Optical Quality Research Articles

High-Order Aberrations: A Key Factor in Accommodative Dysfunctions

This study investigated the relationship between high-order aberrations (HOAs) and accommodative dysfunctions by analyzing their changes with accommodation. Understanding this relationship is important for understanding the mechanisms underlying these conditions. Sixty-three subjects were divided into five groups: control, infacility of accommodation (INFA), excess of accommodation (EA), insufficiency of accommodation (INSA), and symptomatic without dysfunction (SWD). Variations in root-mean-square (RMS) of the 3rd, 4th, 5th, and 6th orders and HOAs, and fluctuations of RMS HOAs, were measured using a Shack–Hartmann aberrometer at different accommodative stimuli and during residual accommodation after their removal, in the following order: 0.00 D, 1.00 D, 0.00 D, 2.45 D, 0.00 D, 4.73 D and 0.00 D. The SWD group showed a significant increase in RMS HOAs during accommodation and residual accommodation. In contrast, the EA group showed an improvement in the ocular optical quality at higher stimuli. Different patterns of changes in the 3rd, 4th, 5th, and 6th orders were observed across all groups, and fluctuations of RMS HOAs increased significantly in the SWD group during accommodation and residual accommodation. These distinct patterns of aberration changes in different accommodative dysfunctions suggest a potential link between their underlying mechanisms, providing insights that may aid their earlier diagnosis and improved management.

In Situ Characterization of Thermal‐Induced Evolution of Structure/Optical Properties of Heterogeneous 3D Chiral Soft Photonic Crystal Polymer

AbstractPolymer stabilized blue phase (PSBP) liquid crystal has aroused wide attention due to its broad temperature range and potential applications in flexible display, multi‐mode monitor, and mirrorless laser based on its well‐compatible stability and multi‐responsiveness, such as electricity, humidity, and temperature. Temperature produces an important effect on the structure/optical properties of PSBP, but there lack of detailed investigation on thermal‐induced deformation and its influence on the optical performance of PSBP. Here, the thermal‐induced evolution of structure/optical properties of PSBP with different polymer content is in situ characterized by variable‐temperature ultra‐small‐angle X‐ray diffraction, Kossel diffraction, and polarized optical microscopy. A restricted deformation of PSBP cubic lattice is revealed by the shift of reflective wavelength and evolution of Kossel diagrams, which is mainly attributed to the thermal‐induced phase transition/separation of non‐polymerized components. The thermal stability of PSBP is improved by increased polymer content based on the limited deformation ability. This work is significant for the design of novel functional material, which paves the way for the preparation of photonic crystal soft materials with high stability and optical quality.

Exploring the tunable micro-/macro-structure enabled by alginate-gelatin bioinks for tissue engineering

This study explores the development of optimized alginate-gelatin (AG) bioinks for advanced 3D bioprinting applications, particularly in tissue engineering. Central to our investigation is the establishment of a method for producing AG bioinks with highly tunable viscoelastic properties and the ability to create both macro- and micro-porous scaffolds through a liquid-liquid emulsion technique applied to chemically crosslinked hydrogels and shaped by microextrusion. Our methodology encompasses a comprehensive evaluation of homogenization, pasteurization techniques, and rheological assessments to optimize the mechanical properties of AG hydrogels, ensuring their suitability for bioprinting.The study demonstrates that dynamic homogenization and conventional pasteurization methods yield superior dissolution and sterility of the bioinks, crucial for maintaining optical quality and biological compatibility. Crosslinking optimization significantly enhanced the elasticity and reduced post-crosslinking shrinkage of the hydrogels, a key factor in achieving desired cell viability and function within the engineered tissues. The incorporation of porosity through a controlled liquid-liquid emulsion process was found to enhance cellular interactions and integration within the bioprinted constructs.Our findings confirm that the rheological properties of bioinks play a crucial role in determining bioprintability, with temperature modulation emerging as a key tool for tailoring these characteristics. The biocompatibility and functional performance of the AG hydrogels were validated through in vitro experiments, demonstrating promising cell viability and proliferation. This research lays the groundwork for the development of advanced bioinks capable of supporting complex tissue architectures in regenerative medicine and tissue engineering. By marrying the versatility of alginate and gelatin with innovative fabrication techniques, our study advances the frontier of 3D bioprinting, paving the way for the creation of biomimetic tissues with enhanced physiological relevance and therapeutic potential.

