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Design of terahertz spectroscopy based optical sensor for chemical detection
摘要： In this article, a new design of circular cladding with a rotated-hexacore in photonic crystal fiber (RH-CPCF) has been suggested for chemical sensing application in the THz regime. The five layers circular cladding and two layers rotated-hexacore in circular shape are designed here. All numerical results are obtained with a procedure of finite element method and perfectly match layered boundary condition in terahertz (THz) wave propagation. After the simulation result, the proposed RH-CPCF shows the high relative sensitivity is 76.44%, 77.16% and 73.20% for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330) at 1 THz. On the other hand, the low confinement losses are 2.33 × 10?03 dB/m, 3.07 × 10?06 dB/m and 2.84 × 10?02 dB/m for same in three chemicals at 1 THz. Moreover, effective area, effective mode index and total power fraction in core air holes are also briefly described here. In addition, this proposed circular photonic crystal fiber (RH-CPCF) can be used especially for chemical sensing in biomedical, industrial quality control, material research, micro-optics and many communication applications in THz technology.
关键词： Terahertz sensor,Sensitivity,Optical loss profile,Photonic crystal fiber,Optical sensor,FEM based analysis
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Erode, India (21–22 November 2019)] SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Adopted octagonal photonic crystal fiber for analyte liquids sensing
摘要： In this paper, octagonal-photonic crystal fiber (O-PCF) has been proposed for studying liquid types for sensing applications. The propagation properties for the proposed O-PCF were studied numerically by utilizing full-vector finite element method (FV-FEM ) using COM SOL M ultiphysics version 5.1. The confinement loss, the relative sensitivity, and the nonlinearity coefficient can be controlled by changing the factors related with the geometry such as the cladding in a range of wavelength, air hole diameter, and the core pitch. The proposed O-PCF is realized with three rings from the air hole in the cladding and two circular rings in the core region. Numerical simulation of the proposed structure is achieving the highest sensitivity by increasing the diameter of the air hole the cladding, while the pitch remains constant. At the same time, the confinement losses have distinguishable decrease with an increase in diameter as well as an increase in the number of rings within the cladding layer. In addition, the effective area and the nonlinear coefficient each of them is affected with every hole of the diameter and with the type of the chemical material used. The proposed model shows that the fiber is of a high efficiency not only in the sensing application, but also being distinguishable with the nonlinear optical application.
关键词： chemical sensor,nonlinearity coefficient,O-PCF,Sensitivity,confinement loss
更新于2025-09-12 10:27:22
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Effect of the electric field induced birefringence on the slab waveguide evanescent-wave sensor sensitivity
摘要： We have investigated the potential of using the E-field induced birefringence for improving the sensitivity of uniaxial anisotropic slab waveguide sensor based on evanescent wave interactions. LiNbO3 waveguide core was used as an example. We have calculated the sensor sensitivity formulas for the two kinds of modes propagating simultaneously in the waveguide sensor. In our study, we have distinguished between two different cases. The first case when the electric field is applied along the optic axis (+c) of the LiNbO3 wave guiding film (positive electric field); the second case when the electric field is applied opposite to the optic axis (?c) of such uniaxial crystal (negative electric field). The obtained results showed that, for positive electric field, increasing the electric field induces an increasing of the total anisotropy which causes decreasing on sensor sensitivity. However, for negative electric field, the increase of absolute values of negative electric field induces a decrease of the total anisotropy, the latter increases the sensor sensitivity. On the other hand, the study of the physical parameters on the sensor sensitivity showed that, to maximize the sensor sensitivity, it is advisable to use isotropic substrate that has a refractive index as closer as possible to the measurand index.
关键词： Evanescent wave,Uniaxial anisotropy,Planar waveguide sensor,Induced birefringence,Sensor sensitivity
更新于2025-09-12 10:27:22
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Three-Dimensional Composition Analysis of SnAg Solder Bumps Using Ultraviolet Femtosecond Laser Ablation Ionization Mass Spectrometry
摘要： The application of a novel UV fs Laser Ablation Ionization Mass Spectrometry approach for chemical depth profiling of low-melting point, high surface roughness SnAg solder bump features is presented. The obtained resolved three-dimensional compositional submicrometer data reveal unprecedented information on the distribution of individual elements inside the solder bump matrix. Moreover, the determination of matrix-matched relative sensitivity coefficients allows the first report on quantitative assessment of the SnAg alloy composition. These results significantly contribute to an in-depth understanding of the SnAg plating process. This experimental procedure may find application in future additive performance screening.
