Wavelength Band Research Articles

Novel Cellulosic Fiber Composites with Integrated Multi-Band Electromagnetic Interference Shielding and Energy Storage Functionalities

In an era where technological advancement and sustainability converge, developing renewable materials with multifunctional integration is increasingly in demand. This study filled a crucial gap by integrating energy storage, multi-band electromagnetic interference (EMI) shielding, and structural design into bio-based materials. Specifically, conductive polymer layers were formed within the 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO)-oxidized cellulose fiber skeleton, where a mild TEMPO-mediated oxidation system was applied to endow it with abundant macropores that could be utilized as active sites (specific surface area of 105.6 m2g-1). Benefiting from the special hierarchical porous structure of the material, the constructed cellulose fiber-derived composites can realize high areal-specific capacitance of 12.44 F cm-2 at 5mAcm-2 and areal energy density of 3.99 mWh cm-2 (2005 mW cm-2) with an excellent stability of maintaining 90.23% after 10,000 cycles at 50mAcm-2. Meanwhile, the composites showed a high electrical conductivity of 877.19 S m-1 and excellent EMI efficiency (> 99.99%) in multiple wavelength bands. The composite material's EMI values exceed 100dB across the L, S, C, and X bands, effectively shielding electromagnetic waves in daily life. The proposed strategy paves the way for utilizing bio-based materials in applications like energy storage and EMI shielding, contributing to a more sustainable future.

Parameter measurement based on photometric images I: The method and the gas-phase metallicity of spiral galaxies

The gas-phase metallicity is a crucial parameter for understanding the evolution of galaxies. Considering that the number of multiband galaxy images can typically reach tens of millions, using these images as input data to predict gas-phase metallicity has become a feasible method. However, the accuracy of metallicity estimates from images is relatively limited. To solve this problem, we propose the galaxy parameter measurement residual network (GPM-ResNet), a deep learning method designed to predict gas-phase metallicity from photometric images of DESI. The parameters of photometric images are labeled with gas-phase metallicity values, which were obtained through spectroscopic methods with a high accuracy. These labeled images serve as the training dataset for the GPM-ResNet method. GPM-ResNet mainly consists of two modules: a multi-order feature extractor and a parameter generator, enhancing the ability to effectively extract features related to gas-phase metallicity from photometric images. The σ of Z_ pred -Z_ true is 0.12 dex, which significantly outperforms the predicted results of the second-order polynomial (σ=0.16 dex) and the third-order polynomial (σ=0.16 dex) fit using the color-metallicity relation on the same dataset. To further emphasize the superiority of GPM-ResNet, we analyzed the predicted results on various network architectures, galaxy sizes, image resolutions, and wavelength bands of images. Moreover, we explored the mass-metallicity relation and recovered the relation successfully by utilizing the predicted values, Z_ pred . Finally, we applied GPM-ResNet to predict the gas-phase metallicity of spiral (EXP) galaxies observed by DESI, resulting in a comprehensive catalog containing 5,095,815 pieces of data.

Generation of CW mid-infrared radiation in the mW power range and tuneable over 400 nm

Miniaturization of mid-infrared (MIR) spectroscopy sources has progressed significantly during the past two decades, but a solution able to provide full integration, high optical power and wide tuneability in the so-called atmospheric window (2.5 - 5 µm) is still missing. In this context, we investigated a broadband frequency-tuneable source relying on difference frequency generation (DFG) in a periodically poled lithium niobate (PPLN) ridge waveguide. By employing tuneable lasers for the pump and signal wavelengths emitting at around 1 µm and 1.55 µm, respectively, we were able to fully cover the ≈ 3 - 3.5 µm spectrum, thus translating the technological maturity of data communication photonic sources to the MIR wavelength band. Moreover, the use of a relatively large cross-section for the here-proposed PPLN ridge waveguide compared to commonly employed thin-film lithium niobate (TFLN) waveguides has allowed us to achieve low propagation and coupling losses together with high damage threshold, thereby allowing us to reach mW-level power in the MIR wavelength band.

Solvatochromism and cis-trans isomerism in azobenzene-4-sulfonyl chloride.

