Polymer Halide Perovskites-Waveguides Integrated in Nanocellulose as a Wearable Amplifier-Photodetector System

Semiconductor organometallic halide (CH 3 NH 3 PbX 3 , X=Cl, Br, I) perovskites (MHP) have emerged as a very high promising material for optoelectronics. Their large absorption coefficients, high electronic mobilities, excellent quantum yield of emission at room temperature and tunable band-gap with the composition resulted in a new generation of photovoltaics and electronic devices. In this work, HPVK materials are successfully incorporated on a nanocellulose (NC) substrate with the intention to exploit the interesting properties of HPVK materials to construct wearable devices. In particular, a bilayer Poly(methyl methacrylate) /HPVK deposited on NC resulted in a suitable waveguide to demo…

Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots

We have investigated the temperature dependent recombination dynamics in two bimodally distributed InAs self assembled quantum dots samples. A rate equations model has been implemented to investigate the thermally activated carrier escape mechanism which changes from exciton-like to uncorrelated electron and hole pairs as the quantum dot size varies. For the smaller dots, we find a hot exciton thermal escape process. We evaluated the thermal transfer process between quantum dots by the quantum dot density and carrier escape properties of both samples. © 2012 American Institute of Physics.

Manipulating spontaneous emission of the CsPbI3 Perovskite NCs using hybrid (HMM-Mie resonator) structures

Birefringent porous silicon membranes for optical sensing

In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model …

Purcell-enhancement of the radiative PL decay in perylenediimides by coupling with silver nanoparticles into waveguide modes

In this work, an interesting approach to enhance the coupling between excitons and plasmons is proposed by integrating highly luminescent perylenediimides (PDIs) and Ag metal nanoparticles (MNPs) in the core of a multilayer dielectric waveguide. The combination of the weak plasmonic coupling and the high scattering of MNPs gives rise to a significant improvement of the PDI photoluminescence and Purcell factor (PF) in forward-scattering geometry. Furthermore, when the PDI-MNP system is used as the core of a multilayer waveguide, a Purcell factor enhancement larger than 10 is observed, which is explained by an increase in the exciton-plasmon coupling under the light confinement in the wavegui…

Outstanding nonlinear optical properties of methylammonium- and Cs-PbX3 (X = Br, I, and Br–I) perovskites: Polycrystalline thin films and nanoparticles

Metal Halide Perovskites (MHPs) have arisen as promising materials to construct cost-effective photovoltaic and light emission devices. The study of nonlinear optical properties of MHPs is necessary to get similar success in nonlinear photonic devices, which is practically absent in the literature. The determination of the third order nonlinear coefficients is typically done by the Z-scan technique, which is limited by the scattering of polycrystalline thin films. In this work, we have studied nonlinear optical properties of polycrystalline CH3NH3PbX3 (MAPbX3) thin films and colloidal CsPbX3 nanoparticles with three different bandgaps (X3 = I3, Br3, and Br1.5I1.5). Their bright generation o…

Tuning optical/electrical properties of 2D/3D perovskite by the inclusion of aromatic cation

The employment of bulky aliphatic cations in the manufacture of moisture-stable materials has triggered the development and application of 2D/3D perovskites as sensitizers in moisture-stable solar cells. Although it is true that the moisture stability increases, it is also true that the photovoltaic performance of 2D/3D PVK materials is severely limited owing to quantum and dielectric confinement effects. Accordingly, it is necessary the synthesis and deep optical characterization of materials with an adequate management of dielectric contrast between the layers. Here, we demonstrate the successful tuning of dielectric confinement by the inclusion of a conjugated molecule, as a bulky cation…

Nonlinear optical properties of CH3NH3PbX3 CsPbX3 (X=Br,I) perovskites

Enhanced nanoscopy of individual CsPbBr3 perovskite nanocrystals using dielectric sub-micrometric antennas

We demonstrate an efficient, simple, and low-cost approach for enhanced nanoscopy in individual green emitting perovskite (CsPbBr3) nanocrystals via TiO2 dielectric nanoantenna. The observed three- to five-fold emission enhancement is attributed to near-field effects and emission steering promoted by the coupling between the perovskite nanocrystals and the dielectric sub-micrometric antennas. The dark-field scattering configuration is then exploited for surface-enhanced absorption measurements, showing a large increase in detection sensitivity, leading to the detection of individual nanocrystals. Due to the broadband spectral response of the Mie sub-micrometric antennas, the method can be e…

