Wavelength Measurements Research Articles

Miniaturized dual-photodiode sensor for simultaneous wavelength and irradiance measurement across the 500–1000 nm range

We introduce what we believe to be a novel chip-scale dual-photodiode sensor capable of simultaneously measuring centroid wavelength and irradiance within the 500–1000 nm range. The sensor employs a dual-photodiode design, where one photodiode is equipped with a coated filter layer to create differential responsivity, allowing for accurate spectral and intensity detection. Our sensor demonstrates high accuracy, with centroid wavelength and intensity measurements within a 5% margin of error for light sources with a full width at half maximum (FWHM) of 50 nm. This design supports the use of optional optical filters tailored to specific wavelength ranges, enhancing adaptability across diverse applications. Experimental validation confirms its practical potential in a variety of fields, including precision agriculture, horticulture, and environmental monitoring, especially for studies involving far-red and near-infrared light sources. The chip-scale fabrication of the sensor ensures cost-effective, portable, and scalable deployment, positioning it as a versatile solution for advancing optical sensing technologies in various scientific and industrial fields.

A novel effective stress sensor based on FBG sensing technology for effective stress measurement in soil

The effective stress in saturated soil is typically indirectly measured in geotechnical engineering. Thus, the present study developed an equal-strength cantilever beam effective stress sensor (ECB-ESS) based on fiber Bragg grating technology that can measure the effective stress directly. ECB-ESS can significantly eliminate the wavelength measurement error caused by uneven strain along the grating because of the advantage of equal strain distribution along the cantilever beam. To further validate the superiority of the equal-strength cantilever beam structure from both initial and actual performance aspects, comparison tests are conducted using both water pressure calibration and earth pressure calibration methods. To fully evaluate the performance of the ECB-ESS, water pressure test, earth pressure test, and temperature test were conducted separately. Additionally, the capability of the sensor to measure effective stress under different loading levels was examined through effective stress test.

Demonstration of an ultra-wideband wavelength self-adaptive and high-precision single-frequency laser linewidth measurement system.

An ultra-wideband wavelength self-adaptive and high-precision single-frequency laser linewidth measurement system (SFLLMS) is constructed. The SFLLMS enables parameter measurement of the laser in the wavelength range of 1-2.05 µm with a 9 Hz linewidth measurement resolution and ±45 Hz linewidth measurement accuracy. The wavelength measurement accuracy of the constructed system is ±0.008 nm, and it consumes less than 4.9 s for a single measurement. The wavelengths and linewidths of lasers in the 1 µm band with a center wavelength of 1064.5222 nm, the 1.5 µm band with a center wavelength of 1550.1973nm, the 1.94 µm band with a center wavelength of 1940.8327 nm, and the 2.05 µm band with a center wavelength of 2049.0460 nm were measured using the constructed SFLLMS. The wavelength measurement accuracy and linewidth measurement accuracy were calculated. The times for single linewidth measurement at different powers of the four lasers were also recorded.

High-fidelity surface reconstruction using complementary colorimetry-encoded fringe projection profilometry.

To solve the challenging issue of uneven reflectance of high-fidelity surface, this paper proposes a three-dimensional (3D) shape measurement method based on surface adaptation complementary colorimetry-encoded fringe projection profilometry. A complete complementary hue extraction method simulates the retina stimulation to establish the complementary conversion relationship between the projected and collected colors of the measurement system. On this basis, a surface reflectance adaptation fringe pattern encoding strategy is proposed to measure the high-fidelity surfaces. The experiments demonstrate that the proposed method is capable of efficiently balancing and adjusting the reflected light intensity of each fidelity surface, thereby suppressing the ambiguity reconstruction texture. The established complementary colorimetry relationship also improves the light wavelength discrimination, saturation avoidance, measurement accuracy and efficiency.

N = 3−3 lines in the extreme ultraviolet spectrum of europium (Z = 63)

Using high-resolution flat-field spectrographs at the LLNL SuperEBIT electron beam ion trap, we have observed extreme ultraviolet spectra (λ 32–43 Å) of highly charged ions of Eu ( Z = 63) under a range of production conditions suitable for Na- through Zn-like ions. Almost 30 lines were identified with the aid of Flexible Atomic Code computations and spectral modeling. While some of the wavelength measurements are among the most accurate in this wavelength range, some of the identifications are still tentative. We discuss how experimental conditions and spectral complexity interact in the analysis process.

