Comparison of the performance of uncooled CdHgTe PC and PEM 10.6 μm detectors

The ultimate performance of uncooled CdHgTe photon detectors for 10.6 μm radiation has been analysed. PC and PEM detectors based on CdHgTe homogeneous epitaxial layers or graded-gap structures are considered. The performance has been calculated numerically using a generalized model of PC and PEM effects in heterogeneous structures. Relatively high ultimate voltage responsivity and normalized detectivity for the detectors mentioned have been predicted. It has been shown that these detectors are better than other types of uncooled detectors as far as high-frequency modulation and the 10.6 μm wavelength range are concerned.     

Effect of nickel-oxide nanoparticle additive concentration and gamma irradiation on the structure and optical properties of polycarbonate

Nanotechnology is one of the world’s most promising new technologies. Pure polycarbonate (PC) and PC–nickel oxide (NiO) nanocomposite films have been deposited using the casting technique. The effects of NiO nanoparticle (NP) concentration (2, 5 and 10?wt%) on the structure and optical properties of PC have been studied. The resultant effect of NiO concentration has been investigated using X-ray diffraction and UV spectroscopy techniques. The results of nanocomposite samples compared to the pristine indicate the proper dispersion of NiO NPs in the PC matrix. Also, the addition of NiO NP to PC with 5% concentration causes a strong intermolecular interaction between NiO and PC, resulted in an increase in refractive index and increase in the amorphous phase. Thus, this sample was chosen to be a subject for further study to investigate the effect of gamma irradiation on its structure and optical properties. Samples from the 5% PC–NiO nanocomposite were irradiated with gamma doses in the range of 20–350?kGy. It is found that the gamma irradiation reduces the optical energy gap that could be attributed to the increase in the structural disorder of the irradiated PC–NiO nanocomposites due to cross-linking. In addition the isotropic character of the nanocomposites has been enhanced, reflected in the increase in refractive index.     

Electro- and magneto-optical switching of defect modes in one- dimensional photonic crystals

The transmission spectra of polarized light waves in a photonic crystal/liquid crystal (PC/LC) cell placed between crossed polarizers and controlled by an electric or magnetic field have been studied experimentally and theoretically. Electro- and magneto-optical switching based on the interference of polarized defect modes has been demonstrated. The transmission spectra of the PC/LC cell have been calculated as a function of the voltage applied to the LC layer and the magnetic field strength. The results of the calculations agree well with the experimental data.     

Photonic crystals and microlasers fabricated with low refractive index material

Although the investigation on photonic band gap materials has been done more than two decades, it is still a big challenge to fabricate three-dimensional photonic crystal (PC) possessing wide band gaps in visible range. In this article, we have reviewed recent progresses on fabricating the PC with low refractive index material in visible range. In contrast to the material with large refractive index, it is cheap to use low refractive index material in fabricating the PC and will be greatly beneficial for future industrial productions. The holographic method to fabricate such a PC has been introduced, applying it to the design of the microlaser has also been discussed.     

Photonic crystals and microlasers fabricated with low refractive index material

Although the investigation on photonic band gap materials has been done more than two decades, it is still a big challenge to fabricate three-dimensional photonic crystal (PC) possessing wide band gaps in visible range. In this article, we have reviewed recent progresses on fabricating the PC with low refractive index material in visible range. In contrast to the material with large refractive index, it is cheap to use low refractive index material in fabricating the PC and will be greatly beneficial for future industrial productions. The holographic method to fabricate such a PC has been introduced, applying it to the design of the microlaser has also been discussed.     

All angle negative refraction with the effective phase index of-1

We theoretically studied a left-hand structure based on a two-dimensional (2D) photonic crystal (PC)with a negative refractive index. The propagation of electromagnetic waves in the proposed PC structure is investigated through dispersion characteristic analysis and numerical simulation of field pattern. The designed PC structure can exhibit all angle negative refraction, and the corresponding effective refractive indices along all directions are almost same and close to the ideal value of -1. A flat lens formed from such a PC has been designed and its imaging properties have been investigated systematically.     