关键词： three-dimensional compositional analysis,chemical depth profiling,SnAg solder bumps,UV fs Laser Ablation Ionization Mass Spectrometry,matrix-matched relative sensitivity coefficients
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Field-Resolved Infrared Transmission Spectroscopy of Strongly Absorbing Samples
摘要： Molecular vibrational spectroscopies provide chemically-specific information on complex samples. The label-free nature of these techniques renders them highly attractive for studies of biological processes and medical diagnosis. Among these methods, the direct, broadband interrogation of molecular vibrations at their fundamental frequencies in the infrared (IR) molecular fingerprint region, profits from large interaction cross-sections, potentially affording a unique combination of detection sensitivity and molecular coverage. However, the strong absorption of (liquid) water in this spectral range has so far severely limited the applicability of IR vibrational spectroscopy (and microscopy) in transmission geometry. In this contribution, we demonstrate the potential of field-resolved infrared spectroscopy (FRS) to overcome these long-standing limitations. FRS relies on the excitation of resonant molecular vibrations with waveform-stable, broadband IR pulses, and electric-field-resolved detection of the emerging fingerprint waveforms via electro-optic sampling, bringing about two major advantages over other IR spectroscopies. Firstly, it directly measures the electric field, resulting in a square root scaling of the signal with the intensity attenuation. Together with quantum-efficiency maximised electro-optic sampling and sensitive photodiodes in the near-infrared, this offers an unprecedented intensity dynamic range. Secondly, the nature of time-domain measurements enables recording resonant fingerprints trailing an impulsive excitation in a background-free manner, rendering FRS mostly immune to intensity noise of the excitation. Assuming a detection immune to intensity noise, and with the DR shown in Fig. 1.a, for our system we model the curve in Fig. 1b for the limit of detection (LOD) of a test molecule, DMSO2, solved in water. For an aqueous layer of 33 μm, we experimentally obtain an LOD of 200 ng/ml (for 45 seconds of measurement time), which validates this model and our assumption. These results predict fast, broadband measurements of aqueous samples as thick as 0.1 mm, with sub-μg/ml detection sensitivities, opening the door to a new realm of applications of vibrational spectroscopy to biological samples such as tissue and live cells.
关键词： detection sensitivity,infrared (IR) molecular fingerprint region,molecular vibrational spectroscopies,electro-optic sampling,field-resolved infrared spectroscopy
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Integrated Optical Fibre — Investigating the Vibrational Response using Optical Frequency Domain Reflectometry
摘要： Integrated Optical Fibre (IOF) is a new technology in integrated optics using flame hydrolysis deposition to permanently attach an optical fibre onto a silicon substrate. This approach combines the low losses of optical fibre with the mechanical integrity of an integrated planar platform. By attaching the fibre with high quality optical glass we create devices that transform the packaging of fibres for sensing applications removing any use of glues, epoxies, adhesives and making it suitable for harsh environments such as aerospace. The binding medium itself can also be used for its optical properties. Aerospace environments are demanding, both for temperature range (-50 to +120 °C), but also for vibration and shock. In this work we are investigating a technique for monitoring the vibration sensitivity and damage points of the IOF under typical structural vibration conditions. In particular, here we report the use of Optical Frequency Domain Reflectometry (OFDR), which can reveal spectral and spatial information of features within a fibre such as Fibre Bragg Gratings (FBGs). This is of particular interest when applied to structural health monitoring, distributed strain and temperature sensing.
关键词： Optical Frequency Domain Reflectometry,vibration sensitivity,structural health monitoring,Integrated Optical Fibre,Fibre Bragg Gratings
更新于2025-09-12 10:27:22
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Fast-pulsing LED-enhanced NMR: A convenient and inexpensive approach to increase NMR sensitivity
摘要： Low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) has recently emerged as a powerful technology for the detection of aromatic amino acids and proteins in solution in the low-micromolar to nanomolar concentration range. LC-photo-CIDNP is typically carried out in the presence of high-power lasers, which are costly and maintenance-heavy. Here, we show that LC-photo-CIDNP can be performed with light-emitting diodes (LEDs), which are inexpensive and much less cumbersome than lasers, laser diodes, flash lamps, or other light sources. When nuclear magnetic resonance (NMR) sample concentration is within the low-micromolar to nanomolar range, as in LC-photo-CIDNP, replacement of lasers with LEDs leads to no losses in sensitivity. We also investigate the effect of optical-fiber thickness and compare excitation rate constants of an Ar ion laser (488 nm) and a 466 nm LED, taking LED emission bandwidths into account. In addition, importantly, we develop a novel pulse sequence (13C RASPRINT) to perform ultrarapid LC-photo-CIDNP data collection. Remarkably, 13C RASPRINT leads to 4-fold savings in data collection time. The latter advance relies on the fact that photo-CID nuclear hyperpolarization does not suffer from the longitudinal-relaxation recovery requirements of conventional NMR. Finally, we combine both the above improvements, resulting in facile and rapid (≈16 s–2.5 min) collection of 1 and 2D NMR data on aromatic amino acids and proteins in solution at nanomolar to low micromolar concentration.
