Photonic Sensor Research Articles

Faraday effect sensing of single-molecules by graphene-based layered structures

To investigate the sensing properties of the Faraday effect in graphene in terahertz (THz), we consider the modulations of Dirac gaps in graphene when gas molecules are adsorbed to its surface. Here, the effect of the associated bandgap opening in graphene’s spectrum on the sensing properties of the Faraday rotation (FR) in a 1D photonic graphene-based sensor with a microcavity defect channel covered by two graphene layers. Our proposed model introduces an optical contact-free mechanism for detecting low-concentration molecules attached to graphene’s surface. We also show that FR angles could reveal reversal signs for a different amount of surface transfer doping. Finally, the effect of increasing the temperature on the Faraday effect at a certain opening gap in graphene’s spectrum is investigated. Interestingly, stronger FR effect it was observed at higher temperatures. Our results could open the path for development of contact-free sensing applications in THz region.

Wavelength multiplexing infrared metasurfaces for protein recognition and trace detection

Abstract Infrared metasurfaces have exhibited exceptional optical properties that differ from naturally occurring metallic and dielectric nanostructure, enabling non-destructive and label-free sensing in a broadband region. However, implementing wavelength multiplexing sensors in broadband infrared has faced significant challenges. These challenges arise from the difficulty in efficiently exciting high Q resonances at specific wavelengths and the inability to individually tune each resonance. Herein, we present a dual resonant metasurface that utilizes a metal–dielectric–metal plasmonic grating and a dielectric–metal channel. By adjusting the vertical and horizontal structures of metasurface, we can independently modify the spectrum of the metasurface in the near-infrared and mid-infrared regions. This broadband infrared metasurface exhibits robust spectral regulation, enabling a polarization-dependent strategy for the dual-resonance. It offers a competitive advantage over traditional metallic nanostructure in refractive index sensing at the second near-infrared window and ultrasensitive vibrational spectroscopy in mid-infrared. Specifically, our proposed metasurface achieves protein concentration sensing and dynamic monitoring of protein concentration in the infrared two-zone. Additionally, it enhances the mid-infrared absorption of amide II with a high Q resonance. The metasurface which combines wavelength multiplexing and polarization dependent switch for protein recognition and trace detection, presents a novel approach for developing high-performance sensors and Integrated photonics sensors in the broadband infrared region.

Sidewall grating slot waveguide microring resonator biochemical sensor.

Integrated microring resonator structures based on silicon-on-insulator (SOI) platforms are promising candidates for high-performance on-chip sensing. In this work, a novel sidewall grating slot microring resonator (SG-SMRR) with a compact size (5 µm center radius) based on the SOI platform is proposed and demonstrated experimentally. The experiment results show that the refractive index (RI) sensitivity and the limit of detection value are 620 nm/RIU and 1.4 × 10-4 RIU, respectively. The concentration sensitivity and minimum concentration detection limit are 1120 pm/% and 0.05%, respectively. Moreover, the sidewall grating structure makes this sensor free of free spectral range (FSR) limitation. The detection range is significantly enlarged to 84.5 nm in lab measurement, four times that of the FSR of conventional SMRRs. The measured Q-factor is 3.1 × 103, and the straight slot waveguide transmission loss is 24.2 dB/cm under sensing conditions. These results combined with the small form factor associated with a silicon photonics sensor open up applications where high sensitivity and large measurement range are essential.

Toward point-of-care diagnostics: Running enzymatic assays on a photonic waveguide-based sensor chip with a portable, benchtop measurement system.

We demonstrate a portable, compact system to perform absorption-based enzymatic assays at a visible wavelength of 639 nm on a photonic waveguide-based sensor chip, suitable for lab-on-a-chip applications. The photonic design and fabrication of the sensor are described, and a detailed overview of the portable measurement system is presented. In this publication, we use an integrated photonic waveguide-based absorbance sensor to run a full enzymatic assay. An assay to detect creatinine in plasma is simultaneously performed on both the photonic sensor on the portable setup and on a commercial microplate reader for a clinically relevant creatinine concentration range. We observed a high correlation between the measured waveguide propagation loss and the optical density measurement from the plate reader and measured a limit-of-detection of 4.5 μM creatinine in the sensor well, covering the relevant clinical range for creatinine detection.