Basic aspects of microindentation in multilayered poly(ethylene terephthalate)/polycarbonate films

The microhardness H of multilayered poly(ethylene terephthalate) (PET)/polycarbonate (PC) films, produced by continuous layer multiplying coextrusion has been determined. These materials present rather uniform laminates up to thousands of layers in the micrometre and submicrometre range. The micromechanical properties have been investigated as a function of layer thickness of the single polymer components, the total number of layers, the film thickness and the influence of heat treatment. The microhardness of the microlayered structure has also been determined across the profile in the parallel direction to the packing of the layers. The hardness in the vicinity of the PET/PC phases has been examined. Results reveal that the influence of the interphase on the H values for the samples with a large number of layers is rather small. The most important parameter in determining the final hardness of the multilayered films is the ratio of the penetration depth to the thickness of the layer. Upon heating, a microhardness increase is observed as a consequence of a double contribution: the crystallization of the PET layers, on the one hand, and the physical ageing of the PC zones on the other.     

Effect of IR illumination on photocurrent spectra in CdS crystals

Low-temperature near-band-edge photoconductivity (PC) spectra of CdS crystals were studied as a function of IR illumination intensity in the PC quenching interval. The photocurrent quenching by IR light of the PC response profile has been investigated. An analysis of these relationships permitted establishing a direct connection between the r photoconductivity centers and the near-band-edge structure of the spectrum. The effect of “pinning” of majoritycarrier lifetime on the semiconductor surface has been discovered and interpreted. It is proposed that surface-acceptor states in CdS crystals play the part of surface photoconductivity centers. Fiz. Tverd. Tela (St. Petersburg) 41, 1181–1184 (July 1999)     

Study of current drain during electrochemical etching of polycarbonate detectors

Polycarbonate (PC) detector is one of the common detectors for neutron and radon gas detection. Using this detector it is possible to measure the dose in mSv, by counting tracks/cm² on an etched surface. In this paper, a special procedure has been suggested to determine the dose based on current drain during the etching process. In these experiments the effects of voltage, frequency, effective etched area, PC detector's thickness, etched area (one side or two sides), etching solution temperature and dose absorbed by the PC foil have been studied.The results obtained show the current drain variation for a voltage of 200–1600 V, a frequency of 2–10 kHz, effective area with a diameter of 2–12 cm, PC thickness of 125–250–375– and a temperature of etching solution of 25–.Lexan PC foils were exposed to doses of of neutrons. The unexposed foils were considered as the background (BG) foils. Most of the experiments were performed at a voltage of 800 V, a frequency of 2 and 8 kHz, foil thickness of , diameter of effective etched area of foils of 2, 6 and 12 cm, temperatures of 25 and and the etching process from 0 up to overload stage. Overload stage occurs when the foil becomes so thin due to growth of the tracks that it leads to sparking between phase and null that makes a hole in the foil.Current drain curves versus the function of the etching time are absolutely different for various doses from zero (BG) to 10 rad (BG up to ). This is true especially for the time interval from 3 h of etching up to overload stage. In this way, it is possible to obtain a calibration of PC detector net current drain based on its absorbed dose.In this experiment, the number and diameter of tracks and their relation with drain current and PC foil residual thickness at overload stage have been studied.The same experiment has been performed for various concentrations of radon gas (Bq/m3) as well.     

Principal-component amplitude compression for the hearing impaired

Principal-component amplitude compression, a means for matching speech to the reduced dynamic range in sensorineural hearing impairments, is a multiband approach aimed at preserving details of spectral shape while reducing overall level variation. The effect of compression has been studied for the first and second principal components (PC1 an PC2) of the short-term speech spectrum, which are roughly representative of overall level and spectral tilt, respectively. Compression of PC1 roughly equalizes consonant and vowel levels while compression of PC2 provides time-varying high-frequency emphasis. The effect on speech intelligibility of sensorineural hearing-impaired listeners of two principal-component compression system implementations, compression of PC1 and compression of both PC1 and PC2, was compared to that of linear amplification (LA), independent compression of multiple bands (MBC), and wideband compression (WC). Results indicate that compression of overall level as provided by compression of PC1 and WC improved intelligibility relative to LA over a 10- to 15-dB range of input levels. While MBC was beneficial in some cases, it did not provide higher intelligibility than WC. Compression of PC2 did not benefit but rather degraded performance relative to LA. Error analyses and band-level measurements indicate that the highest intelligibility is obtained when audibility is improved and the relative spectral shapes of different speech sounds are preserved.     

