Temperature Dependence Of Transmission Research Articles

Influence of intrinsic electronic properties on light transmission through subwavelength holes on gold and MgB2thin films

We show how intrinsic material properties modify light transmission through subwavelength hole arrays on thin metallic films in the THz regime. We compare the temperature-dependent transmittance of Au films and MgB$_{2}$ films. The experimental data is consistent with analytical calculations, and is attributed to the temperature change of the conductivity of both films. The transmission versus conductivity is interpreted within the open resonator model when taking the skin depth into consideration. We also show that the efficiency of this temperature control depends on the ratio of the transmission peak frequency to the superconducting energy gap in MgB$_{2}$ films.

A phenomenological model of electronic band structure in ferroelectric Pb(In 1/2Nb 1/2)O 3–Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 single crystals around the morphotropic phase boundary determined by temperature-dependent transmittance spectra

The optical properties of ferroelectric Pb(In 1/2Nb 1/2)O 3–Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 (PIN–PMN–PT) single crystals around the morphotropic phase boundary (MPB) have been investigated using ultraviolet–infrared transmittance spectra in the temperature range of 8–300 K. Based on the temperature-dependent spectral measurement of the band gap, we propose a phenomenological model of band structure vs. temperature to explain both the negative and positive band narrowing coefficient dE gd / dT in ferroelectric PIN–PMN–PT crystals around the MPB where multiple phases coexist. The peculiar positive coefficient only exists in the fragile multiphase region of the MPB, while the negative coefficient, caused by thermal expansion of the lattice and renormalization of the band structure by electron–phonon interaction, exists in the rhombohedral or tetragonal single-phase region as well as in the stationary multiphase region of the MPB. The origin of the positive coefficient is a long-range increasing fraction of coexistence from the monoclinic phase with small band gap to rhombohedral phase with large band gap at elevated temperature. In agreement with optical transmittance results of PMN–PT/PIN–PMN–PT, the model predicts that these unusual positive band narrowing coefficients may exist for all ferroelectrics around the MPB where the coexistence of phases lacks thermodynamic stability.

Thermochromism of VO2 Nanoparticles: Calculated Optical Properties and Applications to Energy Efficient Windows

ABSTRACTThermochromic materials have temperature-dependent optical properties. This paper discusses the limitations of thermochromic VO2 films for energy efficient fenestration and shows from calculations that nanocomposites containing VO2 can have superior properties and display high luminous transmittance and large temperature-dependent solar transmittance modulation. Even better results may be found for nanoparticles of VO2:Mg.

Fabrication of a Thermoresponsive Biohybrid Double Hydrophilic Block Copolymer by a Cofactor Reconstitution Approach

The fabrication of a thermoresponsive biohybrid double hydrophilic block copolymer (DHBC) by a cofactor reconstitution approach is reported. Poly(N-isopropylacrylamide) (PNIPAM) bearing a porphyrin moiety at the chain terminal, PPIXZn-PNIPAM, is synthesized by the combination of ATRP and a click reaction. The subsequent cofactor reconstitution process between apomyoglobin and PPIXZn-PNIPAM affords well-defined myoglobin-b-PNIPAM protein-polymer bioconjugates. Behaving as typical responsive DHBCs, the obtained myoglobin-b-PNIPAM biohybrid diblock copolymer exhibits thermo-induced aggregation behavior in aqueous solution as a result of the presence of the thermoresponsive PNIPAM block, as revealed by temperature-dependent transmittance, dynamic laser light scattering measurements, transmission electron microscopy, and scanning electron microscopy. This work represents the first report of the preparation of responsive biohybrid DHBCs by the cofactor reconstitution process.