Role of Self-Absorption in the Photoluminescence Waveguided along CsPbBr3 Perovskite Nanocrystals Thin Films

During the last years, perovskite nanocrystals (PNCs) have been intensively studied as nanomaterials with excellent light absorption/emission properties. For example, PNCs have been successfully applied in solar cells, where the high absorption coefficient above the band gap increases the conversion efficiencies; or in optical sources, where the high quantum yield of emission at room temperature allows a low threshold of stimulated emission. In this scenario, an optical waveguide represents a suitable platform to enhance their electrooptical properties and to integrate different photonic functionalities. However, propagation of light along close packed films of PNCs is usually restricted to…

Amplified Spontaneous Emission in Thin Films of CsPbX3 Perovskite Nanocrystals

During the last years, Metal Halide Perovskites (MHPs) have attracted special attention as an efficient conversion films for photovoltaics, or excellent gain media to construct optical sources. In spite of the fact that most of the works have been focussed on CH 3 NH 3 PbX 3 (X=Cl, Br, I) polycrystalline thin films, MHP can be also synthesized as colloidal nanocrystals. In particular, caesium lead halide perovskite CsPbX 3 nanocrystals (NCs) revealed extraordinary properties for optoelectronics. With a high quantum yield of emission (>90%) at room temperature and linewidths less than 100 meV, CsPbX 3 NCs have demonstrated favourable characteristics for active photonics. Indeed, thin films o…

An advance Towards the Synthesis of Ag Nanorod Arrays with Controlled Surface Roughness for SERS Substrates

An innovative approach to produce silver nanorod (NRs) arrays with controlled morphological parameters and surface roughness is presented. The Ag NRs were obtained using a three-stage fabrication process based on the electron beam exposure of a metal-polymer nanocomposite resist on a transparent substrate and development, a post bake and then a series of non-electrochemical metallization steps. After each step the evolution of the Ag NRs was characterized by scanning electron microscopy (SEM) for morphology and optical transmittance (T) measurements for Localized Surface Plasmon Resonance (LSPR). The transmittance measurements were interpreted using models based on the Finite Element Method…

Single-Exciton Amplified Spontaneous Emission in CsPbX3 (X = Br, I) Perovskite Nanocrystals

Plasmonic optical sensors printed from Ag–PVA nanoinks

In this paper we report on the use of a nanocomposite based on silver nanoparticles embedded in PVA as a plasmonic optical sensor to detect and quantify trace amounts of amines in gas and water, respectively. The transduction mechanism of the sensor is based on the changes of the LSPR band of Ag NPs when analyte molecules are chemisorbed on their surface. The Ag–PVA sensors are fabricated by means of a high-precision microplotter, a direct-write technology developed for printing materials from solution. The nanoink is formulated with a metal precursor (AgNO3) and a polymer (PVA) using an adequate mixture of solvents to meet the rheological requirements for the fluid dispensing process. The …

Integration of a perovskite-based amplifier and photodetector system in rigid and solid substrates

During the last years, organometallic lead halide perovskites (LHP) have been widely studied as outstanding materials for photovoltaics and photonics applications [1] . These emerging semiconductors are fabricated by cheap and straightforward solution process techniques on polycrystalline film of the compound CH 3 NH 3 PbX 3 (X=Cl, Br, I). Their outstanding properties of these films include large absorption coefficients above the bandgap, high electronic mobilities, high quantum yield of emission at room temperature or tunable band-gap with the composition [1] . In this work, we exploit the excellent light emitting and photodetection properties of CH 3 NH 3 PbI 3 thin films to integrate a w…

Wearable Amplifier-Photodetector System Based on PMMA/Perovskite Waveguides Integrated on a Wearable Nanocellulose Substrate

Optimization of semiconductor halide perovskite layers to implement waveguide amplifiers

