Optoelectronic Components Research Articles

Nonlinearity Reduction in a Fiber Fabry-Perot Interferometer Interrogated by a Wavelength Scanning Optical Source

A novel method to reduce the nonlinearity effect of a wavelength scanning diode laser interrogating a low-reflectivity Fabry-Perot interferometer is presented. The interferometer is used for refractive index measurement. The proposed method allows improving the resolution of the system from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> ; and generates a temperature insensitive sensing system. Using the resolution improvement and the temperature insensitivity, the proposed system was used to measure the thermo-optic coefficient of two liquid samples with well-known refractive index. To demonstrate the reliability of the proposed system, experimental results of the long-term performance of a six-month interval, using the same samples but different sensing heads, are presented. The proposed method allows the implementation of a standard four-pin diode laser as an optical source and a standard PIN photodetector for signal detection; permitting the implementation of a high-performance fiber sensor system based on small, light, and standard optoelectronic components. These characteristics are important for different applications such as medical and aerospace, for example, to monitor strain, curvature, pressure, and refractive index using fiber interferometers.

Deposition of high-quality Ge film on Si by PECVD using GeCl4/H2 for fabricating near-infrared photodiodes

Direct deposition of high-quality Ge film on Si substrate suitable for fabricating Ge/Si photodiodes was achieved by using plasma-enhanced chemical vapor deposition (PECVD) with GeCl4/H2 as precursors. A tensile-strained, impurity-free, monocrystalline Ge film with a surface roughness of < 1 nm and a threading-dislocation density on the order of 104 cm−2 could be grown at a rate of ca. 80 nm/min at a substrate temperature of 450 °C directly without the need of any kind of buffer layer or post-annealing. When applied to fabricate near-infrared (NIR) photodiodes, a low dark current density and a reasonably good responsivity for the employed photodiode architecture were attained, revealing the potential of this low-temperature fabrication method in monolithic integration of optoelectronic components with Si-based electronic circuits. The success of this technique may be attributed to an atomic-layer-deposition-like process for both nucleation and growth.

Study of High Polarized Nanostructure Light-Emitting Diode

In this study, we investigated the characteristic difference between the two different configurations of the three-dimensional shell–core nanorod LED. We achieve a degree of polarization of 0.545 for tip-free core–shell nanorod LED and 0.188 for tip core–shell nanorod LED by combining the three-dimensional (3D) structure LED with photonic crystal. The ability of low symmetric modes generated by photonic crystals to enhance degree of polarization has been demonstrated through simulations of photonic crystals. In addition, light confinement in GaN-based nanorod structures is induced by total internal reflection at the GaN/air interface. The combination of 3D core–shell nanorod LED and photonic crystals cannot only produce a light source with a high degree of polarization, but also a narrow divergence angle up to 56°. These 3D LEDs may pave the way for future novel optoelectronic components.

Research Progress of High-Sensitivity Perovskite Photodetectors: A Review of Photodetectors: Noise, Structure, and Materials

In recent years, perovskite materials have been widely used in optoelectronic components due to a series of advantages such as a high light absorption coefficient, high carrier mobility, long carrier diffusion length, shallow defect level, and high crystallinity. The photodetector is an important photoelectric device that can convert light radiation signals into electrical signals, so it has significant applications and scientific research value in military, civil, and other fields. Semiconductor materials are an essential part of photodetectors. So far, many semiconductor materials have been used in photodetectors, including silicon, carbon nanotubes, III–V compounds, and quantum dots, and remarkable progress has been made in improving the light detection performance and device structure design. However, photodetectors based on these materials usually require expensive materials, rigorous processes, and complex manufacturing conditions, which hinder their commercial application. Optoelectronic devices based on perovskite materials have the advantages of a simple fabrication process, low cost, and high performance, making them widely considered in optoelectronic applications. This review focuses on the preparation and photoelectric performance of the perovskite photodetector and the effect of noise on the performance of the perovskite detector and how to reduce the detector’s noise to increase the detection rate. In this review, we mainly discuss the following four aspects of work. First, we discuss the various noises of perovskite photodetectors. Then, we explore ways to reduce the noise of perovskite detectors with different structures (photoconductor, photodiode, and phototransistor). We explore corresponding improvement methods for different device structure detectors to reduce noise and improve the detection performance. Next, we discuss the different synthesis methods of all-inorganic perovskites, including solution processing synthesis, vapor-assisted solution synthesis, and chemical vapor deposition. Finally, current challenges of perovskite photodetectors (toxicity, stability, flexibility, and self-powered) are summarized and prospected.