Determination of Phase Transition Temperatures by the Analysis of Baseline Variations in Transmittance Infrared Spectroscopy

A simple method for obtaining phase transition temperatures is proposed. It is based on absolute variations of a baseline in a temperature-dependent mid-infrared transmittance spectral data set recorded for a sample KBr pellet. The method is rapid, inexpensive, and completely free of any personal bias. The method efficiency was corroborated by measuring the phase transitions of mesomorphic (trans-4-heptyl cyclohexanecarboxylic acid) and polymorphic compounds (polycyclic aromatic hydrocarbons and phenylacetylenes). In addition, the exothermic decomposition of phenylacetylenes was also monitored, thereby opening the possibility for simple and rapid monitoring of chemical reactions in solid and liquid phase. A great prospect of the method as an economical way of establishing critical temperature regions for analytical and quality control purposes is foreseen.

Magnetotransmission and magnetoresistance in film manganite/ferrite heterostructures

For a series of epitaxial and polycrystalline manganite/ferrite heterostructures grown on different substrates, the interelation between light transmission in the IR range and electrical resistance, magnetotransmission, and magnetoresistance has been studied in a temperature range of 80–385 K. It has been established that the temperature dependences of transmission and magnetotransmission in the manganite/ferrite heterostructures on different substrates are similar to the temperature dependences in the films of manganites on the same substrates. It has been shown that in a magnetic field of 8 kOe applied perpendicular to the surface of the epitaxial manganite/ferrite heterostructure the magnetotransmission increases by ∼40% relative to its value in the single-layer epitaxial films.

Synthesis and micellization behavior of stimuli-responsive polypeptide hybrid triblock copolymer

Polypeptide hybrid triblock copolymer, poly(L-glutamic acid)-b-poly(propylene oxide)-b-poly (L-glutamic acid) (PLGA-b-PPO-b-PLGA), was synthesized by the ring-opening polymerization of benzyl-L-glutamic N-carboxyanhydride (BLG-NCA) using poly(propylene glycol) bis(2-aminopropyl ether) as initiator, followed by the subsequent deprotection step. The obtained double hydrophilic triblock copolymer exhibits “schizophrenic” micellization behavior in aqueous solution upon dually playing with solution pH and temperature. The multi-responsive micellization behavior of this polypeptide hybrid triblock copolymer has been thoroughly investigated by 1H NMR, laser light scattering (LLS), temperature-dependent optical transmittance, and circular dichroism spectroscopy (CD).

THz transmittance in one-dimensional superconducting nanomaterial-dielectric superlattice

Electromagnetic wave transmission at THz in a one-dimensional superconducting metallo-dielectric superlattice has been theoretically investigated based on the transfer matrix method together with superconductor electromagnetics. The results of transmittance spectra show the existence of a cutoff frequency in such a bilayer periodic structure. Electromagnetic wave is allowed to propagate through the structure when its frequency is higher than cutoff frequency. However, it will be totally reflected at a frequency below cutoff frequency. This cutoff frequency is strongly dependent on thicknesses of the superconductor and dielectric layers, and the temperature as well. In temperature-dependent transmittance, strong oscillations can be seen at higher temperatures.

Synthesis and thermosensitive behavior of dextran graft copolymers containing poly(N-vinylcaprolactam) side chains

New graft copolymers were synthesized by grafting N-vinylcaprolactam onto dextran. Their composition and structure were investigated by elemental analyses, infrared spectra and thermogravimetric analyses. By optical transmittance measurements, it was found that the aqueous solutions of these graft copolymers showed a temperature-dependent transmittance change due to the introduction of thermosensitive poly(N-vinylcaprolactam) graft chains. Moreover, the lower critical solution temperature (LCST) of the graft copolymer in aqueous solution was dependent on its grafting extent and concentration. The LCST value was found to increase with the increase of the grafting extent and decrease with the increase of the copolymer concentration. With these stimuli-response properties, such polysaccharide derivative may hold potential applications in biomedicine and biotechnology.

