Microcavity Device Research Articles

Spectral Narrowing and Enhancement of Directional Emission of Perovskite Light Emitting Diode by Microcavity

AbstractPerovskite light‐emitting diodes (PeLEDs) have attracted much attentions due to the superior optoelectronic properties such as pure spectrum, high photoluminescence quantum yield, tunable emission, and ease of fabrication. Though lots of progresses have been made on PeLEDs and optically pumped lasers, microcavity perovskite lasing device under electrical pumping remains extremely challenging. Microcavity perovskite LEDs can be considered as a step toward laser diode due to the common structure of resonant cavity. In this study, a new type of metal‐dielectric microcavity PeLED is designed and fabricated by using 2.5 pairs of TiO2/SiO2 distributed bragg reflector (DBR) and Al as cavity coplanar mirrors. A microcavity device with forward spectral full‐width at half‐maximum of 11.8 and 9.5 nm, under electrical and optical excitations, respectively, the directional forward emission within 30° is enhanced by 3 times compared to the control device without cavity is realized. To the best of the knowledge, this study demonstrates the narrowest spectrum for three‐demisional PeLEDs so far, it helps to expand the color space in display applications and may also serve as a reference device for solution processed perovskite exciton–polariton electroluminescent devices and electrically driven vertical cavity surface emitting lasers due to the similar device structure and processing.

Prediction of Strong Transversal s(TE) Exciton-Polaritons in C60 Thin Crystalline Films.

If an exciton and a photon can change each other’s properties, indicating that the regime of their strong bond is achieved, it usually happens in standard microcavity devices, where the large overlap between the ’confined’ cavity photons and the 2D excitons enable the hybridization and the band gap opening in the parabolic photonic branch (as clear evidence of the strong exciton–photon coupling). Here, we show that the strong light–matter coupling can occur beyond the microcavity device setup, i.e., between the ’free’ s(TE) photons and excitons. The s(TE) exciton–polariton is a polarization mode, which (contrary to the p(TM) mode) appears only as a coexistence of a photon and an exciton, i.e., it vanishes in the non-retarded limit (). We show that a thin fullerene C crystalline film (consisting of N C single layers) deposited on an AlO dielectric surface supports strong evanescent s(TE)-polarized exciton–polariton. The calculated Rabi splitting is more than meV for , with a tendency to increase with N, indicating a very strong photonic character of the exciton–polariton.

Top-Emitting Microcavity Light-Emitting Diodes Based on All-Thermally Evaporated Lead-Free Copper Halide Self-Trapped-Exciton Emitters.

Lead-free metal halide light-emitting diodes (LEDs) based on cesium copper halide (CsCu2I3) self-trapped-exciton (STE) emissions show great potential in lighting and color display applications, especially because of their nontoxicity and earth abundance. However, so far, the efficiency and color purity of CsCu2I3-based LEDs remain low. Here we demonstrate the emission of a CsCu2I3 emitter can be enhanced and narrowed in a top-emitting microcavity device. Consequently, the CsCu2I3-based LED device with the assistance of a top-emitting microcavity has significantly narrowed and enhanced the emission spectrum with a full width at half-maximum of 59 nm and a maximum forward brightness of 14767 cd m-2. To the best of our knowledge, this work achieves the narrowest CsCu2I3 LED spectra and demonstrates the potential of employing the microcavity effect to increase the efficiency and color purity of STE-based light-emitting devices.

Optical modes in the perovskite CsPbX3 semicircular and circular microcavity

In this paper, we used the finite element method to numerically study the possible optical resonance modes in the all-inorganic metal halide perovskite (CsPbX3, [Formula: see text], Br, I) semicircular and circular microcavities. For the semicircular microcavity, the quasi-three-period mode has the highest quality factor among quasi-whispering gallery mode (WGM), two-period mode and four-period mode. The quality factors of the four resonance modes all increase linearly for the larger cavity size. In addition, the circular perovskite microcavities present the WGM patterns with extremely high-quality factors, which indicates that the circular perovskite microcavity has the potential application in the optical microcavity or laser device.

Detection of β-Lactoglobulin by a Porous Silicon Microcavity Biosensor Based on the Angle Spectrum.