Through-focus performance and off-axis effects in aspheric monofocal intraocular lenses.

This study aimed to determine the through-focus performance and the effect of misalignment on the optical quality of different aspheric monofocal intraocular lenses (IOLs). To this end, optical quality was assessed in three IOL models with different optic surfaces: standard aberration neutral model and two spherical aberration (SA) correcting, one of which utilizes higher-order aspheric terms. The optical quality was measured by means of the modulation transfer function at 3- and 4.5-mm pupils and under monochromatic and polychromatic light with different corneal SA. The optically derived range of vision and tolerance to misalignment were also tested. The study demonstrated that the type of IOL surface affects the monofocal implant's performance. Although a standard primary-SA correction may improve scotopic image quality, misalignment may diminish this advantage. The higher-order aspheric surface used to correct SA provided an improved performance against decentration and offered a higher optical quality than the aberration-neutral design when tested in a model eye. The latter, however, demonstrated a high tolerance to misalignment, offering a slight extension of the range of vision, potentially resulting from uncorrected optical aberrations.

Optical quality changes of the eye during peak SARS-CoV-2 pandemic in young adults

IntroductionTo determine whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection affects corneal morphology and optical quality. MethodsIn this cross-sectional study, ophthalmological indicators were examined during the peak of SARS-CoV-2 infection after adjusting for public health control measures. Participants were divided into control (remained uninfected), A (infected during follow-up), and B (infected prior to the first consultation) groups. Effects of varying SARS-CoV-2 infection levels were determined using reverse transcription polymerase chain reaction. Changes in corneal morphology, backscatter, and aberrations were measured. Corneal parameters, such as flat keratometry, steep keratometry, and surface variance, vertical asymmetry, height asymmetry, and height decentration indices were considered. ResultsOverall, 110 participants (208 eyes, 42.7% male; age 17–31 years) were enrolled. Eighteen (16.3%) were infection-free during the outbreak with unchanged corneal morphology, backscatter, and aberration. In group A, 34.73 ± 9.30 days after infection, the backscatter of the anterior corneal layer and central layer (both p=0.000) decreased. Total low-order aberration, defocus, horizontal coma, and spherical aberration of the cornea increased (p<0.05), while corneal morphology after infection did not change (p>0.05). In group B, a decrease in backscattering in the corneal middle layer and an increase in horizontal coma (p<0.05) were noted. ConclusionBackscattering of the anterior and intermediate layers of the cornea decreased and corneal aberrations increased after SARS-CoV-2 infection, which affected corneal optical quality. However, corneal morphology and thickness remained unchanged. Ophthalmological indicators and optical quality should be monitored during SARS-CoV-2 infection.

Power profile and optical performance of two extended range-of-vision intraocular lens designs.

To assess the power profile and optical performance of 2 extended range-of-vision (ERV) intraocular lenses (IOLs), TECNIS Eyhance (ICB00) and LuxSmart, and compare them with their monofocal counterpart lenses with similar platforms and materials: TECNIS 1-piece (ZCB00) and LuxGood, respectively. Optics and Optometry Faculties of Complutense University (Madrid) and Universitat Politècnica de Catalunya BarcelonaTech (Terrassa) in Spain. Laboratory investigation on optical bench. For each design, the power distribution and (fourth and sixth-order) spherical aberration (SA) across the lens aperture were measured as well as the optical performance using modulation transfer function-based metrics with through-focus evaluation. 3 nominal powers (+10.00 diopters [D], +20.00 D, and +30.00 D) and 3 pupil sizes (2.0 mm, 3.0 mm, and 4.5 mm) were considered to assess whether the base power of the lens and pupillary dynamics have an influence on the depth-of-focus extension. TECNIS Eyhance and LuxSmart IOLs had different power and SA profiles, but both designs shared a positive add power in their central region in comparison with their monofocal counterparts. LuxSmart had a greater add power while TECNIS Eyhance showed higher peak optical quality but smaller depth of focus. Differences of focus extension between the 2 ERV IOL designs are related to differences of power and SA profile. The nominal base power of the IOLs has little effect on their optical quality. However, pupil dynamics plays a key role since it determines the effective add power and optical performance of the ERV IOLs.

