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In recent years, the rapid monitoring of total organic carbon (TOC) in natural waters has attracted increasing attention. Optical methods are a valid tool for measurement. Nevertheless, how to more accurately establish the mapping relationship between spectroscopy and TOC concentrations is currently a challenge. A new method based on UV-VIS spectroscopy with a deep convolutional network is proposed for the quantification of TOC in water in this paper. The Inception network, originally used to process two-dimensional image data, was redesigned as a model capable of processing one-dimensional spectral data, while the convolution and pooling scale were modified to adapt to one-dimensional data. Simultaneously, squeeze and extraction (SE) blocks were applied to the designed network to enhance feature information and to suppress interference from useless information in the regression process. The method was tested on samples collected from the sea and river estuaries in several provinces in China. When compared to the classical least squares support vector machine (LSSVM), the experimental results showed that the proposed 1D-Inception network structure can provide more accurate regression results. The SE block can significantly improve the feature extraction and expression capabilities of the 1D-Inception network structure and suppress redundant information, thereby achieving better model performance.

There are no planets intermediate in size between Earth and Neptune in our Solar System, yet these objects are found around a substantial fraction of other stars. Population statistics show that close-in planets in this size range bifurcate into two classes based on their radii. It is hypothesized that the group with larger radii (referred to as "sub-Neptunes") is distinguished by having hydrogen-dominated atmospheres that are a few percent of the total mass of the planets. GJ 1214b is an archetype sub-Neptune that has been observed extensively using transmission spectroscopy to test this hypothesis. However, the measured spectra are featureless, and thus inconclusive, due to the presence of high-altitude aerosols in the planet's atmosphere. Here we report a spectroscopic thermal phase curve of GJ 1214b obtained with JWST in the mid-infrared. The dayside and nightside spectra (average brightness temperatures of 553 $\pm$ 9 and 437 $\pm$ 19 K, respectively) each show >3$\sigma$ evidence of absorption features, with H$_2$O as the most likely cause in both. The measured global thermal emission implies that GJ 1214b's Bond albedo is 0.51 $\pm$ 0.06. Comparison between the spectroscopic phase curve data and three-dimensional models of GJ 1214b reveal a planet with a high metallicity atmosphere blanketed by a thick and highly reflective layer of clouds or haze., Comment: Published online in Nature on May 10, 2023

Planets orbiting M-dwarf stars are prime targets in the search for rocky exoplanet atmospheres. The small size of M dwarfs renders their planets exceptional targets for transmission spectroscopy, facilitating atmospheric characterization. However, it remains unknown whether their host stars' highly variable extreme-UV radiation environments allow atmospheres to persist. With JWST, we have begun to determine whether or not the most favorable rocky worlds orbiting M dwarfs have detectable atmospheres. Here, we present a 2.8-5.2 micron JWST NIRSpec/G395H transmission spectrum of the warm (700 K, 40.3x Earth's insolation) super-Earth GJ 486b (1.3 R$_{\oplus}$ and 3.0 M$_{\oplus}$). The measured spectrum from our two transits of GJ 486b deviates from a flat line at 2.2 - 3.3 $\sigma$, based on three independent reductions. Through a combination of forward and retrieval models, we determine that GJ 486b either has a water-rich atmosphere (with the most stringent constraint on the retrieved water abundance of H2O > 10% to 2$\sigma$) or the transmission spectrum is contaminated by water present in cool unocculted starspots. We also find that the measured stellar spectrum is best fit by a stellar model with cool starspots and hot faculae. While both retrieval scenarios provide equal quality fits ($\chi^2_\nu$ = 1.0) to our NIRSpec/G395H observations, shorter wavelength observations can break this degeneracy and reveal if GJ 486b sustains a water-rich atmosphere., Comment: 18 pages, 7 figures, 5 tables. Accepted in ApJ Letters. Co-First Authors

A refractive index insensitive triple cladding quartz specialty fiber temperature sensor with D-type microcavity structure is proposed. It consists of a triple cladding quartz specialty fiber(TCQSF) with a D-type microcavity structure fused between two sections of single-mode fiber(SMF). Because the SMF and TCQSF mode fields do not match, the excited modes form a Mach-Zehnder(M-Z) interferometer, resulting in a mode interference phenomenon. Experimental results show that in the range of 30-90°C, the transmission spectrum has a red shift phenomenon, the temperature sensitivity is 138.03 pm/°C, and the wavelength shift has a good linear relationship with temperature change. When the external refractive index changes in the range of 1.3350-1.3466, the sensor has a low sensitivity to the refractive index, which can avoid the cross-sensitivity of simultaneous measurement of temperature and refractive index. The sensor is not only simple to fabricate and high in sensitivity, but also has good repeatability and stable response, and has wide application prospects in the field of sensing.

