Showing papers on "Fresnel equations published in 2023"
TL;DR: In this paper , the authors compare the simulated and experimental spectra at the air/water interface to compare the experiment with theory: an advanced approach taking into account the detailed inhomogeneous interfacial dielectric profile and the Lorentz and slab models.
Abstract: Insights into the microscopic structure of aqueous interfaces are essential for understanding the chemical and physical processes on the water surface, including chemical synthesis, atmospheric chemistry, and events in biomolecular systems. These aqueous interfaces have been probed by heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy. To obtain the molecular response from the measured HD-SFG spectra, one needs to correct the measured ssp spectra for local electromagnetic field effects at the interface due to a spatially varying dielectric function. This so-called Fresnel factor correction can change the inferred response substantially, and different ways of performing this correction lead to different conclusions about the interfacial water response. Here, we compare the simulated and experimental spectra at the air/water interface. We use three previously developed models to compare the experiment with theory: an advanced approach taking into account the detailed inhomogeneous interfacial dielectric profile and the Lorentz and slab models to approximate the interfacial dielectric function. Using the advanced model, we obtain an excellent quantitative agreement between theory and experiment, in both spectral shape and amplitude. Remarkably, we find that for the Fresnel factor correction of the ssp spectra, the Lorentz model for the interfacial dielectric function is equally accurate in the hydrogen (H)-bonded region of the response, while the slab model underestimates this response significantly. The Lorentz model, thus, provides a straightforward method to obtain the molecular response from the measured spectra of aqueous interfaces in the H-bonded region.
3 citations
TL;DR: In this article , a tilted fiber Bragg grating (TFBG) side modes and Fresnel reflection-based sensing system for solution concentration measurement is proposed, and the feasibility of the dip intensity of the TFBG side mode resonance to quantitatively characterize the solution concentration is demonstrated.
Abstract: Solution concentration (SC) measurement is of great significance in various fields. Various optical fiber SC sensors have been developed accordingly, in which the Fresnel refraction-based optical fiber sensor has the advantages of avoiding damage to sensing units, reusability, and low maintenance cost. In this study, a tilted fiber Bragg grating (TFBG) side modes and Fresnel reflection-based sensing system for SC measurement is proposed. Theoretically and experimentally, the nonuniformity of the grating period causing the forming of irregular TFBG side mode fringes is simulated and proved, and the feasibility of the dip intensity of the TFBG side mode resonance to quantitatively characterize the SC is demonstrated. As a result, a maximum concentration sensitivity of −0.471 dB/% at the glycerol SC (GSC) of 95.83% is achieved by increasing outpower of the light source and using an optical circulator. In addition, a method for simultaneous measurement of solution temperature and refractive index (RI) by using one side mode resonance signal is proposed and proved, which can significantly reduce the response time and improve the accuracy of concentration measurement.
TL;DR: In this paper , the authors investigated the scattering coefficients of a representative collection of fifty building materials used for construction and measured the optical and reflection properties of the samples using terahertz time-domain spectroscopy.
Abstract: The future communication technologies are naturally evolving towards higher carrier frequencies in order to satisfy the demand for increasing data rates. Terahertz frequencies appear to make high speed and high data rate communications possible. However, due to the high free-space damping above 100 GHz, communication systems are limited to short range, seldom, non-line-of-sight transmission links which rely mostly on the reflection properties of walls and other surfaces. We have investigated the scattering coefficients of a representative collection of fifty building materials used for construction. The optical and reflection properties of the samples were measured using terahertz time-domain spectroscopy and the scattering coefficients were modeled based on the Fresnel-Rayleigh equations and the Kirchhoff theory. The proposed Kirchhoff-Rayleigh approach is appropriate for the scattering characterisation of rough surfaces with limitations to resolve the scattering coefficients of materials with a complex structure. Nonetheless, the measured data show the reflection potential of materials commonly found in indoor environments, giving important insight into the further modeling of THz communication channels.
TL;DR: In this paper , a normalization method of the Fresnel reflection coefficient was proposed after analyzing the data characteristics of variables in the reflection coefficient, which can effectively reduce the influence of relevant parameters.