In this paper, carbon quantum dot-labelled β-lactoglobulin antibodies were used for refractive index magnification, and β-lactoglobulin was detected by angle spectroscopy. In this method, the detection light is provided by a He-Ne laser whose central wavelength is the same as that of the porous silicon microcavity device, and the light source was changed to a parallel beam to illuminate the porous silicon microcavity’ surface by collimating beam expansion, and the reflected light was received on the porous silicon microcavity’ surface by a detector. The angle corresponding to the smallest luminous intensity before and after the onset of immune response was measured by a detector for different concentrations of β-lactoglobulin antigen and carbon quantum dot-labelled β-lactoglobulin antibodies, and the relationship between the variation in angle before and after the immune response was obtained for different concentrations of the β-lactoglobulin antigen. The results of the experiment present that the angle variations changed linearly with increasing β-lactoglobulin antigen concentration before and after the immune response. The limit of detection of β-lactoglobulin by this method was 0.73 μg/L, indicating that the method can be used to detect β-lactoglobulin quickly and conveniently at low cost.

Dynamic Fano resonance and enhanced harmful gas measurement sensitivity in a universal multimode waveguide-microcavity model

We investigate an approach to measuring harmful gases by enhanced Fano resonance generated in a universal multimode waveguide-microcavity model. Dynamic Fano resonance is theoretically described and experimentally proved to be associated with the phase shift between two waveguide modes as well as their amplitude ratio and coupling coefficient. The spectra can be engineered to form a Lorentz dip, various Fano lineshape, and Lorentz peak by controlling the coupling point in both microbottle and surface nanoscale axial photonics platforms. In principle, the model can be applied to any class of whispering gallery mode microcavity device. With sharp asymmetric lineshape, our model can improve the sensitivity by 51.5 times in theory when measuring the harmful gas refractive index change, which may open up opportunities for advancements in the harmful gas leakage detection applications.

On-Site and Quantitative Detection of Trace Methamphetamine in Urine/Serum Samples with a Surface-Enhanced Raman Scattering-Active Microcavity and Rapid Pretreatment Device.

Here, it reports a high-throughput detection method for reliably quantitative analysis of illegal drugs in complex biological samples by means of a surface-enhanced Raman scattering (SERS) active microcavity and rapid pretreatment device. Based on the well-made hemispherical microcavities that regularly distributed on a glass array, the quality-controllable microcavity device is fabricated by the compact self-assembly of core-shell nanopeanuts (CSNPs) onto the inside surface. Both the CSNPs with a quantifiable internal standard signal of crystal violet acetate anchored inside their gap and the well-made microcavity referred to the physical amplification of the microscale groove surface will do well in trace analysis, which will allow us to realize the accurately quantitative SERS analysis of targeted analytes spread on the bottom area of the microcavity array. As an example, 0.8 nM malachite green and 160 ppb methamphetamine (MATM) have been successively detected in a wide range as standard, while even 0.01 ppm MATM mixed in the urine/serum samples has been efficiently tested by the microcavity device equipped with a rapid pretreatment device (manual monolithic column syringe needle). All of the above suggest that the SERS-active microcavity equipped with a rapid pretreatment device has potential in the on-site quick test of trace amounts of illegal drugs in bodily fluid samples or other field analysis of food sanitation, environmental safety, and public health.

Efficient Low-Cost All-Flexible Microcavity Semitransparent Polymer Solar Cells Enabled by Polymer Flexible One-Dimensional Photonic Crystals.

High-efficiency low-cost all-flexible microcavity semitransparent polymer solar cells (STPSCs) are comparatively studied in both fullerene- and nonfullerene-based systems with the structure strategy, employing polymer flexible one-dimensional photonic crystals (F-1DPCs), as well as indium tin oxide-free UV/ozone plasma-treated polymer/ultrathin metal and PEDOT:PSS transparent electrodes. Based on the reasonable optimization of electrical and optical characteristics in the device, the maximum power conversion efficiency with the use of polymer F-1DPCs can be greatly improved by 24-27% compared to the respective control devices. The improvement in JSC is comprehensively discussed, which is mainly ascribed to the enhancement of effective photon absorption in the device. Although color tunability of fullerene and nonfullerene all-flexible STPSCs can be easily achieved with the use of different photonic band gaps of polymer F-1DPCs, the CIE coordinates of nonfullerene STPSCs differ a lot from the original light source compared to the fullerene ones because of a high absorption coefficient in a narrow wavelength region. This work presents an easy and effective microcavity device strategy incorporated with different elements and demonstrates a new sketch of structure-absorption-performance relationships for fullerene- versus nonfullerene-based all-flexible STPSCs, which is compatible with low-cost roll-to-roll manufacturing and surely has a diversity of potential applications to better meet specific needs.