Semiconductor organometallic halide (CH 3 NH 3 PbX 3 , X=Cl, Br, I) perovskites (HPVK) have been emerged as a potential gain media to construct a new generation of active photonic devices. Indeed, during the last three years a significant effort has been carried out to implement HPVK-based optical amplifiers or lasers with improved quality factors. In particular, minimization of the threshold of stimulated emission has been an important concern to decrease the power consumption, and hence to enhance the performances of the device. For this purpose strategies include a suitable integration of the semiconductor in a photonic structure, or the optimization of the material. Here we propose a no…

Inhomogeneous Broadening of Photoluminescence Spectra and Kinetics of Nanometer-Thick (Phenethylammonium)2PbI4 Perovskite Thin Films: Implications for Optoelectronics

An outstanding potentiality of layered two-dimensional (2D) organic–inorganic hybrid perovskites (2DHPs) is in the development of solar cells, photodetectors, and light-emitting diodes. In 2DHPs, an exciton is localized in an atomically thin lead(II) halide inorganic layer of sub-nanometer thickness as in a quantum well sandwiched between organic layers as energetic and dielectric barriers. In previous years, versatile optical characterization of 2DHPs has been carried out mainly for thin flakes of single crystals and ultrathin (of the order of 20 nm) polycrystalline films, whereas there is a lack of optical characterization of thick (hundreds of nanometers) polycrystalline films, fundament…

Halide perovskite amplifiers integrated in polymer waveguides

Semiconductor organometallic halide perovskites (CH 3 NH 3 PbX 3 , X=Cl, Br, I) (HPVK) have emerged as a new promising material able to improve the optoelectronic technology performance. Although this material has mostly been applied to improve the efficiency of photovoltaic devices, it also shows amazing properties for photonic applications. In particular, HPVK exhibits high photoluminescence (PL) quantum yield (up to 70%) at room temperature together with a tunable band-gap controlled by its chemical composition. In addition, since HPVKs is deposited in solution at room conditions, it can be easily incorporated in different photonic structures to efficiently exploit its emission propertie…

Tunable light emission by exciplex state formation between hybrid halide perovskite and core/shell quantum dots: Implications in advanced LEDs and photovoltaics

A perovskite–quantum dot exciplex has been detected, opening a broad range of possibilities for advanced optoelectronic devices.

Integrated Optical Amplifier-Photodetector on a Wearable Nanocellulose Substrate

Flexible optoelectronics has emerged as an outstanding platform to pave the road toward vanguard technology advancements. As compared to conventional rigid substrates, a flexible technology enables mechanical deformation while maintaining stable performance. The advantages include not only the development to novel applications, but also the implementation of a wearable technology directly in contact with a curved surface. Here the monolithic integration of a perovskite‐based optical waveguide amplifier together with a photodetector on a nanocellulose substrate is shown to demonstrate the feasibility of a stretchable signal manipulation and receptor system fabricated on a biodegradable mater…

Single step deposition of an interacting layer of a perovskite matrix with embedded quantum dots

Hybrid lead halide perovskite (PS) derivatives have emerged as very promising materials for the development of optoelectronic devices in the last few years. At the same time, inorganic nanocrystals with quantum confinement (QDs) possess unique properties that make them suitable materials for the development of photovoltaics, imaging and lighting applications, among others. In this work, we report on a new methodology for the deposition of high quality, large grain size and pinhole free PS films (CH3NH3PbI3) with embedded PbS and PbS/CdS core/shell Quantum Dots (QDs). The strong interaction between both semiconductors is revealed by the formation of an exciplex state, which is monitored by p…

Recycled Photons Traveling Several Millimeters in Waveguides Based on CsPbBr 3 Perovskite Nanocrystals

Reabsorption and reemission of photons, or photon recycling (PR) effect, represents an outstanding mechanism to enhance the carrier and photon densities in semiconductor thin films. This work demonstrates the propagation of recycled photons over several mm by integrating a thin film of CsPbBr3 nanocrystals into a planar waveguide. An experimental set-up based on a frequency modulation spectroscopy allows to characterize the PR effect and the determination of the effective decay time of outcoupled photons. A correlation between the observed photoluminescence redshift and the increase of the effective decay time is demonstrated, which grows from 3.5 to near 9 ns in the best device. A stochast…

Highly Anisotropic Wave Propagation in All-Dielectric Active Waveguides

In this communication, we integrate an active planar waveguide on a birefringent substrate to show experimental evidence of a selective propagation of the spontaneous emission into the propagating. An anisotropic response with significantly-reduced directional excitation along the optic axis as compared with its perpendicular direction is observed. We additionally provide a theoretical modal analysis of the planar microstructure, which is in good agreement with our experimental results.