IoT enabled microfluidic colorimetric detection platform for continuous monitoring of nitrite and phosphate in soil

With the amalgamation of microfluidics and cyber-physical systems, a paradigm shift can be witnessed in the way the devices are conceptualized and developed for many applications, including soil and water monitoring for agricultural application and overall environmental monitoring. Such technological enhancements are leveraged to facilitate on-site detection and quantification by developing miniaturized devices offering multiplexed detection and data transmission across the globe using internet of things (IoT). Herein, a colorimetry-based miniaturized device was developed by incorporating optoelectronic components and employing a poly(dimethylsiloxane) (PDMS) microfluidic device for precise determination of two of the soil macronutrients i.e. nitrogen and phosphorus. Miniaturization and online data monitoring using the IoT and Bluetooth-based modules, along with Arduino microcontroller, lead to generate data, and its monitoring and storage even in the remote locations. Nitrite and phosphorus were detected in a linear range of 1 µM–30 µM and 10 µM–100 µM with limit of detection (LOD) of 0.33 µM (0.021 ppm) and 0.75 µM (0.095 ppm) respectively which is above the prescribed limits. Furthermore, an android app was developed for continuous monitoring using Bluetooth module for short range data transmission. Overall this work demonstrates the microfluidic colorimetric sensing and IoT enabled data monitoring of soil macro nutrients through a cost-effective platform which opens up avenues for the development of miniaturized point-of-care devices.

Single- and narrow-line photoluminescence in a boron nitride-supported MoSe 2 /graphene heterostructure

Heterostructures made from van der Waals materials provide a template to investigate proximity effects at atomically sharp heterointerfaces. In particular, near-field charge and energy transfer in heterostructures made from semiconducting transition metal dichalcogenides (TMD) have attracted interest to design model 2D "donor-acceptor" systems and new optoelectronic components. Here, using of Raman scattering and photoluminescence spectroscopies, we report a comprehensive characterization of a molybedenum diselenide (MoSe$_2$) monolayer deposited onto hexagonal boron nitride (hBN) and capped by mono- and bilayer graphene. Along with the atomically flat hBN susbstrate, a single graphene epilayer is sufficient to passivate the MoSe$_2$ layer and provides a homogenous environment without the need for an extra capping layer. As a result, we do not observe photo-induced doping in our heterostructure and the MoSe$_2$ excitonic linewidth gets as narrow as 1.6~meV, hence approaching the homogeneous limit. The semi-metallic graphene layer neutralizes the 2D semiconductor and enables picosecond non-radiative energy transfer that quenches radiative recombination from long-lived states. Hence, emission from the neutral band edge exciton largely dominates the photoluminescence spectrum of the MoSe$_2$/graphene heterostructure. Since this exciton has a picosecond radiative lifetime at low temperature, comparable with the energy transfer time, its low-temperature photoluminescence is only quenched by a factor of $3.3 \pm 1$ and $4.4 \pm 1$ in the presence of mono- and bilayer graphene, respectively. Finally, while our bare MoSe$_2$ on hBN exhibits negligible valley polarization at low temperature and under near-resonant excitation, we show that interfacing MoSe$_2$ with graphene yields a single-line emitter with degrees of valley polarization and coherence up to $\sim 15\,\%$.