Solvatochromism exhibited by azobenzene-4-sulfonyl chloride (here abbreviated as Azo-SCl) has been investigated in a series of non-polar, polar-aprotic and polar-protic solvents. The UV-vis spectra of Azo-SCl exhibit two long-wavelength bands, observed at 321-330nm (band-I) and 435-461nm (band-II), which are ascribed to the π*-π (S2 ← S0) and π*-n (S1 ← S0) transitions, respectively. The shorter wavelength band indicates a reversal in solvatochromism, from negative to positive solvatochromism, for a solvent with a dielectric constant of 32.66 (which is characteristic of methanol), while the longer wavelength band signposts negative solvatochromism in all range of solvent's dielectric constant investigated, demonstrating different interactions with the solvents in the S2 and S1 excited states. Using Catalán and Kamlet-Taft solvation energy models, we found that the shift in the solvatochromic behavior of band-I (S2 ← S0) happens because solvent dipolarity/polarizability and hydrogen bonding affect the S2 state in opposite ways. Dipolarity/polarizability stabilizes the S2 state compared to the ground state, while hydrogen bonding destabilizes it. In contrast, for S1, both effects work together to destabilize the excited state. For all studied solvents, UV irradiation (λ ≥ 311nm; room temperature) was found to lead to fast trans-cis azo photoisomerization. In the absence of light, the photogenerated cis form quickly converts back to the trans form. Interpretation of the experimental data is supported by quantum chemical calculations undertaken within the Density Functional Theory (DFT) framework, including Time Dependent DFT calculations for excited states.

The greenhouse gas observation mission with Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW): objectives, conceptual framework and scientific contributions

The Japanese Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW) will be an Earth-observing satellite to conduct global observations of atmospheric carbon dioxide (CO2), methane (CH4), and nitrogen dioxide (NO2) simultaneously from a single platform. GOSAT-GW is the third satellite in the series of the currently operating Greenhouse gases Observing SATellite (GOSAT) and GOSAT-2. It will carry two sensors, the Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) and the Advanced Microwave Scanning Radiometer 3 (AMSR3), with the latter dedicated to the observation of physical parameters related to the water cycle. TANSO-3 is a high-resolution grating spectrometer designed to measure reflected sunlight in the visible to short-wave infrared spectral ranges. It aims to retrieve the column-averaged dry-air mole fractions of CO2 and CH4 (denoted as XCO2 and XCH4, respectively), as well as the vertical column density of tropospheric NO2. The TANSO-3 sensor onboard GOSAT-GW will utilize the wavelength bands of 0.45, 0.76, and 1.61 µm for NO2, O2, and CO2 and CH4 retrievals, respectively. GOSAT-GW will fly in a sun-synchronous orbit with a local overpass time of approximately 13:30 and a 3-day ground-track repeat cycle. The TANSO-3 sensor has two observation modes in the push-broom operation: Wide Mode, which provides globally covered maps with a 10-km spatial resolution within 3 days, and Focus Mode, which provides snapshot maps over targeted areas with a high spatial resolution of 1–3 km. The objectives of the GOSAT-GW mission include (1) monitoring atmospheric global-mean concentrations of greenhouse gasses (GHGs), (2) verifying national anthropogenic GHG emissions inventories, and (3) detecting GHG emissions from large sources, such as megacities and power plants. A comprehensive validation exercise will be conducted to ensure that the sensor products’ quality meets the required precision to achieve the above objectives. With a projected operational lifetime of seven years, GOSAT-GW will provide vital space-based constraints on both anthropogenic and natural GHG emissions. These measurements will contribute significantly to climate change mitigation efforts, particularly by supporting the Global Stocktake (GST) mechanism, a key element of the Paris Agreement.

Absorption, Steady-State Fluorescence and Solvent Effect Studies of Fluorescent Haloarchaeal Bacterioruberin.

Fluorescence characterization of halophilic archaeal C50carotenoid-bacterioruberin extracts was investigated using UV/Vis and steady-state fluorescence spectrophotometry in solvents with different polarity. Different extracts showed maximum absorption and fluorescence wavelengths between 369-536nm and 540-569nm. Stokes' shifts varied between 50-79nm depending on the solvent. In particular, water extract showed significant Stokes' shifts with the increase in polarity index; however, fluorescence wavelength (band position) and shape were found to be independent of polarity. According to the obtained results, it is thought that bacterioruberin will be a new alternative material with increasing applications in optics, biosensor/chemosensor, biotechnology, analytical chemistry and nanotechnology due to its fluorescence properties.