Monolithic high-contrast grating planar microcavities

Abstract Semiconductor planar microcavities significantly enhance the interaction between light and matter and are thus crucial as a fundamental research platform for investigations of quantum information processing, quantum dynamics, and exciton-polariton observations. Microcavities also serve as a very agile basis for modern resonant-cavity light-emitting and detecting devices now in large-scale production for applications in sensing and communication. The fabrication of microcavity devices composed of both common materials now used in photonics and uncommon or arbitrary materials that are new to photonics offers great freedom in the exploration of the functionalities of novel microcavity device concepts. Here we propose and carefully investigate two unique microcavity designs. The first design uses a monolithic high-index-contrast grating (MHCG) and a distributed Bragg reflector (DBR) as the microcavity mirrors. The second design uses two MHCGs as the microcavity mirrors. We demonstrate by numerical analysis that MHCG-DBR and MHCG-MHCG microcavities, whose lateral radial dimension is 16 μm, reach very large quality factors at the level of 104 and nearly 106, as well as purposely designed wavelength tuning ranges of 8 and 60 nm in both configurations, respectively. Our MHCG-MHCG microcavities with a very small size of 600 nm in the vertical dimension show extremely large quality factors, which can be explained by treating the optical modes as quasi-bound states in a continuum (BICs). Moreover, we verify our theoretical analysis and calibrate our simulation parameters by comparing to the experimental characteristics of an electrically injected MHCG-DBR microcavity vertical-cavity surface-emitting laser (VCSEL) emitting at a peak wavelength of about 980 nm. We use the calibrated parameters to simulate the emission characteristics of electrically injected VCSELs in various MHCG-DBR and MHCG-MHCG microcavity configurations to illustrate the influence of microcavity designs and their quality factors on the predicted lasing properties of the devices.

Efficient top illuminated microcavity organic solar cells using air stable composite semitransparent electrodes

Abstract An air stable ITO-free nonfullerene organic solar cell with very high power conversion efficiency is achieved by using microcavity based device architecture with PBDB-T-SF:IT-4F BHJ layer less than 100 nm. The microcavity device could strongly enhance light absorption in PBDB-T-SF:IT-4F BHJ layer and decrease reflection rate of overall device. the microcavity device with single BHJ layer has an 10% improvement in Jsc and 10.8% enhancement in PCE comparing with ITO based device leading to a high PCE of 14.02%. Especially, the Ag/Au composite electrode decreases layer thickness and improves light transmittion. The TeO2/MoO3 composite optical capping layer enhances air stability with equal low reflectance using single TeO2 layer. As a result, This device construction benefits for designing strong light absorption, air stable and high PCE OSC devices with nonfullerene acceptor based thin BHJ layer.

The application of porous Si photonic crystals for metal-resonance enhanced fluorescence

This paper has demonstrated the resonance fluorescence enhancement of R6G when gold nanoparticles (Au NPs) deposited in the porous Si photonic crystal device. Both of microcavity (MC) and distributed Bragg reflector (DBR) with different parameters are investigated for making the photon transmission of photonic crystal device play an optimal role in enhancing fluorescence resonance. While minor changes were observed on the DBR substrates, a significant change in the intensity of enhanced fluorescence varies with the defect modes of MC substrates. Particularly, the strongest enhancement has been presented as the MC defect mode wavelength located at the maximum absorption wavelength of Au NPs. In this case, the fluorescence intensity of R6G on MC device is 2.5 times of that of R6G based on DBR device.

Demonstration of polarization control GaN-based micro-cavity lasers using a rigid high-contrast grating reflector

We reported on GaN microcavity (MC) lasers combined with one rigid TiO2 high-contrast grating (HCG) structure as the output mirror. The HCG structure was directly fabricated on the GaN structure without an airgap. The entire MC structure comprised a bottom dielectric distributed Bragg reflector; a GaN cavity; and a top HCG reflector, which was designed to yield high reflectance for transverse magnetic (TM)- or transverse electric (TE)-polarized light. The MC device revealed an operation threshold of approximately 0.79 MW/cm2 when pulsed optical pumping was conducted using the HCG structure at room temperature. The laser emission was TM polarized with a degree of polarization of 99.2% and had a small divergence angle of 14° (full width at half maximum). This laser operation demonstration for the GaN-based MC structure employing an HCG exhibited the advantages of HCGs in semiconductor lasers at wavelengths from green to ultraviolet.

