Transverse-electric/transverse-magnetic polarization converter using 1D finite biaxial photonic crystal

We show that by using a one-dimensional anisotropic photonic structure, it is possible to realize optical wave polarization conversion by reflection and transmission processes. Thus a single incident S(P) polarized plane wave can produce a single reflected P(S) polarized wave and a single transmitted P(S) polarized wave. This polarization conversion property can be fulfilled with a simple finite superlattice (SL) constituted of anisotropic dielectric materials. We discuss the appropriate choices of the material and geometrical properties to realize such structures. The transmission and reflection coefficients are calculated in the framework of the Green's function method. The amplitude and the polarization characteristics of reflected and transmitted waves are determined as functions of frequency, wave vector k(parallel) (parallel to the interface), and the orientations of the principal axes of the layers constituting the SL. Specific applications of these results are given for a SL consisting of alternating biaxial anisotropic layers NaNO(2)/SbSI sandwiched between two identical semi-infinite isotropic media.     

Simultaneous heat and moisture transport in porous building materials: evaluation of nonisothermal moisture transport properties

The paper presents a mathematical model for calculating the nonisothermal moisture transfer in porous building materials. The simultaneous heat and moisture transfer problem was modeled. Vapor content and temperature were chosen as principal driving potentials. The coupled equations were solved by a numerical method. An experimental methodology for determining the temperature gradient coefficient for building materials was also proposed. Both the moisture diffusion coefficient and the temperature gradient coefficient for building material were experimentally evaluated. Using the measured moisture transport coefficients, the temperature and vapor content distribution inside building materials were predicted by the new model. The results were compared with experimental data. A good agreement was obtained.     

Ionic Glass–Gated 2D Material–Based Phototransistor: MoSe2 over LaF3 as Case Study

Modulating the carrier density of 2D materials is pivotal to tailor their electrical properties, with novel physical phenomena expected to occur at a higher doping level. Here, the use of ionic glass as a high capacitance gate is explored to develop a 2D material–based phototransistor operated with a higher carrier concentration up to 5 × 10¹³ cm^?2, using MoSe₂ over LaF₃ as an archetypal system. Ion glass gating reveals to be a powerful technique combining the high carrier density of electrolyte gating methods while enabling direct optical addressability impeded with usual electrolyte technology. The phototransistor demonstrates I_ON/I_OFF ratio exceeding five decades and photoresponse times down to 200 µs, up to two decades faster than MoSe₂ phototransistors reported so far. Careful phototransport analysis reveals that ionic glass gating of 2D materials allows tuning the nature of the carrier recombination processes, while annihilating the traps' contribution in the electron injection regime. This remarkable property results in a photoresponse that can be modulated electrostatically by more than two orders of magnitude, while at the same time increasing the gain bandwidth product. This study demonstrates the potential of ionic glass gating to explore novel photoconduction processes and alternative architectures of devices.     

缝纫针使用时间对缝制质量的影响

缝纫针是缝纫机上的一个小部件,但它对缝纫质量起着十分重要的作用,并最终影响缝纫外观。从缝纫强力和线迹弹伸性两方面论述了缝纫针的使用时间对缝制质量的影响。     

Ac-electronic and dielectric properties of semiconducting Phthalocyanine compounds: A comparative study

The AC-electronic and dielectric properties of different phthalocyanine films(ZnPc,CuPc,FePc,and H2Pc)were investigated over a wide range of temperature.Both real and imaginary parts of the dielectric constant("D"1–i"2/were found to be influenced by temperature and frequency.Qualitatively the behavior was the same for those compounds;however,the central atom,film thickness,and the electrode type play an important role in the variation of their values.Therelaxationtime,,wasstronglyfrequency-dependentatalltemperaturesandlowfrequencies,whileaweak dependency is observed at higher frequencies.The relaxation activation energy was derived from the slopes of the fitted lines of ln and the reciprocal of the temperature(1/T).The values of the activation energy were accounted forthehoppingprocessatlowtemperatures,whileathermallyactivatedconductionprocesswasdominantathigher temperatures.Themaximumbarrierheight,Wm,wasfoundtobetemperatureandfrequencydependentforallphthalocyanine compounds.The value Wm depends greatly on the nature of the central atom and electrode material type.The correlated barrier hopping model was found to be the appropriate mechanism to describe the charge carrier’s transport in phthalocyanine films.     

Étude de la génération d’impulsions brèves d’un laser DFB à trois contrôles de phases (3QWS-DFB)

The purpose of this paper is to study the generation of short pulses of the three quarter wave shift distributed feedback (3Qws-dfb) laser by using switching gain technique. We have used the temporal domain model (Tdm) which is a multimode spatio-temporal model that considers simultaneously all the modes of the overall intra-cavity field as well as the two following nonlinear effects, the spectral hole burning (Shb) and the gain saturation. Obtained results showed that a 3Qws-dfb laser can generate short pulses in accordance with Fourier criteria. These results show that 3Qws-dfb lasers are potential candidates as monomode optical sources for long distance high bit rate telecommunications.