A Novel Electromagnetic Wavelength Measurement Method Based on Photoacoustic Effect and Photoacoustic Response Characteristics of Nanomaterials

This study proposes a differential wavelength measurement method based on the electromagnetic-induced photoacoustic effect. The differential method involves irradiating the sample with multiple wavelengths and utilizing differences in absorption characteristics across different materials to calculate and measure the excitation light wavelengths. Compared to traditional detection methods, this approach combines the unique properties of electromagnetic-induced photoacoustic effect, offering high sensitivity and a wider detection range from microwave to light. Furthermore, the system is structurally simple and stable, suitable for non-destructive testing of various materials, including wavelength-sensitive biological tissues. The experimental results demonstrate that combined with Polymers Benzodithiophene Triazole–Quinoxaline (PBTQ) and Single-Walled Carbon Nanotubes (SWCNTs) as absorbing media, this technique provides a rapid and cost-effective means of wavelength measurement, achieving an uncertainty of approximately 2.33 nm within the range of 680–800 nm, and it can be used for wavelength/frequency measurement of various electromagnetic waves.

Staring laser situation awareness technology with wide-FOV and high-angle positioning accuracy based on two-dimensional grating and two-channels

Current and future battlefields face the emerging threat of laser weapon development. Existing laser situation awareness technology cannot provide simultaneous operation of wide field-of-view (FOV) and high angle positioning accuracy. This study introduces a system employing a two-dimensional grating and dual-channel approach that offers high precision in situation awareness about laser wavelengths and angle positioning across a wide FOV. The system consists of two main components: an approximate measurement channel and an accurate measurement channel. The former includes a wide-FOV lens and a focal plane array detector (FPA1), acquiring preliminary angle information of the laser. The latter, comprising a two-dimensional grating, a narrow-FOV lens, and a FPA2, captures the incoming laser’s wavelength and precise azimuth and pitch through the analysis of diffraction spot position and distance. Experimental findings confirm that the accuracies of angle and central wavelength measurements exceed 0.05° and 8 nm, respectively, for a FOV of 120°.

Snapshot Multi-Wavelength Birefringence Imaging.

A snapshot multi-wavelength birefringence imaging measurement method was proposed in this study. The RGB-LEDs at wavelengths 463 nm, 533 nm, and 629 nm were illuminated with circularly polarized light after passing through a circular polarizer. The transmitted light through the birefringent sample was captured by a color polarization camera. A single imaging process captured light intensity in four polarization directions (0°, 45°, 90°, and 135°) for each of the three RGB spectral wavelength channels, and subsequently measured the first three elements of Stokes vectors (S0, S1, and S2) after the sample. The birefringence retardance and fast-axis azimuthal angle were determined simultaneously. An experimental setup was constructed, and polarization response matrices were calibrated for each spectral wavelength channel to ensure the accurate detection of Stokes vectors. A polymer true zero-order quarter-wave plate was employed to validate measurement accuracy and repeatability. Additionally, stress-induced birefringence in a PMMA arch-shaped workpiece was measured both before and after the application of force. Experimental results revealed that the repeatability of birefringence retardance and fast-axis azimuthal angle was better than 0.67 nm and 0.08°, respectively. This approach enables multispectral wavelength, high-speed, high-precision, and high-repeatability birefringence imaging measurements through a single imaging session.

Optical Disc Structures and Diffraction Patterns: Theoretical Foundations and Experimental Applications

Abstract This investigation advances the experimental exploration of optical discs' diffraction phenomena, meticulously constructing optical pathways to ascertain the track pitch within the disc employing both transmission and reflection grating paradigms. Furthermore, this study devises a novel apparatus and methodology for the precise measurement of optical wavelengths, aiming to elucidate the intricate diffraction patterns and the underlying mechanisms of optical discs' structure. This endeavor not only validates the methodological soundness and efficacy of the proposed approach but also pioneers new avenues for research into physics experiments leveraging optical discs. The application of optical discs in educational settings transcends traditional experimental pedagogy, fostering students' capabilities to independently conceptualize experiments and delve into scientific explorations.