A study on performance boost of a 17 m class Cherenkov telescope with a SiPM-based camera

The current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), comprised of major installations such as the MAGIC, H.E.S.S. and VERITAS telescopes, is sometimes called the 3rd generation of such instruments. These telescopes use multipixel cameras composed of hundreds up to thousands photomultiplier tubes (PMTs). The supremacy of PMTs is currently being challenged by photon sensors, rapidly spreading in popularity: the silicon photomultipliers (SiPMs), that are becoming a valid alternative thanks to their high PDE, low operating voltage and flexibility in installation. In this report, we investigate the performance of an existing 3rd generation IACT array (taking as a working example MAGIC), in which PMTs would be replaced with SiPMs, applying generalized simulations, not tuned for a specific hardware solution. We find an energy-dependent improvement in sensitivity, reaching a factor of three at the current trigger threshold energy. Interestingly, we also find that the stronger sensitivity of SiPMs in the red part of the spectrum, a source of background for IACTs, does not affect this performance.

Design and analysis of a high-sensitivity fan-shaped photonic crystal fiber sensor based on surface plasmon resonance

Design and analysis of a high-sensitivity fan-shaped photonic crystal fiber sensor based on surface plasmon resonance

Dual-channel high sensitivity photonic crystal fiber sensor based on rectangular air holes

This paper proposes a dual-channel high sensitivity photonic crystal fiber sensor with rectangular air holes, which can detect the refractive index of a single sample or detect the refractive index of two samples simultaneously, to increase the detection efficiency and wavelength sensitivity of the sample refractive index. The sensor can reduce the times of filling, emptying and cleaning of the sample to be tested and save labor and time costs. The finite element method is used to thoroughly analyze the proposed structure’s sensing properties. The results show that when the sensor detects a single sample, the maximum wavelength sensitivity is 67,300[Formula: see text]nm/RIU, and the highest figure of merit (FOM) is 547 RIU[Formula: see text]. When the sensor detects two samples synchronously, the maximum wavelength sensitivity is 64,100[Formula: see text]nm/RIU, which is the highest level among the known sensors of the same kind. It has good application prospect in the field of high sensitivity refractive index detection.

Monitoring the abundance of flying insects and atmospheric conditions during a 9-month campaign using an entomological optical sensor

Monitoring the dynamics of insect populations is key to assessing the impact of human activities on insect populations. However, traditional methodologies relying on physical traps have inherent limitations in accurately monitoring insect abundance. Here, we present findings from a 9-month campaign conducted in New Jersey, USA, utilizing a near-infrared optical sensor known as eBoss. From April to December 2022, the eBoss derived the aerial density (insect/m3) and biomass density (mg/m3) with a 1-min resolution from a total of 302,093 insect observations. The data collected were analyzed in relation to air temperature, relative humidity, and wind speed. The results revealed that the abundance of flying insects exhibited an initial increase from April to June, reaching a peak of 0.094 insect/m3 and 1.34 mg/m3, followed by a subsequent decline towards the end of the year. Our investigation showed a surge in insect abundance above 12.5 °C, with particularly high levels observed between 19 and 31 °C. The impact of relative humidity and wind speed on insect populations was also explored. Overall, this campaign demonstrated the efficacy of photonic sensors in gathering novel and extensive data for the field of entomology, paving the way for improved understanding and management of insect populations.

