Line Shape Of Spectra Research Articles

Single Spectral Line Method for TDLAS Imaging of Temperature and Water Vapor Concentration

A single spectral line method for gas temperature as well as concentration extraction was proposed by using iterations with a fuzzy proportional–integral-derivative (PID) controller in tunable diode laser absorption spectroscopy (TDLAS). Usually, two or more spectral lines are essential to extract temperatures from coupled gas concentration and pressure. The proposed method utilized the line shape of a single absorption spectrum to decouple gas parameters along the laser path simultaneously and simplified the optical implementations. Differential equations of the Voigt profile were introduced at multiple wavenumbers to extract gas parameters from a single spectral line. A fuzzy PID controller was utilized to iteratively achieve the single spectral line from widely existed overlapping spectra. A relative temperature error within 2.5% at reference temperatures ranged from 300 to 2300 K was achieved by using the spectral line of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7444.35\,\,{\mathrm {cm}}^{-1}$ </tex-math></inline-formula> from noise free data. At low temperatures below 350 K, the proposed method using the single spectral line of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7181.14\,\,{\mathrm {cm}}^{-1}$ </tex-math></inline-formula> yielded smaller errors in noisy cases, and the temperature errors were verified within 5 °C on the water-based thermostat below 100 °C using the single spectral line. Experiments of axisymmetric counterflow flames at different heights were also implemented. The proposed method effectively reconstructed distributions of flame temperature and water vapor concentration inside, by only using a single spectral line of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7444.35\,\,{\mathrm {cm}}^{-1}$ </tex-math></inline-formula> .

Four-wave mixing properties in bilayer graphene nanosystem

Graphene thin films are often used to manufacture various optoelectronic nanodevices owing to their advantages such as light weight, small size, high quality factor, and good conductivity. So far, there have been few studies of the four-wave mixing characteristics in a bilayer graphene nanosystem, especially theoretical research. In this work, we study theoretically the four-wave mixing properties in a bilayer graphene nanosystem. Firstly, the analytical formula of the four-wave mixing signal is derived by quantum mechanical method, which is divided into three steps. 1) Total Hamiltonian of the system is written in the rotating wave approximation. 2) By using the Heisenberg equation of motion and the commutation relations between different operators, the corresponding density matrix equations are obtained. 3) To solve these density matrix equations, we make an ansatz and obtain the analytical formula of the four-wave mixing signal. Secondly, we explore the dependence of the four-wave mixing signal on the phonon-exciton coupling strength, pumping intensity and the detuning between the exciton and the pump field. The calculated results show that the lineshape of four-wave mixing spectrum can be switched among two-peaked, three-peaked, four-peaked, five-peaked and six-peaked by adjusting the phonon-exciton coupling strength, the pumping intensity, and the detuning between the exciton and the pump field. In a weak phonon-exciton coupling regime (i.e. phonon-exciton coupling strength &lt;i&gt;g&lt;/i&gt; &lt; dephasing rate of exciton &lt;i&gt;Γ&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt;), the intensity of the left peak and right peak of four-wave mixing signal first increase and then decrease with the increase of the pumping intensity &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$ {\varOmega }_{{\text{pu}}}^{\text{2}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. In the intermediate and strong phonon-exciton coupling regime (i.e. &lt;i&gt;g&lt;/i&gt; = &lt;i&gt;Γ&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt; and &lt;i&gt;g&lt;/i&gt; &gt; &lt;i&gt;Γ&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt;), the four-wave mixing spectrum exhibits a two-peaked structure. The maximum values of these two peaks increase as &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ {\varOmega }_{{\text{pu}}}^{\text{2}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; increases, and their spacing is equal to 2&lt;i&gt;g&lt;/i&gt;. Especially, for a given pumping intensity &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ {\varOmega }_{{\text{pu}}}^{\text{2}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230012_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; (= 10 THz&lt;sup&gt;2&lt;/sup&gt;), the maximum value of the peak for &lt;i&gt;g&lt;/i&gt; = 4 THz becomes 0.4% of that for &lt;i&gt;g&lt;/i&gt; = 1 THz, indicating that the phonon-exciton coupling inhibits the enhancement of the four-wave mixing signal to a certain extent. Our findings can not only offer an efficient way to measure the phonon-exciton coupling strength in the bilayer graphene system, but also help one to further explore the underlying physical mechanism in such a nanosystem.