Adaptive underwater monitoring system through visible light

Abstract Currently, underwater visible light communication (VLC) in fields such as underwater resource development, scientific research, and monitoring has become a research hotspot. However, challenges persist in underwater optical communication distances and quality monitoring due to factors such as light attenuation and scattering. Therefore, we propose an adaptive underwater visible light communication monitoring system to increase underwater communication distances and facilitate underwater environmental monitoring. First, we design a parallel multi-hop structure for underwater VLC nodes to enhance underwater communication distances, which not only amplifies the received signal power but also dynamically selects the optimal signal transmission path. Second, we implement a low-cost early warning mechanism that utilizes transmission rate variations under different underwater concentrations to indicate bit error rates (BER) macroscopically. By setting appropriate thresholds, monitoring information is reported to the system. Extensive experiments demonstrate that the designed system can achieve a transmission distance and monitor concentration changes within the range of 0.0018g / ml to 0.0073g / ml.

Significantly improved optical and radiation transmission performance of borate glasses via Tb and Yb rare earth doping

The present study was intended to present new borate glass structure with attractive properties useful for optical and radiation shielding purposes. Therefore, a novel series of B2O3-glass samples defined as: 75B2O3 – 10Li2O – (15-x-y)PbO – x(Yb2O3) – y(Tb2O3), where the corresponding oxide fractions are expressed in mol percent and x and y varied between 1 and 2 mol%, were prepared by employing the well-known melting-and-quenching technique. The structural, physical, optical, and radiation interaction qualities of the glasses were probed based on established experimental and theoretical processes. There was a thin line between the density and molar volumes of the glasses, fluctuating between 3.168 and 3.224 g/cm3 and 28.602 and 29.117 cm3/mol, respectively. All the glass samples exhibited a transparency of over 80 % in the visible range and most parts of the infrared spectrum. The analysis of the gamma photon interaction parameters showed that density and chemical composition greatly influence the shielding abilities of the glasses. The mean free paths of the studied glasses were lower than some known shielding glasses and other materials. The value of ΣR for 1Y0T, 1Y1T, 1Y2T, and 2Y1T is 0.1059, 0.1066, 0.1051, and 0.1063 cm−1, respectively. The half value layers of the glasses had almost a constant minimum value of 0.005 cm at the minimum energy (0.015 MeV) and maximum values of 7.192, 7.100, 7.152, and 7.035 cm for 1Y0T, 1Y1T, 1Y2T, and 2Y1T, respectively at 10.000 MeV. The glasses are potentially more effective for radiation shielding and also desirable where there is lack of space for thicker shield designs. The present glasses had better fast neutron moderating capacities compared to some conventional moderators. None of the studied borate glasses showed a clear performance advantage to the others in terms of absorbing electrons, protons, alpha particles and heavy carbon ions. The studied borate glasses are recommended as transparent and effective radiation protection barriers in ionizing radiation facilities.

Low-loss and low-temperature Al2O3 thin films for integrated photonics and optical coatings

Amorphous aluminum oxide (Al2O3) is a key material in optical coatings due to its notable properties, including a broad transparency window (ultraviolet to mid-infrared) and excellent durability. Moreover, its higher refractive index contrast relative to silica cladding layers and high solubility of rare-earth ions make it well suited for optical waveguides and the development of various functionalities in integrated photonics. In many coatings and integrated photonics applications, the substrates are temperature and stress sensitive, while relatively thick (∼1 μm) alumina layers are required; thus, it is crucial to fabricate low optical loss alumina thin films at low deposition temperatures, while maintaining high deposition rates. In this study, plasma-assisted reactive magnetron sputtering, operated in an alternating current mode, is investigated as a reliable, straightforward, and wafer-scale compatible technique for the deposition of high optical quality and uniform Al2O3 thin films at low temperature. One-micrometer-thick amorphous Al2O3 planar waveguides, deposited at 150 °C and a rate of 23.3 nm/min, exhibit optical losses below 1 dB/cm at 638 nm and as low as 0.1 dB/cm in the conventional optical communication band.

