Optoelectronic Unit Research Articles

Upconversion-nanoparticle-assisting near-infrared photosensitive effect at 1550 nm in organic photorefractive devices

The near-infrared (NIR) photosensitive photorefractive device is a promising optoelectronic unit in the optical signal/information processing and telecommunication. In this work, the upconversion-assisting NIR photosensitive device is presented by adding the upconversion nanoparticles (UCNPs) to the photorefractive composite with (Vlieg et al., 2022; Vlieg et al., 2022) [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as visible photosensitizer. The XRD and TEM results indicated the hexagonal β-phase nanoparticles of UCNPs. The PL measurement under the 1550-nm excitation showed the upconversion emission peaks of NaYF4:Er@NaYF4 nanocrystals at the visible lights of 525 nm, 545 nm and 650 nm. The SEM images revealed that the CRA-DR1 photorefractive composite takes on a good morphology due to the uniform distribution of UCNPs. The two-beam coupling (TBC) experiment without external electric filed indicated the coupling gain coefficient of 77.4 cm−1 at 1550 nm in the CRA-DR1/ECZ/PC61BM/(5 %)UCNPs composite. This upconversion-assisting photosensitive effect will open up the novel approaches for organic NIR photorefractive devices.

Near‐Zero Segregation on Strongly Exciton Confined Mixed Halide Perovskites Quantum Dots via Octahedron Alloying Reconstruction Engineering

AbstractThe state‐of‐the‐art mixed‐halide perovskite (MHP) quantum dots (QDs) open up promising applications in photovoltaic and optoelectronic communities, yet are limited by huge halide segregation. In contrast to the previous A‐site alloy method, customizing other octahedral units for replacing the fundamental optoelectronic unit of [PbX6]4− (X = Cl, Br, or I), the so‐called B‐site alloying strategy, is expected to inhibit halide segregation fully. Here, a halide octahedron alloying reconstruction engineering is reported to fabricate MHP QDs with near‐zero halide segregation due to their strongly confined excitons. This unprecedented regime is obtained at a water–oil interfacial reaction system using amino‐silane ion exchange accelerator and transition metal hydroxy‐halides salts, introducing abundant [MX6]4− (M = Zn, Ni, Co, Mn, and Cu) octahedron block and finally fabricating transition metal‐alloyed MAPbX3 QDs. Photo‐induced excitons in strongly dielectric‐confined Zn‐alloyed perovskite QDs are hardly thermally dissociated and transferred, as featured by ultra‐high exciton binding energy (Eb), fast fluorescence lifetimes (τavg), and near 100% photoluminescence quantum yield (PLQY). The fabricated mixed‐halide MAPb1‐xZnxX3 QDs with reduced Pb content over 40% exhibit near‐zero halide segregation, marking the emergence of a practical solution to the detrimental segregation problem, which paves the wave for emerging solar cells and lighting display applications.

Supramolecular assembly of blue and green halide perovskites with near-unity photoluminescence.

The metal-halide ionic octahedron is the optoelectronic unit for halide perovskites, and a crown ether-assisted supramolecular assembly approach can pack various ionic octahedra into tunable symmetries. In this work, we demonstrate near-unity photoluminescence quantum yield (PLQY) blue and green emission with the supramolecular assembly of hafnium (Hf) and zirconium (Zr) halide octahedral clusters. (18C6@K)2HfBr6 powders showed blue emission with a near-unity PLQY (96.2%), and green emission was also achieved with (18C6@K)2ZrCl4Br2 powders at a PLQY of 82.7%. These highly emissive powders feature facile low-temperature solution-based synthesis conditions and maintain high PLQY in solution-processable semiconductor inks under ambient conditions, and they were used in thin-film displays and emissive three-dimensional-printed architectures that exhibited high spatial resolution.

Visible–infrared dual-band detection with a polarization sensitivity based on GeSe/Ge heterojunction field effect transistor