Radon peak-picker based on a neural network

Serial acquisition of one-dimensional NMR spectra appears in many contexts, e.g. in variable-temperature studies or reaction monitoring. In a conventional approach, the spectra are processed separately, and standard peak-picking is performed in each of them. Yet, when chemical shifts change linearly between spectra, the Radon transform (RT) is more effective than conventional data processing, since it provides sensitivity and resolution gains. RT results in a two-dimensional (2D) spectrum with one dimension corresponding to resonance frequencies and the other to their rates of change. However, the lineshapes in 2D RT spectra are not 2D lorentzians, and thus available spectral peak-pickers cannot effectively deal with them. We propose a solution to this problem — a peak-picker dedicated to 2D RT spectra and based on a U-Net neural network. The software contains a user-friendly graphical interface. We test the program on three challenging serial data sets to demonstrate the robustness to peak overlap, complex multiplet structures and low signal-to-noise ratio.

Impact of intense ultrashort laser on Interatomic Coulombic decay in the NeAr dimer

The exposure of Ne-Ar dimer to an intense ultrashort laser can trigger a variety of competing ionization processes in addition to the already predicted interatomic Coulombic decay (ICD). The question of how and to what extent these competing ionization processes influence the line shape of the electron spectrum obtained for an ICD is addressed to in this work. The calculations predict that ionization from the ICD and final ionic states significantly influences the line shape of the electron spectrum. The time resolved electron spectrum for an only ICD process was calculated by employing an analytical expression. A line splitting in the ICD spectrum is observed at a comparatively higher peak intensity and systematic analysis involving time resolved electron spectrum indicates that the splitting is caused due to the effect of photoionization from the final ionic state. The effects of the ponderomotive shift of the free electron released prior to the ICD step on the ICD electron spectra were also estimated.

Dual-frequency comb spectroscopy studies of ionic strength effects in time-resolved ATR-SEIRAS

• DFCS allows sub-millisecond resolution of temporal processes occurring at an electrode surface. • IR transient time constants are directly proportional to the RC cell constant. • Absorption spectra line shape depends on coverage. Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies of the potential induced desorption/adsorption of a model organic monolayer is described using a paradigm-challenging dual frequency comb spectrometer. Experimentally measured ATR-SEIRAS transients reveal that both the rates of adsorption and desorption of 4-dimethylaminopyridine (DMAP) are dependent on the ionic strength of the supporting electrolyte. The characteristic time scales of monolayer desorption are found to be directly proportional to the spectroelectrochemical cell time constant indicating that the rate of film dissolution is much faster than the RC charging of the interface. The slow response of the interfacial charging process relative to the kinetics of the film re-organization/desorption processes means that the transient is parametrically linked to the potential dependent DMAP adsorption isotherm. The transients also reveal that the line shape of the molecular IR absorption feature exhibits a temporal dependence. A Lorentzian band is seen at early stages of the desorption transient but increasingly exhibit an anomalous bimodal line-shape at longer times. The development of the anomalous line shape is more pronounced at equivalent times in higher ionic strength electrolytes. Such an effect has been modelled using effective medium theory and is explained by the fact that the fraction of organic layer in the SEIRAS active film influences the observed apparent absorption features. The observation of a coverage dependence on SEIRAS line shapes adds new complexity to previous reports that linked anomalous absorption features exclusively to the metal film morphology and metal volume fraction.

