Showing papers on "Nanolaser published in 2013"

Polytypic InP Nanolaser Monolithically Integrated on (001) Silicon

Abstract: On-chip optical interconnects still miss a high-performance laser monolithically integrated on silicon. Here, we demonstrate a silicon-integrated InP nanolaser that operates at room temperature with a low threshold of 1.69 pJ and a large spontaneous emission factor of 0.04. An epitaxial scheme to grow relatively thick InP nanowires on (001) silicon is developed. The zincblende/wurtzite crystal phase polytypism and the formed type II heterostructures are found to promote lasing over a wide wavelength range.

Fabrication challenges of electrical injection metallic cavity semiconductor nanolasers

Abstract: The recently emerged metallic-cavity nanolasers have opened a new phase of miniaturization of semiconductor lasers down to sub-wavelength scale. This new type of semiconductor lasers is suitable for many low-power applications due to its small size, tight optical confinement and good heat dissipation. However, there are major technical challenges in the fabrication of such nanolasers that must be overcome to make high-quality devices with high yield needed for practical applications. Here we will discuss several fabrication issues that are critical to the device performance. These issues, including device patterning, pillar etching, surface passivation and metal deposition, will determine both optical and electrical properties, especially the lifetime, threshold, and efficiency of a nanolaser.

An electrical injection metallic cavity nanolaser with azimuthal polarization

Abstract: We demonstrated for the first time an azimuthally polarized laser source from an electrically driven metallic cavity nanolaser with a physical cavity volume of 0.146 λ3 (λ = 1416 nm). Single TE01 mode lasing at 78 K was achieved by taking the advantages of the large free spectral range in such nanoscale lasers and the azimuthal polarization of lasing emission was verified experimentally. Mode shift controlled by device cavity radius was observed over a large wavelength range from 1.37 μm to 1.53 μm. Such metallic cavity nanolaser provides a compact electrically driven laser source for azimuthally polarized beam.

All-analytical semiclassical theory of spaser performance in a plasmonic nanocavity

Abstract: Experimental approaches to manipulating light-matter interaction at the nanoscale level have quickly advanced in recent years, leading to the use of surface plasmon amplification by stimulated emission of radiation (spaser) in plasmonic nanocavities. Yet, a well-understood analytical theory to quantitatively explain certain characteristics of the spaser system has still been lacking and is greatly needed. Here, we develop an all-analytical semiclassical theory to investigate the energy exchange between active materials and fields and the spaser performance in a plasmonic nanocavity. The theory incorporates the four-level atomic rate equations in association with the classical oscillator model for active materials and Maxwell's equations for fields, thus allowing one to uncover the relationship between the characteristics of the spaser (the output power, saturation, and threshold) and the nanocavity parameters (quality factor, mode volume, loss, and spontaneous emission efficiency), atomic parameters (number density, linewidth, and resonant frequency), and external parameters (pumping rate). The semiclassical theory has been employed to analyze previous spaser experiments and shows that using a single gold nanoparticle plasmonic nanocavity to ignite the spaser is very difficult due to its high threshold. The theory can be commonly used in understanding and designing all novel microlaser, nanolaser, and spaser systems.

Theory of nanolaser devices: Rate equation analysis versus microscopic theory

Abstract: A rate equation theory for quantum-dot-based nanolaser devices is developed. We show that these rate equations are capable of reproducing results of a microscopic semiconductor theory, making them an appropriate starting point for complex device simulations of nanolasers. The input-output characteristics and the modulation response are investigated and the limits of the rate equation approach are discussed.

Unequivocal differentiation of coherent and chaotic light through interferometric photon correlation measurements

Abstract: We present a novel experimental technique that can differentiate unequivocally between chaotic light and coherent light with amplitude fluctuations, and thus permits us to characterize unambiguously the output of a laser. This technique consists of measuring the second-order intensity cross correlation at the outputs of an unbalanced Michelson interferometer. It is applied to a chaotic light source and to the output of a semiconductor nanolaser whose ``standard'' intensity correlation function above threshold displays values compatible with a mixture of coherent and chaotic light. Our experimental results demonstrate that the output of such lasers is not partially chaotic but is indeed a coherent state with amplitude fluctuations.