Electronic and optoelectronic devices based on two-dimensional (2D)/three-dimensional (3D) semiconductor heterostructures, combining their respective advantages, have attracted wide attention. In this work, we fabricate a mixed-dimensional GeSe/Ge heterojunction field effect transistor (HJFET), which combines high carrier mobility of 2D GeSe and near-infrared detection of 3D bulk Ge. A significant on/off ratio of 5 × 102 and a transconductance of 0.23 μS are obtained, indicating a convincing gate control ability. Under 532 nm illumination, the HJFET exhibits an excellent photoresponse with high responsivity, detectivity, and external quantum efficiency (88.4 A/W, 2.25 × 1012 Jones, and 3280%), and it also can detect the infrared light of 1550 nm due to the absorption of Ge gate. The photogenerated electrons at 532 nm flow to Ge back gate when HJFET works at the reverse voltage bias, which prolongs the lifetime of photogenerated holes in the GeSe channel, thus increasing photocurrent and obtaining better the detection properties. Additionally, the transistor also exhibits polarization-sensitive behavior with a dichroic ratio of 2.37, which can be attributed to the strong anisotropic absorption property of GeSe in armchair and zigzag directions. These results indicate that the device has promising potential as a multifunctional optoelectronic unit, including on/off characteristic, broadband photodetection, and polarization sensitivity.

Detection of fluorescence-labeled DNA with in-plane organic optoelectronic devices.

We present a system efficiency analysis of a monolithic integrated organic optoelectronic unit for the detection of fluorescence labeled single-stranded DNA (ssDNA) for veterinary disease testing. The side-by-side integration of an organic light emitting diode (OLED) and an organic photodetector (OPD) with 0.5 mm by 0.5 mm device sizes has the potential to enable compact and low-cost fluorescence point-of-care (POC) devices for decentral multiplex biomedical testing. Here, we used two 6-FAM and BHQ1 labeled complementary ssDNA strands to form the Förster resonance transfer (FRET) upon the hybridization of the DNA. In this work we successfully show ssDNA hybridization sensing with samples diluted in TE buffer and investigate the detection of covalently bound 6-FAM-ssDNA on a glass surface for multiplex biomarker measurements.

Electro-Microfluidic Assembly Platform for Manipulating Colloidal Structures inside Water-in-Oil Emulsion Droplets.

Colloidal assembly is a key strategy in nature and artificial device. Hereby, an electromicrofluidic assembly platform (eMAP) is proposed and validated to achieve 3D colloidal assembly and manipulation within water droplets. The water-in-oil emulsion droplets autoposition in the eMAP driven by dielectrophoresis, where the (di)electrowetting effect induces droplet deformation, facilitating quadratic growth of the electric field in water droplet to achieve "far-field" dielectrophoretic colloidal assembly. Reconfigurable 3D colloidal configurations are observed and dynamically programmed via applied electric fields, colloidal properties, and droplet size. Binary and ternary colloidal assemblies in one droplet allow designable chemical and physical anisotropies for functional materials and devices. Integration of eMAP in high throughput enables mass production of functional microcapsules, and programmable optoelectronic units for display devices. This eMAP is a valuable reference for expanding fundamental and practical exploration of colloidal systems.

Mixed‐Dimensional MoS2/Ge Heterostructure Junction Field‐Effect Transistors for Logic Operation and Photodetection

AbstractThere has been a growing interest in electronic and optoelectronic devices based on heterostructures between atomically thin 2D and 3D semiconductor materials. This paper proposes a 2D molybdenum disulfide (MoS2)/3D germanium (Ge) junction field‐effect transistor (JFET). Typical electrical characteristics of the JFET are observed, with a low subthreshold swing of ≈88 mV/dec and a high on/off ratio of ≈105. The device exhibits a bidirection photoresponse in which the photocurrent polarity is reversed depending on the wavelength of light. Under visible illumination at 532 nm, the positive photoresponsivity of this device can be modulated by the gate voltage, reaching a peak value of 66 A W−1. In contrast, the device exhibits a tunable negative photoresponse behavior under an infrared illumination of 1550 nm. This is attributed to the competition between the negative photoresponse from the bolometric effect in MoS2 and the positive photoresponse from photogenerated carriers in Ge. Based on these interesting characteristics in this JFET, three controllable current states (−1, 0, and 1) are realized by changing the gate voltage and infrared light. These results indicate that the device has promising potential as a multifunctional optoelectronic unit, including signal amplification, broadband photodetection, and multilogic calculations.

