-2-ol, and the printing of the photoactive layers of planar photoconductors with scalable, large-area coating techniques under ambient conditions. When surface traps are passivated with [6,6]-phenyl-C61-butyric acid methyl ester fullerene (PCBM), a high photoconductive gain (exceeding 200 in the blue) and reduced noise produce record-high specific detectivities exceeding 7 × 1013 cmHz0.5/W and gain-bandwidth product values of 7.5 × 106 Hz. Given the extreme simplicity of the presented device architecture and the straightforward processing, yielding printable light detectors rivalling established technologies, the present work promises a short-term deployment of printed perovskite detectors in a multitude of opto-electronic applications.

Transition Metal and Rare Earth Element Doped Zinc Oxide Nanowires for Optoelectronics

Even though intrinsic semiconductor nanowires have already extraordinary optical properties, doping with optically active impurities significantly expands the potpourri of optoelectronic applications, such as for nanowire lasers or single photon emitters. This feature article therefore supplies a snapshot of the most recent progress on the structural and optical properties of transition metal and rare earth element doped zinc oxide (ZnO) nanowires using ion beam doping. Here, ion implantation is advantageous, as concurrent defect generation and diffusion upon subsequent annealing allows the formation of defect complexes. This scenario is in many cases even inevitable for the optical activation of the intra‐shell luminescence of the implanted impurities, as density functional theory calculations demonstrate. Finally, this article also provides the optimum preparation conditions for intense optical activity and a review on the specific luminescence properties of various optical centers in ZnO nanowires.

Near-Infrared Lasing at 1 μm from a Dilute-Nitride-Based Multishell Nanowire.

A coherent photon source emitting at near-infrared (NIR) wavelengths is at the heart of a wide variety of applications ranging from telecommunications and optical gas sensing to biological imaging and metrology. NIR-emitting semiconductor nanowires (NWs), acting both as a miniaturized optical resonator and as a photonic gain medium, are among the best-suited nanomaterials to achieve such goals. In this study, we demonstrate the NIR lasing at 1 μm from GaAs/GaNAs/GaAs core/shell/cap dilute nitride nanowires with only 2.5% nitrogen. The achieved lasing is characterized by an S-shape pump-power dependence and narrowing of the emission line width. Through examining the lasing performance from a set of different single NWs, a threshold gain, gth, of 4100-4800 cm-1, was derived with a spontaneous emission coupling factor, β, up to 0.8, which demonstrates the great potential of such nanophotonic material. The lasing mode was found to arise from the fundamental HE11a mode of the Fabry-Perot cavity from a single NW, exhibiting optical polarization along the NW axis. Based on temperature dependence of the lasing emission, a high characteristic temperature, T0, of 160 (±10) K is estimated. Our results, therefore, demonstrate a promising alternative route to achieve room-temperature NIR NW lasers thanks to the excellent alloy tunability and superior optical performance of such dilute nitride materials.