Ultralow dark current in near-infrared perovskite photodiodes by reducing charge injection and interfacial charge generation

Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density (JD) and noise current (in). This is commonly accomplished using charge-blocking layers to reduce charge injection. By analyzing the temperature dependence of JD for lead-tin based PPDs with different bandgaps and electron-blocking layers (EBL), we demonstrate that while EBLs eliminate electron injection, they facilitate undesired thermal charge generation at the EBL-perovskite interface. The interfacial energy offset between the EBL and the perovskite determines the magnitude and activation energy of JD. By increasing this offset we realized a PPD with ultralow JD and in of 5 × 10−8 mA cm−2 and 2 × 10−14 A Hz−1/2, respectively, and wavelength sensitivity up to 1050 nm, establishing a new design principle to maximize detectivity in perovskite photodiodes.

Double-sided Polishing Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance

In this paper, we propose a high-sensitivity double-sided polishing photonic crystal fiber biosensor based on surface plasmon resonance. The performance of the sensor was analyzed by finite element method, including the influence of different pore sizes and position, polishing depth, pore spacing, metal thickness, refractive index(RI), and manufacturing error (5%) on the sensing performance. We also analyze the performance of the modified sensor in early cancer detection applications. Our use of a double-sided polishing structure and coating with a gold layer not only increases the contact area between the analyte and gold layer but also provides a large enough space for the analysis channel, which is conducive to the actual manufacture and use. The sensor has a detection range of 1.35-1.39, the maximum wavelength sensitivity of 21500 nm/RIU, the average wavelength sensitivity is 9550 nm/RIU, the amplitude sensitivity of -1057.1756 RIU-1, the maximum resolution is 4.68×10-6, R2 of 0.98265, figure of merit is 250, and the maximum resolution of 4.68×10-6, which can be used in the cancer detection and other biological areas.

Analysis of Wavelength Sensitivity of Coupling Coefficients and Inter-core Crosstalk in a 9 core Multi-core Fiber

Wavelength dependence of coupling coefficients and inter-core crosstalk in a 9-core homogeneous multi-core optical fiber (MCF) are investigated analytically. The analysis is further extended to evaluate the mean crosstalk power at the output of any core with light launched into other core of the MCF. Propagation length dependence of mean crosstalk power is investigated using both coupled mode theory (CMT) and coupled power theory (CPT). CPT based results show that mean crosstalk power linearly dependent on propagation distance, and it is higher for higher values of coupling coefficient. On the other hand, the mean crosstalk power is found to oscillate with the propagation distance in case of CMT. It is also observed that the mean crosstalk power (dB) is more prominent at a lower wavelength for a given propagation distance. The behavour of relative crosstalk power is also investigated analytically where it is noticed that the relative crosstalk power increases almost linearly with core pitch and with wavelength. It is also seen that the relative crosstalk power (dB) is more in an MCF with lower number of cores when it is varied with respect to wavelength. This is due to the increase of core pitch under the same cladding diameter and cladding thickness limitations.

Dual scaled approach SPR-based PCF RI sensor with ultra-low loss

We demonstrate an ultra-low loss photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR)in this paper. In this refractive index (RI) sensor, we explored hexagonal-arrangement of airholes and employed only two different sizes of it. The formation of airholes makes the confinement loss (CL) surprisingly low. The maximum CL is as low as 10.71 and 28.58 dB/cm for x and y-pol modes, respectively within a range of refractive indices 1.33-1.40. The maximum gained amplitude sensitivity is -1212 RIU−1 and -2430 RIU−1, and the maximum figure of merit is as high as 583 and 467 respectively for x and y-polarization (pol) modes respectively. In addition to that, we got a maximum wavelength sensitivity, Sw of 14,000nm/RIU for both x and y-pol modes with a minimum sensor resolution of 7.143x10−6. Gold is preferred over other materials as the plasmonic material for its inert behaviour and higher chemical stability. The analysis was carried out using the finite element method (FEM). This sensor, with its elegant configuration, fabrication feasibility, ultra-low loss, stands out to be an effective and eminent prospect in the current burgeoning SPR sensor realm and also prompts further creative exploration in its hexagonal lattice arrangements.

Evolutionary history limits species' ability to match color sensitivity to available habitat light

The spectrum of light that an animal sees - from ultraviolet to far red light - is governed by the number and wavelength sensitivity of a family of retinal proteins called opsins. It has been hypothesized that the spectrum of light available in an environment influences the range of colors that a species has evolved to see. However, invertebrates and vertebrates use phylogenetically distinct opsins in their retinae, and it remains unclear whether these distinct opsins influence what animals see, or how they adapt to their light environments. Systematically utilizing published visual sensitivity data from across animal phyla, we found that terrestrial animals are more sensitive to shorter and longer wavelengths of light than aquatic animals, and that invertebrates are more sensitive to shorter wavelengths of light than vertebrates. Controlling for phylogeny removes the effects of habitat and lineage on visual sensitivity. Closed and open habitat terrestrial species have similar spectral sensitivities when comparing across the Metazoa, and deep water animals are more sensitive to shorter wavelengths of light than shallow water animals. Our results suggest that animals do adapt to their light environment, however the invertebrate-vertebrate evolutionary divergence has limited the degree to which animals can perform visual tuning.