Thermal decay of acoustic phonons and its effect in the 2LO mode on resonant Raman spectra of CdTe

In this work, we show that the superposition of transverse acoustic (TA) harmonic phonons in the longitudinal optical overtone (2LO) phonon of the resonant Raman spectrum of CdTe is considerably reduced by slightly cooling the substrate. This effect not only modifies the line shape of the resonant Raman spectrum around the 2LO mode, but also significantly reduces the relative intensity of the line shape. A detailed spectral analysis allowed us to identify three contributions: a decaying exponential function due to TA harmonics, a component due to LO phonon overtones, and a component due to multi-phonon around the 2LO mode. The agreement between the experimental data and the simulations was good. Furthermore, a mathematical expression for the intensity of 2LO in terms of temperature is reported for the first time to our knowledge. The results reported here contributes to the understanding of the vibrational properties of CdTe.

Leveraging Space-based Data from the Nearest Solar-type Star to Better Understand Stellar Activity Signatures in Radial Velocity Data

Stellar variability is a key obstacle in reaching the sensitivity required to recover Earth-like exoplanetary signals using the radial velocity (RV) detection method. To explore activity signatures in Sun-like stars, we present SolAster, a publicly distributed analysis pipeline 10 10 https://tamarervin.github.io/SolAster/ that allows for comparison of space-based measurements with ground-based disk-integrated RVs. Using high-spatial-resolution Dopplergrams, magnetograms, and continuum filtergrams from the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory (SDO), we estimate “Sun-as-a-star” disk-integrated RVs due to rotationally modulated flux imbalances and convective blueshift suppression, as well as other observables such as unsigned magnetic flux. Comparing these measurements with ground-based RVs from the NEID instrument, which observes the Sun daily using an automated solar telescope, we find a strong relationship between magnetic activity indicators and RV variation, supporting efforts to examine unsigned magnetic flux as a proxy for stellar activity in slowly rotating stars. Detrending against measured unsigned magnetic flux allows us to improve the NEID RV measurements by ∼20% (∼50 cm s−1 in a quadrature sum), yielding an rms scatter of ∼60 cm s−1 over five months. We also explore correlations between individual and averaged spectral line shapes in the NEID spectra and SDO-derived magnetic activity indicators, motivating future studies of these observables. Finally, applying SolAster to archival planetary transits of Venus and Mercury, we demonstrate the ability to recover small amplitude (<50 cm s−1) RV variations in the SDO data by directly measuring the Rossiter–McLaughlin signals.

Unraveling Urbach Tail Effects in High-Performance Organic Photovoltaics: Dynamic vs Static Disorder

The origin of Urbach energy (EU) in organic semiconductors and its effect on photovoltaic properties remain a topic of intense interest. In this letter, we demonstrate quantitative information on the EU value in emerging Y-series molecules by an in-depth analysis of the line shape of the temperature-dependent quantum efficiency spectra. We found that the static disorder (EU(0)), which is dominated by the conformational uniformity in Y-series acceptors, contributes 10–25 meV to the total Urbach energy. Particularly, this static contribution in organic solar cells (OSCs) is much higher than those (EU(0) ≈ 3–6 meV) in inorganic/hybrid counterparts, such as CH3NH3PbI3 perovskite, crystalline silicon (c-Si), gallium nitride (GaN), indium phosphide (InP), and gallium arsenide (GaAs). More importantly, we establish clear correlations between the static disorder and photovoltaic performance and open-circuit voltage loss. These results suggest that suppressing the static disorder via rational molecular design is clearly a path for achieving higher performance.

Dynamic control of Fano resonances in a coupled dual microring resonator system

We propose a coupled optical microresonator system that can be used as a new and flexible platform to form asymmetric Fano-like resonances and dynamically control their line shapes and frequencies. The coupled microresonator system was formed using two microring resonators coupled via a 3 × 3 coupler. The upper microring resonator is the add-drop type, whereas the lower one is the all-pass type, providing the (semi-) continuum and discrete states, respectively. We simulated the behavior of the coupled system using the finite-difference time-domain method and observed asymmetric Fano line shapes in the transmission spectra. We demonstrated that the line shapes and frequencies of Fano resonances can be controlled by dynamically varying the refractive index of a small region of the upper or lower microring resonators. We also introduced a small gap in the upper microring resonator to control the continuum state more efficiently. The proposed coupled microresonator concept is simple, easy to fabricate and sufficiently flexible to be engineered for different applications.

