Average Wavelength Research Articles

High Single-Mode Stability Tunable In-Series Laser Array With High Wavelength-spacing Uniformity

Multi-wavelength distributed feedback laser array based tunable semiconductor lasers have been widely used owing to their high mode stability and simple tuning scheme. Comparing with the in-parallel laser array, the in-series one can avoid a large power loss caused by the optical combiner. However, the single-mode stability of an in-series laser array is vulnerable to the reflections of other lasers. Here we experimentally demonstrated a tunable in-series laser array with high single-mode stability and high uniformity of wavelength spacing. To reduce the impact of such reflections, the Bragg gratings in different lasers were designed in phase, and the grating phase error was reduced by utilizing the reconstruction-equivalent-chirp technique. Besides, a three-section laser structure was applied in each laser to increase the priority of the dominant lasing mode. Four lasers with small wavelength-spacings of 2.5 nm were integrated in the in-series laser array. According to the measurement results of 40 in-series laser arrays (160 lasers), wavelength deviations of 90.6% lasers were within ±0.2 nm, average wavelength spacings of 97.5% of the measured laser arrays were deviated from the design within ±0.2 nm, and SMSRs of 96.3% lasers were above 45 dB. The output power was above 25 mW and the relative intensity noise was below -130 dB/Hz. Like the in-parallel laser array, the proposed laser array can be applied in either continuous wavelength tuning or fast channel switching. For the continuous wavelength tuning applications, the 10-nm tuning range was obtained with a temperature tuning range of less than 20 °C. For the fast channel switching applications, four channels with 2.5-nm spacing are available, and the switching time between two channels was less than 300 ns.

Acquisition of Post-Depositional Effects on Stable Isotopes (δ18O and δD) of Snow and Firn at Dome A, East Antarctica

Water stable isotopes (δ18O and δD) in Antarctic snow pits and ice cores are extensively applied in paleoclimate reconstruction. However, their interpretation varies over some climate change processes that can alter isotope signals after deposition, especially at sites with a low snow accumulation rate (<30 mm w.e. year−1). To investigate post-depositional effects during the archival processes of snow isotopes, we first analyzed δ18O and δD variations in summer precipitation, surface snow and snow pit samples collected at Dome A. Then, the effects of individual post-depositional processes were evaluated from the results of field experiments, spectral analysis and modeling simulations. It was found that the sublimation–condensation cycle and isotopic diffusion were likely the dominant processes that modified the δ18O at and under the snow–air interface, respectively. The sublimation–condensation cycle can cause no significant isotopic modification of δ18O from field experiments with ~3 cm snow. The diffusion process can significantly erase the original seasonal variation of δ18O driven by atmospheric temperature, leading to an apparent cycle of ~20 cm average wavelength present in the δ18O profile. Through the comparison with the artificial isotopic profile, the noise input from the diffusion process was the dominant component in the δ18O signal. Although some other processes (such as drifting, ventilation and metamorphism) were not fully considered, the quantitative understanding for the sublimation–condensation and diffusion processes will contribute to the paleoclimate construction using the ice core water isotope records at Dome A.

An optical-fiber sensor with double loss peaks based on surface plasmon resonance

A novel D-shaped photonic crystal fiber sensor based on surface plasmon resonance has been designed in this paper. The refractive index sensing with double loss peaks are studied in detail. Numerical simulation shows that the average wavelength sensitivities of the primary peak and the secondary peak can reach 18900 and 17500 nm/RIU in the refractive index range of 1.35-1.38, and the corresponding resolutions are 5.291 × 10-6 and 5.714 × 10-6 RIU, respectively. In addition, it is found that the resonance wavelengths do not shift as the sensing length increases. Moreover, the coupling characteristics between fundamental mode and the surface plasmon polarization (SPP) mode are investigated. It worth noting that the sketch diagram about specific operation is presented. It can except that the research results can be applied into the fields of double-loss-peak detection, which improves the practicability of the sensor.