Plasmonic Sensor based on Microstructure PCF: Performance Analysis with Outside Detecting Approach

In this microarticle, we design a microstructure photonic crystal fiber (PCF) based external sensing surface plasmon resonance (SPR) sensor. The performance of the design is numerically evaluated incorporating the finite element method (FEM) with Perfectly Matched Layer (PML) boundary condition of scattering case. Modal analysis is performed using finer mesh anlaysis. At the optimized thickness (40nm) of chemically stable gold(Au) layer, the ever been maximum reported wavelength sensitivity (WS) and standard amplitude sensitivity (AS) are to 75,000 nm per RIU and 480 per RIU correspondingly. The sensor also exposed high polynomial fit (𝐑𝟐 = 𝟎. 𝟗𝟗) as well as high figure of merit (FoM) of 280.77 per RIU. Since very much high sensitivity, high detecting range and figure of merit, lowing the cost of fabrication, the proposed design can be a pleasant competitor in detection of the analyte refractive index (RI). At the last, to prove performance ability of our designed sensor all the performance parameter calculated results compare with the existing sensors.

Designing magnetic field sensor based on tapered photonic crystal fibre assisted by a ferrofluid

A novel magnetic field sensor is proposed based on the combination of in-line tapered photonic crystal fibre (PCF) Mach–Zehnder interferometer and magnetic nanoparticles. The sensor is theoretically investigated and experimentally realized. The effect of the mechanical strain and the magnetic field on the sensitivity of the sensor is studied. It is found that the proposed sensor shows a wavelength-sensitivity of $$-\,0.072\,\text {nm/mT}$$ - 0.072 nm/mT and a strain-sensitivity of $$1\,\text {pm/}\upmu \,\epsilon \,$$ 1 pm/ μ ϵ . To evaluate the effect of the magnetic nanoparticles on the output light intensity, the sensitivity response of the device has been measured under different magnetic field strengths for different length scales. The experimental results show refractive index changes of the magnetic nanoparticles-infiltrated PCF—acting as fibre cladding—under the applied magnetic field leads to variations of the interferometric output. The sensitivity of magnetic field measurement with the sensor with $$30\,\text {mm}$$ 30 mm and $$40\,\text {mm}$$ 40 mm PCF could reach up to $$0.021\,\text {dB/mT}$$ 0.021 dB/mT and $$0.017\,\text {dB/mT}$$ 0.017 dB/mT , respectively. The results show a very good linear response that is an essential requirement for the practical sensors. The proposed magnetic field sensor finds applications in various areas, such as optical sensing, military, power industry, and tunable photonic devices.

Disinfection of SARS-CoV-2 using UVC reveals wavelength sensitivity contributes towards rapid virucidal activity

SARS-CoV-2 is a pathogen that can be disinfected using UVC. For effective inactivation strategies, design and implementation of UVC disinfection, knowledge of wavelength sensitivity, and disinfection rate of the relevant pathogen are required. This study aimed to determine the inactivation profile of SARS-CoV-2 using UVC irradiation with different wavelengths, in addition to validating surrogate models for SARS-CoV-2. Specifically, the study determined dosage, inactivation levels, and wavelength sensitivity of SARS-CoV-2. Assessment of SARS-CoV-2 (Strain USA/WA1-2020) inactivation at peak wavelength of 259, 268, 270, 275 and 280 nm was performed using plaque assay method. The UVC dose of 3.1 mJ/cm2 using 259 and 268 nm arrays yielded LRV2.32 and LRV2.44 respectively. With a dose of 5mJ/cm2, arrays of peak wavelengths at 259 and 268 nm obtained similar inactivation (LRV2.97 and LRV 2.80 respectively). The remaining arrays of longer wavelength, 270, 275 and 280 nm, demonstrated lower performances (LRV2.0 or less) with 5mJ/cm2. Additional study with the 268 nm array revealed that a dose of 6.25 mJ/cm2 (with 5 seconds or irradiation) is enough to obtain LRV3. These results determine that 259 and 268 nm are the most efficient wavelengths compared to longer UVC wavelengths, allowing the calculation of disinfection systems efficacy, and providing a benchmark for surrogates.

Parallel shifts of visual sensitivity and body colouration in replicate populations of extremophile fish.

Visual sensitivity and body pigmentation are often shaped by both natural selection from the environment and sexual selection from mate choice. One way of quantifying the impact of the environment is by measuring how traits have changed after colonization of a novel habitat. To do this, we studied Poecilia mexicana populations that have repeatedly adapted to extreme sulphidic (H2S containing) environments. We measured visual sensitivity using opsin gene expression, as well as body pigmentation and water transmission for populations in four independent drainages. Both visual sensitivity and body pigmentation showed significant parallel shifts towards greater medium wavelength sensitivity and reflectance in sulphidic populations. The light spectrum was only subtly different between environments and overall, we found no significant correlations between the light environment and visual sensitivity or body pigmentation. Altogether we found that sulphidic habitats select for differences in visual sensitivity and pigmentation; our data suggest that this effect is unlikely to be driven purely by the water's spectral properties and may instead be from other correlated ecological changes.