Stochastically sustained population oscillations in high-β nanolasers

Abstract: Nonlinear dynamical systems involving small populations of individuals may sustain oscillations in the population densities arising from discrete changes in population numbers due to random events. By applying these ideas to nanolasers operating with small numbers of emitting dipoles and photons at threshold, we show that such lasers should display photon and dipole population cycles above threshold, which should be observable as a periodic modulation in the second-order correlation function of the nanolaser output. Such a modulation was recently reported in a single-mode vertical-cavity surface-emitting semiconductor laser.

Self-pulsing nanocavity laser

Abstract: We propose a scheme to achieve controllable self-pulsing operation in a semiconductor photonic-crystal nanolaser. The scheme is based on coupling two asymmetric nanocavities and pumping only one of them. As a result, either periodic or chaotic subnanosecond $Q$-switched pulses can emerge. A coupled-mode approach is used to model the system and study the bifurcation diagram. An experimental realization is proposed on the basis of two evanescently coupled photonic-crystal nanocavities.

Dynamical Properties of Nanolasers Based on Few Discrete Emitters

Abstract: We investigate the dynamical properties of nanolasers comprising a few two-level emitters coupled to an optical cavity. A set of rate equations is derived, and is shown to agree very well with a solution of the full master equation model. Using a linearized version of these rate equations, we can analytically express the response of the nanolaser to a modulation of the pumping rate. These results are compared with the modulation response obtained directly from the master equation using a novel method. We show that contrary to conventional semiconductor lasers, the nanolaser is typically over-damped and displays a dip in the modulation bandwidth as the two-level systems become inverted. Both these features can be traced back to the use of discrete emitters that are incoherently pumped.

Hybrid Single Quantum Well InP/Si Nanobeam Lasers for Silicon Photonics

Abstract: We report on a hybrid InP/Si photonic crystal nanobeam laser emitting at 1578 nm with a low threshold power of ∼14.7 μW. Laser gain is provided from a single InAsP quantum well embedded in a 155 nm InP layer bonded on a standard silicon-on-insulator wafer. This miniaturized nanolaser, with an extremely small modal volume of 0.375(λ/n)^3, is a promising and efficient light source for silicon photonics.

Dynamical properties of nanolasers based on few discrete emitters

Abstract: We investigate the dynamical properties of nanolasers comprising a few two-level emitters coupled to an optical cavity. A set of rate equations is derived, which agree very well with a solution of the full master equation model and makes it simple to investigate the properties of the system. Using a linearized version of these rate equations, we can analytically express the response of the nanolaser to a modulation of the pumping rate. These results are compared to the modulation response obtained directly from the master equation using a novel method. Using the rate equation method, we calculate the modulation bandwidth and show that, contrary to conventional semiconductor lasers, the nanolaser is typically over-damped and displays a dip in the modulation bandwidth as the two-level systems become inverted. Both these features can be traced back to the modeling of the emitters as two-level systems that are incoherently pumped.

Linewidth enhancement in spasers and plasmonic nanolasers

Abstract: The concept of spaser as the coherent near-field generator and nanolaser based on nanoscale plasmonic resonators has been successfully demonstrated in number of experiments. Here we have developed the theoretical framework for the basic linewidth description of these active plasmonic structures and, in particular, linewidth enhancement - additional line broadening due to the resonator noise. In order to achieve this, we have introduced explicitly the time dependence in the quasistatic description of localized surface plasmon resonances via inclusion of the dispersion of a spectral parameter defining the resonant frequency. Linewidth enhancement factor was estimated for semiconductor gain medium and was found to be of order of 3 to 6, strongly depending on carrier density in the active layer, and resulting in more than order of magnitude broader linewidth compared to that, predicted by the Schawlow-Townes theory.

Carrier saturation in multiple quantum well metallo-dielectric semiconductor nanolaser: Is bulk material a better choice for gain media?