Application of Machine Learning Solutions to Optimize Parameter Prediction to Enhance Automatic NMR Metabolite Profiling.

The quality of automatic metabolite profiling in NMR datasets from complex matrices can be affected by the numerous sources of variability. These sources, as well as the presence of multiple low-intensity signals, cause uncertainty in the metabolite signal parameters. Lineshape fitting approaches often produce suboptimal resolutions to adapt them in a complex spectrum lineshape. As a result, the use of software tools for automatic profiling tends to be restricted to specific biological matrices and/or sample preparation protocols to obtain reliable results. However, the analysis and modelling of the signal parameters collected during initial iteration can be further optimized to reduce uncertainty by generating narrow and accurate predictions of the expected signal parameters. In this study, we show that, thanks to the predictions generated, better profiling quality indicators can be outputted, and the performance of automatic profiling can be maximized. Our proposed workflow can learn and model the sample properties; therefore, restrictions in the biological matrix, or sample preparation protocol, and limitations of lineshape fitting approaches can be overcome.

Local Plasmon Phase Delay Effect in Plasmon–Exciton Coupling

AbstractManipulating plasmon–exciton coupling is a pivotal desire for many potential applications. Here, it is found that the plasmonic phase delay can modulate the interference‐induced asymmetrical spectrum line shape of the plasmon–exciton coupling system considerably. The phase effect in a hybrid system consisting of monolayer WSe2 and an individual gold nanorod is demonstrated. The phase delay can modulate the relative intensities of the coupling modes but not the splitting energy, effective in both weak and strong coupling regimes. There is an excellent agreement between the numerical calculations and the experimental results. The findings reveal that the local phase delay can act as an effective way to manipulate plasmon−exciton coupling properties at the nanoscale.

A Theoretical Investigation about Photoswitching of Azobenzene Adsorbed on Ag Nanoparticles

The optical properties of hybrid systems composed of silver nanoparticles (NPs) and azobenzene molecules were systematically investigated by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the classical electrodynamics finite difference time domain (FDTD) technique for the solution of Maxwell’s equations. In order to reflect the chemical interaction between azobenzene and metal more exactly, except for adsorbed molecules, a Ag cluster separated from NP was also dealt, using RT-TDDFT. We studied the different factors affecting the surface-enhanced absorption spectra. It was found that the electric field amplified by plasmon resonance of Ag NPs can have an overall enhancement to the molecular light absorption throughout the whole energy range. The resonance between the electron and the plasmon excitation results in a larger percentage of enhancement in the absorption spectrum the closer the resonance peak is. The enhancement ratio of the resonance peak is the largest. The plasmon–exciton coupling and the optical properties of different isolate isomers influence the line shape of the absorption spectra. The dipole interaction and electronic transfer between azobenzene molecules and Ag NPs also change the shape of spectroscopy from the absorption enhancement ratio and the location of the peak. Physical and chemical factors lead to photoswitching in these hybrid systems together.

Lineshape study of optical force spectra on resonant structures.

Understanding the frequency spectrum of the optical force is important for controlling and manipulating micro- and nano-scale objects using light. Spectral resonances of these objects can significantly influence the optical force spectrum. In this paper, we develop a theoretical formalism based on the temporal coupled-mode theory that analytically describes the lineshapes of force spectra and their dependencies on resonant scatterers for arbitrary incident wavefronts. We obtain closed-form formulae and discuss the conditions for achieving symmetric as well as asymmetric lineshapes, pertaining, respectively, to a Lorentzian and Fano resonance. The relevance of formalism as a design tool is exemplified for a conceptual scheme of the size-sorting mechanism of small particles, which plays a role in biomedical diagnosis.