Nanomechanical characterization of single phospholipid bilayer in ripple phase with PF-QNM AFM

Topography and nanomechanical properties of the supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) single bilayer in the ripple phase were investigated by atomic force microscopy with the use of PeakForce Quantitative Nanomechanical Mapping (PF-QNM) mode under liquid conditions. The DMPC single bilayer was deposited on the mica surface by Langmuir-Blodgett and Langmuir-Schaefer techniques combined. Next, the sample was stored overnight at 4 °C under buffer solution (pH = 7.6) in the presence of tris(hydroxymethyl)aminomethane, (Tris), and then, AFM imaging was performed at 21 °C using the same buffer. The AFM topography images revealed the presence of a periodic structure with an average wavelength of 96.0 ± 7.8 nm and an average amplitude of 0.97 ± 0.03 nm. This macro-ripple structure was asymmetric and formed by long ripples composed of two stripes of different heights. The changes in topography were accompanied by local changes in the Young's modulus, which indicate that the nanomechanical properties of the bilayer are not evenly distributed, namely, the higher stripes are characterized by a lower Young's modulus than that calculated for lower stripes of the ripples. This indicates that the ripple phase is composed of phospholipid molecules of periodically changed orientation and conformation characteristic for fluid-like and gel-like state of DMPC.

Effect of Cobalt Chloride as Filler and PVP on the Optical Properties of PVA/PEG/PVP Blends

Different concentrations of PVA/PEG/PVP blends as well as different composites of cobalt chloride, as filler, embedded in apolymeric blend as a hosting matrix, were prepared by solution casting method. The samples were characterized by a powerful technique as X-ray diffraction (XRD) which shows that the value of crystallite sizes (D) was mainly depending on the content of both of PVP and cobalt chloride (CoCl2). The studying of the optical properties for the samples was investigated through understanding the obtained results of the absorption and reflection measurements. The absorption spectrum was increasing with increasing each of PVP content in PVA/PEG/PVP blends and the filler content in all the composites of CoCl2/PVA/PEG/PVP. Also, the concentrations of PVP and CoCl2 had an influence on the magnitude of the calculated values of the static dielectric constants (e∞), the static refractive index (n0), the moments of the optical spectrum (M1 and M3), the average interband oscillator wavelength (λ0) and the oscillator length strength (S0). The estimated values of both of the oscillator energy gap E0, and the dispersion energy Ed, were decreasing by increasing the content of CoCl2 in the composites CoCl2/PVA/PEG/PVP 72/5/23 wt %.

Difração e interferência: medição do comprimento da onda do espectro de luz visível

O trabalho tem como intuito estabelecer e melhorar os processos de ensino e aprendizagem, através de uma atividade experimental realizada no laboratório de Física, no curso de licenciatura em Física IFMA- Campus são João dos Patos. Visando conhecer e compreender os fenômenos de difração e interferência, tendo como objetivo principal mostrar e calcular o comprimento médio da onda do espectro visível (380-740nm) através de uma rede de difração, podendo desta forma enriquecer os conceitos estudados, por meio de uma análise reflexiva quanto ao experimento de Young, estimulando a criação de novas teóricas, servindo para mostrar aos alunos o comportamento da luz como onda, sabendo que a difração é o desvio de uma trajetória retilínea, que ao passar por um orifício ou ser obstruída por um obstáculo sofre um alargamento ou encurvamento, propagando-se para diferentes regiões, agindo como se fosse novas fontes, causando o espalhamento da luz. Desta forma, incentivando ao professor a utilizar e criar metodologias processuais, possibilitando ao aluno um ambiente propício a participar e desenvolver suas competências e habilidades intelectuais, podendo assim, associar a teoria com a prática, validando os conceitos e as equações para calcular o comprimento da onda, obtendo como resultado a verificação da eficácia do cálculo a partir da simetria das intensidades luminosas em relação o central, podendo comparar os valores calculados das radiações com os das literaturas. Podendo assim, através das práticas, instigar, estabelecer e despertar aos alunos o desejo do saber pela ciência.