Luminescence and Faraday rotation properties of Tb2O3 and Tb:Y2O3 single crystals

Heavily-doped and fully concentrated 2.78% Tb:Y2O3 and Tb2O3 single crystals with high optical quality and very low levels of impurities have been grown and studied for their luminescence and Faraday rotation properties. Absorption, emission and fluorescence decay measurements performed vs excitation wavelength and temperature and their confrontation with Judd-Ofelt and crystal-field calculations show the contributions of two types of luminescent centers: dominant ones with a 5D4 emission lifetime of 23 μs corresponding to coupled near-neighbor Tb3+ ions, all in C2 symmetry sites, and minority ones with a 5D4 emission lifetime of about 2 ms corresponding to coupled Tb3+ ions in C2 and C3i near-neighbor symmetry sites. Faraday rotation measurements confirm Tb2O3 as the Tb-based Faraday crystalline material with the largest ever measured Verdet constant, at all temperatures and from the visible to the near-infrared. They also show that the dominant luminescent centers contribute more particularly to this large Verdet constant thanks to a favorable crystal-field splitting of their 7F6 ground multiplet and also to the contributions of both types of spin-allowed and spin-forbidden 4f-5d absorption bands.

(Keynote) Epitaxial Si/SiGe Multi-Stacks: From Stacked Nano-Sheet to Fork-Sheet and CFET Devices

After a short description of the evolution of metal-oxide-semiconductor (MOS) device architectures and the corresponding requirements on epitaxial growth processes, the manuscript describes the material properties of complicated Si/SiGe multi-layer stacks used for complementary field effect transistor (CFET) devices. They contain two different Ge concentrations and have been grown using conventional process gases. A relatively high growth temperature is used to obtain acceptable Si and SiGe growth rates. Still island growth has been suppressed for Ge concentrations up to 40%. Excellent structural and optical material properties of the Si/SiGe multi-layer stack will be reported, with up to 3 + 3 Si channels in the top and bottom part of the stack, respectively. The absence/presence of lattice defects has been verified by room temperature photoluminescence measurements. Photoluminescence measurements at low temperatures are used to study band-to-band luminescence from individual sub-layers and to illustrate the optical material quality of the CFET stack.

Optical parameters and gamma shielding quality of sodium-borate glasses: The relative contribution of Bi2O3, SrO, and Li2O

The optical quality and compositional flexibility of borate glasses make them attractive materials for optical applications, nuclear waste containment, transparent radiation shields and many other applications in the nuclear and allied industries. This study presents the physical, optical, and gamma transmission data of the sodium borate glass structure: 75B2O3 – 15Na2O – 9.5x – 0.5Nd2O3; for x = Bi2O3 (BiNd), SrO (SrNd), and Li2O (LiNd). The glasses were prepared using the traditional melt-and-quench technique. The influence of Bi2O3, SrO, and Li2O on the physical attributes, optical constants, and gamma radiation interaction coefficients was probed using standard laboratory procedures and software. The density of BiNd, SrNd, and LiNd was 3.32, 2.43, and 2.24 g/cm3, respectively. The molar volume of the glasses followed the trend: BiNd > SrNd > LiNd. The optical constants of the glasses, such as refractive index, metallization criterion, molar refractivity, molar polarizability, reflectance loss, and optical transmission, showed a wide fluctuation with respect to glass composition. The values of the gamma mass attenuation coefficients for 15 keV–15 MeV photons were in the range 0.0316–45.0225 cm2/g for BiNd, 0.0206–5.4940 cm2/g for SrNd, and 0.0184–3.4603 cm2/g for LiNd. Generally, density has a positive correlation with the gamma absorption prowess of the investigated xNd glasses. A correlation between the optical and shielding parameters was highlighted in this study. The xNd glasses, especially SrNd and BiNd, are preferred as transparent radiation protection barriers, in contrast to some conventional Pb-based glasses, from environmental and public health perspectives. This glass composition is therefore unique and its properties are essentially useful in optical and radiation technologies.

