Full Wave Half Maximum Research Articles

A theragnostic HIFU transducer and system for inherently registered imaging and therapy.

One big challenge with high intensity focused ultrasound (HIFU) is the difficulty in accurate prediction of focal location due to the complex wave propagation in heterogeneous medium even with imaging guidance. This study aims to overcome this by combining therapy and imaging guidance with one single HIFU transducer using the vibro-acoustography (VA) strategy. Based on the VA imaging method, a HIFU transducer consisting of 8 transmitting elements was proposed for therapy planning, treatment and evaluation. Inherent registration between the therapy and imaging created unique spatial consistence in HIFU transducer's focal region in the above three procedures. Performance of this imaging modality was first evaluated through in-vitro phantoms. In-vitro and ex-vivo experiments were then designed to demonstrate the proposed dual-mode system's ability in conducting accurate thermal ablation. Point spread function of the HIFU-converted imaging system had a full wave half maximum of about 1.2 mm in both directions at a transmitting frequency of 1.2 MHz, which outperformed the conventional ultrasound imaging (3.15 MHz) in in-vitro situation. Image contrast was also tested on the in-vitro phantom. Various geometric patterns could be accurately 'burned out' on the testing objects by the proposed system both in vitro and ex vivo. Implementation of imaging and therapy with one HIFU transducer in this manner is feasible and it has potential as a novel strategy for addressing the long-standing problem in the HIFU therapy, possibly pushing this non-invasive technique forward towards wider clinical applications.

Modelling and parameter quantification of plasmonic sensor based on external sensing for analysis of body liquids

This work introduces a new plasmonic refractive index (RI) sensor to detect and analyze human body liquids. Human body liquids consist of several fluids present in the human body. These liquids are water, blood, urine, sweat, breast milk, saliva, semen, etc. A RI sensor based on the RI variation is presented in this work to analyze these human body liquids. The RI sensor performance is investigated using traditional sensor parameters like confinement loss (CL), amplitude sensitivity (AS), wavelength sensitivity (WS), sensor resolution (SR), full wave half maximum (FWHM) and figure of merit (FOM). Dual mode investigation is performed in this work for the sensor model. The sensor model has presented WS more than 12000nm/RIU for the x−pol. and y−pol. respectively. AS reported for both polarization modes is more than 10000RIU−1. The SR evaluated is in the order of 10−6. The FOM of the sensor model is 91.60RIU−1 and 87.54RIU−1 for x−pol. and y−pol. respectively. Thus the sensor model presented in this work has shown sensitive parameters for detecting human body liquids.

Design of novel Penta core PCF SPR RI sensor based on fusion of IMD and EMD techniques for analysis of water and transformer oil

This work presents a “refractive index” sensor based on “photonic crystal fiber” and “surface plasmon resonance” phenomenon. A combination of Gold (Au) with Titanium Nitride (TiN) is used as a metallic layer in the presented sensor design. Water and transformer oil having RI1.330 and RI1.340 are analyzed through a developed spectroscopy setup which lays the condition for the RI sensor designing. A new relationship between transmission (%), absorbance (AU), and refractive index (RI) is developed and presented in this article. The sensor analysis is performed using the “finite element method” and “perfectly matched layer” conditions. The proposed sensor has obtained a “wavelength sensitivity (WS) ” of 10000nm/RIU and 11000nm/RIU correspondings to TM mode and TE mode, respectively. A high “amplitude sensitivity (AS) ” of 11280RIU-1 and 7550RIU-1 is obtained for TM mode and TE mode, respectively. The “sensor resolution (SR) ” of 1.00×10-5RIU and 9.09×10-6RIU are reported for TM mode and TE mode, respectively. High linear fitting between resonance wavelength and RI, “full-wave half maximum (FWHM)” and “figure of merit (FOM)” are also reported for the proposed sensor. The peak values of the sensing parameters are obtained for RI1.330 and RI1.340, corresponding to the TM mode and TE mode, respectively.