Surface plasmon resonance sensor based on a D-shaped photonic crystal fiber for high and low refractive index detection

A D-shaped photonic crystal fiber sensor based on surface plasmon resonance effect is proposed in this paper. Experimental results show that the D-shaped sensor can perform sensing detection in high or low refractive index regions. In addition, the refractive index of different analytes can be double calibrated by peaks and troughs. For high refractive index region from 1.3621 to 1.4010, the average sensitivity of the peaks and troughs is only 30.0 nm/RIU and 72.7 nm/RIU, respectively. However, in the low refractive index region of 1.3415–1.3468, the average wavelength sensitivity reaches 842.6 nm/RIU. The research in this paper has important reference value and positive scientific significance for exploring novel D-shaped photonic crystal fiber sensors.

Theoretical assessment of D-shaped optical fiber chemical sensor associated with nanoscale silver strip operating in near-infrared region

In present work, we propose a surface plasmon resonance based D-shaped fiber for the chemical sensor using nanoscale silver strip deposited over polished surface of single mode fiber. Various parameters of the designed sensors are optimized to achieve the maximum wavelength sensitivity. The sensing properties are investigated using finite element method based on COMSOL Multiphysics. An average wavelength sensitivity of 2100 nm/RIU is obtained for wide range of refractive index (RI) varying between 1.34 and 1.42 and a maximum wavelength and amplitude sensitivity of 3240 nm/RIU and 192 RIU−1 is achieved for RI range varying between 1.38 and 1.42 with 3.08 × 10−5 RIU resolution. The results indicate that our designed sensor perform effectively in high RI range and hence can be used in chemical and biological sensing.

Chromaticity analysis of diffraction pattern of white light under the grating

From the D65 daylight source, the ten monochromatic lights were evenly selected to be mixed into white light. After grating diffraction, color mixing was performed by using the chromaticity method with the relative intensity as the proportionality factor. The mixed color and its chromaticity parameters at specific diffraction angle positions were obtained to calculate L*, a*, b* and dominant wavelength. The relationship between the parameters of the grating and the chromaticity parameters of the mixed color was studied separately. The results showed that the color of the white light diffraction pattern at the diffraction angle θ = 2° is most significantly affected by d, followed by N. There is well linear correlation between b and L*, a*, b* values; but the effect of b on the color is not obvious. Then the relationship between the light intensity of ten kinds of monochromatic lights and the grating constant according to the grating diffraction intensity equation were drew, and the “rainbow” phenomenon was found. Current method for calculating the average wavelength of mixed colors directly from the “rainbow” graph is verified to be equivalent to the chromaticity method.

Plasma stopping-power measurements reveal transition from non-degenerate to degenerate plasmas

Physically realized electron gas systems usually reside in either the quantum non-degenerate or fully degenerate limit, where the average de Broglie wavelength of the thermal electrons becomes comparable with the interparticle distance between electrons. A few systems, such as young brown dwarfs and the cold dense fuels created in imploded cryogenic capsules at the National Ignition Facility, lie between these two limits and are partially degenerate. The National Ignition Facility has the unique capability of varying the electron quantum degeneracy by adjusting the laser drive used to implode the capsules. This allows experimental studies of the effects of the degeneracy level on plasma transport properties. By measuring rare nuclear reactions in these cold dense fuels, we show that the electron stopping power, which is the rate of energy loss per unit distance travelled by a charged particle, changes with increasing electron density. We observe a quantum-induced shift in the peak of the stopping power using diagnostics that measure above and below this peak. The observed changes in the stopping power are shown to be unique to the transition region between non-degenerate and degenerate plasmas. Our results support the screening models applied to partially degenerate astrophysical systems such as young brown dwarfs. Transitions between non-degenerate and degenerate plasma are observed in laser-driven implosions of cryogenic capsules at the National Ignition Facility. The observed partially degenerate regime is relevant to the physics of young brown dwarfs.