Secure communications using nonlinear silicon photonic keys.

We present a secure communication system constructed using pairs of nonlinear photonic physical unclonable functions (PUFs) that harness physical chaos in integrated silicon micro-cavities. Compared to a large, electronically stored one-time pad, our method provisions large amounts of information within the intrinsically complex nanostructure of the micro-cavities. By probing a micro-cavity with a rapid sequence of spectrally-encoded ultrafast optical pulses and measuring the lightwave responses, we experimentally demonstrate the ability to extract 2.4 Gb of key material from a single micro-cavity device. Subsequently, in a secure communication experiment with pairs of devices, we achieve bit error rates below 10-5 at code rates of up to 0.1. The PUFs' responses are never transmitted over the channel or stored in digital memory, thus enhancing the security of the system. Additionally, the micro-cavity PUFs are extremely small, inexpensive, robust, and fully compatible with telecommunications infrastructure, components, and electronic fabrication. This approach can serve one-time pad or public key exchange applications where high security is required.

Tunable InGaN quantum dot microcavity light emitters with 129 nm tuning range from yellow-green to violet

An electrically pumped wavelength-tunable InGaN quantum dot (QD) based microcavity (MC) lighter emitter with a large tuning range of 129 nm was demonstrated. The multi-mode emission spectrum was tuned by injected current from 564 nm (yellow-green) to 435 nm (violet). The MC light emitter is featured with a double dielectric distributed Bragg reflector structure and a copper substrate fabricated using substrate transfer and laser lift off techniques. By utilizing an InGaN QD active layer with a tunable broad emission spectrum and a Fabry-Pérot cavity which allows multi-longitudinal mode resonating, the emission spectrum could be tuned among several particular cavity modes, which are decided by the gain enhancement factor. In addition, both the enhancement and suppression of MC emission modes caused by the gain enhancement factor were observed in a single MC device. As the first electrically driven III-V nitride semiconductor based tunable MC light emitter with a tuning range of 129 nm, the device is promising for applications such as in wide-gamut compact displays and projectors.

Pump-Power-Driven Mode Switching in a Microcavity Device and Its Relation to Bose-Einstein Condensation

We investigate the switching of the coherent emission mode of a bimodal microcavity device, occurring when the pump power is varied. We compare experimental data to theoretical results and identify the underlying mechanism to be based on the competition between the effective gain on the one hand and the intermode kinetics on the other. When the pumping is ramped up, above a threshold the mode with the largest effective gain starts to emit coherent light, corresponding to lasing. In contrast, in the limit of strong pumping it is the intermode kinetics that determines which mode acquires a large occupation and shows coherent emission. We point out that this latter mechanism is akin to the equilibrium Bose-Einstein condensation of massive bosons. Thus, the mode switching in our microcavity device can be viewed as a minimal instance of Bose-Einstein condensation of photons. We, moreover, show that the switching from one cavity mode to the other occurs always via an intermediate phase where both modes are emitting coherent light and that it is associated with both superthermal intensity fluctuations and strong anticorrelations between both modes.

Microcavity Laser Based on a Single Molecule Thick High Gain Layer.

The ability to confine excitons within monolayers has led to fundamental investigations of nonradiative energy transfer, super-radiance, strong light-matter coupling, high-efficiency light-emitting diodes, and recently lasers in lateral resonator architectures. Vertical cavity surface emitting lasers (VCSELs), in which lasing occurs perpendicular to the device plane, are critical for telecommunications and large-scale photonics integration, however strong optical self-absorption and low fluorescence quantum yields have thus far prevented coherent emission from a monolayer microcavity device. Here we show lasing from a monolayer VCSEL using a single molecule thick film of amphiphilic fluorescent dye, assembled via Langmuir-Blodgett deposition, as the gain layer. Threshold was observed when 5% of the molecules were excited (4.4 μJ/cm2). At this level of excitation, the optical gain in the monolayer exceeds 1056 cm-1. High localization of the excitons in the VCSEL gain layer can enhance their collective emission properties with Langmuir-Blodgett deposition presenting a paradigm for engineering the high gain layers on the molecular level.