Abstract: Although multi quantum well (MQW) structure is frequently suggested as the appropriate medium for providing optical gain in nanolasers with low threshold current, we demonstrate that in general bulk gain medium can be a better choice. We show that the high threshold gain required for nanolasers demands high threshold carrier concentrations and therefore a highly degenerate condition in which the barriers between the quantum wells are heavily pumped. As a result, there occurs spontaneous emission from the barrier in very dissipative low Q modes or undesired confined higher Q modes with resonance wavelengths close to the barrier bandgap. This results in a competition between wells and barriers that suppresses lasing. A complete model involving the optical properties of the resonant cavity combined with the carrier injection in the multilayer structure is presented to support our argument. With this theoretical model we show that while lasing is achieved in the nanolaser with bulk gain media, the nanolaser with MQW gain structure exhibits well emission saturation due to the onset of barrier emission.

Nanolaser generator using graphene electrode and method for manufacturing the same

Abstract: The present disclosure relates to a nanolaser generator using a transparent graphene electrode, a method for manufacturing the same, and a single nanopillar LED using the same. The nanolaser generator includes a microdisk resonator, a protruding dielectric ring provided to surround a boundary surface of the microdisk resonator, an external dielectric ring provided at an outer side of the microdisk resonator, and a transparent graphene electrode provided at upper surfaces of the microdisk resonator, the protruding dielectric ring and the external dielectric ring. Therefore, the processes required for generating a nanolaser may be reduced by half in comparison to a general technique, and a nanolaser may be generated just with a micro current.

A comparison between experiment and theory on few-quantum-dot nanolasing in a photonic-crystal cavity

Abstract: We present an experimental and theoretical study on the gain mechanism in a photonic-crystal-cavity nanolaser with embedded quantum dots. From time-resolved measurements at low excitation power we find that four excitons are coupled to the cavity. At high excitation power we observe a smooth low-threshold transition from spontaneous emission to lasing. Before lasing emission sets in, however, the excitons are observed to saturate, and the gain required for lasing originates rather from multi-excitonic transitions, which give rise to a broad emission background. We compare the experiment to a model of quantum-dot microcavity lasers and find that the number of excitons that must be included to fit the data largely exceeds the measured number, which shows that transitions involving the wetting layer can provide a surprisingly large contribution to the gain.

Waveguide-coupled nanolasers in III–V membranes on silicon

Abstract: Semiconductor nanolasers provide an attractive route towards high density photonic integrated circuits in low power applications such as optical interconnects. In this paper we present the concept of a waveguide-coupled nanolaser for integration in a CMOS compatible photonic platform. We exploit metallic and dielectric confinement to provide high quality factors exceeding 500 in a wavelength-scale cavity, that provides efficient cooling and cross-talk immunity due to the metal coverage. We present simulations detailing the design considerations for high quality factors and efficient waveguide coupling. Optical and electrical simulations predict room temperature operation at 1.55 μm with a threshold current of 120 μA and a differential quantum efficiency of 0.16. We also discuss briefly the challenges of fabricating these devices and integrating them in the photonic platform.

Photonic crystal nanolaser sensors with ALD coating

Abstract: Nanolaser sensors achieve ultrahigh sensitivity for biomolecules while unexpected noise was an issue. In this study, it was suppressed by ALD coating. Higher permittivity coating improved the sensitivity, suggesting unknown principles of this sensor.

Design of Ultra-Small Metallic-Semiconductor Nano-Ring Cavity Lasers

Abstract: We present design and analysis of metallic-semiconductor nanoring laser lasing at around 1450 nm wavelength, utilizing a body-of-revolution finite-difference-time-domain (BOR-FDTD) simulation incorporated with a semiclassical multilevel model for semiconductor gain medium and the Drude-Lorentz model for metal, which is developed for efficient simulation of disk/ring plasmonic laser. As compared to other literature, our nanoring laser works in radial mode with resonance cycle, m=1, which could facilitate potential in-plane out-coupling, and is wafer bonded onto Si platform for potential electronic-photonic integration. The total footprint, the physical device volume, and the effective mode volume of the nanolaser are only about 0.038 μm2, 1.1(λ/2n)3, and 0.001(λ/2n)3, respectively, where n is the average refractive index of the gain medium. To the best of our knowledge, our nanolaser is the smallest reported to date.