Performance of the most recent Microchannel-Plate PMTs for the PANDA DIRC detectors at FAIR

In the PANDA experiment at the FAIR facility at GSI two DIRC (Detection of Internally Reflected Cherenkov light) detectors will be used for π/K separation up to 4GeV/c. Due to their location in a high magnetic field and other stringent requirements like high detection efficiency, low dark count rate, radiation hardness, long lifetime and good timing, MCP-PMTs (microchannel-plate photomultiplier) were the best choice of photon sensors for the DIRC detectors in the PANDA experiment. This paper will present the performance of some of the latest 2 × 2inch 2 MCP-PMTs from Photek and Photonis, including the first mass production tubes for the PANDA Barrel DIRC from Photonis. Performance parameters like the collection efficiency (CE), quantum efficiency (QE), and gain homogeneity were determined. The effect of magnetic fields on some properties like gain and charge cloud width was investigated as well. Apart from that the spatial distribution of many internal parameters like time resolution, dark count rate, afterpulse ratio, charge sharing crosstalk and recoil electrons were measured simultaneously with a multihit capable DAQ system. The latest generation of Photonis MCP-PMTs shows a unexpected ”escalation” effect where the MCP-PMT itself produces photons.

High angular sensitivity refractive index sensors based on 1D single-defect magneto-optical photonic crystals

Strong localization and enhancement of fields may arise in the defect layer of an 1D single-defect magneto-optical photonic crystal (1DSDMOPC), which has been applied to design and fabricate several types of optical devices. In this work, we demonstrate numerically that, for the case that a linearly polarized light is normally incident on a selected 1DSDMOPC, rotation angle induced by polar linear magneto-optical Kerr effect may strongly depend on refractive index of the fluid encountered by the transmission, which indicates that 1DSDMOPC is promising to be applied as a refractive index sensor based on Kerr angle detection. Furthermore, it is shown that sensitivity and detection range of the sensor can be adjusted by either modifying refractive index of the dielectric layers or altering number of layers of the 1DSDMOPC. An angular sensitivity in the order of 104 °/RIU is inferred, a value much larger than both the one usually encountered in photonic crystal sensors and the surface plasmon resonance based sensors (the angular sensitivity usually in the order of 101 or 102 °/RIU). Our work may provide a new possible way to design and manufacture high angular sensitivity sensors by using 1DSDMOPCs.

Photonic Crystal Sensor Evaluating the Effectiveness of Medical Products under Different Storage Conditions.

The effectiveness of time- and temperature-sensitive medical products (TTSMPs) (vaccines, medicines, and biological agents) is generally evaluated by sporadically checking the storage conditions recorded in electronic thermometers. However, electronic thermometers do not achieve all-time and all-regional record, resulting in the wrong evaluation of a single TTSMP and seriously endangering public health. Herein, we report a photonic crystal sensor for evaluating the effectiveness of a single TTSMP processing storage environment. The photonic crystal sensor assembled by colloidal microspheres (WO3-x nanospheres were added into the microsphere gap) generates a fascinating composite color of angle-dependent structural color (maximum reflectivity = 45%) and durative color (WO3-x coloration). Effectiveness evaluation principle reveals that the pattern on the sensor, which was printed by the composite color, fades sensitively to time and temperature, thus having different visible periods (0-21 days affected by temperature). The visible periods of the patterns can be used to evaluate a single TTSMP's effectiveness stored under different temperatures. Furthermore, the photonic crystal sensor shows outstanding flexibility and slight adhesion, offering a promising application toward the effectiveness evaluation of TTSMPs throughout storage, transportation, and sales processes.

Integrated Flexible Microscale Mechanical Sensors Based on Cascaded Free Spectral Range-Free Cavities.

Photonic mechanical sensors offer several advantages over their electronic counterparts, including immunity to electromagnetic interference, increased sensitivity, and measurement accuracy. Exploring flexible mechanical sensors on deformable substrates provides new opportunities for strain-optical coupling operations. Nevertheless, existing flexible photonics strategies often require cumbersome signal collection and analysis with bulky setups, limiting their portability and affordability. To address these challenges, we propose a waveguide-integrated flexible mechanical sensor based on cascaded photonic crystal microcavities with inherent deformation and biaxial tensile state analysis. Leveraging the advanced multiplexing capability of the sensor, for the first time, we successfully demonstrate 2D shape reconstruction and quasi-distributed strain sensing with 110 μm spatial resolution. Our microscale mechanical sensor also exhibits exceptional sensitivity with a detected force level as low as 13.6 μN in real-time measurements. This sensing platform has potential applications in various fields, including biomedical sensing, surgical catheters, aircraft and spacecraft engineering, and robotic photonic skin development.