All Solid‐State Flexible Electrochromic‐Organic Light‐Emitting Diode Devices on Single‐Plastic Substrate for See‐Through Display Technologies

AbstractThe development of solid‐state electrochromics (EC) represents an emerging challenge towards effective integration with other optoelectronic units, such as the EC‐organic light‐emitting diode devices (EC‐OLEDs). By a simultaneous or independent control of optical contrast (EC function) and OLED emission upon electrical activation, these fascinating systems are capable of adaptively modulating solar radiation and display lighting. Here, we report a flexible ECOLED on a single‐plastic substrate demonstrating how the rational design of a highly efficient and durable solid‐state EC cell enables an increase of overall performances and the integration with OLED on larger area and flexible substrate. The resulting device shows high transparency and optical contrast (ΔT650nm = 60%), with lower operating voltages (0.5–3 V), faster coloring/bleaching switching times (5–10 s), and enhanced stability (1000 switching cycles) if compared to similar systems. The OLED unit reveals a luminance of 1000 cd m−2 (at 10 mA cm−2) and a current efficiency of about 10 cd A−1, making it suitable for both display and lighting applications. These results can represent a novelty in the field of next‐generation smart windows and transparent displays, including all technologies based on see‐through OLED displays, electronic devices for augmented reality, lighting panels and smart glasses.

The effect of constructing discontinuous side chain D-A structure on high-performance poly (ether sulfone)s optoelectronic materials

The unconjugated high-performance polymers have been developing rapidly in the field of optoelectronics, due to the effective donor-acceptor (D-A) structure design strategy. Poly (ether sulfone) (PES) shows tremendous application potential in the field of optoelectronics by combining with optoelectronic units. Herein, an isolated D-A structure was constructed in the side chain of PES, in which the triphenylamine (TPA) structure was the donor and the imide structure was the acceptor. Electrochemical test showed that the onset potential of PES-TPAs was low (0.55 V). The PES-TPAs as a kind of electrochromic materials could improving their EC cycling stabilities from single-digit cycle times to 52 cycles (20% contrast reduction). To the best knowledge, no detail data was reported on the EC cycling stability of PES-type polymers before this work. Meanwhile, PES-TPAs as a kind of memory storage polymers exhibited a low threshold voltage (−3.03 V). These performances showed a wide application prospect of PES in the field of optoelectronics. More importantly, designing the molecular structure in this way would provide a new select for creating more types of optoelectronic polymers.

Modeling the Physical Properties of ZnO Nanoparticles with Selective Hydrogen Using DFT

The impact of hydrogen on the conductivity and vibration for zinc oxide (ZnO) nanoparticles had implicated for nanoscale optoelectronic units. Infrared reflectance spectra for ZnO hydrogen-annealed nanoparticles were calculated at incidence. The theory of density functional theory is applied to the reflectance model and absorption spectra. There is an agreement between both the model suggesting that the nanoparticles have inhomogeneous carriers’ concentrations and the experimental results. A significant decrease in carrier concentration resulted from exposure to oxygen for several hours, according to the adsorption on the nanoparticle surface of negative oxygen molecules. Also, the density of states in deferent wurtzoid’s size has been studied. The experimental energy gap values of bulk ZnO, HOMO and LUMO levels as a function of the total Zn and O atoms number in ZnOH diamondoids were determined, as well as the bond length in deferent wurtzoid’s size where the experimental ZnO bond length at 1.9767 Å has been calculated. The tetrahedral angles in deferent wurtzoid’s size were studied, deferent wurtzoid’s size Reduced mass as a vibration frequency function and force constant as a function of vibrational frequency in deferent wurtzoid’s size were determined. A good result for infrared as a vibration frequency function in deferent wurtzoid’s size has been found, as well as Raman as a vibration frequency function in deferent wurtzoid’s size.

Using the next generation combined digital transformers

The paper considers and analyzes the use of new generation combined digital instrument transformers (DIT) with an optoelectronic conversion unit and a combining module or a stand-alone combining module, an external synchronization source or an internal clock generator and digital interfaces.

Nano-engineering and functionalization of hybrid Au-MexOy-TiO2 (Me = W, Ga) hetero-interfaces for optoelectronic receptors and nociceptors.

Bio-inspired nano-electronic devices are key instruments for the development of advanced artificial intelligence systems, which will shape the future of humanoid nano-robotics. An emerging demand is realized for an accurate reception of environmental stimuli via visual perception, processing and realization of optical signals. The present study demonstrates the capability of functionalized all-oxide heterostructured two-dimensional (2D) plasmonic devices for the self-adaptive recognition of visual optical pulses. Specifically, the nano-engineering of the metal/semiconductor interface and co-modulation of heterostructured 2D semiconductor hetero-interfaces of Au/WO3 : TiO2 and Au/Ga2O3 : TiO2 facilitated the receptive and nociceptive detection of visible light pulses. A decrease in the dark current of the Au/WO3 : TiO2 unit resulted in the development of sensitive visible light photoreceptors. Furthermore, the modulation of charge transfers at the Au/Ga2O3 : TiO2 hetero-interfaces were the key parameter to determine the optical reception characteristics and nociceptive performance of all-oxide optoelectronic devices. Specifically, the rapid thermal annealing (RTA) of 2D Ga2O3 in N2 atmosphere ensured the modulation of charge transfer at Au/Ga2O3 : TiO2 hetero-interfaces in plasmonic devices. Thus, hetero-interface engineering enabled the effective control of charge transfer at 2D hetero-interfaces for an adaptive perception of visible optical pulses. Consequently, the fabricated sensitive Au/Ga2O3 (N2) : TiO2 bio-inspired unit emulated the optical functionalities of corneal nociceptors.