关键词： LED,LC-photo-CIDNP,13C RASPRINT,NMR sensitivity,laser,hyperpolarization
更新于2025-09-12 10:27:22
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In Vivo Reflection-Mode Photoacoustic Microscopy Enhanced by Plasmonic Sensing with an Acoustic Cavity
摘要： Relying on high-sensitivity refractive index sensing and a highly constrained evanescent field of surface plasmon resonance (SPR), broadband photoacoustic (PA) pressure transients were measured using an SPR sensor instead of routinely used piezoelectric ultrasonic transducers. An acoustic cavity made from stainless steel and having a designed ellipsoidal inner surface redirected laser-induced PA waves from the PA excitation spot to the SPR sensor. By incorporating the SPR sensor with the acoustic cavity, we developed optical-resolution photoacoustic microscopy (OR-PAM) with multiple advantages, including reflection-mode signal capture, improved PA detection sensitivity, increased PA spectral bandwidth as broad as ～98 MHz, and micrometer-scale lateral resolution. This allowed label-free volumetric PA imaging of vasculature in not only the thin ear but also the thick forelimb of living mice. With these combined advantages, our OR-PAM system potentially offers more opportunities for biomedical investigation, for example, when studying microcirculations in the eye and cortex.
关键词： reflection mode,high sensitivity,surface plasmon resonance,in vivo vascular imaging,photoacoustic imaging
更新于2025-09-12 10:27:22
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Comparing Dry Eye Disease After Small Incision Lenticule Extraction and Laser Subepithelial Keratomileusis
摘要： To compare dry eye disease parameters between small incision lenticule extraction (SMILE) and laser subepithelial keratomileusis (LASEK). This prospective, nonrandomized study included 39 eyes of 39 patients who underwent SMILE (n = 19) and LASEK (n = 20). Dry eye disease parameters included Ocular Surface Disease Index (OSDI), tear breakup time, Schirmer I test (SIT) value, corneal esthesiometry result, tear meniscus area, meibomian gland evaluation result, lipid layer thickness, and blink rate. Evaluations were performed before surgery and at 1 and 6 months after surgery. Compared with the LASEK group, the SMILE group showed lower corneal esthesiometry values at 1 month and higher OSDI scores and lower SIT values at 6 months after surgery. The SMILE group showed significantly higher OSDI scores at 1 and 6 months after surgery than before, but significantly lower OSDI scores at 6 months than at 1 month showed significantly decreased after corneal sensitivity at 1 month after surgery, which increased to the preoperative level 6 months after surgery. The change in OSDI scores at 1 month after surgery positively correlated with changes in the total and partial blink rates, whereas the change in corneal sensitivity at 1 month after surgery negatively correlated with the total and partial blink rates. Both SMILE and LASEK groups showed temporary decreases in corneal sensitivity, which recovered to baseline levels. Although subjective symptoms worsened after SMILE, SIT values improved after LASEK. Compared with SMILE, LASEK yielded better results regarding subjective symptoms, tear production, and corneal sensitivity.
关键词： corneal sensitivity,dry eye disease,small incision lenticule extraction,laser subepithelial keratomileusis
更新于2025-09-12 10:27:22
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A DOUBLE-MASKED, RANDOMIZED, SHAM-CONTROLLED, SINGLE-CENTER STUDY WITH PHOTOBIOMODULATION FOR THE TREATMENT OF DRY AGE-RELATED MACULAR DEGENERATION
摘要： The LIGHTSITE I study investigated the efficacy and safety of photobiomodulation (PBM) treatment in subjects with dry age-related macular degeneration. Thirty subjects (46 eyes) were treated with the Valeda Light Delivery System, wherein subjects underwent two series of treatments (3· per week for 3–4 weeks) over 1 year. Outcome measures included best-corrected visual acuity, contrast sensitivity, microperimetry, central drusen volume and drusen thickness, and quality of life assessments. Photobiomodulation-treated subjects showed a best-corrected visual acuity mean letter score gain of 4 letters immediately after each treatment series at Month 1 (M1) and Month 7 (M7). Approximately 50% of PBM-treated subjects showed improvement of $5 letters versus 13.6% in sham-treated subjects at M1. High responding subjects ($5-letter improvement) in the PBM-treated group showed a gain of 8 letters after initial treatment (P , 0.01) and exhibited earlier stages of age-related macular degeneration disease. Statistically significant improvements in contrast sensitivity, central drusen volume, central drusen thickness, and quality of life were observed (P , 0.05). No device-related adverse events were reported. Photobiomodulation treatment statistically improved clinical and anatomical outcomes with more robust benefits observed in subjects with earlier stages of dry age-related macular degeneration. Repeated PBM treatments are necessary to maintain benefits. These pilot findings support previous reports and suggest the utility of PBM as a safe and effective therapy in subjects with dry age-related macular degeneration.
关键词： contrast sensitivity,best-corrected visual acuity,light-emitting diode,vision loss,low-level light therapy,mitochondria,photobiomodulation,dry age-related macular degeneration,drusen
更新于2025-09-12 10:27:22