Assessing the Cosmic Infrared Background Monopole from Far-infrared to Millimeter Wavelengths

We measured the cosmic infrared background (CIB) monopole for the COBE Diffuse Infrared Background Experiment (DIRBE) and Planck High-Frequency Instrument (HFI) bands with an updated model for the Galactic dust emission. This model includes a dust excess recently observed in 25% of the sky mainly at high latitude compared to the prediction from N H I. We correlated observations from COBE/DIRBE and Planck-HFI with this model to extract the zero levels of the sky maps. We corrected for the isotropic interplanetary dust (IPD) emission and calibration gains and obtained CIB values of 1.4 ± 8.0, 24.5 ± 3.9, 15.4 ± 4.9, 6.8 ± 2.0, 3.2 ± 0.3, 1.5 ± 0.1, 0.40 ± 0.05, 0.11 ± 0.04, 0.014 ± 0.027, and 0.008 ± 0.012 nW m−2 sr−1 at 60, 100, 140, and 240 μm, and 857, 545, 353, 217, 143, and 100 GHz. We compared those numbers with previous direct CIB measurements and extragalactic source counts. We obtain CIB values lower than previous measurements for wavelengths above 140 μm. Below this value, the large uncertainty related to the IPD emission prevents a clear interpretation.

Test-retest reliability and follow-up of muscle magnetic resonance elastography in adults with and without muscle diseases.

We investigated the potential of magnetic resonance elastography (MRE) stiffness measurements in skeletal muscles as an outcome measure, by determining its test-retest reliability, as well as its sensitivity to change in a longitudinal follow-up study. We assessed test-retest reliability of muscle MRE in 20 subjects with (n=5) and without (n=15) muscle diseases and compared this to Dixon proton density fat fraction (PDFF) and volume measurements. Next, we measured MRE muscle stiffness in 21 adults with Becker muscular dystrophy (BMD) and 21 age-matched healthy controls at baseline, and after 9 and 18months. We compared two different methods of analysing MRE data in this study: 'Method A' used the stiffness maps generated by the Philips MRE software, and 'Method B' applied a custom-made procedure based on wavelength measurements on the MRE images. Intraclass correlation coefficients (ICC) of muscle stiffness ranged from good (0.83 for left vastus medialis, P<0.001) to poor (0.19 for right rectus femoris, P=0.212) for the examined thigh muscles with Method A, but we did not find a significant test-retest reliability with Method B (P>0.050 for all). The ICC of muscle PDFF and volume measurements was excellent (>0.90; P<0.001) for all muscles. At baseline, the average stiffness of all thigh muscles was significantly lower in adults with BMD than in controls for both Method A (-0.2kPa, P=0.025) and Method B (-0.6kPa, P<0.001). Regardless of which method was used, there was no significant difference in the evolution of muscle stiffness in patients and controls over 18months. Test-retest reliability of muscle MRE using a simple 2D technique was suboptimal, and did not reliably measure muscle stiffness changes in adults with BMD as compared with controls over 18months. While the results provide motivation for testing more advanced 3D MRE methods, we conclude that the simple 2D MRE implementation used in this study is not suitable as an outcome measure for characterizing thigh muscle in clinical trials.

Wireless wavelength measurement system with temperature compensation using filter-free wavelength sensors

Abstract Portable wavelength detection systems have been developed for various environmental and biochemical applications. Conventional systems have some limitations as they are unable to adapt to changes in wavelength and rely on optical filters or slits to distinguish between different wavelengths. To address these limitations, a filter-free wavelength sensor system was proposed, utilizing the absorption coefficient of silicon to identify wavelengths. The proposed system comprises an analog circuit for measuring photocurrent from a filter-free wavelength sensor, integrated with a temperature sensor and microcontroller for signal processing. The proposed system can measure currents with a resolution of 1.2 pA within a 30 nA range, achieving a coefficient of determination of 0.999 for measured currents in relation to light intensity. The microcontroller features a temperature compensation algorithm, enabling wireless control and data transmission. Applying temperature compensation reduced the rate of errors in the data by 61%. By eliminating the need for optical components, a wireless measurement system was developed that can accurately identify wavelengths.