Abstract: Spaceborne GNSS-R technology is a new remote sensing method for soil moisture monitoring. Focusing on the significant influence of water on the surface reflectivity of CYGNSS, this paper improved the removal method of water influence according to the spatial resolution of CYGNSS data. Due to the disturbance effect of the incident angle, microwave frequency and soil type on the Fresnel reflection coefficient in surface reflectivity, a normalization method of Fresnel reflection coefficient was proposed after analyzing the data characteristics of variables in the Fresnel reflection coefficient. Finally, combined with the soil moisture retrieval method of linear equation, the accuracy was compared and verified by using measured data, SMAP products and official CYGNSS products. The results indicate that the normalization method of the Fresnel reflection coefficient could effectively reduce the influence of relevant parameters on the Fresnel reflection coefficient, but the normalization effect became worse at large incident angles (greater than 65°). Compared with the official CYGNSS product, the retrieval accuracy of optimized soil moisture was improved by 10%. The method proposed in this paper will play an important reference role in the study of soil moisture retrieval using spaceborne GNSS-R data.
01 Feb 2023
TL;DR: In this paper , a multi-measurand fiber-optic probe within a differential scanning calorimeter was used to infer the evolution of the refractive index during the cross-linking of an epoxy/amine thermosetting resin.
Abstract: The cross-correlation of cross-linking kinetic data obtained from different analytical equipment is not straightforward because the experimental conditions are seldom identical (temperature gradient, mass of the sample and substrate containing the analyte). Furthermore, the measurement principles can also be different (thermal, optical, rheological, etc). This paper reports on the design and implementation of a multi-measurand fibre-optic probe within a differential scanning calorimeter. The probe consisted of two components: (i) a low-cost and disposable cleaved-end of an optical fibre that served as a Fresnel refection sensor; and (ii) an array of non-contact optical fibres that enabled FTIR spectra to be acquired from within the calorimeter. The Fresnel reflection sensor was used as an immersion device to infer the evolution of the refractive index during the cross-linking of an epoxy/amine thermosetting resin. The array of optical fibres enabled FTIR spectra to be acquired during the cross-linking of the thermosetting resin. The motivation for developing this capability was to demonstrate cross-correlation between the quantitative FTIR spectral data, the qualitative Fresnel reflection sensor and the output from the differential scanning calorimeter. The cross-linking kinetics were determined for the two optical techniques and an excellent correlation was found between them and the data obtained from the calorimeter. The feasibility of using the same Fresnel reflection sensor, after cross-lining of the resin, for detecting the glass transition temperature was demonstrated.
TL;DR: In this article , the incidence of nonuniform waves between two dissipative media with finite conductivity and with a nonlinear response to the applied electric field, which is associated with the Kerr effect, is studied.
Abstract: We present a theoretical study of the incidence of nonuniform waves between two dissipative media with finite conductivity and with a nonlinear response to the applied electric field, which is associated with the Kerr effect. From the Adler–Chu–Fano formulation, the complex propagation vectors, transmitted and reflected angles, and Fresnel coefficients are obtained for the two linear polarization states. In addition, the modification of the total internal reflection, the phase shift, the Goos–Hänchen effect, as well as the interface interaction with bright solitons are explored. Calculations are performed for fused silica, the chalcogenide As 2 S 3 glass, and gold in glass media.
TL;DR: In this paper , an experimental study of the Fresnel coefficients of quartz glass using a linearly polarized diode laser with a wavelength of 660 nm was presented. And the results showed that the reflectance and transmittance remained constant for lower incident angles but varied with polarization for specific angles, following the Fresne coefficients.
TL;DR: In this article , the authors numerically examined the utilization of surface arrays composed of Fresnel nanosystems (Fresnel arrays), which are reminiscent of the known Fresnel lenses, for the realization of ultra-thin silicon PV cells.
Abstract: Omnidirectional broadband absorption of the solar radiation is pivotal to solar energy harvesting and particularly to low-cost non-tracking photovoltaic (PV) technologies. The current work numerically examines the utilization of surface arrays composed of Fresnel nanosystems (Fresnel arrays), which are reminiscent of the known Fresnel lenses, for the realization of ultra-thin silicon PV cells. Specifically, the optical and electrical performances of PV cells integrated with Fresnel arrays are compared with those of a PV cell incorporated with an optimized surface array of nanopillars (NP array). It is shown that the broadband absorption of specifically tailored Fresnel arrays can provide an enhancement of ∼20% over that of an optimized NP array. The performed analysis suggests that broadband absorption in ultra-thin films decorated with Fresnel arrays is driven by two light trapping mechanisms. The first is light trapping governed by light concentration, induced by the arrays, into the underlying substrates, which increases the optical coupling between the impinging illumination and the substrates. The second mechanism is light trapping motivated by refraction, as the Fresnel arrays induce lateral irradiance in the underlying substrates, which increases the optical interaction length and hence the overall probability for optical absorption. Finally, PV cells incorporated with surface Fresnel arrays are numerically calculated, with short-circuit current densities (Jsc) which are ∼50% higher than that of a PV cell incorporated with an optimized NP array. Also, the effect of increased surface area, due to the presence of Fresnel arrays, and its effect on surface recombination and open-circuit voltage (Voc) are discussed.