Surface plasmon-polariton amplifiers

Propagation of surface plasmons at metal surfaces is receiving much interest nowadays because of its broad range of potential applications, like subwavelength photonics or biosensing. Although plasmonic devices achieve unique properties, surface plasmons suffer from high attenuation because of the absorption losses in the metal. This limitation can be overcome by providing the material adjacent to the metal with optical gain. Under these conditions, absorption losses are compensated and the propagation length of the plasmon is significantly increased. In this work, a review of plasmonic amplifiers is presented. To this end, the state of the art of such devices and the propagation characteri…

Efficient Optical Amplification in a Sandwich-Type Active-Passive Polymer Waveguide Containing Perylenediimides

Polymer waveguides doped with luminescent materials serve as a suitable flexible platform for active elements (lasers and amplifiers) in on-chip optical circuits. However, at present, the best parameters (lowest thresholds) achieved with these devices are obtained with the use of the stripe excitation technique in the framework of which external illumination of an active material along the whole length of the waveguide is realized that is not convenient for the waveguide on-chip integration and requires high peak energies due to the large excitation area. In the present work, an elegant method is proposed to overcome this obstacle and provide efficient active material pumping along the whol…

UV-patternable nanocomposite containing CdSe and PbS quantum dots as miniaturized luminescent chemo-sensors

In this study, a novel multifunctional hybrid polymer-based luminescent material, particularly formulated for photolithography, was developed, fabricated and tested as a miniaturized chemosensor. This nanocomposites were formulated with either luminescent CdSe (for the visible) or PbS (for the near-IR) colloidal QDs embedded in a polyisoprene-based photoresist (PIP). We checked the sensing capability of the nanocomposite by exposing 1 cm2 CdSe nanocomposite patterns to vapours of some analyte solutions such as 2-mercaptoethanol (MET) and ethylenediamine (EDA). The transduction mechanism of the sensor is based on changes of the QD photoluminescence (PL) when molecules are adsorbed on the QD …

Structural quality of CH3NH3PbI3 perovskites for photovoltaic applications analyzed by electron microscopy techniques

Simulation of surface-modified porous silicon photonic crystals for biosensing applications

In this work realistic biosensing structures based on the integration of porous silicon photonic crystals with polymer coating technology are presented. Microcavities and rugate filters are chosen as the photonic crystal configuration. The deposition of a polymer layer on the pore walls of these structures is proposed to improve the selectivity and sensitivity of the sensing function. A complete effective refractive index model including the polymer layer, the target and external effects like silicon oxidation has been developed in order to accurately simulate the structures. It is expected that the proposed structures could be used as low cost, highly integrated and highly sensitive biolog…

Temperature Sensor Based on Colloidal Quantum Dots PMMA Nanocomposite Waveguides

In this paper, integrated temperature sensors based on active nanocomposite planar waveguides are presented. The nanocomposites consist of cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) matrix. When the samples are heated in a temperature range from 25$^{circ}{rm C}$ to 50 $^{circ}{rm C}$, the waveguided photoluminescence of QDs suffers from a strong intensity decrease, which is approximately quadratic dependent on temperature. Moreover, the wavelength peak of the waveguided emission spectrum of CdTe-PMMA shows a blue shift of 0.25 ${rm nm}/^{circ}{rm C}$, whereas it remains constant in the case of CdSe-PMMA. A temperature…

Enhancement of the Performance of Perovskite Solar Cells, LEDs, and Optical Amplifiers by Anti-Solvent Additive Deposition

The efficiency of perovskite optoelectronic devices is increased by a novel method; its suitability for perovskite solar cells, light-emitting diodes, and optical amplifiers is demonstrated. The method is based on the introduction of organic additives during the anti-solvent step in the perovskite thin-film deposition process. Additives passivate grain boundaries reducing non-radiative recombination. The method can be easily extended to other additives.