High performance TM-pass polarizer using multimode Bragg grating waveguide

A novel ultra-broadband TM-pass polarizer with high polarization extinction ratio (PER) and low reflection has been proposed and demonstrated by utilizing multimode Bragg grating waveguide (MBGW) and two tapered waveguides. By optimizing the period of the MBGW, the injected TE0 mode is coupled into the backward TE2 mode and effectively leaked into the cladding. Meanwhile, the injected TM0 mode propagates through the polarizer without any negative impact. The operation bandwidth can be significantly expanded by cascading multiple MBGW structures, each of which operates at a different central Bragg wavelength. The simulation results indicate that the designed polarizer can achieve an insertion loss (IL) below 0.24 dB and a PER above 39 dB simultaneously across a bandwidth of 300 nm (1400 nm∼1700nm), while the reflected signal is below −9.1 dB. The experiment results demonstrate that the fabricated polarizer can realize an IL below 0.56 dB and a PER above 33 dB in a 160 nm bandwidth ranging from 1470 nm to 1630 nm. Due to limitations in the equipment used, measurements for other wavelength ranges are not conducted. With these merits, the proposed device would find significant applications in optical communication systems.

Wavelength measurement of narrowband terahertz radiation using a diffraction grating

We propose a reflective binary amplitude grating-based setup for determining the frequency of narrowband terahertz radiation. Theoretical analysis was conducted on transmissive and reflective configurations utilizing binary and phase gratings. Simulations were performed to determine the parameters of metallic diffraction gratings with millimeter-scale constants, which were produced using laser cutting techniques. Our implementation consists of a cost effective and easy-to-implement setup that operates within the 0.15–1 THz range. The grating is installed on a rotary stage. The experimental results obtained align closely with the theoretical calculations. By understanding the setup parameters and the angle of the 1st diffraction order, we could calculate the frequency of the unknown radiation. The relative error in determining the frequency was less than 2%.

Single-shot wavelength meter on a chip based on exponentially increasing delays and in-phase quadrature detection

A solid-state wavelength measuring instrument based on a SiO2 photonics platform is presented. The chip-scale wavemeter device has no moving parts and allows instantaneous wavelength measurement with high precision and accuracy over a nominal bandwidth of 40 nm in the O-band. The wavemeter design is based on multimode interferometer (MMI) couplers and a multi-band Mach–Zehnder interferometer (MZI) structure with exponentially increasing optical path differences. Design of the MMI couplers is supported by simulations using the Finite-Difference Time-Domain (FDTD) method. A hydrogen fluoride gas cell is used in conjunction with the chip-scale wavemeter to determine the wavelength relative to traceable absorption lines. This approach does not rely on knowledge of the effective or group refractive indices to estimate wavelength. The fabrication, experimental evaluation and calibration of the device are discussed. Observed performance indicates a spectral support of 37.378 nm (i.e., frequency bandwidth 6.608 THz), with a resolution of 6.1 pm (1.1 GHz) at 1σ, corresponding to 1 part in 6,127.

Easy method to establish the dispersion relation of capillary waves on water jets

A simple, intuitive, and low-cost setup for generating and measuring capillary waves is presented enabling a precise determination of the dispersion relation for a cylindrical water jet. By setting the phase velocity and measuring the wavelength of capillary waves directly, this method provides an intuitive way for students to understand the dispersion relation of a cylindrical water jet. The setup produced measurements of wavelength versus phase velocity over a broader range of values than earlier work. The resulting data are generally consistent with earlier results but show an error of up to 15% at both the higher and lower end of the measured range of wavelengths compared to the theoretical dispersion relation of cylindrical water jets. For the shorter wavelengths, the deviation is in the opposite direction from that of earlier work.

Speckle wavemeter based on a multi-core fiber and compressive imaging.

Random speckle patterns contain valuable information about the incident light. Researchers have successfully constructed spectrometers and wavemeters by utilizing the speckles generated by inter-mode interferences of a multimode fiber (MMF). However, cameras were often employed to record the speckle data in previous reports. The camera's high cost (especially in the near-infrared range), large size, and low response speed limit the applications in optical communications, metrology, and optical sensing. A seven-core fiber (SCF) was fused with an MMF to capture the speckle pattern, where each core coupled part of the speckle field. Furthermore, we take advantage of the space division multiplexing capability of the SCF by incorporating an optical switch. This allows the variety of speckles generated by the incidence of different cores into the MMF. A convolutional neural network (CNN) regression algorithm was designed to analyze the complicated speckle data. The experimental results show that the proposed wavemeter can resolve adjacent wavelengths of 1pm with an error of about 0.2pm. We also discussed how different lengths of MMF influence the wavelength resolution. In conclusion, our research presents a robust and cost-effective approach to a wavelength measurement device by use of a seven-core optical fiber.