High-brightness 300 W fiber laser at ~950 nm.

Fiber lasers operating in the 900 nm wavelength band have garnered significant interest due to their extensive array of applications. However, their development is still hindered by various factors, with the output power currently being restricted to the hundred-watt level. Despite numerous proposed solutions, achieving higher power outputs in this wavelength band remains a challenge. In this Letter, we have pioneered a new approach that harnesses stimulated Raman scattering within a fiber nonlinear gain framework. We have engineered a high-brightness laser diode source by utilizing techniques such as spectral beam combining and polarization beam combining, which are then employed directly for pumping. Through meticulous optimization of the fiber laser system and by incorporating brightness enhancement strategies such as multimode fiber beam cleaning and resonant cavity spatial mode selection, we have achieved a record-breaking output power of 315 W with an outstanding beam quality factor of M2 = 2.45 for high-brightness fiber lasers at ∼950 nm.

Highly Efficient and achromatic mid-infrared silicon nitride meta-lenses

Inverse design with topology optimization considers a promising methodology for discovering new optimized photonic structure that enables to break the limitations of the forward or the traditional design especially for the meta-structure. This work presents a high efficiency mid infra-red imaging photonics element along mid infra-red wavelengths band starts from 2 to 5 µm based on silicon nitride optimized material structures. The first two designs are broadband focusing and reflective meta-lens under very high numerical aperture condition (NA = 0.9). The two designs are modeled by inverse design with topology optimization problem with Kreisselmeier–Steinhauser (k–s) aggregation objective function, while the final design is depended on novel inverse design optimization problem with double aggregation objective function that can target bifocal points along the wavelength band producing high efficiency achromatic broadband multi-focal meta-lens under very high numerical apertures ().

Deciphering the Photophysical Properties of Nonplanar Heterocyclic Compounds in Different Polarity Environments.

Nonplanar (butterfly-shaped) phenothiazine (PTZ) and its derivative's (M-PTZ) photophysical and spectral properties have been tuned by varying the solvents and their polarity and investigated employing spectroscopic techniques such as UV-Vis, steady-state and time-resolved fluorescence, and TDDFT calculations. The UV-Vis absorption studies and TDDFT calculations reveal two distinct bands for both compounds: a strong π-π* transition at shorter wavelengths and a weaker n-π* transition, which displays a little bathochromic shift in polar solvents. The detailed emission studies reveal that such dual emission is a result of the photoinduced excited-state conjugation enhancement (ESCE) process. The band at a shorter wavelength corresponds to the locally excited (LE) state, while the longer wavelength band arises from the planarized excited state resulting from ESCE. With the increase in solvent polarity, the LE band is less affected, whereas strong positive solvatochromism is observed for the ESCE band. As the solvent polarity increases, the ESCE band demonstrates significant positive solvatochromism, while emission intensity decreases with higher solvent polarity, suggesting stabilization of the excited state. The biexponential decay of fluorescence lifetimes further corroborates the dual emission behavior of PTZ and M-PTZ. PTZ exhibits a higher photoluminescence quantum yield (PLQY) than that observed for M-PTZ, and the solvent viscosity influences the PLQY, indicating that nonradiative decay is activated during the planarization of the excited state, also known as excited-state conjugation enhancement. Furthermore, the (time-dependent) density functional theory (TD) DFT calculations performed to understand the geometrical parameters and the electronic transitions of these model molecules further corroborate experimental findings. These findings underscore the significant influence of solvent polarity and molecular structure on the dual emission and excited-state dynamics of PTZ and M-PTZ, which eventually hold substantial implications for advanced photophysical applications.