Photonic-Assisted Wideband Phase Noise Analyzer Based on Optoelectronic Hybrid Units

We demonstrate a photonic-assisted wideband phase noise analyzer based on optoelectronic hybrid units comprising a microwave photonic phase shifter (MPS) and a microwave true time delayer. The MPS and the microwave true time delayer are achieved by a dual-drive Mach-Zehnder modulator (DMZM) incorporating with a broadband microwave frequency up-convertor (MFC) and an optical fiber delay line (ODL), respectively. Our scheme, which is analogous to the conventional microwave delayed homodyne self-reference method, can effectively improve its accuracy using longer time delay with minimum power consumption. In the scheme, the microwave signal is up-converted using the MFC and then down-converted using optical mixing in a photo-detector (PD). Meanwhile, the microwave signal is phase shifted using the MPS and time delayed using the ODL and are finally homodyne mixed with reference signals for converting phase fluctuations to voltage fluctuations. The motivation of this work lies in the fact that the previously reported phase noise measurement configurations based on photonic techniques are hard to accurately measure phase noise of microwave oscillators working at low frequencies. The microwave signals are phase tuned over 360° at frequency range of 0.5–9 GHz to achieve a photonic-assisted phase detector. Microwave signals at the frequency of 3-, 9-GHz are measured with a phase noise of –70.9 and –66 dBc/Hz at 1 kHz offset frequency, respectively.

High-accuracy device for measuring the twist angle

This paper describes a high-accuracy optoelectronic device for measuring the twist angle, based on an autocollimation method and using a reflector in the form of a unit of right-angle prisms. The device makes it possible to measure the relative twist angle of objects in the range ±2.5° when there is a distance of 2.5–3.5 m between the reflector and the optoelectronic unit of the device. The rms deviation of the measured angle from the true value in this case does not exceed 2′′ in the range ±2.5°, and it does not exceed 1′′ in the range ±10′. A specially shaped mark is used in the device that makes it possible to measure the auxiliary angle between the direction of the edge of the prism reflector and a plane perpendicular to the optical axis of the device. The installation can be used to transfer the azimuthal direction vector.

Low-Cost PCB-Integrated 10-Gb/s Optical Transceiver Built With a Novel Integration Method

A novel integration method for the production of cost-effective optoelectronic printed circuit boards (OE PCBs) is presented. The proposed integration method allows fabrication of OE PCBs with manufacturing processes common to the electronics industry while enabling direct attachment of electronic components onto the board with solder reflow processes as well as board assembly with automated pick-and-place tools. The OE PCB design is based on the use of polymer multimode waveguides, end-fired optical coupling schemes, and simple electro-optic connectors, eliminating the need for additional optical components in the optical layer, such as micro-mirrors and micro-lenses. A proof-of-concept low-cost optical transceiver produced with the proposed integration method is presented. This transceiver is fabricated on a low-cost FR4 substrate, comprises a polymer Y-splitter together with the electronic circuitry of the transmitter and receiver modules and achieves error-free 10-Gb/s bidirectional data transmission. Theoretical studies on the optical coupling efficiencies and alignment tolerances achieved with the employed end-fired coupling schemes are presented while experimental results on the optical transmission characteristics, frequency response, and data transmission performance of the integrated optical links are reported. The demonstrated optoelectronic unit can be used as a front-end optical network unit in short-reach datacommunication links.