Controllable synthesis of multicolor Alq3:DCM single-crystalline microrods for optical waveguides

It has been demonstrated that organic semiconductor micro-/nanocrystals with multicolor emission/waveguide characterizations would be widely utilized as ideal building blocks for the next generation of miniaturized optical, electronic and logic operation devices. However, rational synthesis of one dimensional micro-/nanocrystals with multicolor emission and optical waveguide performances are highly desirable and still remain a challenge. Here, the DCM doped Alq 3 single-crystalline microrods are fabricated via a facile solution-exchange method. It is found that a redshift in light-emission frequency is extremely sensitive to the doping concentration of 4-(dicyano-methylene)-2-methyl-6-(4-dimethylamino-styryl)-4Hpyran (DCM) guest molecule. The green emission at 527 nm of Alq 3 is the main emitting peak when doping concentration of DCM in Alq 3 :DCM is less than 150:1. Then, when the doping concentration of DCM in Alq 3 :DCM is larger than 100:2 such as 100:10, the red emission at 635 nm becomes the dominant emitting peak, the redshift amounts can reach to roughly 108 nm. In addition, the DCM-doped Alq 3 microrods exhibit a lower optical loss of 0.019 dB/μm as a multicolored waveguide material. Therefore, it is demonstrated that the DCM-doped organic micro/nano crystals can be utilized as a promising building block for various optoelectronic components. Herein, the DCM doped Alq 3 single-crystalline microrods were controllably fabricated via a facile solution-evaporation method. It is found that a redshift in light-emission frequency is extremely sensitive to the dopant concentration of DCM guest molecule. Interestingly, when the doped ratio of Alq 3 to DCM are 100:1 and 100:1.5, there is an obvious peak at 557 nm, besides, a weak peak at 613 nm appears. In addition, the DCM:Alq 3 microrods exhibits a lower optical loss of 0.019 dB/μm as a waveguide material. • The DCM doped Alq 3 single-crystalline microrods are fabricated firstly via a facile solution-exchange method. • The light-emission frequency is highly sensitive to the doping concentration of DCM guest molecule. • The DCM-doped Alq 3 microrods exhibits a lower optical loss of 0.019 dB/μm as a multicolored waveguide material.

Thermal and optical performance characterization of bare and phosphor converted LEDs through package level immersion cooling

Increased demand for high flux electronics requires creative and affordable thermal management approaches to meet the performance and lifetime expectations. In the present study, optical and thermal improvements of a new package level liquid coolant encapsulation that directly targets heat generation zones are studied for bare and phosphor converted LEDs. As heat both at chip and phosphor composite regions are being generated, a series of detailed experimental and theoretical characterization is performed in order to examine the capability of the new cooling method. The findings can be used to extend the application of precisely controlled liquid packing on the heat source region of optoelectronic components. This method has shown a 15% reduction in thermal resistance and a 7% increase in power conversion efficiency of LED packages. The capacity of this method is mainly limited to the thermal conductivity of the coolant while a significant ability for improvement can be expected by utilizing thermally conductive particles such as hexagonal boron nitride inside the coolant.

Large-Scale and Wide-Gamut Coloration at the Diffraction Limit in Flexible, Self-Assembled Hierarchical Nanomaterials.

Unveiling physical phenomena that generate controllable structural coloration is at the center of significant research efforts due to the platform potential for the next generation of printing, sensing, displays, wearable optoelectronics components, and smart fabrics. Colors based on e-beam facilities possess high resolutions above 100k dots per inch (DPI), but limit manufacturing scales up to 4.37cm2 , while requiring rigid substrates that are not flexible. State-of-art scalable techniques, on the contrary, provide either narrow gamuts or small resolutions. A common issue of current methods is also a heterogeneous resolution, which typically changes with the color printed. Here, a structural coloration platform with broad gamuts exceeding the red, green, and blue (RGB) spectrum in inexpensive, thermally resistant, flexible, and metallic-free structures at constant 101 600DPI (at the diffraction limit), obtained via mass-production manufacturing is demonstrated. This platform exploits a previously unexplored physical mechanism, which leverages the interplay between strong scattering modes and optical resonances excited in fully 3D dielectric nanostructures with suitably engineered longitudinal profiles. The colors obtained with this technology are scalable to any area, demonstrated up to the single wafer (4 in.). These results open real-world applications of inexpensive, high-resolution, large-scale structural colors with broad chromatic spectra.