High-sensitivity miniaturized spectrometers using photonic crystal slab filters.

Miniaturized spectrometers have emerged as pivotal tools in numerous scientific and industrial applications, offering advantages such as portability, cost-effectiveness, and the capability for onsite analysis. Despite these significant benefits, miniaturized spectrometers face critical challenges, particularly in sensitivity. Reduced dimensions often lead to compromises in optical path length and component quality, which can diminish detection limits and limit their applications in areas such as low-light-level measurements. Here we developed a compact spectrometer that integrates an array of photonic crystal slab filters with band-stop spectral transmission characteristics into an image sensor. Compared to traditional gratings or bandpass filter strategies, where each detector can only read light of a single wavelength component, our band-stop strategy allows each detector to read the light of all wavelengths except the band-stop wavelength. This maximizes energy extraction from incident signals, significantly improving the sensitivity of the spectrometer. Spectral reconstruction is achieved mathematically using pre-calibrated band-stop responses combined with a single coded image. Our spectrometer delivers a spectral resolution of 1.9 nm and demonstrates sensitivity more than ten times greater than that of conventional grating spectrometers during fluorescence spectroscopy of Ascaris lumbricoides. The design is fully compatible with complementary metal-oxide-semiconductor (CMOS) technology, allowing for mass production at low costs and thus promising broad deployment in sensitive applications.

Granite waste as a source of network former for soda-lime glass production: Evaluation of their potential use in proportions higher than 70%

Granites correspond to around 40% of the Brazilian ornamental stones production. However, there is a negative environmental impact due to the large amounts of waste produced. In this work, we evaluate the potential use of granite waste in proportions higher than 70% as an alternative raw material for soda-lime glass production. The glasses were produced by the conventional melt-quenching method. The nominal compositions were 70%, 75%, and 80% (wt%) of waste and complementary amounts of sodium and calcium carbonates. The glasses presented chemical composition compatible to soda-lime glasses and good optical quality, allowing up to 70% light transmission. Thus, the glasses produced proved to be efficient in immobilizing granite waste, which contributes to reducing environmental impacts.

Bio-inspired colloidal photonic crystal pattern with multiple optical variable images

Colloidal photonic crystals (CPCs) are highly significant for display and anti-counterfeiting applications due to their vibrant structural colors and light-manipulating properties. Efficient and extensive CPC patterns is required for practical applications. Additionally, it is essential to incorporate complex optical elements or responsive qualities to the CPC patterns in order to enhance their performances for security applications. Herein, we proposed CPC patterns with alterable images revealed by changes in viewing angle or exposure to certain vapors. The CPC patterns were prepared by inkjet printing method. Through substrate modification to achieve varying wettability, angle-dependent optical adaptable images could potentially be shown by the patterns. The mesoporous silica nanoparticles (MSNs) were employed as building blocks to impart vapor-chromic characteristics to the CPC patterns. The CPC complex patterns responsive optical characteristics rendered them suitable for use in public authentication and anti-counterfeiting applications.

Analysis of the optical performance of intraocular lenses using profilometric measurements.