Hazardous Gases-Responsive Photonic Crystals Cryogenic Sensors Based on Antifreezing and Water Retention Hydrogels.

Nowadays, the sensing of hazardous gases is urgent for the consideration of public safety and human health, especially in extreme conditions of low temperatures. In this study, a photonic crystals (PhCs) sensor with water retention and antifreezing properties was developed and applied to visual hazardous gases sensing at low temperature, passively. The sensor was prepared by dip-coating with poly(methyl methacrylate) (PMMA) colloidal microspheres followed by embedding in k-carrageenan/polyacrylamide-ethylene glycol (k-CA/PAM-EG) hydrogel. The sensor responded to hazardous gases, including ammonia, toluene, xylene, acetone, methanol, ethanol, and 1-propanol, with a change in the reflection wavelength and visible structural color. At room temperature, the reflection wavelength of the sensor blue-shifted 49 nm in ammonia, and the structural color changed from red to yellow. For low temperatures, the sensor showed great water retention and antifreezing properties even at -57 °C due to the double network. The sensor still had a great response to hazardous gases after freezing at -20 °C for 12 h and testing at 0 °C, and the obtained results were similar to those at room temperature. Based on this excellent stability and visual sensing at low temperature, the sensor demonstrates the potential for detection of hazardous vapors in extreme environments.

Performance comparison and analysis of D-type single and dual-core PCF-SPR sensors

Surface plasmon resonance sensors, based on photonic crystal fibers, have demonstrated immense potential in various application fields, owing to their structural design flexibility, operability, and superior sensing capabilities. Despite the potential, the design of photonic crystal fibers with various structures has been a challenging task, due to manufacturing constraints. Thus, this paper aims to explore the design rules of photonic crystal fibers based on surface plasmon resonance, by proposing and designing four photonic crystal fiber sensors with distinct structures. The study investigates the influence of single-core, double-core, and large and small air holes on the sensor’s performance, through theoretical analysis, numerical simulation, data acquisition, and analysis. Through our research, we have discovered that by altering the size of pores surrounding the fiber core, as well as the fiber core’s single-mode and dual-mode configurations, we were able to increase the sensitivity of the sensor from its lowest value of 266 nm RIU−1 to as high as 2066 nm RIU−1, an improvement of nearly eightfold. The findings suggest that the sensor with double-core air hole structure exhibits relatively better performance. This analysis is expected to aid in the design of high-performance photonic crystal fiber-based surface plasmon resonance sensors.

Detection of SARS‐CoV‐2 Virus Concentration Using a Simple Structure of Binary Photonic Crystal Sensor

The scientific community works hard on developing reliable, rapid, highly sensitive, and low‐cost techniques to detect severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). The current techniques can occasionally produce false‐positive results. The development of novel approaches for the identification of SARS‐CoV‐2 is a significant area of research because of the limitations of current methods. A biosensor based on a defective binary photonic crystal (PCL) is proposed to detect SARS‐CoV‐2 concentration herein. The model of pathogen concentration‐dependent refractive index of the analyte is taken into consideration. The concept of operation of the PCL sensor is based on the defect mode shift when any change in the refractive index of the defect layer occurs. The transmission spectra of the PCL are plotted and studied. An optimum incident angle of 80° and a defect layer thickness of 5 μm are found. The relationship between the defect mode's wavelength and the concentration of SARS‐CoV‐2 is investigated and a sensitivity of 2648.3 nm RIU−1 is attained.

A Polished-D-Shape SPR-Based Photonic Crystal Fiber Sensor with High Sensitivity for Measuring Refractive Index

In the correspondence, a novel polished-D-shape photonic crystal fiber sensor structure on the basis of surface plasmon resonance is proposed for measuring analyte refractive index. With the help of the finite element method, sensing performances of the structure have been analyzed through numerical simulations along with a step-by-step optimization . In this design, different capillaries are gathered and processed to form a D-shape silica structure and nano-scale gold material is coated on the flattened surface. With utilization of a thin gold film and solid silica background, the resonance effect is excited and the loss curve has red shift along with an increase in refractive index, which is applied for sensing. From the simulation and calculation results, the final sensor structure achieves the optimal performance where values of maximum and average sensitivity reach 32,000 and 12,167 nm/RIU along with a sensing coverage of refractive index from 1.26 to 1.32. Also, the proposed design obtains a range of resonant wavelength from 1810 to 2540 nm. We believe the proposed sensor can be a potential candidate for organic and biological detection and related applications.