Design of a waveguide-coupled nanolaser for photonic integration

Abstract: Semiconductor nanolasers with metallo-dielectric cavities are considered as promising light sources for ultra-dense photonic integration. We present the design of a waveguide-coupled nanolaser based on optical and electrical simulations.

Metallic nanowire lasers

Abstract: We investigate a nanolaser structure with a gold nanowire that supports long-range surface plasmon polaritons (LR-SPPs). A high refractive index semiconductor gain medium surrounding the nanowire allows the LR-SPPs to be well bound to the nanowire even for a small radius of ∼15 nm with sufficiently small attenuation. An outermost gold shield with a radius of 400 nm is introduced to prohibit the mode from radiating out to free space when the modal cutoff-like feedback structure is used to confine the propagating mode longitudinally. Numerical simulations for an optimized structure show that the quality factor and lasing threshold gain of the resonant mode at room temperature are 158 and 1590 cm−1, respectively. We also find that the nanolaser supports another type of plasmonic resonant mode with localized surface plasmons on the nanowire with the outermost gold shield, which possesses a quality factor of 220 and a threshold gain of 950 cm−1. These gain coefficients can be obtained in bulk semiconductors.

Nanolaser in the self-generated nonequilibrium environment: Quantum fluctuations and entanglement

Abstract: We investigate the dynamics of the spaser-based nanolaser in the strong incoherent pumping regime in the quantum limit when the photon number is the order of unity. We consider the situation where the newly irradiated photon finds itself in the cloud of earlier irradiated photons that are not thermalized. As the result the entanglement of nanoparticle with quantum dot degrees of freedom in the nanolaser and the lasing intensity increases several times. In fact the nonthermal bath effectively makes the nanolaser "more quantum" and master equation for the nanolaser density matrix nonlinear and selfconsistent.

All-color plasmonic nanolasers with ultralow thresholds

Abstract: Diffraction-unlimited semiconductor nanolasers are demonstrated by using single shape-controlled InGaN/GaN core-shell nanorods as laser gain media on Ag films epitaxially grown on Si substrates. The use of atomically smooth Ag films allows us to fabricate low-loss plasmonic cavities for ultralow-threshold, continuous-wave (CW) nanolaser operation above liquid nitrogen temperature. Furthermore, the tunable band-gap energy of the InxGa1-xN alloy makes it possible to realize laser emission in the full visible spectrum.

Selective detection of sub-atto-molar streptavidin in 10^13 fold impure sample using nanoslot photonic crystal nanolaser

Abstract: Biosensors which can selectively detect a very small amount of biomarker protein in human blood are desired toward early diagnoses of severe diseases. However, no methods simultaneously satisfy the requirements such as high sensitivity, high selectivity, simple detection, and immediacy. We succeeded in detecting ultra-low-concentration streptavidin (SA) even in a highly impure sample using nanoslot photonic crystal (PC) nanolasers. This nanolaser consists of GaInAsP semiconductor slab with a periodic airhole array. Since the total device area is no larger than 20 × 20 μm 2 , highthroughput fabrication is possible even using e -beam lithography. Moreover, it is easy to operate by photopumping through free-space optics. Since the evanescent wave of the laser mode penetrates from the PC slab, the laser wavelength changes sensitively to the environmental index. In the sensing experiment, we first functionalized the devices with biotin, and then measured the wavelength in ultrapure water before and after immersing in the solutions with various concentrations of SA. As a result, we evaluated that the detection limit of SA is 16 zM. In another experiment, we put 1 μM BSA into the solution as a contaminant, and repeated the same measurement. We detected 100 zM SA even in the impure solution only when biotin is functionalized in advance, meaning a selectivity ratio (BSA / SA) of 10 13 . Thus this device achieves unprecedentedly high sensitivity and selectivity in addition to the simple fabrication and fast sensing. It is very promising as a point of care device for medical diagnoses.