TL;DR: In this paper , the antireflection microstructures (ARMs) were fabricated on the surface of a LiGaSe2 crystal using a single-pulse femtosecond laser ablation method.
Abstract: LiGaSe2 is a propitious material for nonlinear parametric conversion in the mid-infrared (mid-IR) range. Its refractive index of n = 2.25 in the 2-12 µm wavelength range results in significant losses due to Fresnel reflection. However, the conventional method of increasing the transmittance with antireflection coatings (ARCs) significantly reduces the damage threshold of the material. Fabrication of the antireflection microstructures (ARMs) is an alternative approach for increasing the surface transmittance. In this work, ARMs were fabricated on the surface of a LiGaSe2 crystal using a single-pulse femtosecond laser ablation method. An average transmittance of 97.2% in the 2-8 µm spectral range and the maximum transmittance of 98.6% at 4.1 µm were achieved.
TL;DR: In this article , the influence of magnetic field intensity (H MF) on the refractive index of magnetic fluid (n MF) at room temperature was analyzed using the optical fiber end reflection method based on the Fresnel principle.
Abstract: The influence of magnetic field intensity(H MF) on the refractive index of magnetic fluid (n MF) at room temperature is analyzed. The optical fiber end reflection method based on the Fresnel principle is used to carry out relevant experiments. The corresponding relationship between n MF and applied magnetic field is studied in detail. n MF controls characteristic curve of magnetic fluid with a volume fraction of 0.36% is obtained. According to the experimental results, the H MF sensitivity of MF is about 0.937~0.948 RIU / T.
TL;DR: In this paper , a 4-bounce achromatic quarter-wave Fresnel rhomb retarder is proposed, which can easily change the input beam's ellipticity by rotating the retarder's fast axis.
Abstract: Achromatic terahertz (THz) quarter-wave retarder is widely desired to manipulate the polarization states of broadband THz beams, which are essential for spectroscopic applications, such as circular dichroism spectroscopy and steering THz vortex beams. A retarder based on Fresnel reflection exhibits the potential for designing an achromatic THz quarter-wave retarder. However, special care should be taken to make a Fresnel retarder capable of manipulating the beam ellipticity by simply rotating its fast axis without affecting its propagation path. Hereby, we design a 4-bounce achromatic quarter-wave Fresnel rhomb retarder free of affecting beam propagation, which can easily change the input beam's ellipticity by simply rotating the retarder's fast axis.
TL;DR: In this paper , a polydimethylsiloxane microfluidic chip (M-chip) was used for the measurement of aqueous samples, and the effects of the cavity depth of the M-chip on the THz spectra were investigated.
Abstract: The integration of a microfluidic chip into terahertz time-domain attenuated total reflection (THz TD-ATR) spectroscopy is highly demanded for the accurate measurement of aqueous samples. Hitherto, however little work has been reported on this regard. Here, we demonstrate a strategy of fabricating a polydimethylsiloxane microfluidic chip (M-chip) suitable for the measurement of aqueous samples, and investigate the effects of its configuration, particularly the cavity depth of the M-chip on THz spectra. By measuring pure water, we find that the Fresnel formulae of two-interface model should be applied to analyze the THz spectral data when the depth is smaller than 210 μm, but the Fresnel formula of one-interface model can be applied when the depth is no less than 210 μm. We further validate this by measuring physiological solution and protein solution. This work can help promote the application of THz TD-ATR spectroscopy in the study of aqueous biological samples.
TL;DR: In this article , a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry was presented, where the spatial resolution of the optical fiber was intentionally lowered to observe the Rayleigh scattered signal for the first time without the need for a frequency shifter.
Abstract: We present a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry. By intentionally lowering the spatial resolution of the system, we observe the Rayleigh scattered signal for the first time without the need for a frequency shifter. Using this method, we simultaneously measure the transmission loss, location, and loss of faulty connections along a 10 km long fiber under test by performing distributed reflected-power measurements of Rayleigh scattering and Fresnel reflection.
15 Mar 2023
TL;DR: In this article , a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry was presented, where the spatial resolution of the optical fiber was intentionally lowered to observe the Rayleigh scattered signal for the first time without the need for a frequency shifter.
Abstract: We present a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry. By intentionally lowering the spatial resolution of the system, we observe the Rayleigh scattered signal for the first time without the need for a frequency shifter. Using this method, we simultaneously measure the transmission loss, location, and loss of faulty connections along a 10-km-long fiber under test by performing distributed reflected-power measurements of Rayleigh scattering and Fresnel reflection.