Color Determination from a Single Broadband Organic Photodiode

AbstractEstablishing the color of incident light is essential for many applications, such as machine vision, but generally requires either a dispersive component or multiple spectrally selective photodetectors. In contrast, here an incident spectrum is parametrized using a single broadband organic photodiode (OPD). This is achieved by exploiting the incident wavelength dependence of charge extraction caused by optically induced trap states in a metal oxide electron extraction layer, which results in an atypical spectral dependence of the reverse bias photocurrent density vs voltage (J–V) characteristics. Such dependence is augmented by confining the active layer within an optical microcavity to influence the light absorption profile and thus metal oxide trap state density. The average wavelength of an (approximately normally distributed) incident spectrum is then calculated to within ≈5 nm by algorithmically minimizing the difference between a measured J–V curve and one determined from the overlap integral of a trial spectrum with previously acquired voltage bias dependent external quantum efficiency (EQE) spectra.

Electromagnetic Conception of Color Vision in Additive Mixing of Colors. Application in the Photography. Art and Psychology

Vision (visual perception) is a process of psycho-physiological processing of the images of surrounding objects, carried out by the visual system, which allows getting an idea of ​​the size, shape and color of surrounding objects, their relative position and distance between them. The vision analyzer can perceives waves of a certain length - from 380 to 770 nm with pigments – rhodopsin and iodopsin.The aim of the research is the mechanism of color perception by the visual analyzer having the ability to analyze certain ranges of the optical spectrum. The colors were studied along with an analysis of the additive mixing of two colors. In 2008 Marinov and Ignatov shown that at the mixing of electromagnetic waves with different wavelengths, the visual analyzer perceive them as separate or average wave length corresponding to mix color. Keywords : vision, rhodopsin, iodopsin, additive color mixing DOI: 10.7176/JMPB/64-02 Publication date: February 29 th 2020

Interstellar Extinction in the Direction of the Young Open Cluster NGC 6530

We present UBVRI polarization observations of 12 B-type stars in the direction of the young open cluster NGC 6530, nine of them confirmed as probable members. The maximum degree of polarization for our target stars ranges from 0.16% to 2.84%, with an average value of 1.1%. We note variations of the polarization vector orientations across the cluster field. We use the polarization data to infer the wavelength of maximum polarization and obtain the total-to-selective extinction ratio for each star. Based on all 12 observed stars, the weighted average wavelength of the maximum degree of polarization is 0.563 ± 0.001 μm. This yields an average value of R = 3.15 ± 0.06 for the total-to-selective extinction associated with this field. Despite slight variations, RV is not abnormal. Using UBV photometry combined with recent photometric calibrations yields average E(B − V) = 0.38 ± 0.07 (s.d.) mag and average AV = 1.20 ± 0.24 (s.d.) mag. Both RV and E(B − V) show star-to-star variations. Our study yields a photometry-based distance of 1.6 kpc. For more precise distance estimates, especially when seeking agreement with the Gaia parallaxes, better evaluation of peculiarity and duplicity of these stars is needed. We studied comparisons between the photometric UBV absolute magnitudes, Gaia-based absolute magnitudes and magnitudes obtained from direct measurements of the Balmer discontinuity and discuss the presently existing disagreements for the cluster field.

A Refractive Index Sensor Based on H-Shaped Photonic Crystal Fibers Coated with Ag-Graphene Layers.

An Ag-graphene layers-coated H-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor with a U-shaped grooves open structure for refractive index (RI) sensing is proposed and numerically simulated by the finite element method (FEM). The designed sensor could solve the problems of air-holes material coating and analyte filling in PCF. Two big air-holes in the x-axis produce a birefringence phenomenon leading to the confinement loss and sensitivity of x-polarized light being much stronger than y-polarized. Graphene is deposited on the layer of silver in the grooves; its high surface to volume ratio and rich π conjugation make it a suitable dielectric layer for sensing. The effect of structure parameters such as air-holes size, U-shaped grooves depth, thickness of the silver layer and number of graphene layers on the sensing performance of the proposed sensor are numerical simulated. A large analyte RI range from 1.33 to 1.41 is calculated and the highest wavelength sensitivity is 12,600 nm/RIU. In the linear RI sensing region of 1.33 to 1.36; the average wavelength sensitivity we obtained can reach 2770 nm/RIU with a resolution of 3.61 × 10−5 RIU. This work provides a reference for developing a high-sensitivity; multi-parameter measurement sensor potentially useful for water pollution monitoring and biosensing in the future.