Green OLED based on double metallic mirrors in microcavity structures and double light-emitting structure

Green microcavity organic light-emitting diodes (OLEDs) are fabricated by using double metallic mirrors in microcavity structures and double light-emitting structures. The structure of the device consists of Al(15 nm)/MoO3(4 nm)/2T-NATA(10 nm)/NPB(15 nm)/NPB:C545T(x%, 20 nm)/Alq3:C545T(4%, 20 nm)/Bphen(35 nm)/LiF(1 nm)/Al (200 nm), where x is the doping concentration. When the doping concentration is 3%, the device has the best photoelectric properties, which is named as device B1.The reference device B2 is prepared based on ITO, for the analysis of microcavity effect. B1 and B2 CIE are (0.2889, 0.620) and (0.3168, 0.5571), so the microcavity device could emit more green light. At 100 mA/cm2, the brightness of devices B1 and B2 is 5076 cd/m2 and 4818 cd/m2, and the maximum brightness of the both devices are 9277.7 cd/m2 and 10440 cd/m2. At 100 mA/cm2, luminance efficiency of devices B1 and B2 are 6.0 cd/A and 5.61 cd/A, and the luminance efficiency of the both devices are 8.6 cd/A and 7.97 cd/A. Compared with the reference devices, green microcavity device has a higher current efficiency and better color purity, which attributes to the microcavity effect.

High-Performance Low-Bandgap Polymer Solar Cells With Optical Microcavity Employing Ultrathin Ag Film Electrode

In this paper, the performance of indium-tin-oxide (ITO) free microcavity polymer solar cells based on the thieno[3,4-b]thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC71 BM) blend and transparent Ag electrode is systematically investigated by optical simulation. Here, the device has a structure of glass/opaque Ag/FPI-PEIE/PTB7:PC71BM/MoO3/ultrathin Ag/TeO 2, where the fulleropyrrolidine ethoxylated polyethylenimine (FPI-PEIE) and MoO3 act as charge transport layers and optical spacers, and the TeO2 serves as a transmittance enhancement layer. Compared to ITO-based devices, the microcavity device shows an obviously increased optical electric field intensity for the incident light wavelength from 600 to 750 nm, which agrees well with the better light absorption and lower reflectivity at relatively long wavelength. Further, enhanced performance is obtained from an optimizing top-illuminated device. It is noted that a remarkably enhanced short-circuit current density of 19.50 mA/cm2 is achieved for the microcavity device at optimized layer thicknesses, which is 11% higher than that of ITO-based devices. The improved performance of the microcavity device could be attributed to optically confined and reinforced incident light between two Ag reflective electrodes induced by the coherent interference, which boosts the light harvesting in the active layer, especially the long-wavelength incident photons. The results could provide a promising optical design for low-bandgap polymer solar cells.

High-brightness blue organic light emitting diodes with different types of guest-host systems

We demonstrate high-brightness blue organic light emitting diodes (OLEDs) using two types of guest-host systems. A series of blue OLEDs were fabricated using three organic emitters of dibenz anthracene (perylene), di(4-fluorophenyl) amino-di (styryl) biphenyl (DSB) and 4,4'-bis[2-(9-ethyl-3-carbazolyl)vinyl]biphenyl (BCzVBi) doped into two hosting materials of 4,4'-bis(9-carbazolyl) biphenyl (CBP) and 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) as blue emitting layers, respectively. We achieve three kinds of devices with colors of deep-blue, pure-blue and sky-blue with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.10), (0.15, 0.15) and (0.17, 0.24), respectively, by employing PBD as host material. In addition, we present a microcavity device using the PBD guest-host system and achieve high-purity blue devices with narrowed spectrum.

Controlled waveguide coupling for photon emission from colloidal PbS quantum dot using tunable microcavity made of optical polymer and silicon

A tunable microcavity device composed of optical polymer and Si with a colloidal quantum dot (QD) is proposed as a single-photon source for planar optical circuit. Cavity size is controlled by electrostatic micromachine behavior with the air bridge structure to tune timing of photon injection into optical waveguide from QD. Three-dimensional positioning of a QD in the cavity structure is available using a nanohole on Si processed by scanning probe microscope lithography. We fabricated the prototype microcavity with PbS-QD-mixed polymenthyl methacrylate on a SOI (semiconductor-on-insulator) substrate to show the tunability of cavity size as the shift of emission peak wavelength of QD ensemble.