Design and fabrication of off-axis meta-lens with large focal depth

<sec>A kind of off-axis meta-lens with large focal depth based on a single-layer metasurface is designed and fabricated. Our proposed off-axis focus is realized by combining the two functions of deflection and focus through phase superposition method, and the focal depth can be increased by optimizing the input aperture and off-axis deflection angle. Three-dimensional finite difference time domain (FDTD) method is used for numerical simulation to construct the off-axis meta-lens, then the off-axis meta-lens is fabricated and its focus performance is tested in a microwave anechoic chamber.</sec><sec>Experimental results indicate that at the designed electromagnetic wave frequency (9 GHz), the measured off-axis deflection angle is 27.5° and the focal length is 335.4 mm, which agree with the designed values of 30° and 350 mm. The measured full-wave half-maximum (FWHM) at the focal point is 48.2 mm, however, the simulated FWHM is 40.2 mm, which means that the imaging quality of the measured focus spot is slightly worse than the simulated one. This is mainly due to the fact that the actual parameters of the fabricated meta-lens are inconsistent with simulated parameters. In addition, during the measurement, the large sampling interval in the x- direction also leads to experimental errors.</sec><sec>The focusing efficiency of the off-axis meta-lens at the working frequency of 9 GHz is calculated to be 16.9%. The main reason for the low focusing efficiency is that the plasmonic metasurface works in the transmission mode, which can manipulate only the cross-polarized component of the incident wave, and the maximum efficiency will not exceed 25%. Moreover, the focal depths at 8 GHz, 9 GHz and 10 GHz are 263.2 mm, 278.5 mm and 298.2 mm, respectively, which are 7.02 times, 8.36 times and 9.98 times the corresponding wavelengths, indicating that a larger focal depth off-focus meta-lens is achieved. </sec><sec>This kind of off-axis meta-lens has a simple structure, good off-axis focus ability and large focal depth, which has potential applications in a compact and planar off-axis optical system and large focal depth imaging system. Although the working waveband in this article is the microwave band, according to the size scaling effect of the metasurface, it is also possible to design a large focal depth off-axis meta-lens in other bands such as visible light and terahertz bands by using the same method.</sec>

Effect of Franz–Keldysh absorption on the short optical pulse generation in Transistor Laser

In this work, the effect of Franz–Keldysh (FK) absorption on the short optical pulse generation in Transistor Laser (TL) is analyzed. Franz–Keldysh (F–K) Absorption coefficient is incorporated in the rate equations and solved numerically by fourth order Runge–Kutta (R–K) method. Short optical pulses are generated for various values of collector to base voltage. The output optical power is found to decrease with increasing reverse collector to base voltage. The magnitude of peak optical power and full width half maximum (FWHM) are predicted for various values of VCB. The collector base reverse bias voltage is varied from 0 V to 3 V. The peak optical pulse power is found to decrease with increasing reverse collector to base voltage. Full width half maximum is found to increase with increasing reverse collector to base voltage (VCB). The maximum peak optical power of 156.2 mW and minimum FWHM of 17.97 ps are predicted for the unbiased VCB at the base current amplitude of 128 mA. The optimum value of peak optical pulse power of 45.89 mW and full wave half maximum of 24.21 ps are obtained for the VCB value of 1.5 V at the base current amplitude of 96 mA.

Synthesis and characterisation of VG nanosheets on silica aerogel by plasma‐enhanced chemical vapour deposition method

Vertical graphene (VG) nanosheets are directly grown on silica aerogel and silicon substrate (100) by plasma-enhanced chemical vapour deposition process in the presence of hydrogen as a reducing agent at atmospheric pressure at 800°C. The physiochemical properties of the nanohybrid were thoroughly characterised by Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The presence of full wave half maximum of D, G and D′ indicates VG nanowalls. The height (≅50 nm) of the VG nanowalls were confirmed by SEM and Raman spectroscopy but AFM reveals it as ≅ 15 nm. Surface and cross-sectional SEM show the uniform distribution of vertical growth of nanowalls and the AFM revealed surface morphology of VG nanowalls.

Electrocatalytic Activity of Functionalized Carbon Paper Electrodes and Their Correlation to the Fermi Level Derived from Raman Spectra

Carbon paper electrodes are employed for different electrochemical applications such as flow batteries and fuel cells. However, redox reactions such as VO2+/VO2+ in a vanadium redox flow battery have been found to possess relatively slow kinetics, resulting in significant activation losses during operation. In this work, we demonstrate a facile and scalable method for nitrogen doping of carbon paper electrodes, leading to superior electrocatalytic activity. The effects of pyrolytic pretreatments under different conditions on the performance of carbon paper were also studied to elucidate their electrocatalytic activity from a material physics perspective, using Raman spectroscopy. The 2D Raman signature, a specific feature of the carbon structures, was employed to understand the effect of different pretreatments on the Fermi level of the carbon papers, which could help us elucidate their intrinsic electron transfer kinetics. The full wave half-maximum of the 2D Raman band and the intensity ratio I2D/IG wer...