In order to cover the bandwidth of optical fiber communication, a LP

A few mode fiber temperature sensor filled with PDMS based on vernier effect is proposed. It uses single mode fiber (SMF), few mode fiber (FMF), and polydimethylsiloxane (PDMS) to form the SMF-air microcavity-FMF-PDMS-FMF structure. It is to slot the glass capillary tube, place the two FMFs in the slot at a suitable distance, and fill the slot with PDMS multiple times and seal it. The PDMS is used as a sensing microcavity. We insert the SMF from the other end of the glass capillary tube, adjust the distance, fix the SMF and seal the connection. Two end faces of the SMF and the first FMF form an air reference microcavity. Since the refractive index of each medium is different, multiple reflective surfaces are formed to reflect. Because the second FMF is infinitely long, whose right end is beveled, it is considered that the sensor has four reflected beams. When the temperature changes, the length and refractive index of the PDMS microcavity will change, which will cause a change in the interference spectrum of the sensor. And because the vernier effect is formed by the superposition of the two microcavities, the temperature sensitivity can be amplified and the temperature can be measured with high sensitivity. The experimental results show that in the range of 40–56°C, the transmission spectrum of the sensor appears red shift with the increase of temperature, and the temperature sensitivity can reach 3.89nm/°C. The sensor is simple to manufacture, has high sensitivity, and has good application prospects.

In this paper, an Ag nanoparticles (AgNPs) modified multimode fiber (MMF) SERS probe prepared based on sol self-assembly method is proposed and fabricated. Different fiber SERS probes (AgNPs-MMF-x, x is the self-assembly time) are obtained by adjusting the self-assembly time. Using rhodamine 6G (R6G) solution as the probe molecule, the far-end performances of the prepared fiber SERS probe are studied, and the AgNPs-MMF-30 probe with obvious advantages in SERS performance is obtained. The limit of detection (LOD) for R6G is as low as 10−9 M, demonstrating the high sensitivity of AgNPs-MMF-30 probe. The enhancement factor (EF) of AgNPs-MMF-30 probe to 10−7 M R6G is about 1.36 × 108. In addition, the AgNPs-MMF-30 probe has an outstanding reproducibility across the entire area with the maximum value of relative standard deviation (RSD) of less than 10.94%. The AgNPs-MMF-30 probe exhibit a long-term stability regarding Raman enhancement of up to 35 days. Importantly, the high-performance AgNPs-MMF-30 probe is further applied as a highly sensitive SERS platform for the trace detection of antibiotic in milk. The fiber SERS probe has the characteristics of fast, effective, remote real-time detection and so on, so it has great potential application in biochemical sensing and food security.

We present the most complete emission spectrum for inflated hot Jupiter HAT-P-41b combining new HST WFC/G141 spectrum from the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program with archival Spitzer eclipse observations. We found a near blackbody-like emission spectrum which is best fitted with an isothermal temperature-pressure (TP) profile that agrees well with the dayside heat redistribution scenario assuming zero Bond albedo. The non-inverted TP profile is consistent with the non-detection of NUV/optical absorbers in the transit spectra. We do not find any evidence for significant H$^-$ opacity nor a metal-rich atmosphere. HAT-P-41b is an ideal target that sits in the transitioning parameter space between hot and ultra-hot Jupiters, and future JWST observations will help us to better constrain the thermal structure and chemical composition., Accepted for publication in AJ

JWST is here. The early release observation program (ERO) provides us with the first look at the scientific data and the spectral capabilities. One of the targets from ERO is HAT-P-18b, an inflated Saturn-mass planet with an equilibrium temperature of $\sim$850K. We present the NIRISS/SOSS transmission spectrum of HAT-P-18b from 0.6 to 2.8$\mu m$ and reveal the planet in the infrared beyond 1.6$\mu m$ for the first time. From the spectrum, we see clear water and escaping helium tail features in an otherwise very hazy atmosphere. Our free chemistry retrievals with ATMO show moderate Bayesian evidence (3.79) supporting the presence of methane, but the spectrum does not display any clearly identifiable methane absorption features. The retrieved methane abundance is $\sim$2 orders of magnitude lower than that of solar composition. The methane-depleted atmosphere strongly rejects simple equilibrium chemistry forward models with solar metallicity and C/O ratio and disfavors high metallicity (100 times) and low C/O ratio (0.3). This calls for additional physical processes such as vertical mixing and photochemistry which can remove methane from the atmosphere., Comment: Accepted to ApJL, JWST is awesome!