Toward Metal Halide Perovskite Nonlinear Photonics.

The possibility of controlling light using the nonlinear optical properties of photonic devices opens new points of view in information and communications technology applications. In this Perspective, we review and analyze the potential role of metal halide perovskites in a framework different from their usual one in photovoltaic and light-emitting devices, namely, the one where they can play as nonlinear photonic materials. We contextualize this new role by comparing the few extant results on their nonlinear optical properties to those of other known nonlinear materials. As a result of this analysis, we provide a vision of future developments in photonics that can be expected from this new…

Optical Amplification in Hollow-Core Negative-Curvature Fibers Doped with Perovskite CsPbBr3 Nanocrystals

| openaire: EC/H2020/820423/EU//S2QUIP We report a hollow-core negative-curvature fiber (HC-NCF) optical signal amplifier fabricated by the filling of the air microchannels of the fiber with all-inorganic CsPbBr3 perovskite nanocrystals (PNCs). The optimum fabrication conditions were found to enhance the optical gain, up to +3 dB in the best device. Experimental results were approximately reproduced by a gain assisted mechanism based on the nonlinear optical properties of the PNCs, indicating that signal regeneration can be achieved under low pump powers, much below the threshold of stimulated emission. The results can pave the road of new functionalities of the HC-NCF with PNCs, such as op…

Signal Amplification in CsPbBr3 Nanoparticle-Doped Photonic Crystal Fibers

Nanoparticles (NPs) have been proved for various photonic and optoelectronic applications with superior performance. Doping holey-fibers with colloidal NPs is an idea with precedents in the optical literature. For example, CdZnS/ZnS core-shell quantum dots (QDs) based lasers at visible wavelengths [1, 2]; and PbS QDs doped fiber amplifiers operating at telecommunication wavelengths [3]. In this paper we harness the potential of photonic crystal fibers (PCFs) doped with chemically synthesized CsPbBr 3 Colloidal-NPs [4] to demonstrate gain functionalities in all-fiber optical microdevices.

Optical Optimization of the TiO2 Mesoporous Layer in Perovskite Solar Cells by the Addition of SiO2 Nanoparticles

In this work, SiO2 nanoparticles (NPs) were integrated into the mesoporous TiO2 layer of a perovskite solar cell to investigate their effect on cell performance. Different concentrations of SiO2/ethanol have been combined in TiO2/ethanol to prepare pastes for the fabrication of the mesoporous layer with which perovskite solar cells have been fabricated. Addition of SiO2 NPs of 50 and 100 nm sizes produces an enhancement of cell performance mainly because of an improvement of the photocurrent. This increment is in good agreement with the theoretical predictions based on light scattering induced by dielectric SiO2 NPs. The samples using modified scaffolds with NPs also present a significant l…

Metalenses with high-NA, enhanced resolution and apodization

Dielectric microlenses employed in imaging and focusing for optoelectronics are currently prospects to be substituted by metalenses showing an extraordinary optical performance within notably reduced volumes. Here we present some proposals to achieve an enhanced resolution in metallodielectric metasurface-based lenses established on either efficient arrangements with high numerical aperture or spatial filtering enabling to surpass the limit of resolution derived by the Rayleigh criterion.

Purcell Enhancement and Wavelength Shift of Emitted Light by CsPbI3 Perovskite Nanocrystals Coupled to Hyperbolic Metamaterials

Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of i…

Color Tuning and White Light by Dispersing CdSe, CdTe, and CdS in PMMA Nanocomposite Waveguides

In this paper, active nanocomposite waveguides based on the dispersion of CdS, CdTe, and CdSe colloidal quantum dots (QDs) in PMMA are proposed. Their propagation properties are studied as a function of the concentration of nanoparticles in the polymer using the variable length stripe method. When the three nanostructures are dispersed in the same film, the structure is able to waveguide the three basic colors: red (CdSe), green (CdTe), and blue (CdS), it being possible to engineer any waveguided color by an appropriate choice of the filling factor of each QD in the PMMA matrix. For this purpose, it is important to take into account reabsorption effects and the Förster energy transfe…