Influence of CuO and Al2O3 addition on the optical properties of sodium zinc phosphate glass absorption filters

The phosphate glasses having chemical composition of 45P2O5-(35-y)ZnO-(20-x)Na2O-xCuO-yAl2O3 (0≤x≤5, 0≤y≤4) have been prepared using the melt quenching technique. XRD analysis has been carried out on the investigated samples in order for confirming the amorphous nature. The density has been measured using Archimedes method and then the molar volume has been calculated. It is found that the density, unlike molar volume, increases with increasing CuO content. This is due to the difference in atomic weight between Cu and Na. Addition of Al2O3 causes a slight decrease in density and a large increase in molar volume. The ionic concentration, inter ionic distance and oxygen packing density have been calculated for all investigated glasses. Using optical absorption, the optical bandgap has been calculated and found to decrease with increasing CuO concentration. This decrease becomes slower in the presence of Al2O3 which makes an increase in the bandgap at the the absence of CuO. The transmission spectrum of the investigated glasses shows that the samples containing CuO behave as bandpass filters. the characterized parameters of these filters, i.e. area, center, width, height and full wave half maximum (FWHM) of bandpass, have been estimated. These parameters have been found to be more affected by CuO and Al2O3 addition. The refractive index, extinction coefficient, real and imaginary part of the dielectric constant have also been calculated at the bandpass.

Clear manifestation of phonon anomaly in single-layer graphene by chemical p-type doping

A phenomenon of phonon anomaly is clearly observed in single-layer graphene (SG) doped chemically with AuCl3 by using electric field effect-induced Raman spectroscopy. The variations of G-mode frequency and full-wave half-maximum in pristine graphene are asymmetric for positive and negative charging, but become more symmetric after the p-type doping due to the softening of the G band. The shows a steplike variation at doping concentrations of 10 and 20 mM because the AuCl3 doping is uniformly done, thereby making the charge density of graphene uniformly distributed, consistent with theoretical expectation. A flat region of between Fermi levels = ± ħωG/2, instead of its two logarithmic divergences as theoretically expected, is observed even in doped SG. These results suggest that the observation of the phonon anomaly is facilitated due to the charge uniformity improved by the doping even though it is not enough to show such divergences.

Proposal of BeZnTe/ZnSeTe superlattice quasi-quaternaries on InP substrates for yellow/green light emitting devices

We proposed BeZnTe/ZnSeTe superlattice quasi-quaternaries (SLQQs) as an active layer material replaced with BeZnSeTe quaternaries for yellow/green light emitting devices. BeZnTe/ZnSeTe SLQQs with various layer thickness combinations of BeZnTe and ZnSeTe were grown on InP substrates by a molecular beam epitaxy (MBE). In photoluminescence (PL) measurements at room temperature, high PL intensities were obtained for the SLQQs compared with BeZnSeTe. The peak wavelength was controlled from 589 to 480nm by changing the layer thickness combination (BeZnTe/ZnSeTe) from 1 monolayer (ML)/20ML to 4ML/2ML. Applying the SLQQ for the active layer, LEDs were fabricated on n-type InP substrates. Single-peak yellow electroluminescence at 584nm was observed with the full wave half maximum (FWHM) of 105meV.

Synthesis, characterization and microwave dielectric properties of nanocrystalline CaZrO3 ceramics

Abstract The synthesis, characterization and microwave dielectric properties of ceramic calcium zirconate (CaZrO 3 ) nanoparticles synthesized by combustion process are reported in this paper. The X-ray diffraction studies confirm that phase formation is complete on annealing the as-prepared sample at 700 °C. The average particle size calculated from full wave half maximum (FWHM) using Scherer formula is ∼33 nm. The phase purity of CaZrO 3 ceramic has been examined using differential thermal analysis (DTA), thermo gravimetric analysis (TGA) and Fourier transform of infrared spectroscopy (FTIR). The nanopowder was sintered at an optimized temperature1500 °C for 4 h and obtained about 98% of the theoretical density. The morphology of the sintered pellet was studied with scanning electron microscopy (SEM). The dielectric constant of 23.8, quality factor of ( Q u × f ) of 30600 GHz and a temperature coefficient of resonant frequency ( τ f ) of 1.4 ppm/°C is observed at 5.65 GHz. The high quality factor and very low τ f makes this sample suitable for microwave dielectric resonator applications.