Exoplanets in reflected starlight with dual-field interferometry. A case for shorter wavelengths and a fifth Unit Telescope at VLTI/Paranal

The direct observation of cold and temperate planets within 1 to 10 AU would be extremely valuable for uncovering their atmospheric compositions but remains a formidable challenge with current astronomical methods. Ground-based optical interferometry, capable of high angular-resolution imaging, offers a promising avenue for studying these exoplanets. Our objective is to explore the fundamental limits of dual-field interferometry and assess its potential for characterising exoplanets in reflected light using the Very Large Telescope Interferometer (VLTI). We developed analytical expressions to describe the performance of dual-field interferometry and integrated these with simulations of atmospheric wavefronts corrected by extreme adaptive optics. An analytical solution for optimal phase apodization was formulated to enhance starlight rejection when injected into a single-mode fibre. This framework was applied to determine the detectability of known exoplanets in reflected light across various wavelength bands for both the current VLTI and a proposed extended version. Our results indicate that employing shorter wavelengths improves detectability, enabling at least seven Jupiter-mass exoplanets to be observed in the J band with current VLTI's baselines. Adding new baselines with lengths beyond 200 meters significantly enhances VLTI's capabilities, increasing the number of detectable exoplanets and revealing potential habitable zone candidates such as τ Ceti e and Proxima Centauri b. To substantially improve the VLTI's exoplanet characterisation capabilities, we recommend developing instrumentation at wavelengths shorter than 1$,μ$m, and increasing the baselines length by the addition of a fifth Unit Telescope (UT5).

Investigation of the Ocular Response and Corneal Damage Threshold of Exposure to 28 GHz Quasi-millimeter Wave Exposure.

Electromagnetic radiation energy at millimeter wave frequencies, typically 30 GHz to 300 GHz, is ubiquitously used in society in devices for telecommunications; radar and imaging systems for vehicle collision avoidance, security screening, and medical equipment; scientific research tools for spectroscopy; industrial applications for non-destructive testing and precise measurement; and military and defense applications. Understanding the biological effects of this technology is essential. We have been investigating ocular responses and damage thresholds comparing various frequencies using rabbit eyes and dedicated experimental apparatus. In this study we investigated the 28 GHz quasi-millimeter wave band (wavelength: 10.7 mm), a candidate for 5G communication. Similar to millimeter wave frequencies, ocular damage from exposure to 28 GHz for 6 min (400 mW cm-2) included corneal epithelial damage, corneal edema, and opacity. The incident power density threshold, indicating a 50% probability of ocular damage from exposure for 6 min, was found to be 359 mW cm-2 for 28 GHz. Comparing the ocular exposure area for various millimeter wave frequencies (40, 75, 95 GHz) and 28 GHz quasi-millimeter waves using a thermosensitive liquid crystal capsule, we found that for millimeter waves, even at identical incident power densities, the ocular exposure area decreases as the frequency increases (lens effect). However, this lens effect was not observed at 28 GHz, where the entire anterior segment area was exposed to radio waves.

Van der Waals Photonic Bipolar Junction Transistors Capable of Simultaneously Discerning Wavelength Bands and Dual-Function Chip Application.

The exponential growth of the Internet of Things (IoTs) has led to the widespread deployment of millions of sensors, crucial for the sensing layer's perception capabilities. In particular, there is a strong interest in intelligent photonic sensing. However, the current photonic sensing device and chip typically offer limited functionality, and the devices providing their power take up excessive amounts of space. There is a pressing need for smart, multifunctional sensing chips with the capability of intelligent recognition. Here, we propose and demonstrate the functionalities of a two-dimensional van der Waals photonic bipolar junction transistor (2D-vdW photonic BJT) in simultaneous sensing and discerning different wavelength bands of light. Also, a dual-function chip application is given. The optoelectronic detection characteristics in the vision-near-infrared (vis-NIR) band and photovoltaic characteristics are systematically studied. It exhibits negative photoconductivity (NPC) for the 1064 nm laser while maintaining positive photoconductivity (PPC) for the 638 and 1550 nm lasers. Also, the electrical tunable response is realized. Moreover, the function of this chip under real-application conditions has shown its efficacy in applications such as detecting dim light with ∼10 lx illuminance, identifying wavelength bands, and generating power photovoltaically. This work provides a solution for the interconnection of everything.

Shell Dependence of Highly Tunable Circular Dichroism in Chiral Hybrid Plasmonic Nanomaterials for Chiroptical Applications.