Design of ultrasmall plasmonic coaxial lasers on Si

Abstract: An ultrasmall plasmonic coaxial laser made of metal-semiconductor-metal on a sil- icon substrate through an interlayer bonding was designed. From the effective refractive indices and the transparent material gain, the nanoscale structural dimensions with both the radius and the width at 80 nm for the coaxial plasmonic waveguide were decided. The influence of the interlayer bonding material on the optimization of resonant wavelength and Q-factor was evalu- ated. A three-dimensional body-of-revolution finite-difference time-domain method was used to show that a coaxial cavity with a SiO2 interlayer can laze at around 1480-nm wavelength with a net optical threshold power density of about 800 W∕cm 2 and a subwavelength mode volume of 0.014ðλ∕2nÞ 3 . This nanolaser on silicon platform will benefit those working on nanophotonic integrated circuits. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1 .JNP.7.070598)

Specific Detection of Marker Protein Related with Alzheimer's Disease Using Nanolaser Sensor Array Based on Photonic Crystal

Abstract: することができる。本研究ではフォトニック結晶ナノレーザセンサを用いて,細胞に強制発現さ せた CRMP2 の検出を試みた。 HEK293T 細胞に CRMP2 を強制発現させ,細胞を破砕することで CRMP2 を含む細胞破砕液を 得た。CRMP2 を検出するため,ナノレーザセンサ表面に抗 CRMP2 抗体を固定した。また,比較 対象群として,同じ CRMP ファミリーである CRMP1 を認識する抗 CRMP1 抗体を固定したナノ レーザも合わせて用いた。まず、非特異吸着を抑制するため、予めウシ血清アルブミン(BSA)を抗 体未固定の領域に吸着させた。その後、各濃度に調整した CRMP2 溶液にナノレーザを浸漬させ た。この時の波長シフトを図 1 に示す。どちらの抗体を固定したナノレーザにおいても、BSA の 物理吸着によって波長シフトが生じた。次に CRMP2 を含む溶液にナノレーザを浸漬させたとこ ろ、抗 CRMP2 抗体を固定したナノレーザでは濃度依存的に波長シフトが増加した。一方、抗 CRMP1 抗体を固定したナノレーザでは波長シフトが観察されなかった。構造の似ているタンパク

Self-pulsing and fast excitable response in micropillar and nano-lasers with saturable absorber

Abstract: We present recent experimental and theoretical results on the nonlinear dynamics of semiconductor micro and nano-lasers. First, fast excitable, neuron-like, dynamics is experimentally evidenced in a micropillar laser with intracavity saturable absorber with fast response times in the 200ps range. We study also the refractory time in this system and show the existence of a relative refractory period, analogue to what is found in neurons. Second, we propose a scheme for achieving self-pulsing in nanolasers based on asymmetrically coupled cavities and study theoretically its implementation in a photonic-crystal based system. Short pulses with duration as short as 35ps with multi-GHz repetition rates are found, as well as a region giving rise to a chaotic dynamics. We also predict a parameter region where the self-pulsing bifurcation can lead to ultra-fast excitable dynamics in such a nanolaser.

Label-free imaging of live cell using large-scale photonic crystal nanolaser array

Abstract: We integrated 441 photonic crystal nanolasers and applied it to label-free live cell imaging. Since the mechanical strength of the nanolaser array was improved by bonding on a glass substrate, the imaging area was expanded from previous 25 × 25 μm 2 to 100 × 100 μm 2 . We successfully acquired cell images, which should reflect the intracellular and/or the attachment conditions. By continuously mapping the wavelengths of all nanolasers, we successfully observed the time-dependent images displaying the cell behaviors. Reagents were injected to stimulate the cells, and the observation was continued until the cell reaction was saturated. The results show the reasonable behaviors against the reagents.