Ramie composites have been widely used in automobiles, daily necessities, aerospace, ships, cruise lines, etc., but their flame retardant properties are relatively poor, which is difficult to meet the flame retardant performance requirements of composites for rail transit. In order to improve the properties of ramie reinforced composites, flame retardant treatment is necessary. In this paper, phosphorus flame retardant phytic acid (PA) was used to modify ramie fabric, and then the composites were prepared. The flame retardancy and mechanical properties of ramie reinforced composites were investigated. It was found that the flame retardancy of ramie composites was improved after flame retardant modification with phytic acid, but the mechanical properties were decreased. In order to improve the mechanical properties of PA ramie composites, two kinds of layered PA ramie/glass fiber hybrid composites were prepared by replacing part of ramie with glass fiber. The results show that the addition of glass fiber can improve the mechanical properties and flame retardancy of composites.

Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot Jupiter WASP-74b into the ever growing dataset of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope (HST) and Spitzer Space Telescope (\textit{Spitzer}), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 $\mu m$ band. Future James Webb Space Telescope (JWST) follow up observations are needed to confirm these results., Comment: 23 pages, 18 figures, accepted to AJ

In order to cover the bandwidth of optical fiber communication, a LP01-LP11 ultra-broadband mode converter based on triple superimposed long period grating in PCF is proposed and demonstrated. The transmission spectra of the D-SLPG with gratings pitches and the T-SLPG were simulated and analyzed. The simulation results on the D-SLPG indicate that the 3 dB bandwidth of the D-SLPG is more than 1.5 times than the 3 dB bandwidth of the independent LPG and the 3 dB bandwidth of T-SLPG approaches 2.6 times as much as the independent LPG. In the experiment, the mode converter based on PCF-T-SLPG covers the wavelength of S + C + L with 3 dB bandwidth of 121 nm from 1498 nm to 1619 nm. In addition, the mode converter based on PCF-T-SLPG can accomplish ultra-broadband transmission in any wavelength by adjusting the period of gratings.

In recent years, as the development of aerospace, road bridge, precisioninstrument and other fields, the requirements of curved detection have become more and more precise and multi-point, and the advantages of fiber curvature sensors have become increasingly obvious. Based on the principle of mode interference, we proposed a cascade single-mode fiber, few-mode fiber and dual-core photonic crystal fiber curvature sensor, which can measure the distribution curvature, and solve the problem of measurement of multiple points that cannot be measured using one sensor. The experiment results show that within 0 to 1.06m−1 curvature range, each test point curvature sensitivity and linearity are −1.58 nm/m−1 and 0.98135, −1.62 nm/m−1 and 0.99504, −1.56 nm/m−1 and 0.98301, −1.74 nm/m−1 and 0.99701, and −1.31 nm/m−1 and 0.97315, respectively.

A cascaded fiber sensor for measuring different curvature ranges based on the cladding mode resonance in double-cladding fiber is proposed. It is formed by double-cladding fiber and single-mode fiber. Based on the evanescent wave coupling principle, the cladding mode resonance phenomenon in double-cladding fiber is illustrated. The transmission spectrum with different length are also analyzed. The experimental results show that the resonance wavelength changes with the length of double-cladding fiber. When the fiber length is 22 mm, the transmission spectrum is blue-shifted as the curvature increases in minor range of 0–0.204 m−1, the corresponding curvature sensitivity can be up to −19376.48 pm/m−1. When the fiber length is 20 mm, the corresponding curvature sensitivity can be up to −4161.73 pm/m−1 as the curvature increases in large range of 0–1.06 m−1. The proposed curvature sensor has the characteristics of simple structure and high sensitivity, so it has a good application prospects in large bridges, industrial buildings and other curvature measurement situations.