Chiral plasmonic nanomaterials with fascinating physical and chemical properties show emerging chirality-dependent applications in photonics, catalysis, and sensing. The capability to precisely manipulate the plasmonic chirality in a broad spectral range plays a crucial role in enabling the applications of chiral nanomaterials in diverse and complex scenarios; however, it remains a challenge yet to be addressed. Here we demonstrate a strategy to significantly enhance the tunability of circular dichroism (CD) spectra of chiral nanomaterials by constructing core-shell hybrid metal-semiconductor structures with tailored shells. In a typical case, chiral Au@Cu2O nanostructures exhibit shell-dependent tunable CD signals in both asymmetry factors and band wavelengths. The shell-dependent CD was demonstrated experimentally by CD and single-particle spectroscopy and theoretically through numerical simulations. By deliberately controlling the geometry of the chiral core and the composition of the achiral shell, we show the versatility of our strategy for constructing chiral hybrid nanostructures with increasing architectural and compositional complexity as well as enhanced plasmonic chirality. Furthermore, the chiral Au@Cu2O nanostructure exhibits intriguing asymmetric color modulation. This work opens an advancing strategy and provides an important knowledge framework for the rational design of multifunctional chiral hybrid nanostructures toward emerging chirality-dependent applications.

Design of the Waveguide Integrated GeSn PDs on a SiN Platform in $2\,\mathrm{\mu m}$ Wavelength Band

Design of the Waveguide Integrated GeSn PDs on a SiN Platform in $2\,\mathrm{\mu m}$ Wavelength Band

HOLISMOKES

The Hubble tension is one of the most relevant unsolved problems in cosmology today. Strongly gravitationally lensed transient objects, such as strongly lensed supernovae, are an independent and competitive probe that can be used to determine the Hubble constant. In this context, the time delay between different images of lensed supernovae is a key ingredient. We present a method to retrieve time delays and the amount of differential dust extinction between multiple images of lensed type IIP supernovae (SNe IIP) through their color curves, which display a kink in the time evolution. With several realistic mock color curves based on an observed SN (not strongly lensed) from the Carnegie Supernova Project (CSP), our results show that we can determine the time delay with an uncertainty of approximately ± 1.0 days. This is achievable with light curves with a 2-day time interval and up to 35% missing data due to weather-related losses. Accounting for additional factors such as microlensing, seeing, shot noise from the host and lens galaxies, and blending of the SN images would likely increase the estimated uncertainties. Differentiated dust extinction is more susceptible to uncertainties because it depends on imposing the correct extinction law. Further, we also investigate the kink structure in the color curves for different rest-frame wavelength bands, particularly rest-frame ultraviolet (UV) light curves from the Neil Gehrels Swift Observatory (SWIFT), finding sufficiently strong kinks for our method to work for typical lensed SN redshifts that would redshift the kink feature to optical wavelengths. With the upcoming Rubin Observatory Legacy Survey of Space and Time (LSST), hundreds of strongly lensed supernovae will be detected, and our new method for lensed SN IIP is readily applicable to provide delays.

Innovative MIM diplexer with neural network enhanced refractive index detection for advanced photonic applications

This study introduces a high-performance 4-channel Metal-Insulator-Metal (MIM) diplexer, employing silver and Teflon, optimized for advanced photonic applications. The proposed diplexer, configured with two novel band-pass filters (BPFs), operates across four distinct wavelength bands (843 nm, 1090 nm, 1452 nm, 1675 nm) by precisely manipulating the passband dimensions. Utilizing Finite-Difference Time-Domain (FDTD) simulations, the designed diplexer achieves exceptional sensitivity values of 3500 nm/RIU, 4250 nm/RIU, 3375 nm/RIU, and 4003 nm/RIU, along with high figures of merit (FOM) ranging from 113.4 to 124.7 1/RIU. Also, the compact design (400 nm × 830 nm) underscores its suitability for integrated photonic circuits and advanced sensing applications. Furthermore, to further enhance accuracy in detecting refractive index (RI) changes, a multilayer perceptron (MLP) neural network was employed, ensuring the highest sensor accuracy. The accuracy of the MIM diplexer’s RI measurements was statistically validated through a one-sample t-test, confirming the sensor’s reliability. Comparative analysis with existing sensors highlights the diplexer’s superior sensitivity and efficiency, setting a new benchmark in optical communication and photonic sensing technologies. This work paves the way for future advancements in miniaturized, high-sensitivity optical devices, offering robust solutions for next-generation communication and sensing systems.