High Mobility Graphene on EVA/PET.

Transparent conductive film on a plastic substrate is a critical component in low cost, flexible and lightweight optoelectronics. CVD graphene transferred from copper- to ethylene vinyl acetate (EVA)/polyethylene terephthalate (PET) foil by hot press lamination has been reported as a robust and affordable alternative to manufacture highly flexible and conductive films. Here, we demonstrate that annealing the samples at 60 C under a flow of nitrogen, after wet etching of copper foil by nitric acid, significantly enhances the Hall mobility of such graphene films. Raman, Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the morphology and chemical composition of the graphene.

A Lab-on-a-Chip Based Automatic Platform for Continuous Nitrites Sensing in Aquaculture.

In aquaculture, the density of fish stock, use of feeding, and surrounding environmental conditions can easily result in an excessive concentration of harmful compounds that require continuous monitoring. Chemical sensors are available for most of these compounds, however, operative conditions and continuous monitoring in water make the development of sensors suitable for long and unattended deployments difficult. A possible solution is the development of engineered automatic labs where the uptake of sample and the contact with water is reduced and the use of a minimal quantity of reagents enables the implementation of reliable chemical assays. In this paper, a platform for automatic chemical assays is presented. The concept is demonstrated with the detection of nitrites based on the well-known colorimetric Griess reaction. The platform is centered around a lab-on-a-chip where reagents and water samples are mixed. The color of the reaction product is measured with low-cost optoelectronic components. Results show the feasibility of the approach with a minimum detectable concentration of about 0.1 mg/L which is below the tolerance level for aquaculture farms.

The influence of substitutes on the room temperature photoluminescence of 2-amino-4-oxobut-2-enoic acid molecular crystals

Highly photoluminescent organic crystals are the cornerstone of organic optoelectronics and photonics. Here we report on rational design of new organic crystal based on 2-amino-4-oxobut-2-enoic acid. An ability to tune the structure of the acid during the synthesis allows obtaining a series of organic crystals with high structural rigidity at ambient conditions. The crystals also demonstrate a chemically driven efficiency and a shape of red photoemission, allowing us to tune their functionalities. Moreover, scaling of the crystals from a single microcrystal to large-scale thin films retains the PL properties, thus makes it possible to utilize them as active nano and macro components in optoelectronics.

Large-area transparent biocomposite films based on nanocellulose and nanochitin via horizontal centrifugal casting

In this study, we introduce the horizontal centrifugal casting (HCC) process that enables centrifugal force-assisted, scalable production of large-area (10 in.) polymer composite films based on nanocellulose (CNF) and nanochitin (ChNF). The HCC employs a cylinder mold with its rotation pivot being in a horizontal posture to harness centrifugal force to help flatten the film being cast, from which polymer composite films with excellent uniformity and flatness can be reliably produced in the size of the lateral surface of the cylinder mold. The combination of centrifugal force and horizontal layout of cylinder mold can allow reliable fabrication of large-area self-standing films from both polymeric solution and/or suspension in a scalable and simple fashion, which is a task not readily achieved in common film-forming techniques, such as solvent casting and vacuum filtration. We demonstrate such reliability and versatility of the HCC process by fabricating typical biocomposite films out of both a solution blend of ChNF/silk fibroin and a colloidal suspension of CNF/nanoclay as well as investigating their processing-structure-property relation as an optically transparent composite film targeting for structural component for flexible green optoelectronics and fire-retardant film, respectively.

