Optical Thin Layer Research Articles

Effect of Holding Time on Optical Structure Properties of Ba(Zr0.5Ti0.5)O3 Thin Film Using Sol-Gel Method

The ferroelectric thin film material of barium zirconium titanate (BZT) on the fluorine-doped tin oxide (FTO) glass substrate was successfully prepared using the sol-gel method. The purpose of this study was to determine the effect of crystal size on the variation of holding time. The lattice parameter data has a value of a = b of 3.918 Å and for c it is 4.01 Å. The results of this study indicate that the crystal structure of BZT is tetragonal because the lattice parameter has the same values a and b but not equal to c. To obtain the bandgap energy, a thin film plot method of Ba(Zr0,5Ti0,5)O3 was used at a temperature of 700 °C with a holding time of 30 minutes, 1 hour, 1 hour 30 minutes, and 2 hours. The optical thin layer bandgap energy of Ba(Zr0.5Ti0.5)O3 was calculated using the Tauc plot. The absorbance values obtained were 3.277 a.u, 3.0654 a.u, 3.323 a.u, and 3.424 a.u. The maximum transmission (TM) occurs at 1 hour holding time which gives a percentage of TM1 44.477% and TM2 20.568%. While the 2 hour hold time gives a minimum transmission (Tm) of Tm1 10.859% and Tm2 7.759%, respectively.

Mathematical Model of Heat Exchange and Approximate Methods of Solution of Radiation Transfer Equation in the Melting Furnace Tank

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Surface acoustic wave characterization of optical sol-gel thin layers

Controlling the thin film deposition and mechanical properties of materials is a major challenge in several fields of application. We are more particularly interested in the characterization of optical thin layers produced using sol-gel processes to reduce laser-induced damage. The mechanical properties of these coatings must be known to control and maintain optimal performance under various solicitations during their lifetime. It is therefore necessary to have means of characterization adapted to the scale and nature of the deposited materials. In this context, the dispersion of ultrasonic surface waves induced by a micrometric layer was studied on an amorphous substrate (fused silica) coated with a layer of ormosil using a sol-gel process. Our ormosil material is a silica-PDMS mixture with a variable polydimethylsiloxane (PDMS) content. The design and implementation of Surface Acoustic Wave InterDigital Transducers (SAW-IDT) have enabled quasi-monochromatic Rayleigh-type SAW to be generated and the dispersion phenomenon to be studied over a wide frequency range. Young’s modulus and Poisson’s ratio of coatings were estimated using an inverse method.

Stratification and mixing regimes in biological thin layers over the Mid‐Atlantic Bight

We use density and microstructure data to characterize the properties and physical setting of optical thin layers observed over the New Jersey shelf in the summer of 2006. Layers were differentiated into two types by their vertical position in the water column, fluorescence intensity, and possibly community composition or cell condition as indicated by the measured differences in the ratio of fluorescence to optical backscatter. Both layer types were associated with gradients in stratification; but, the turbulent mixing environment for the two layer types differed significantly. Shallow layers were located within the pycnocline near the maximum stratification and were exposed to strong turbulence within the surface mixed layer. Consequently, turbulent mixing of buoyancy may have been a key factor in maintaining shallow layers. In contrast, relatively weak density gradients and mixing indicate that turbulent processes may have been less critical for deep layers, which were located at the base of the pycnocline. More generally, both shallow and deep layers were geographically located in regions of low median and high mean turbulent kinetic energy dissipation, i.e., regions of rare yet intense mixing events. This work highlights the need to understand the detailed statistics of mixing at time and vertical scales relevant to thin layers, and more specifically, the need to discern the time history of mixing of the fluid that composes layers.

Optical fiber hydrogen sensor based on light reflection and a palladium-sliver thin film

Thin alloy films of palladium (Pd) and silver (Ag) are deposited onto glass substrates via the direct current (DC) magnetron technique. The hydrogen sensor probe consists of optical fiber bundle and Pd/Ag optical thin film. When the sensor is exposed to hydrogen, the refractive index of Pd/Ag optical thin layer will diminish and cause attenuation changes of the reflective light. It is observed that the thickness of Pd/Ag alloy layer can affect the hydrogen sensor signal. Under different substrate temperatures, several Pd/Ag samples are coated with different thicknesses of Pd/Ag alloy, and the results of a hydrogen sensor based on reflective light from the Pd/Ag alloy thin film are discussed.

Integrated measurements of acoustical and optical thin layers II: Horizontal length scales

The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.

Integrated measurements of acoustical and optical thin layers I: Vertical scales of association