Effect of polymer blend types and gamma radiation on the physico-chemical properties of polycarbonate

Samples from polycarbonate (PC) were classified into two main groups. The first group was blended with Abietic acid (Rosin) with different compositions, while the second group was blended with ethylene-vinyl acetate (EVA) copolymer with almost the same composition. A comparative study of the effect of both Rosin and EVA concentration on the thermal stability of PC has been investigated using thermogravimetric analysis. The results show that blending with Rosin causes the dominance of degradation. Samples from PC with 20% Rosin blend were irradiated with gamma at the dose of range 20–300?kGy. The resultant effect of gamma radiation on the structural properties of the 20% Rosin/ 80%PC blend has been investigated using Fourier Transform Infrared FTIR spectroscopy. The results indicate that degradation of the polymer blend dominates, thus increases the creation of hot free radicals that leads to the formation of color centers in PC. In addition, the transmission of the 20% Rosin/80%PC samples as well as color changes was studied. The color intensity ΔE was greatly increased with increasing the gamma dose up to 300?kGy, accompanied by a significant increase in the blue color component.     

蟾毒灵对脂质体双分子层结构的影响:31P NMR研究

应用³¹P NMR方法研究了蟾毒灵(BF)对脂质体双分子层结构的影响.研究结果表明对于未经超声波处理的卵磷脂(PC),BF对磷脂双分子层膜具有稳定作用.另一方面,当PC经过超声波处理后,首次观测到纯PC的双分子层膜转变为胶束或微胞,后者的比例随着超声波处理的时间的增加而增加;而BF的存在可加速PC由双分子层结构向胶束相的转变.     

Integration of 2D photonic crystals with ridge waveguide lasers

2D triangular photonic crystals (PCs) have been integrated as laser mirrors in electrically pumped InGaAs/AlGaAs ridge waveguide lasers. The investigated PC lattice constants range from 160 to 400 nm with light incident along both main symmetry directions M and K. The observed cw laser performance is strongly dependent on both orientation and period of the PC. This behaviour is discussed using a 2D transfer matrix calculation of the PC reflectivity. As a demonstrator device relying on the 2D light confining properties of the PC, an active beamsplitter with a bending radius of 5 m is presented. Here, the PC is successfully used as cladding material in the S-bent regions of the ridge waveguide, significantly reducing the bending loss.     

Influence of gamma radiation on optical properties of Halloysite nanotubes incorporated polycarbonate nanocomposites

In the current research investigation, polycarbonate/hallyosite nanotubes (PC/HNTs) nanocomposite (NC) films have been successfully fabricated by solution intercalation technique using ultrasound energy in facile way which helps complete exfoliation of the HNTs in the matrix. The effect of Gamma irradiation-induced modifications of PC/HNTs NC have been studied in the dose range 200–500?kGy, irradiated with Co⁶⁰ source. The NC films have been evaluated by UV–visible spectroscopy, Fourier Transform Infrared spectroscopy, X-ray diffraction and scanning electron microscopic techniques in order to probe the effect of gamma radiation on the structural behaviors. The obtained results have been indicated that as the Gamma irradiation dosage increases from 200 to 500?kGy, phenolic group forms through scissoring of ester link of PC, which may cause PC to degrade and lose their property. At lower dosage (200?kGy), the effect is less and at higher dosage (500?kGy), the effect is significant and at 300 and 400?kGy, the effect is moderate and NC films retained their properties. The irradiation effect is most significant and effective at the higher dosage range. UV–visible spectroscopy shows a noticeable reduction in the energy band gap due to gamma irradiation.     

Photoconduction in tunnel-coupled Ge/Si quantum dot arrays

The photoconduction in a tunnel-coupled Ge/Si quantum dot (QD) array has been studied. The photoconductance (PC) sign can be either positive or negative, depending on the initial filling of QDs with holes. The PC kinetics has a long-term character (10²?10⁴ s at T = 4.2 K) and is accompanied by persistent photoconduction (PPC), whereby the PC value is not restored on the initial level even after relaxation for several hours. These phenomena are observed upon illumination by light with photon energies both greater and smaller than the silicon bandgap. A threshold light wavelength corresponding to a long-term PC kinetics depends on the QD filling with holes. A model describing the observed PC kinetics is proposed, according to which the main contribution to the PC is related to the degree of QD filling with holes. By applying the proposed model to the analysis of PC kinetics at various excitation levels, it is possible to determine the dependence of the hopping conductance on the number of holes per QD. The rate of the charge carrier density relaxation exponentially depends on the carrier density.     