InNAsSb Single Crystals with Cutoff Wavelength of 11–13.5 µm Grown by Melt Epitaxy

We grew, for the first time, InNAsSb single crystals with a room temperature cutoff wavelength of 11–13.5 µm on (100) InAs substrates by melt epitaxy (ME). The crystals were characterized using X-ray diffraction, electron-probe microanalysis (EPMA), temperature-dependent transmittance and Van der Pauw measurements. An obvious redshift of cutoff wavelength was observed with increasing N concentration from 13 to 19% in the epilayers. The cutoff wavelength varies from 12.5 to 8.9 µm in the temperature range from 300 to 77 K. The thick epilayers show a good macroscopic homogeneity of the composition. An electron mobility of 55,800 cm2/Vs with a carrier density of 1.08×1016 cm-3 was obtained at 77 K, indicating possible applications for infrared photodevices.

Temperature Dependence of Transmission and Emission Spectra in MOCVD-Grown AlGaN Ternary Alloys

Optical absorption, emission, and carrier recombination characteristics of Al x Ga 1-x N epilayers (x = 0.17, 0.26, and 0.33) were systematically studied by means of transmission, photoluminescence (PL), and time-resolved PL spectroscopy, respectively. A typical energy-gap shrinkage behaviour with temperature was confirmed for all the Al x Ga 1-x N epilayers by transmission measurements. However, we observed anomalous PL temperature dependences such as a decrease-increase-decrease behavior of the PL peak energy shift and an increase-decrease-increase behavior of the spectral width broadening with increasing temperature. The anomalous temperature-induced emission shift is attributed to energy tail states due to alloy potential inhomogeneities in the Al x Ga 1-x N epilayers with large Al content.

Temperature Dependence of Transmission and Emission Spectra in MOCVD-Grown AlGaN Ternary Alloys

Optical absorption, emission, and carrier recombination characteristics of Al x Ga 1-x N epilayers (x = 0.17, 0.26, and 0.33) were systematically studied by means of transmission, photoluminescence (PL), and time-resolved PL spectroscopy, respectively. A typical energy-gap shrinkage behaviour with temperature was confirmed for all the Al x Ga 1-x N epilayers by transmission measurements. However, we observed anomalous PL temperature dependences such as a decrease-increase-decrease behavior of the PL peak energy shift and an increase-decrease-increase behavior of the spectral width broadening with increasing temperature. The anomalous temperature-induced emission shift is attributed to energy tail states due to alloy potential inhomogeneities in the Al x Ga 1-x N epilayers with large Al content.

Microwave properties of a composite superconducting structure in the mixed state

A theoretical study on microwave properties of a composite layered structure of twin high- T c superconducting thin-films separated by a nonlinear dielectric is presented. Microwave reflectance and transmittance are calculated within the framework of the self-consistent treatment of vortex dynamics for the superconducting films in the mixed state. The effects of nonlinear field- and temperature-dependent dielectric permittivity of SrTiO 3 are specifically discussed. Two significant peaks arising from nonlinearity of the permittivity are found in the temperature-dependent microwave reflectance and transmittance. As for the field-dependent microwave response, we suggest that the strongly field-dependent nonlinear permittivity of SrTiO 3 at low temperature does not affect the microwave transmittance and reflectance.

Effect of monoacrylate type in UV curable PU acrylate based bicontinuous polymer/liquid crystal networks

Polymer network liquid crystals (PNLC) have been prepared from ultraviolet-curable polyurethane acrylate (PUA) and a nematic liquid crystal mixture (BL002). Effects of monoacrylate type on film morphology, temperature-dependent off-state transmittance, and electro-optic performance of the film have been studied. Among three types of monoacrylates incorporated (EHA(2-ethyl hexyl acrylate), MMA (methylmethacryalte), NVP (N-vinylpyrrolidone)), EHA-based PUAs gave the greatest polymer–LC phase separation, lowest threshold (V10), and operating (V90) voltages, and the effect was more pronounced in monoacrylate/triacrylate systems than in monoacrylate/diacrylate systems. Contact angle measurement offers a clue to the observed morphology and electro-optic behavior. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1393–1399, 1998

Temperature-dependent ozone transmittance in a mono-layer atmospheric model

Abstract The need for information on spectral ozone transmittance arises from the temperature-dependence of the ozone absorption coefficients in Hartley-Huggins bands (200–360 nm). The methodological approach reported here employs the convolution between vertical profiles of ozone and temperature to determine the ozone layer's effective temperature. Introducing temperature makes it possible better to approximate UV-spectral ozone transmittance values computed by LOWTRAN-7.