A novel dual focus objective lens for DVD/CD pick-up head

A new dual focus objective lens of combining aspherical surfaces of DVD and CD for DVD/CD pick-up head was designed. Numerical analysis based on the diffraction model were studied to trade off the spot size, side lobe, and energy ratio of DVD and CD. The hybrid aspherical surfaces of DVD and CD are optimized for low aberration. The spot size of full wave half maximum (FWHM) are 0.553 and 0.88 /spl mu/m for DVD and CD, respectively, measured from thus constructed double rings lens.

The influence of annealing processes on the structural, compositional and electro-optical properties of CuIn0.75Ga0.25Se2 thin films

Crystalline defects, such as the density of voids, grain boundaries and dislocations, in Cu(In,Ga) Se2 absorber layers depend on the fabrication conditions and determine to a large extent the efficiency of photovoltaic devices. The material properties, however, can be improved significantly by using post-deposition processes. In this paper, the effects of post-deposition heat treatments on properties of CuIn0.75Ga0.25Se2 (CIGS) thin films are investigated. Selected flash evaporated samples were subsequently processed under several sets of conditions, including vacuum, selenium, inert (argon) and forming gas (a 9:1 mixture of N2:H2) ambients, at different temperature and times. Structural, compositional and electro-optical properties of both as-deposited and annealed films were studied using a variety of analytical techniques. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies of the films showed a columnar grain structure with strong preferred orientation, which after heat treatments relaxed to give a chalcopyrite structure. Raman analysis showed that the annealing process reduced the full-wave half-maximum (FWHM) value from 20 to 10 cm−1 indicating a change in both film composition and microstructure. In addition, X-ray fluorescence (XRF) and Rutherford backscattering spectroscopy (RBS) revealed that the composition was approaching that of the polycrystalline starting material. Both n- and p-type conductivities were observed with resistivity values in the range 10−1 to 106 Ω cm. Annealing in selenium atmosphere altered the n-type conductivity to p-type. To confirm improvements in optical properties of annealed films, photoacoustic spectroscopy (PAS) was employed.

Characterization of Light Emitting Porous Polycrystalline Silicon Films

AbstractPolycrystalline silicon (poly-Si) thin films (∼700nm) were deposited by LPCVD, doped with 950°C phosphorous diffusion, and rendered porous by anodization and stain etching. From x-ray photoelectron spectroscopy, poly-Si films have atomic concentration of C(ls):0(ls):Si(2p) = 6%:15%:79%. However, porous poly-Si (PPS) films with weak photoluminescence (PL) have C:O:Si of 20%:38%:42%. For PPS films with strong PL, C:O:Si is 11%:38%:51%. From micro-Raman, scattered spectra for 632nm laser source has peak at 735nm and full wave half maximum (FWHM) of 76nm, and is similar to the PL spectra excited by 400nm uv laser source. High resolution transmission electron microscopy (TEM) study shows that PPS film is of complex structure and composes of numerous Si nano-crystals (1∼10nm) surrounded by amorphous materials.

Impact of annealing processes on the properties of CuIn 0.75Ga 0.25Se 2 thin films

The efficiency of a solar cells utilizing polycrystalline Cu(In,Ga)Se 2 is to a large extent limited by crystalline defects of the semiconductor. Depending on the fabrication process the density of grain boundaries and dislocations, can vary considerably. However, the material properties can be improved significantly by the subsequent processing steps. In this paper results obtained using various post deposition methods to improve the structural and electro-optical properties of CuIn 0.75Ga 0.25Se 2 (CIGS) thin films have been presented and discussed. Films deposited by the evaporation of pre-reacted polycrystalline CIGS onto glass substrate were subsequently processed under several sets of conditions including vacuum, selenium, inert and forming gas ambients at different temperature and times. The structural and electro-optical properties of both as-deposited and annealed films were studied using a variety of analytical techniques. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies of the films showed a columnar structure with strong <112> orientation, which after heat treatments was relaxed to form a chalcopyrite structure. Raman analysis showed that full wave half maximum (FWHM) value reduced from 20 to 10 cm −1 with the annealing process indicating a change in both film composition and microstructure. In addition, investigations using energy dispersive X-ray analysis (EDAX), X-ray fluorescence (XRF) and Rutherford backscattering spectroscopy (RBS) revealed that the composition was approaching that of the starting polycrystalline material. Both n- and p-type conductivities were observed and gave resistivity values in the range 10 −1 to 10 6 Ω cm. Annealing in selenium changed the observed n-type conductivity of the as-deposited films to p-type. Photoacoustic spectroscopy (PAS) have also been applied to verify the improvement in the optical properties of annealed films.