Identification of Heracleum sosnowskyi-Invaded Land Using Earth Remote Sensing Data

H. sosnowskyi (Heracleum sosnowskyi) is a plant that is widespread both in Lithuania and other countries and causes abundant problems. The damage caused by the population of the plant is many-sided: it menaces the biodiversity of the land, poses risk to human health, and causes considerable economic losses. In order to find effective and complex measures against this invasive plant, it is very important to identify places and areas where H. sosnowskyi grows, carry out a detailed analysis, and monitor its spread to avoid leaving this process to chance. In this paper, the remote sensing methodology was proposed to identify territories covered with H. sosnowskyi plants (land classification). Two categories of land cover classification were used: supervised (human-guided) and unsupervised (calculated by software). In the application of the supervised method, the average wavelength of the spectrum of H. sosnowskyi was calculated for the classification of the RGB image and according to this, the unsupervised classification by the program was accomplished. The combination of both classification methods, performed in steps, allowed obtaining better results than using one. The application of authors’ proposed methodology was demonstrated in a Lithuanian case study discussed in this paper.

Analysis of a highly sensitive flat fiber plasmonic refractive index sensor.

In this paper, we propose an efficient double-layered flat fiber (DLFF) plasmonic refractive index sensor having high resolution and linearity. Thin gold film is used as surface plasmon resonance (SPR) active material protected by a titanium dioxide layer, both deposited on the upper flat surface of DLFF. The sensor consists of an analyte channel in the central core hole as well as on the top of the fiber. Structural parameters of DLFF and thickness of gold and titanium dioxide layer are analyzed based on the finite element method. The optimized structure is studied based on wavelength and amplitude interrogation techniques in the near-infrared region. Numerical results show average wavelength sensitivity of 12172 nm/RIU with a resolution of 8.21×10-6RIU (refractive index unit) in the highly refractive index (RI) range from 1.445 to 1.490. Further, amplitude sensitivity of this probe is found to be 2910RIU-1 with a resolution of 3.44×10-6RIU, which is the highest among all reported PCF SPR sensors, as per the authors' best knowledge. Compared with traditional photonic crystal fiber, the designed DLFF makes the sensor configuration simple to fabricate as well as a potential candidate for developing biochemical sensors and portable devices.

Action recognition and control of mechanical simulated arm: electromyographic signal detection

Electromyography (EMG) signal contains a large amount of human motion information, which can be used to classify human actions. In this study, based on the detection of surface electromyography (sEMG) signal, three actions were designed, the sEMG signal was collected by the EMG acquisition system. Four feature values, including root-mean-square value, average absolute value (MAV), wavelength, and Zero crossing point, were extracted from the signal. Then these values were taken as the input of Back-Propagation neural network (BPNN) to recognize different actions, thereby realizing the real-time control of mechanical simulated arm. The experiment found that the training time of the BPNN method designed in this study was short, 11.36 s, and the average recognition accuracy rate reached 92.2%. In the real-time control experiment of mechanical simulated arm, the recognition accuracy of different actions reached more than 90%, and the running time was short. The experimental results verifies the effectiveness of the proposed method and make some contributions to the efficient control of the mechanical simulation arm.