High‐Bandwidth InGaAs Photodetectors Heterogeneously Integrated on Silicon Waveguides Using Optofluidic Assembly

AbstractLight‐induced manipulation techniques have been utilized to transport, trap, or levitate microscopic objects for a wide range of applications in biology, electronics, and photonics. Without making direct physical contact, they can provide simple yet powerful means for high‐precision assembly of microscale functional blocks and components within the integrated circuit platforms, thereby offering a viable alternative to the conventional heterogeneous integration techniques, such as wafer/die bonding and transfer printing. Using a microbubble‐based optofluidic pick‐and‐place assembly process, heterogeneous integration of compact III‐V semiconductor photodetectors on a silicon‐based photonic integrated circuit chip, enabling direct high‐speed vertical electrical contacts for significantly improved photogenerated carrier transit distance/time, is experimentally demonstrated. The microdisk‐shaped InGaAs p‐i‐n photodetector integrated on the silicon waveguide has a 3 dB bandwidth exceeding 50 GHz under the applied bias voltage of −1 V for near‐infrared wavelengths around 1.55 µm. The light‐induced optofluidic assembly will provide a promising route for seamless heterogeneous integration of various optoelectronic components with high‐speed and low‐noise electrical interconnection on the fully processed silicon photonic/electronic integrated circuit platforms.

Ultra-fast germanium photodiode with 3-dB bandwidth of 265\u2009GHz

On a scalable silicon technology platform, we demonstrate photodetectors matching or even surpassing state-of-the-art III–V devices. As key components in high-speed optoelectronics, photodetectors with bandwidths greater than 100 GHz have been a topic of intense research for several decades. Solely InP-based detectors could satisfy the highest performance specifications. Devices based on other materials, such as germanium-on-silicon devices, used to lag behind in speed, but enabled complex photonic integrated circuits and co-integration with silicon electronics. Here we demonstrate waveguide-coupled germanium photodiodes with optoelectrical 3-dB bandwidths of 265 GHz and 240 GHz at a photocurrent of 1 mA. This outstanding performance is achieved by a novel device concept in which a germanium fin is sandwiched between complementary in situ-doped silicon layers. Our photodetectors show internal responsivities of 0.3 A W−1 (265 GHz) and 0.45 A W−1 (240 GHz) at a wavelength of 1,550 nm. The internal bandwidth–efficiency product of the latter device is 86 GHz. Low dark currents of 100–200 nA are obtained from these ultra-fast photodetectors.

Automotive optoelectronic components submitted to thermal shock: Impact of component architecture on mechanical reliability

New LED technologies & modules allow glare-free automotive lighting. Valeo solutions include the first high-definition LED lighting system. These LEDs technology endure extreme tests conditions in form of thermal shocks or mechanical vibrations to insure reliability under the lifetime of automotive usage. Strict regulations require lead-free solders. Advanced optimization of LEDs for automotive lighting led to multilayered and miniaturized stack-ups. The first lead-free solders were revealed as a weak part of the electronic components and LED assembly. Enormous efforts have been spent on optimizing the lead-free solder material, design and reflow process. However, component miniaturization can also lead to high thermal gradients. Present work analyses the relation between component architectures and thermal shock induced fatigue damage. First, damage after N1 and N2 thermal shock cycles was characterized experimentally. Genuine sample preparations by a Cross polisher followed by high-resolution SEM observations reveal void growth in the solder material and cracking in the current circuit Layer. A two-scale finite element model reproduces both damage types. Simulation results can help to provide design improvements on the component architectures and modules to avoid (minimize) both damage types.