A high-sensitivity D-shaped photonic crystal fiber surface plasmon resonance sensor for low refractive index detection

A high-sensitivity D-shaped photonic crystal fiber surface plasmon resonance sensor for low refractive index detection

An Ultrasensitive SPR biosensor for RNA detection based on robust GeP5 nanosheets

Ultrasensitive and rapid detection of biomarkers is among the upmost priorities in promoting healthcare advancements. Improved sensitivity of photonic sensors based on two-dimensional (2D) materials have brought exciting prospects for achieving real-time and label-free biosensing at dilute target concentrations. Here, we report a high-sensitivity surface plasmon resonance (SPR) RNA sensor using metallic 2D GeP5 nanosheets as the sensing material. Theoretical evaluations revealed that the presence of GeP5 nanosheets can greatly enhance the plasmonic electric field of the Au film thereby boosting sensing sensitivity, and that optimal sensitivity (146° RIU−1) can be achieved with 3-nm-thick GeP5. By functionalizing GeP5 nanosheets with specific cDNA probes, detection of SARS-CoV-2 RNA sequences were achieved using the GeP5-based SPR sensor, with high sensitivity down to a detection limit of 10 aM and excellent selectivity. This work demonstrates the immense potential of GeP5-based SPR sensors for advanced biosensing applications and paves the way for utilizing GeP5 nanosheets in novel sensor devices.

Silicate-glass based photonic crystal fiber for rapid petro-chemical sensing: Design and analysis

The distillation method for extracting anhydrous ethanol from the volatile benzene water requires continuous supervision in the petro-chemical industry. This paper describes the design process and numerical analyses of a PCF sensor with a hollow core for sensing the petro-chemical constituents, namely ethanol, water, and benzene, in the 2 THz range. Photonic crystal fiber sensors have many possible applications in the petro-chemical industry, environmental monitoring, biomedicine, and food preservation. An optical fiber-based sensor with simultaneous low loss and enhanced sensitivity is intended to detect this petro-chemical effectively and safely. The Finite Element Method (FEM) framework is used to quantify the exhibition of the suggested fiber sensor. The simulation outcomes on the suggested sensor model demonstrate very satisfactory results on the relative sensitivity as 99.55 %, 99.44 % and 99.59 % confinement loss as 2×10−17 dB/cm, 1×10−16 dB/cm and 1.17×10−16 dB/cm, Effective Material Loss (EML) as 0.00043 cm−1, 0.00054 cm−1 and 0.00038 cm−1 for Ethanol, Water and Benzene, respectively and the Effective areas (EAs) are 2.85×10−7m2 for Ethanol, 2.91×10−7m2 for Water and 2.82×10−7m2 for Benzene at 2 THz frequency regime.

Optimization of the quality factor and sensitivity of one-dimensional photonic crystal methane sensor with cryptophane A cavity

In this work, we introduce a sensor for measuring different methane concentration levels. The model is based on a defective one-dimensional photonic crystal composed of alternating layers of air and Silicon with a cryptophane A cavity. We assume that the refractive index of silicon depends on temperature. The transmittance spectrum was calculated using the transfer matrix method. This work also assessed the effects of temperature and methane concentration on the wavelength shift of a localized mode within the photonic band gap. The results show the shift of this localized mode toward longer wavelengths as temperature increases, with the quality factor reaching its maximum value at around 8994.35. When maintaining a constant temperature, we observed a blue-shift when the methane concentration is in a range of 0.0–3.5%, and the quality factor decreases to 6358.26, with a maximum sensitivity of 144.485 nm by RIU. Due to its excellent performance to store energy within the cavity, this sensor can be used to detect different gas concentrations.