Two rest-frame wavelength measurements of galaxy sizes at z &amp;lt; 1: the evolutionary effects of emerging bulges and quenched newcomers

ABSTRACT We analyse the size evolution of 16 000 star-forming galaxies (SFGs) and 5000 quiescent galaxies (QGs) with mass M* &amp;gt; 109.5 M⊙ at 0.1 &amp;lt; z &amp;lt; 0.9 from the COSMOS field using deep CLAUDS + HSC imaging in two rest-frame wavelengths, 3000 Å (UV light) and 5000 Å (visible light). With half-light radius (Re) as proxy for size, SFGs at characteristic mass M0 = 5 × 1010 M⊙ grow by 20 per cent (30 per cent) in UV (visible) light since z ∼ 1 and the strength of their size evolution increases with stellar mass. After accounting for mass growth due to star formation, we estimate that SFGs grow by 75 per cent in all stellar mass bins and in both rest-frame wavelengths. Redder SFGs are more massive, smaller and more concentrated than bluer SFGs and the fraction of red SFGs increases with time. These results point to the emergence of bulges as the dominant mechanism for the average size growth of SFGs. We find two threshold values for the stellar mass density within central 1 kpc (Σ1): all SFGs with log Σ1 ≳ 9 are red and only QGs have log Σ1 ≳ 9.7. The size of M* = M0 QGs grows by 50 per cent (110 per cent) in the UV (visible) light. Up to $\sim 20~{{\rm per\,cent}}$ of this increase in size of massive QGs is due to newcomers (recently quenched galaxies). However, newcomers cannot explain the observed pace in the size growth of QGs; that trend has to be dominated by processes affecting individual galaxies, such as minor mergers and accretion.

Biofabrication of silver nanoparticles with Feijoa sellowiana tailored by box-behnken design: An eco-friendly approach to enhance antifungal properties in Children's toothpaste

Oral candidiasis and its association with dental caries necessitate the development of toothpaste with enhanced antifungal properties, particularly for children at high risk of infection. This study aims to investigate the antifungal efficacy of children's toothpaste incorporating biosynthesized silver nanoparticles (AgNPs) using Feijoa sellowiana. Silver fluoride and Feijoa leaf extract were used for the synthesis of AgNPs. The independent variables were the concentration of AgF, pH of the extract, and temperature. The optimized formula was obtained using Design Expert software and Box-Benken design. The physicochemical properties of AgNPs were evaluated by UV-absorption wavelength measurements, SEM, and TEM analyses. Finally, the powder of optimized AgNPs was added to Colgate Kids Toothpaste® and its antifungal effect was evaluated using the standard agar well diffusion method. The optimization process identified an AgF concentration of 8 mM, a pH value of 9.56, and a temperature of 58 °C as influential factors for the formulation. The optimized AgNPs exhibited a size of 42.75 nm, and SEM and TEM analyses confirmed their spherical shape. Both toothpaste formulations, with and without AgNPs, demonstrated antifungal activity. Although the antifungal effect of both toothpaste types against Candida glabrata did not show a significant difference (p > 0.088), the toothpaste containing AgNPs exhibited significantly higher antifungal efficacy against Candida albicans (p < 0.014). In conclusion, the biosynthesis of silver nanoparticles using silver fluoride and Feijoa leaf extract as an eco-friendly approach can effectively enhance the antifungal potency of toothpaste against C. albicans.

Precision measurement of M1 optical clock transition in Ni12+

Highly charged ions (HCIs) have drawn significant interest in quantum metrology and in the search for new physics. Among these, Ni12+ is considered as one of the most promising candidates for the next generation of HCI optical clocks, due to its two E1-forbidden transitions M1 and E2, which occur in the visible spectral range. In this work, we used the Shanghai-Wuhan electron beam ion trap to perform a high-precision measurement of the M1 transition wavelength. Our approach involved an improved calibration scheme for the spectra, utilizing auxiliary Ar+ lines for calibration and correction. Our final measured result of the M1 transition wavelength demonstrates a fivefold improvement in accuracy compared to our previous findings, reaching the subpicometer level accuracy. In combination with our rigorous atomic-structure calculations to capture the electron correlations and relativistic effects, the quantum electrodynamic corrections were extracted. Published by the American Physical Society 2024