Efficient excitation of photoluminescence in a two-dimensional waveguide consisting of a quantum dot-polymer sandwich-type structure

International audience; In this Letter, we study a new kind of organic polymer waveguide numerically and experimentally by combining an ultrathin (10–50 nm) layer of compactly packed CdSe/ZnS core/shell colloidal quantum dots (QDs) sandwiched between two cladding poly(methyl methacrylate) (PMMA) layers. When a pumping laser beam is coupled into the waveguide edge, light is mostly confined around the QD layer, improving the efficiency of excitation. Moreover, the absence of losses in the claddings allows the propagation of the pumping laser beam along the entire waveguide length; hence, a high-intensity photoluminescence (PL) is produced. Furthermore, a novel fabrication technology is develo…

Polymer waveguide couplers based on metal nanoparticle–polymer nanocomposites

In this work Au nanoparticles (AuNPs) are incorporated into poly(methyl methacrylate) (PMMA) waveguides to develop optical couplers that are compatible with planar organic polymer photonics. A method for growing AuNPs (of 10 to 100 nm in size) inside the commercially available Novolak resist is proposed with the intention of tuning the plasmon resonance and the absorption/scattering efficiencies inside the patterned structures. The refractive index of the MNP-Novolak nanocomposite (MNPs: noble metal nanoparticles) is carefully analysed both experimentally and numerically in order to find the appropriate fabrication conditions (filling factor and growth time) to optimize the scattering cross…

MWP true time delay implemented in PbS-SU8 waveguides

Es presenta un nou tipus de dispositiu de retard en temps real de microones (TTD) basat en la dispersió de punts quàntics col·loïdals PbS (QD) en el fotoresist SU8 disponible comercialment. Amb aquest propòsit, els nanocompostos PbS-SU8 s’integren en una plataforma de silici en forma de guies d’ones de cresta. Quan aquestes estructures es bomben a longituds d’ona per sota de l’interval de banda dels PbS QD, es realitza un desplaçament de fase en un senyal de microones transmès òpticament (a 1550 nm) i, per tant, es produeix un retard temporal. A més, es milloren els resultats mitjançant la implementació d’una nova guia d’ones de doble capa de cresta composta per un nanocompost PbS-SU8 i una…

Charge Transport in Trap-Sensitized Infrared PbS Quantum-Dot-Based Photoconductors: Pros and Cons

Control of quantum-dot (QD) surface chemistry offers a direct approach for the tuning of charge-carrier dynamics in photoconductors based on strongly coupled QD solids. We investigate the effects of altering the surface chemistry of PbS QDs in such QD solids via ligand exchange using 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The roll-to-roll compatible doctor-blade technique was used for the fabrication of the QD solid films as the photoactive component in photoconductors and field-effect phototransistors. The ligand exchange of the QD solid film with MPA yields superior device performance with higher photosensitivity and detectivity, which is due to less dark cur…

Single-Exciton Amplified Spontaneous Emission in Thin Films of CsPbX3 (X = Br, I) Perovskite Nanocrystals

CsPbX3 perovskite nanocrystals (PNCs) have emerged as an excellent material for stimulated emission purposes, with even more prospective applications than conventional colloidal quantum dots. However, a better understanding of the physical mechanisms responsible for amplified spontaneous emission (ASE) is required to achieve more ambitious targets (lasing under continuous wave optical or electrical excitation). Here, we establish the intrinsic mechanisms underlying ASE in PNCs of three different band gaps (CsPbBr3, CsPbBr1.5I1.5, and CsPbI3). Our characterization at cryogenic temperatures does not reveal any evidence of the biexciton mechanism in the formation of ASE. Instead, the measured …

Mechanisms of Spontaneous and Amplified Spontaneous Emission in CH3NH3PbI3 Perovskite Thin Films Integrated in an Optical Waveguide