Light-scattering analysis of the temperature-dependent transmittance of a polymer-dispersed liquid-crystal film in its isotropic phase.

We have measured the temperature-dependent transmittance of a polymer-dispersed liquid-crystal (PDLC) film in its isotropic phase. We show that the measured transmittance can be quantitatively described within experimental error over a wide temperature range using Rayleigh-Gans light-scattering theory with film parameters previously determined from refractive-index studies and scanning electron microscopy; no freely adjustable parameters or normalization constants are necessary to describe the measured transmittance data. We obtained equally good agreement between theory and experiment regardless of whether or not we included droplet correlation effects in our transmittance calculations. The precision with which the refractive index of the matrix material in a cured PDLC film can be determined is the main factor preventing us from quantitatively assessing the role of droplet correlation effects in PDLC films at this time. We have also compared the transmittance characteristics of our PDLC film with the published transmittance of a film composed of liquid crystal in the pores of a solid matrix. We find that the published results are consistent with the form of the equations of scattering theory; however, quantitative agreement between measured and calculated transmittance would require film parameters different from those published.

The temperature-dependent absorption edge of MBE-grown Pb0.82Sn0.18Te film in the infrared region

The changes in the absorption spectra and the variation of the band edge with temperature have been investigated for an MBE-grown Pb0.82Sn0.18Te film for temperature-dependent transmittance spectra recorded over the temperature range 90 to 600 K. Analysis of these spectra showed that below 175 K the possible fundamental transition is direct, while at higher temperature it is indirect. Below 425 K dEg1/dT was 4*10-4 eV K-1 with Eg1(0)=0.102 eV for the direct transition. dEg2/dT and Eg2(0) were 3*10-4 eV K-1 and 0.116 eV respectively for the indirect transition. Above 425 K, dEg3/dT and Eg3(0) were 1.1*10-4 eV K-1 and 0.218 eV for the direct transition. dEg4/dT and Eg4(0) were 1.2*10-4 eV K-1 and 0.192 eV respectively for the indirect transition. These results can be explained well using the proposed band model for this material.

Temperature-dependent transmittance of luminous and solar radiation for quartz fibers immersed in carbon tetrachloride

We study thermochromism in fiber composites with a view to their possible use for controlling the transmission of luminous and solar radiation. Spectrophotometric measurements of collimated and total transmittance were carried out for quartz fibers in carbon tetrachloride. The collimated transmittance showed a peak structure consistent with index matching. The total transmittance was almost featureless; the integrated luminous and solar transmittance decreased by ~20% as the temperature went from 0 to 35 degrees C if the fiber fraction was ?5 vol %. The optical properties could be reconciled with a four-flux model with parameters obtainable from the Mie theory. Specifically, we treated scattering off cylindrical objects in the Rayleigh- Gans limit.

A Note on the Temperature Dependent Transmittance of Residual Films on Glasses

A Note on the Temperature Dependent Transmittance of Residual Films on Glasses

Temperature-Dependent Etalon Effects in Laser Systems

This paper deals theoretically with the variety of temperature-dependent extracavity and intracavity etalon effects that must be considered in the design of laser systems. All examples refer to carbon dioxide lasers and materials appropriate for use with carbon dioxide lasers, although the analyses and results are valid for other lasers as well. Etalon effects in extracavity flats and lenses are examined, and the temperature-dependent transmittance is calculated. It is shown that the transmission of a ten-surface optical system, assumed to be uniform in temperature with 1% antireflectance coatings on each surface, can vary 18% as the system temperature varies. Temperature-dependent variations in the performance of a carbon dioxide laser are analyzed with respect to etalon effects of the laser resonator and with respect to etalon-within-an-etalon effects due to intracavity elements, e.g., an electrooptic modulator crystal. It is shown that etalon effects can produce line hopping that cannot be prevented by tuning of the laser.