The aim of this study was to develop a methodology, based on profilometer measurements to assess the optical behaviour of Intraocular Lenses (IOls). The "Modulation Transfer Function through-object" (MTF through-object) based on vergence object displacement was calculated for different pupil sizes and pseudophakic eyes. Tilt and decentration were also analysed in a realistic cornea eye model. For comparison between the different IOLs, an optical quality criterion based on a minimum value the MTF through-object and the recognition of simulated vision optotypes was introduced. Five IOLs were used in this study: Tecnis Eyhance, Mini Well, Tecnis Symfony, Tecnis Synergy and RayOne EMV. The technique was validated with previous methodologies. A general narrowing of the through-object MTF curve compared to the through-focus MTF curve was shown, resulting in greater distances between near and intermediate points and less depth of field around the far peak. The comparison between the IOLs showed that variations in corneal aberrations, pupil size and decentration caused relevant changes in IOL performance. A decrease of the SA produced a hypermetropic shift of the far focus between + 0.3 D and + 0.4 D. Most of IOLs worsen the optical quality as pupil size increased, even the MTF through-object shape changed. Decentration was an important factor in IOL implantation, causing a significant change in MTF through-object shape in most of IOLs. This study highlights the need to evaluate pre-operative patients for corneal aberrations and pupillary size to have the best optical success after cataract surgery in multifocal or extended depth of focus IOLs. What is known MTF(Modulation Transfer Function)through-focus curves (calculated in image space by moving the detector plane) can be obtained from optical bench assembly or from commercial devices. Recently, some studies proposed to characterize the lens surface design based on the profilometric measurements What is new A novel methodology based on profilometer measurements to assess the optical behaviour of Intraocular Lenses (IOls) was shown. The "Modulation Transfer Function through-object" based on vergence object displacement was introduced in order to analyse five premium IOLs. MTF through-object curve is more appropriate for studying clinical behaviour, as it provides further near and intermediate points distances and lower depth of focus around far peak compare to MTF through-focus curves. The optical behaviour of the five IOLs can vary considerably depending on the eye model and pupil size. The effect of tilt and decentration on the MTF through-object the IOLs was analysed.

Influence of germanium concentration on the microstructure and optical transparency of terbium gallium garnet ceramics

AbstractIn recent years, transparent terbium gallium garnet (TGG) ceramics have garnered significant interest for their application in high‐power Faraday isolators. However, challenges in achieving high transparency have led researchers to explore the addition of various sintering aids as a key strategy to enhance the optical quality of TGG ceramics. Through this work, the effect of germanium (Ge) addition on the microstructure and optical transparency of TGG magneto‐optical ceramics was investigated. TGG powders were synthesized by the co‐precipitation method, and the source Ge was Ge ethoxide added through a ball‐milling step. Transparent TGG ceramics were prepared by air pre‐sintering combined with hot isostatic pressing post‐treatment and subsequent annealing. The ceramics containing 200 ppm Ge exhibit optimal transmittance of 81.3% at 1064 nm (a value of theoretical transmittance), the Verdet constant was −133.0 rad·T−1·m−1 at 633 nm. When the addition of Ge reaches 600 ppm, a secondary phase can be observed on the surface of ceramic. Subsequently, TGG ceramics prepared from 1425°C to 1500°C with 200 ppm of Ge were analyzed, which revealed that the optimal pre‐sintering temperature is 1450°C.

Comparison of objective visual quality between SMILE and FS-LASIK in moderate-to-high myopia.