In this paper, the physical mechanisms responsible for optical gain in ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{Pb}\mathrm{I}}_{3}$ (MAPI) polycrystalline thin films are investigated experimentally and theoretically. Waveguide structures composed by a MAPI film embedded in between PMMA and silica layers are used as an efficient geometry to confine emitted light in MAPI films and minimize the energy threshold for amplified spontaneous emission (ASE). We show that photogenerated exciton density at the ASE threshold is as low as $(2.4\ensuremath{-}12)\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.1em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, which is below the Mott transition den…

Photoluminescence waveguiding in CdSe and CdTe QDs–PMMA nanocomposite films

In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are fo…

Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping

The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi3+ can partially substitute Pb2+ homogeneously in the commonly studied MAPbI3, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n2) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI3. Higher doping inhibits the nonlinear parameters; however, the samples show higher f…

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

[EN] The structural and morphological features of bimodal-sized InAs/(In) GaAs quantum dots with density in the low 10(9) cm(-2) range were analyzed with transmission electron microscopy and atomic force microscopy and were related to their optical properties, investigated with photoluminescence and time-resolved photoluminescence. We show that only the family of small quantum dots (QDs) is able to emit narrow photoluminescence peaks characteristic of single-QD spectra; while the behavior of large QDs is attributed to large strain fields that may induce defects affecting their optical properties, decreasing the optical intensity and broadening the homogeneous linewidth. Then, by using a rat…

MWP phase shifters integrated in PbS-SU8 waveguides

[EN] We present new kind of microwave phase shifters (MPS) based on dispersion of PbS colloidal quantum dots (QDs) in commercially available photoresist SU8 after a ligand exchange process. Ridge PbS-SU8 waveguides are implemented by integration of the nanocomposite in a silicon platform. When these waveguides are pumped at wavelengths below the band-gap of the PbS QDs, a phase shift in an optically conveyed (at 1550 nm) microwave signal is produced. The strong light confinement produced in the ridge waveguides allows an improvement of the phase shift as compared to the case of planar structures. Moreover, a novel ridge bilayer waveguide composed by a PbS-SU8 nanocomposite and a SU8 passive…

Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques.

Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) has demonstrated excellent performance to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prep…

Multilayers of CdSe/CdS/ZnCdS Core/Wings/Shell Nanoplatelets Integrated in a Polymer Waveguide

In this work, fabrication of multilayers of colloidal CdSe/CdS/ZnCdS core/wings/shell nanoplatelets (NPls) on solid substrates by layer-by-layer deposition technology is successfully demonstrated for the first time. Integration of multilayers of nanoplatelets into polymeric waveguide resulted in strong dichroism in absorption and polarization effects in photoluminescence with preferable absorption and emission of TE (horizontal) mode that evidences about in-plane orientation of NPls relative to the planar waveguide. The propagation of the excitation and emission light along the waveguide was thoroughly investigated both theoretically and experimentally for different number of NPl layers.

Propagation length enhancement of surface plasmon polaritons in gold nano-/micro-waveguides by the interference with photonic modes in the surrounding active dielectrics

Abstract In this work, the unique optical properties of surface plasmon polaritons (SPPs), i.e. subwavelength confinement or strong electric field concentration, are exploited to demonstrate the propagation of light signal at 600 nm along distances in the range from 17 to 150 μm for Au nanostripes 500 nm down to 100 nm wide (30 nm of height), respectively, both theoretically and experimentally. A low power laser is coupled into an optical fiber tip that is used to locally excite the photoluminescence of colloidal quantum dots (QDs) dispersed in their surroundings. Emitted light from these QDs is generating the SPPs that propagate along the metal waveguides. Then, the above-referred propagat…

Highly-sensitive anisotropic porous silicon based optical sensors

The modeling, fabrication and characterization of PSi fabricated from both (110) and (100) surface oriented silicon for optical sensing is thoroughly reported. First, based on the generalized Bruggeman method, the birefringence and sensitivity of the fabricated membranes were calculated as a function of the fabrication parameters such as porosity and pore sizes; and external effects, such as the pores surface oxidation. Thereafter we report on the fabrication of PSi membranes from (110) and (100) surface oriented silicon with pore sizes in the range of 50 - 80 nm, and the characterization of their birefringence using a polarimetric setup. Their sensitivities were determined by filling the p…