Preparation and characterization of phospholipid stabilized uniform sized magnetite nanoparticles

The effects of phosphatidylcholine (PC) on the growth of magnetite superparamagnetic particles have been investigated. These coated particles give stable suspension in solvents like chloroform and were used for magnetoliposome preparation. The superparamagnetic particles and magnetoliposomes were characterized by X-ray diffraction (XRD), FTIR, Transmission electron microscopy (TEM) and SQUID measurements. The result shows that PC acts as capping agent to restrict the growth of the particles.     

Understanding the patterns in the BZ reagent

Conclusion It has been pretty well established that the PC system examined in this talk is a realistic model for the spatially distributed BZ reagent under commonly occurring parameter conditions. The analysis of the system is straightforward and provides a clear picture of the mechanism behind the appearance of fronts, trains, solitary pulses, and target patterns, and behind the generation of spirals, under those conditions. In fact, the PC model has been remarkable successful in reflecting observed phenomena (see a discussion of this point in Ref. 34). Spiral-like structures in 3-space have been called scrolls by A. Winfree; their generation can also be easily understood along these same lines, as resulting from local disturbances of plane solitary waves propagating through 3-space. Fully developed spirals can likely be understood in this same PC context as solutions of the free boundary problem presented in Section 7; more mathematical and numerical work should be done on that problem.Very possibly other parameter conditions exist for which similar spatial patterns can be seen in the BZ reagent, but for which the PC framework is not appropriate; and very likely other excitable biological or chemical media, supporting such patterns, may require other models for their understanding. Nevertheless, it appears likely that models having many of the properties of the one studied here will play a significant role in the unraveling of these more complex systems.     

The single-longitudinal-mode operation of a ridge waveguide laser based on two-dimensional photonic crystals

An electrically driven, single-longitudinal-mode GaAs based photonic crystal (PC) ridge waveguide (RWG) laser emitting at around 850 nm is demonstrated. The single-longitudinal-mode lasing characteristic is achieved by introducing the PC to the RWG laser. The triangle PC is etched on both sides of the ridge by photolithography and inductive coupled plasma (ICP) etching. The lasing spectra of the RWG lasers with and without the PC are studied, and the result shows that the PC purifies the longitudinal mode. The power per facet versus current and current-voltage characteristics have also been studied and compared.     

基于PC机的一种多功能声显微镜及可视化技术的研究

近来研制成功了一种基于ＰＣ机、我们称为“ＴＨＳＡＭＭ”型的多功能声显微镜。在ＰＣ机内插入采样率１ＧＳＰＳ的超高速Ａ／Ｄ卡和信号产生和接收卡,利用软件完成信号检测、处理、显示功能。仪器工作频率为１－１００ＭＨｚ;在检测样品时,同时多层显示Ａ、Ｂ、Ｃ扫描结果。根据声学理论、Ｍａｒｃｈｉｎｇ Ｃｕｂｅ等值面抽取方法和ＯｐｅｎＧＬ技术完成了三维数据的可视化处理,显示样品的内部三维结构。该系统已成功应用于多     

Morphology-property relationships in polycarbonate-based blends. I. Modulus

The tensile, dynamic mechanical and morphological properties of PC/HDPE, PC/LDPE and PC/PS blends have been investigated with the intent of clarifying the major factors governing the modulus of these essentially incompatible blends. Scanning electron microscopy shows that all of the PC/HDPE, PC/LDPE and PC/PS blends have a domain structure whose morphology is strongly dependent on the concentration of the dispersed phase; when the dispersed phase concentration is less than 15%, the domains are mostly of spherical shape, while above 20% agglomeration takes place to form rodlike structures. Dynamic mechanical data shows there is essentially no adhesion at the PC-HDPE and PC-LDPE boundaries, while there is appreciable adhesion at the PC-PS interface. The existence of an intermixed zone was postulated to explain this interfacial adhesion. Morphological and thermal analysis results also indicate that both the HDPE and LDPE inclusions are loosely sitting in the holes in the PC matrix while the PS inclusions are compactly embedded in the PC matrix. These differences in boundary nature give marked effects on the tensile properties including the modulus. For the modulus, PC/HDPE and PC/LDPE blend systems can be regarded to be mechanically equivalent to a PC matrix alone with holes in it when the dispersed phase concentration is lower than 15%, while in the case of PC/PS blends the PS inclusions contribute substantially to the sample's overall modulus.