State 1st class working standard for units of wavelength in the range from 1.25 to 20.00 μm and wavenumber in the range from 500 to 8000 cm–1

The 1st class Working Standard for units of wavelength in the range from 1.25 to 20.0 μm and wavenumber in the range from 500 to 8000 cm–1 developed in VNIIOFI based on Fourier-Transform Infrared Spectrometer is presented. Dissemination of wavelength and wavenumber units to the 1st class Working Standard is carrying out from FTIR-spectrometer measurements of two peaks of lasers from the State primary special standard of units of signal propagation length and duration in the optical fiber of the average power, attenuation and wavelength for optical fiber communication systems and information transmission GET 170-2011. Spectral scale realization by the Working Standard is carrying by interferogram of internal He–Ne-laser during spectral intensity measurements of internal source. Dissemination for units of wavelength in the range from 1.25 to 20.00 μm and wavenumber in the range from 500 to 8000 cm–1 is provided by corresponding correction factor to measurement results. The developed accuracy chart that set traceability for wavelength and wavenumber measurement instruments to GET 170-2011 is presented.

Single Cell Analysis of Neutrophils NETs by Microscopic LSPR Imaging System.

A simple microengraving cell monitoring method for neutrophil extracellular traps (NETs) released from single neutrophils has been realized using a polydimethylsiloxane (PDMS) microwell array (MWA) sheet on a plasmon chip platform. An imbalance between NETs formation and the succeeding degradation (NETosis) are considered associated with autoimmune disease and its pathogenesis. Thus, an alternative platform that can conduct monitoring of this activity on single cell level at minimum cost but with great sensitivity is greatly desired. The developed MWA plasmon chips allow single cell isolation of neutrophils from 150 µL suspension (6.0 × 105 cells/mL) with an efficiency of 36.3%; 105 microwells with single cell condition. To demonstrate the utility of the chip, trapped cells were incubated between 2 to 4 h after introducing with 100 nM phorbol 12-myristate 13-acetate (PMA) before measurement. Under observation using a hyperspectral imaging system that allows high-throughput screening, the neutrophils stimulated by PMA solution show a significant release of fibrils and NETs after 4 h, with observed maximum areas between 314–758 µm2. An average absorption peak wavelength shows a redshift of Δλ = 1.5 nm as neutrophils release NETs.

Regional scale soil moisture content estimation based on multi-source remote sensing parameters

ABSTRACT Soil moisture content (SMC) is a basic condition for crop growth, and a key parameter for crop yield prediction and drought monitoring. An advantage of large-scale synchronous observation using remote sensing technology is that it provides the possibility of dynamic monitoring of soil moisture content in a large area. This study aimed to explore the feasibility of accurately estimating soil moisture content at a regional scale by combining ground hyper-spectral data with multispectral remote sensing (Sentinel-2) data. The results showed that the different mathematical transformations increased the correlation between soil spectral reflectance and SMC to varying degrees. Hyper-spectral optimized index normalized difference index (NDI) ((B 769~797 – B 848~881/B 769~797 + B 848~881); (B 842 – B 740/B 842 + B 740)) derived from the transformed reflectance (the first-order derivate of reciprocal-logarithm (Log (1/R))′, second-order derivate of reciprocal-logarithm (Log (1/R)) ′′) showed significant correlation (correlation coefficient (r) = 0.61; r = 0.47) with SMC, and the correlation coefficient values higher than difference index (DI) and ratio index (RI). From the performance of 12 prediction models which were taken optimized indices as independent variables, the central wavelength reflectance model (Log (1/R))′′ and the average wavelength reflectance model ((Log (1/R)) ′ presented higher validation coefficients (coefficient of determination (R 2) = 0.61, root mean square error (RMSE) = 4.09%, residual prediction deviation (RPD) = 1.82; R 2 = 0.69, RMSE = 3.48%, RPD = 1.91) compared with other models. When verifying the accuracy, the model yields R 2 values of 0.619 and 0.701. These results indicated that the two-band hyper-spectral optimized indices (NDI) as an optimal indicator for quickly and accurately soil moisture content estimation. Combining the ground hyper-spectral data and satellite remote sensing image regional scale soil moisture content prediction provides a scientific reference for land-space integrated soil moisture content remote sensing monitoring.