Integration of solution processed materials in polymer waveguides

Active solution processed nanomaterials have emerged as a very high promising candidates for photonic applications. The reason of this arises from the facts that they exhibit high quantum yield emission at room temperature and wavelength tunability, other than their processing involves easy and cheap fabrication techniques and a versatile integration on different substrates. In this way, active properties of different solution processed materials, as colloidal quantum dots, organic dyes and rare earth nanoparticles, have been exploited to demonstrate spontaneous emission or optical modulation in photonic devices. However, in spite of such an attractiveness of these nanomaterials, little has…

Polymer/Perovskite Amplifying Waveguides for Active Hybrid Silicon Photonics

The emission properties of hybrid halide perovskites are exploited to implement a stable and very low power operation waveguide optical amplifier integrated in a silicon platform. By optimizing its design with a poly(methyl methacrylate) (PMMA) encapsulation, this novel photonic device presents a net gain of around 10 dB cm−1 and 3–4 nm linewidth with an energy threshold as low as 2 nJ pulse−1 and exhibiting no degradation after one year. This work was supported by Generalitat Valenciana (Project No. ISIC/2012/008), the Universitat Jaume I (Project No. 12I361.01/1), Spanish MINECO (Projects Nos. MAT2013-47192-C3-1-R and TEC2014-53727-C2-1-R) and EU-NAVOLCHI (Project No. 288869).

Silicon Nanocrystals Produced by Nanosecond Laser Ablation in an Organic Liquid

Small (3−5 nm in diameter following HRTEM images) Si nanocrystals were produced in a two-stage process including (1) nanosecond laser ablation of a Si target in an organic liquid (chloroform) that results in formation of big composite polycrystalline particles (about 20−100 nm average diameter) and (2) ultrasonic post-treatment of Si nanoparticles in the presence of HF. The post-treatment is responsible for disintegration of the composite Si particles, release of small individual nanocrystals, and reduction of their size due to HF-induced etching of Si oxide. The downshift and broadening of the ∼520 cm−1 Raman phonon band of the small Si nanocrystals with respect to the bulk Si Raman band i…

Delayed Luminescence in Lead Halide Perovskite Nanocrystals

The mechanism responsible for the extremely long photoluminescence (PL) lifetimes observed in many lead halide perovskites is still under debate. While the presence of trap states is widely accepted, the process of electron detrapping back to the emissive state has been mostly ignored, especially from deep traps as these are typically associated with nonradiative recombination. Here, we study the photophysics of methylammonium lead bromide perovskite nanocrystals (PNCs) with a photoluminescence quantum yield close to unity. We show that the lifetime of the spontaneous radiative recombination in PNCs is as short as 2 ns, which is expected considering the direct bandgap character of perovskit…

Interpretation of the photoluminescence decay kinetics in metal halide perovskite nanocrystals and thin polycrystalline films

Abstract In this paper we present critical analysis of different points of view on interpretation of the photoluminescence (PL) decay kinetics in lead halide perovskites prepared in the form of well passivated nanocrystals (PNCs) or thin polycrystalline layers. In addition to the literature data, our own measurements are also considered. For PNCs, a strong dependence of the PL lifetimes on the type of passivating ligand was observed with a consistently high PL quantum yield. It is shown that such ligand effects, as well as a decrease in the PL lifetime with decreasing temperature, are well qualitatively explained by the phenomenological model of thermally activated delayed luminescence, in …

Continuous Broadband MWP True-Time Delay with PbS-PMMA and -SU8 waveguides

[EN] A new microwave true-time delay (TTD) photonic unit based on the dispersion of PbS colloidal quantum dots (QDs) in a Polymethyl methacrylate (PMMA) and the SU8 photoresist is presented. With this aim, the PbS-PMMA and PbS-SU8 nanocomposites are integrated on a silicon platform in the form of a planar and ridge waveguides, respectively. When PbS QDs on those structures are pumped below their band-gap, a phase shift and a temporal delay in an optically conveyed (at 1550 nm) microwave signal is performed. The results of these devices show potential benefits over current TTD technologies, since the proposed photonic waveguide structures allows real-time adjustment of the temporal delay by …