Microstructure and defects of 0.1P2O5–0.65ZnO–0.25(xTeO2–(1-x)MoO3) quaternary glass nanocomposites using positron annihilation and correlated experimental methods

This study reports the spectroscopic examination of positron annihilation to characterize structural defects in glass nanocomposite systems of 0.1P2O5–0.65ZnO–0.25(xTeO2–(1-x)MoO3), consisting of two ternary (x = 0.0 and 1.0) and several intermediate quaternary (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.6, and 0.8) samples prepared by the melt quenching process. The lifetimes of the positrons, the relative intensities, and the parameters of the Doppler-broadened lineshape of the positron annihilation gamma ray spectra indicated porous-type defects inside the amorphous glassy matrices formed in samples of x = 0.05–0.2 and free volume defects in interfaces of the newer nanocrystallites at higher stages of modification (x ≥ 0.3). The results of X-ray diffraction confirmed the amorphous character of the samples and transmission electron micrographs confirmed the formation of the nanocrystallites. Selected area electron diffraction patterns revealed that the nanocrystallites were superimposed on the amorphous glass matrices. The spectra of energy-dispersive X-ray analysis revealed the presence of elemental constituents of the nanocomposites according to the required stoichiometries. A detailed Rietveld analysis of the X-ray diffraction patterns was used to identify the dispersed nanocrystallites and ascertain their stoichiometries. The work here is important in the context of developing technologically relevant glass nanocomposites from metal oxides with suitable physical characteristics. However, defects like vacancies that are formed during preparation may play a crucial role in determining their physical properties as well as the formation of free volumes and new nanocrystallites, where the latter were adequately dispersed over the glassy network. This can help transform the material into novel archetypes.

Fluorescence of carotenoids: Probing binding site interactions and conformational motion in carotenoproteins.

The function of carotenoids in carotenoproteins is optimized by the electrostatic and steric interactions between the carotenoid and its surrounding binding site. Binding to the protein distorts the conformation of the carotenoid and induces a charge-transfer character. This chapter shows how the line shape of the fluorescence spectrum, the fluorescence quantum yield, and the fluorescence anisotropy of the second excited singlet state of a carotenoid, S2, can be used to probe the structure and dynamics of carotenoids in carotenoproteins. The experimental approach and a brief introduction to the theory we used to detect hydrogen bonding interactions with the active ketocarotenoids in the orange carotenoid protein are discussed here as an example. Fluorescence anisotropy is then introduced as a probe of the conformational motions that follow optical excitation of a carotenoid using results from a study of β-carotene in solution over a range of temperatures.

Simulating action-2D electronic spectroscopy of quantum dots: insights on the exciton and biexciton interplay from detection-mode and time-gating.

Action-2D electronic spectroscopy is emerging as a powerful technique to investigate exciton dynamics in molecular aggregates and nanostructures. While maintaining the power of highlighting coherent evolution between the laser pulses, action detection is based on measuring the incoherent signal proportional to the excited-state populations generated by an additional laser pulse. Numerical simulations of the action signal play a crucial role in aiding the interpretation of the spectral features, which may differ from those of the analog coherent technique in a non-trivial way. We present a numerical investigation of the action response of a model of quantum dot as a case study to unravel the exciton and biexciton contributions in the 2D-spectra of nanostructures. The simulation protocol is based on a non-perturbative treatment of the light-matter interaction by solving the Lindblad quantum master equation and the different contributions to the non-linear response are disentangled using a phase-modulation scheme. We analyze how the relative weights of the exciton and biexciton signals determine the lineshape of the spectrum, how they depend upon the physical nature of the detected signal, i.e., fluorescence or photocurrent, and on the relaxation dynamics during the detection-time. Compatibly with the experimental conditions, the choice of the detection-mode and the use of time-gating may eventually facilitate the evaluation of relevant parameters, such as the biexciton binding energy and the timescale of the biexciton relaxation.

Plasmonic crescent nanoarray-based surface lattice resonance sensor with a high figure of merit.