Finite-Difference Time-Domain Simulation of Double-Ridge Superimposed Structures for Optimizing Light-Trapping Characteristics in Ternary Organic Solar Cells

The double-ridge superimposed structures (DRSSs), formed by the superposition of a nano-ridged textured ZnO layer and a ternary organic active layer (PTB7:PC70BM:PC60BM) with self-assembled nano-ridged (SANR) structures, have been preliminarily examined experimentally for its positive effects in light-trapping for organic solar cells (OSCs). To obtain DRSSs with higher-performance light-trapping effects and enhance the light absorption of OSCs, the present work carried out prior theoretical simulations of the light-trapping characteristics of the DRSS using the finite-difference time-domain (FDTD) algorithm. The results show that the DRSS exhibits a significant light-trapping effect, with an active layer absorption peak around 530 nm due to the light-trapping effect. This helps the active layer capture more high-energy photons, significantly enhancing the photon utilization of the DRSS. Interestingly, the intensity of the light-trapping absorption peak is solely dependent on the height or width of the active layer ridges in the DRSS, while the position of the peak is jointly determined by both the ZnO and active layer ridges. By controlling the aspect ratio (W/H) of the dual ridges, the light-trapping absorption peak position can be fine-tuned, enabling precise light-trapping management for specific wavelength bands. It is certain that the outcomes of this work will provide theoretical foundations and practical guidance for the fabrication of light-trapping OSCs.

A Spectrum-Tailored Polymer Dispersed Liquid Crystal Film for Energy-Saving Smart Windows.

The polymer dispersed liquid crystal (PDLC) holds potential application in smart windows, owing to its feasibility in regulating the transmittance of specific wavelength bands to improve energy utilization. Herein, a composite PDLC smart window is designed, which showcases high emissivity of 93.79% in the mid-infrared region and features the regulation of ultraviolet (UV), visible, and near-infrared (NIR) light. Titanate nanomaterials with diverse morphologies are synthesized and doped to endow the PDLC film with perfect UV shielding property and excellent electro-optical (E-O) performance. Subsequently, the E-O performance is further improved by modifying the structure of acrylate monomers, with the maximum transmittance exceeding 80%. Furthermore, the LaB6 layer is incorporated to effectively shield NIR light. Due to the synergistic effect of sunlight modulation and passive radiative cooling, the composite PDLC smart window can effectively lower the indoor temperature compared with traditional PDLC films. Eventually, the fabricated LaB6/PVA/PDLC smart window displays high contrast (210.65), a low threshold voltage (6.68V), and remarkable passive radiative cooling performance (cooling power of 131.24 m2K-1). Overall, the composite presents switchable transmittance in visible region, excellent UV-blocking (>99%), and high NIR shielding capacities, thereby broadening its potential application in the field of smart windows.

Optimization of Low-Loss, High-Birefringence, Single-Layer, Annular, Hollow, Anti-Resonant Fiber Using a Surrogate Model-Assisted Gradient Descent Method

This paper proposes a novel optimization method for hollow-core, anti-resonant fiber based on a gradient descent algorithm assisted via a radial basis-function surrogate model. This approach significantly reduces the number of optimization iterations, achieving a stable improvement in birefringence performance by an order of magnitude across the operating wavelength band. Furthermore, various optimization algorithms were compared, and the indicators of their Pareto sets were analyzed to demonstrate the effectiveness of the proposed method in multi-objective optimization.

Machine Learning-Based Spectral Reconstruction for Equivalence Ratio Measurement in Premixed Air-Methane Flames Using RGB Imaging

ABSTRACT This paper introduced a machine learning-based method for reconstruction spectral information from RGB images for measurements of the equivalence ratio (Φ) of premixed air-methane flames. Digital color cameras capture color and spatial information of hydrocarbon premixed flames in the visible band. The color of the flame is the result of spectral integration of chemiluminescence in the visible wavelength band, and direct use for flame equivalence ratio measurements would result in large errors due to low spectral resolution. The mapping function was used to reconstruct the spectral characteristics of the premixed methane flame for the RGB image, which were built by three types of machine learning methods: support vector regression (SVR), random forest (RF) regression, and Levenberg-Marquardt backpropagation neural network (LM-BPNN), respectively. Finally, LM-BPNN-based reconstructed spectral features are used for the development of Φ measurement model, which measurement error below 0.01, accurately measures the equivalence ratio of premixed methane flames within the range of 0.73 to 1.47. Further analyze the two-dimensional spatial distribution of flame equivalence ratio.