This study aims to compare the changes in the corneal wavefront aberrations and the objective visual quality resulting from two types of eye surgery-small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK)-in patients with moderate-to-high myopia. A prospective analysis was performed on 98 eyes of 51 patients who underwent SMILE. Additionally, 88 eyes of 45 patients who underwent FS-LASIK were analyzed. All patients underwent ocular examination preoperatively and at 1 day, 1 week, 1 month, and 3 months postoperatively. Corneal aberrations and objective visual quality were measured using the Optical Quality Analysis System II (OQAS II) and Optical Path Difference Scan III (OPD-Scan III). At postoperative 1 day and 1 week, there was a statistically significant difference in uncorrected distance visual acuity (UDVA) between SMILE and FS-LASIK (P < 0.05). Postoperative spherical (S), cylinder (C) and spherical equivalent refraction (SE) were similar between the two groups (P > 0.05). In both groups, the absolute magnitude of total higher-aberrations (tHOA), piston, vertical tilt, vertical coma, and spherical aberration (SA) increased after surgery compared to preoperative values (P < 0.05). There was no significant difference in Δhorizontal tHOA, Δhorizontal tilt, Δhorizontal coma, and Δhorizontal trefoil between the two groups (P > 0.05), and the FS-LASIK had higher Δvertical trefoil and ΔSA (P < 0.05) but lower Δpiston, Δvertical tilt, and Δvertical coma than the SMILE group (P < 0.05). There was a rise in objective scattering index (OSI) and a decline in both modulation transfer function (MTF) cutoff and Strehl ratio (SR) after surgery compared to preoperative values in both groups (P < 0.05). There was a statistically significant difference in the OSI at 1 day and 3 months between the two groups (P < 0.05). Postoperative MTF cutoff and SR were similar between the two groups (P > 0.05). Postoperative OSI was positively correlated with corneal tHOA (0.261 ≤ R ≤ 0.483, P < 0.05) and was negatively correlated with vertical tilt and vertical coma (-0.315 ≤ R ≤ -0.209, P < 0.05) in both groups. While both SMILE and FS-LASIK can effectively correct moderate-to-high myopia, there is an increase in corneal aberrations and a postoperative delay in objective visual quality. The cornea may require a longer recovery period in the SMILE. OPD-Scan III combined with OQAS II is a useful supplementary inspection for assessing the optical quality following refractive surgery.

Effects of Dislocation Filtering Layers on Optical Properties of Third Telecom Window Emitting InAs/InGaAlAs Quantum Dots Grown on Silicon Substrates.

Integrating light emitters based on III-V materials with silicon-based electronics is crucial for further increase in data transfer rates in communication systems since the indirect bandgap of silicon prevents its direct use as a light source. We investigate here InAs/InGaAlAs quantum dot (QD) structures grown directly on 5° off-cut Si substrate and emitting light at 1.5 μm, compatible with established telecom platform. Using different dislocation defect filtering layers, exploiting strained superlattices, and supplementary QD layers, we mitigate the effects of lattice constant and thermal expansion mismatches between III-V materials and Si during growth. Complementary optical spectroscopy techniques, i.e. photoreflectance and temperature-, time- and polarization-resolved photoluminescence, allow us to determine the optical quality and application potential of the obtained structures by comparing them to a reference sample-state-of-the-art QDs grown on InP. Experimental findings are supported by calculations of excitonic states and optical transitions by combining multiband k•p and configuration-interaction methods. We show that our design of structures prevents the generation of a considerable density of defects, as intended. The emission of Si-based structures appears to be much broader than for the reference dots, due to the creation of different QD populations which might be a disadvantage in particular laser applications, however, could be favorable for others, e.g., in broadly tunable devices, sensors, or optical amplifiers. Eventually, we identify the overall most promising combination of defect filtering layers and discuss its advantages and limitations and prospects for further improvements.

Perovskite Nanocrystals Initiate One‐Step Oxygen Tolerant PET‐RAFT Polymerization of Highly Loaded, Efficient Plastic Nanocomposites

AbstractLead halide perovskite nanocrystals (LHP‐NCs) incorporated within polymer matrices have emerged as promising materials for various photonic applications. However, challenges persist in achieving high‐quality nanocomposites due to low monomer conversion yields, restricted LHP‐NCs loadings, and difficulty in maintaining NCs integrity post‐polymerization. A novel protocol for synthesizing LHP‐NCs/poly(methyl methacrylate) nanocomposites in a single step via the NC‐initiated photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) method is presented. Polymerization initiation mediated by NCs surfaces under blue light enables the fabrication of homogeneous nanocomposites with NCs loadings up to 7% w/w and ≈90% monomer conversion even in the presence of oxygen. This process preserves the optical quality of the NCs and passivates NCs surface defects, resulting in nanocomposites exhibiting near unity luminescence efficiencies. The potential of this approach for producing highly loaded nanocomposites for radiation detection is validated by radioluminescence measurements showing light yield values of 6000 ph MeV−1 and fast scintillation dynamics with effective lifetime of 490 ps, showing promise for time‐of‐flight radiometry.