Conjugate momentum estimate using non-linear dynamic model of the sit-to-stand correlates well with accelerometric surface data

The purpose of this study was the development of a non-linear double inverted constrained pendulum model for the analysis of the movement of sit-to-stand (STS) transition. Ten able-bodied subjects perform five trials in their natural speed. Kinematics, kinetics as well as body worn accelerometer data were collected during the STS task using optoelectronic motion capture, force plate and inertial measurement unit, respectively. The conjugate momentum for the whole body which includes linear and angular motion correlates well with the accelerometric surface spanned by the accelerometer data. The partitioning of the conjugate momentum indicates a clear coordination between upper and lower limb after seat-off period. Moreover, the normalization procedure indicates a clear minimal and somehow invariant threshold value of the conjugate momentum to approximately 0.3 (body mass×body length) to perform the sit-to-stand for able-bodied subject. This threshold correlates well with the data obtained from accelerometeric index. The proposed accelerometric index is relevant to assess STS performance and to detect failed STS in clinics and outside a laboratory for patients with reduced mobility.

Qualification of a truly distributed fiber optic technique for strain and temperature measurements in concrete structures

Structural health monitoring is a key factor in life cycle management of infrastructures. Truly distributed fiber optic sensors are able to provide relevant information on large structures, such as nuclear power plants or nuclear waste disposal facilities. The sensing chain includes an optoelectronic unit and a sensing cable made of one or more optical fibers. A new instrument based on Optical Frequency Domain Reflectometry (OFDR), enables to perform temperature and strain measurements with a centimeter scale spatial resolution over hundred of meters and with a level of precision equal to 1 μ strain and 0.1 °C. Several sensing cables are designed with different materials targeting to last for decades, either embedded in the concrete or attached to the surface of the structure. They must ensure an optimal transfer of temperature and strain from the concrete matrix to the optical fiber. Based on the European guide FD CEN/TR 14748 “Non-destructive testing – Methodology for qualification of non-destructive tests”, a qualification method was developed. Tests were carried out using various sensing cables embedded in the volume or fixed to the surface of plain concrete specimens and representative-scale reinforced concrete structural elements. Measurements were performed with an OFDR instrument, while mechanical solicitations were imposed to the concrete element. Preliminary experiments seem very promising since measurements performed with distributed sensing systems are found comparable to values obtained with conventional sensors used in civil engineering and with the Strength of Materials Modelling. Moreover, the distributed sensing system makes it possible to detect and localize cracks appearing in concrete during the mechanical loading.

Fiber Optic Sensors for Biomedical Applications

Biomedicine is surely the area where the optical fibre sensors can play an important role. Thanks to their potential miniaturisation and their easy handling they are offering unique performances in invasive or minimally invasive applications. The immunity to electromagnetic interference and the absence of electrical contact make the optical fibres useful also in the case of non invasive applications for the setting of the interrogation optoelectronic unit in a safer location, keeping only the sensing element close to the patients bedside. As a matter of fact, there are many optical fibre sensors designed for biomedical applications and described in the literature, but the greater part of them stops at the prototype level, without entering the hospital. The clinical validation, which is the necessary step after the characterisation of the laboratory prototype, is often an insurmountable obstacle due to the requirements of compliance with the European Directives on Medical Devices or with the regulations of the Food and Drug Administration. The strategy followed for the clinical validation in the case of optical fibre sensors developed at the Institute of Applied Physics for the detection of bile-containing refluxes, gastric carbon dioxide and interstitial pH is described. An example for potential non-invasive applications in point of care testing is also given with a novel optical platform for the interrogation of optical biochips.

Doubly Ortho-Linked cis-4,4‘-Bis(diarylamino)stilbene/Fluorene Hybrids as Efficient Nondoped, Sky-Blue Fluorescent Materials for Optoelectronic Applications

The titled hybrids bearing a central dibenzosuberene optoelectronic unit with functional C3 and C7, N,N-diarylamino appendages, and spiro-fluorene junction act as blue fluorescent OLED materials. Sharp blue fluorescent (464 nm, Δλfwhm = 47−60 nm) OLED devices can thus be furnished with a high ηext of 7.9%, L20 of 2689 cd/m2, ηc of 13.6 (cd/A), and ηp of 8.2 (lm/W) at 20 mA/cm2.

Lateral polishing of bends in plastic optical fibres applied to a multipoint liquid-level measurement sensor

A new liquid-level sensor with a multipoint layout is presented, which is based on power loss arising in laterally polished bent sections prepared along a plastic optical fibre. The polishing is applied to the fibre surface on top of several U-shaped bends until part of the core is also removed. The resultant bare flat area on the core is an elliptic surface in direct contact with the medium surrounding the fibre. Any variation in the optical and geometric parameters characterising our multimode fibre is analysed, since it will cause changes in the propagation of light along the polished bends. Experimental results included in the paper correspond to the prototype for our sensor, which consists of eight sensing probes placed sequentially along the fibre, in combination with an optoelectronic unit working as a liquid-level transducer.