Due to the natural accumulation of radiation losses arising from the localization and random arrangement of nanoparticles, the figure of merit (FOM) of localized surface plasmon resonance (LSPR) sensors is usually very low (the value is usually less than 5 RIU-1). However, radiation losses of individual particles will be offset by adjusting the phase of the scattered field which is dependent on the structure parameters of arrays. Based on this, a two-dimensional periodic crescent nanoarray-based surface lattice resonance (SLR) sensor with a high FOM is proposed in this work. Some significant results have been obtained by mode field analysis and adjustment of structural parameters. On the one hand, the line-shape of the SLR spectrum is divided into a Fano-like line and a separate line. And the former usually has an FOM of 101 magnitude while the latter has an FOM of 103 magnitude. On the other hand, the relative size of the excitation wavelengths between SLR and LSPR is also vital. The FOM is higher but resonance depth decreases faster when the relative size increases. In this work, a full width at half-maximum (FWHM) of less than 0.5 nm and FOM of more than 1000 RIU-1 (the quality factor is more than 3000) are achieved by the proposed crescent nanoarrays. In addition, this structure demonstrates that plasmonic nanoarray-based SLR has enormous potential in trace substance detection.

Recoil lineshapes in hard X-ray photoelectron spectra of large molecules - free and anchored-on-surface 10-aminodecane-1-thiol.

Core-level photoelectron spectroscopy of molecules presents unique opportunities but also challenges in the Hard X-ray Spectroscopy (HAXPES) realm. Here we focus on the manifestation of the photoelectron recoil effects in core-level photoemission spectra, using the independent normal-mode oscillators approach that allows to model and investigate the resulting recoil lineshapes for molecules of large sizes with only a slight computational effort. We model the recoil lineshape for N 1s and C 1s photoemission using the 10-aminodecane-1-thiol molecule as an example. It represents also a class of compounds commonly used in creating self-assembled monolayers (SAMs) on surfaces. Attachment of the -SH head group to the surface is modelled here in a simplified way by anchoring the sulfur atom of a single molecule. The effects of the orientation of photoemission in the molecular frame on the recoil lineshape of such anchored molecules are illustrated and discussed as a possible geometry probe. Time-evolution of the recoil excitations from the initial emission site across the entire molecule is also visualized.

Impact of skin effect on permeability of Permalloy films

We investigated the impact of skin effect on permeability of Permalloy films with different thicknesses. With eliminating multi domain structure by measuring field permeability spectrum, the picture of permeability determined by natural resonance and modulated by skin effect was demonstrated. It is found that both the value of permeability and line shape of the field permeability spectrum depend on thickness significantly due to skin effect. The real part of field permeability spectrum decreases from 974 (0.04 μm) to 14 (4 μm) at 3.2 GHz, and two loss peaks appear in the imaginary part in films thicker than 2 μm, which can't be explained by previous work. We established a skin effect-related model of permeability with which the experimental permeability spectra can be well fitted. The calculated cut-off frequency is significantly reduced by skin effect from 3.5 GHz (0.02 μm) to 0.3 GHz (4 μm), which is dominated by the natural resonance frequency (t ≤ 1.46 μm) and the additional loss peak frequency caused by skin effect (t > 1.46 μm) successively.

Plasmon-induced transparency sensor for detection of minuscule refractive index changes in ultra-low index materials

Detection of low-index materials such as aerogels and also detection of refractive index variations in these materials is still a challenging task. Here, a high figure of merit (FOM) sensor based on plasmon-induced transparency (PIT) is proposed for the detection of aerogel refractive index changes. In the proposed PIT sensor, the transparency window in an opaque region arises from the coupling between surface plasmon polariton (SPP) mode and planar waveguide mode. By comprising sub-wavelength grating (SWG) in the planar waveguide region, the maximum of the electric field of waveguide occurs in a low index media. This facilitates detection of the aerogels when they are used as the low index material (sensing material). Application of the subwavelength grating waveguide also improves the sensitivity of the sensor by a factor of six compared to a conventional structure with a homogenous waveguide. The proposed structure has a quality factor of Q ≥ 1800, and a reflection of 86%, and can detect the refractive index changes as low as Δn = 0.002 (around n = 1.0). The lineshape, Q-factor, and resonant wavelength of the transparency spectrum can be controlled by tailoring the structural parameters. Our work also has potential application in switching, filtering, and spectral shaping.