Based on the principle of Fabry-Perot (F-P) interference, a new type of optical fiber curvature sensor is presented, which is fabricated by single-mode fiber (SMF), ceramic tube and double-cladding fiber (DCF). And the curvature sensing properties are analyzed, and the double-peak method is used to demodulate the cavity length. The experimental results show that the F-P interference spectrum shifts toward long wavelengths with increasing the curvature. And the sensors are placed in different positions on the cantilever to get their different curvature sensitivities. Smaller initial cavity length gives greater sensor sensitivity. The best curvature sensitivity is achieved as 2 554.53 pm/m-1 in 0.71—1.18 m-1. By demodulating the length of the F-P cavity, the cavity length of sensor 4 is changed by 0.08 mm. Therefore, the sensor has some potential for measure the small displacement.

A curvature sensor based on the triple cladding quartz specialty fiber (TCQSF) is proposed. The TCQSF is spliced between two single mode fibers. The curvature sensor is performed by cladding mode resonance. The TCQSF with the length of 10 mm, 35 mm, and 50 mm is prepared and applied to the curvature measurement experiment. The bending model is created and analyzed by the finite element method theoretically. The experiment results show that the curvature sensitivity of sensor with different length are −1.83001 nm/m−1, −1.56231 nm/m−1 and −1.0114 nm/m−1 in the curvature range of 0 ∼ 0.94m−1.

A refractive-index sensitivity-enhanced sensor based on triple cladding quartz specialty fiber is proposed. The sensor is fabricated by core-offset splicing between the triple cladding quartz specialty fiber and single-mode fiber. The relationship between the core-offset and the transmission loss spectrum is studied in the sensor preparation. The refractive-index experiments are performed in different core-offset. The experimental results show that the refractive-index sensitivity can be up to 543.7527 nm/RIU when the core-offset is 11.2 µm. Thus, this proposed sensor can be used in many areas, such as industrial production, biological medicine, precision machining and so on.

The spatial phase distortion caused by a rough target causes a decoherence effect which, in turn, produces system sensitivity degradation. The decoherence phenomenon is the primary problem that restricts the application of active optical heterodyne detection, e.g., synthetic aperture radar and long-range coherent laser detection and ranging. By establishing a one-to-one correspondence between the combination of array signals and the system signal-to-noise ratio (SNR), a scheme for spatial phase distortion correction based on the intelligent optimization algorithm is proposed in this paper. The calculation of phase adjustments for each array signal is transformed into an optimization problem for the combination of array signals, experiments are conducted using rough target heterodyne images, and the parallel genetic algorithm (PGA) is used to calculate the phase adjustment of each array element. The results show that the spatial random phase distortion is corrected effectively without prior knowledge, and the PGA achieves an excellent computational performance which, along the efficiency of the proposed technology, has wide-scale implications for the application of active heterodyne detection and optical coherent communication.

A seven-core fiber torsion sensor with microcavity structure based on intensity measurement is proposed. It is composed of a seven-core fiber (SCF) and two multi-mode fibers (MMF). The first end of the SCF has a microcavity structure. Because the mode fields between the MMF and SCF do not match at the splicing point, the phenomenon of mode interference will be formed between cladding modes and core modes. Experimental results show that in a clockwise situation, the intensity of transmission spectrum increases in the torsion range of 0 ∼ 70°, the torsion sensitivity is 0.098 dB/ ∘ . And in a counterclockwise situation, the intensity of transmission spectrum decreases, the torsion sensitivity is 0.103 dB/ ∘ . The sensor has a simple structure and easy to fabricate, so it has wide application prospects in the field of torsion sensing.

A temperature insensitive curvature sensor is proposed based on cascading photonic crystal fiber. Using the arc fusion splicing method, this sensor is fabricated by cascading together a single-mode fiber (SMF), a three layers air holes structure of photonic crystal fiber (3PCF), a five layers air holes structure of photonic crystal fiber (5PCF) and a SMF in turn. So the structure SMF-3PCF-5PCF-SMF can be obtained with a total length of 20 mm. During the process of fabrication, the splicing machine parameters and the length of each optical fiber are adjusted to obtain a high sensitivity curvature sensor. The experimental results show that the curvature sensitivity is −8.40 nm/m−1 in the curvature variation range of 0–1.09 m−1, which also show good linearity. In the range of 30–90 °C, the temperature sensitivity is only about 3.24 pm/°C, indicating that the sensor is not sensitive to temperature. The sensor not only has the advantages of easy fabricating, simple structure, high sensitivity but also can solve the problem of temperature measurement cross sensitivity, so it can be used for different areas including aerospace, large-scale bridge, architectural structure health monitoring and so on.