Laser-Induced Forward Transfer (LIFT) Technique as an Alternative for Assembly and Packaging of Electronic Components

Current trends in microelectronics chip bonding and assembly encompass ultra-fine pitch components with flexible form factors and advanced die-attach materials, which can sustain conformal strain without compromise in adhesion and reliability. These trends have highlighted the need for advanced microfrabrication technologies, which allow the on-demand digital fabrication of interconnections and die-attach bumps on chip carriers and interposers with challenging topographies. Laser printing, based on the laser induced forward transfer (LIFT) technique, has addressed such micromanufacturing challenges over the past decade. Several previous demonstrations of highly resolved and conformal interconnections for the bonding and packaging of micro and opto-electronic components are summarized in this paper. Latest advances in the laser printing and laser sintering of highly viscous nanopastes for achieving planar or three-dimensional (3D) structures consisting of Ag paste are demonstrated. The latter is achieved by stacking of arrays or bumps in a digital manner. The reported results verify that LIFT offers control over both the lateral and vertical dimensions. This control can facilitate the soldering process of heterogeneous components, whose pads have significant height and pitch dissimilarities. The applicability of LIFT in the fields of packaging and assembly of flexible and heterogeneous integration schemes, is further validated.

Morphological and Orientational Controls of Self-Assembly of Gold Nanorods Directed by Evaporative Microflows.

Evaporative self-assembly of noble metal nanoparticles into ordered structures holds great promise for fabricating optical and plasmonic devices by virtue of its low cost, high efficiency, and ease of operation. However, poor control of Marangoni flows is one of the challenges accounting for realizing a well-defined assembly. Herein, based on the theoretical analysis of the influence of evaporative intensity on the assembly, two simple but reliable flow-field-confinement platforms are designed to control the evaporative microflows and to work concurrently with depletion forces to enable the regulated self-assembly of gold nanorods. Orientationally ordered assemblies are realized by the designed strong unidirectional microflow in a capillary, and a device-scale assembly of monolayer membrane is obtained by the created weak convection in homemade glass cells. Morphologically diversified superstructure assemblies, such as spherulite-like, boundary-twisted, chiral spiral assemblies, and merging membranes with a π-twisted domain wall, are obtained due to the spontaneous symmetry breaking or in the presence of defects, such as surface steps and screw dislocations. Optical anisotropy and polarization-dependent behaviors of these assemblies are further revealed, implying the potential applications in plasmonic coupling devices and optoelectronic components. An understanding of the entropy-driven assembly behaviors and control of evaporative microflows to guide the self-assembly of gold nanorods provides insights into the general bottom-up approach that is helpful for constructing complex yet robust nanosuperstructures.

A Review of Self-Coherent Optical Transceivers: Fundamental Issues, Recent Advances, and Research Directions

This paper reviews recent progress on different high-speed optical short- and medium-reach transmission systems. Furthermore, a comprehensive tutorial on high-performance, low-cost, and advanced optical transceiver (TRx) paradigms is presented. In this context, recent advances in high-performance digital signal processing algorithms and innovative optoelectronic components are extensively discussed. Moreover, based on the growing increase in the dynamic environment and the heterogeneous nature of different applications and services to be supported by the systems, we discuss the reconfigurable and sliceable TRxs that can be employed. The associated technical challenges of various system algorithms are reviewed, and we proffer viable solutions to address them.

Advanced Functional Luminescent Metallomesogens: The Key Role of the Metal Center.

The use of liquid crystals for the fabrication of displays incorporated in technological devices (TVs, calculators, screens of eBook's, tablets, watches) demonstrates the relevance that these materials have had in our way of living. However, society evolves, and improved devices are looked for as we create a more efficient and safe technology. In this context, metallomesogens can behave as multifunctional materials because they can combine the fluidic state of the mesophases with properties such as photo and electroluminescence, which offers new exciting possibilities in the field of optoelectronics, energy, environment, and even biomedicine. Herein, it has been established the role of the molecular geometry induced by the metal center in metallomesogens to achieve the self-assembly required in the liquid-crystalline mesophase. Likewise, the effect of the coordination environment in metallomesogens has been further analyzed because of its importance to induce mesomorphism. The structural analysis has been combined with an in-depth discussion of the properties of these materials, including their current and potential future applications. This review will provide a solid background to stimulate the development of novel and attractive metallomesogens that allow designing improved optoelectronic and microelectronic components. Additionally, nanoscience and nanotechnology could be used as a tool to approach the design of nanosystems based on luminescent metallomesogens for use in bioimaging or drug delivery.