This study combined measurements from multiple platforms with acoustic instruments on moorings and on a ship and optics on a profiler and an autonomous underwater vehicle (AUV) to examine the relationships between fluorescent, bioluminescent, and acoustically scattering layers in Monterey Bay during nighttime hours in July and August of 2006 and May of 2008. We identified thin bioluminescent layers that were strongly correlated with acoustic scattering at the same depth but were part of vertically broad acoustic features, suggesting layers of unique composition inside larger biomass features. These compositional thin layers nested inside larger biomass features may be a common ecosystem component and are likely to have significant ecological impacts but are extremely difficult to identify as most approaches capable of the vertical scales of measurement necessary for the identification of sub-meter scale patterns assess bulk properties rather than specific layer composition. Measurements of multiple types of thin layers showed that the depth offset between thin phytoplankton and zooplankton layers was highly variable with some layers found at the same depth but others found up to 16 m apart. The vertical offset between phytoplankton and zooplankton thin layers was strongly predicted by the fraction of the water column fluorescence contained within a thin phytoplankton layer. Thin zooplankton layers were only vertically associated with thin phytoplankton layers when the phytoplankton in a layer accounted for more than about 18–20% of the water column chlorophyll. Trophic interactions were likely occurring between phytoplankton and zooplankton thin layers but phytoplankton thin layers were exploited by zooplankton only when they represented a large fraction of the available phytoplankton, suggesting zooplankton have some knowledge of the available food over the entire water column. The horizontal extent of phytoplankton layers, discussed in the second paper in this series, is likely an important factor contributing to this selective exploitation by zooplankton. The pattern of vertical offset between phytoplankton and zooplankton layers was consistent between studies in different years and using different combinations of platforms, indicating the importance of the relationship between zooplankton layers and the fraction of phytoplankton within a layer at night within Monterey Bay. These results highlight the value of integrating measurements of various types of organisms to understand thin layers processes and the importance of assessing ecological interactions in plankton thin layers within the context of the properties of the entire water column, like the animals themselves do.

Hydrogen-Containing Amorphous Carbon Layers as Optical Materials in the Near-IR Spectral Range

Hydrogenated amorphous carbon layers were deposited on various substrates by means of a plasma CVD process with a RF substrate bias as well as an ECR plasma source. The optical properties of the a-C:H layers were obtained via spectroscopic ellipsometry and correlated with their mechanical and chemical properties. The layers from pure RF plasma exhibit a higher absorption constant in the visible spectral range and a higher refractive index. All layers are nearly transparent in the NIR spectral range making them candidates for optical thin layer systems. The laser damage behaviour of the a-C:H layers was investigated with ultrashort pulses. The damage thresholds were consistent with the absorption constants of the layers. Interesting damage morphologies were observed indicating a sensitivity of this experiment to sub-structures in the layer.

Enhancement of second harmonic generation signal in thermally poled glass ceramic with NaNbO3 nanocrystals

Glass ceramic composites were prepared by bulk crystallization of NaNbO3 in sodium niobium borate glasses. A homogeneous bulk crystallization of the NaNbO3 phase takes place during heat treatments that produces visible-near infrared transparent materials with ∼30nm NaNbO3 nanocrystallites. Upon thermal poling, a strong Na+ depleted nonlinear optical thin layer is observed at the anode side that should induce a large internal static electric field. In addition, the χ(2) response of the poled glass ceramic composites increases from 0.2 up to 1.9pm∕V with the rate of crystallization. Two mechanisms may be considered: a pure structural χ(2) process connected with the occurrence of a spontaneous ferroelectric polarization or an increase of the χ(3) response of the nanocrystallites that enhances the electric field induced second harmonic generation process.

Multiple wavelength fluorescence enhancement on glass substrates for biochip and cell analyses

In microarrays experiments, a serious limitation is the unreliability of low signal intensities data and the lack of reproducibility for the resulting ratios between samples and controls. Most of the light emitted by a fluorophore at the air/glass interface of a glass slide is absorbed by the glass so just a part of the emitted fluorescence is detected. To improve the sensitivity of the fluorescence detection of both common fluorophores Cy3 and Cy5 in DNA microarrays and fluorescent cell analyses, we have designed a multi layer mirror with alternative thin layers of SiO2 and HfO2. This mirror (MOTL) prevents fluorescence absorption, allows the simultaneous enhancement of the fluorescence signals and increases the dynamic range of the slides. Using MOTL slides, Cy3 and Cy5 intensities are enhanced by 5-8-fold, consequently, the fluorescence analysis becomes easier and should allow the detection of low copy number genes or weakly fluorescent cells. With the same approach, other multiple optical thin layer slides could be designed for other series of fluorophores, extending the field of their applications.

Photo-acoustic detection of laser induced damages.

Photo-acoustic (PA) signals induced by Kr F laser irradiations on to the optical thin layers have been measured to detect the small absorptions and the damage thresholds of dielectric coatings. Extremely low absorption with the extinction coefficient of 10-4 is detectable for the single-layer coatings with optical thickness of 1.5 wavelength at 248nm. The pre-damage detections have been studied with the assistance of laser scattering damage detection techniques. Thechanges of the slope and the variation of the PA signals have been observed at the irradiation of Kr F laser of lower fluence compared with the damage thresholdsby microscopic measurements. The pre-damage thresholds detected by the PA signaldetection agreed well with the laser scattering method for low index fluoridecoatings. Typical features of the laser induced damages related to the linear absorption and the refractive index will be discussed about the coating materials forshort wavelength lasers.

Optical thin layers of MgF_2 produced by decomposition of organic magnesium-fluoro compounds

Polycrystalline magnesium fluoride is extensively applied as an optical thin layer. Some of its optical, chemical, and mechanical properties are discussed in this paper. Vacuum as well as nonvacuum techniques are suitable for its production and the latter are described in detail, including chemical aerosol decomposition of a few magnesium-fluoro compounds as well as spinning or dipping of solutions of one of the magnesium-fluoro compounds. This subject is presented in the broader context of potential methods of mass-producing optical thin MgF2 layers and of potential industrial applications. The pros and cons of four relevant processes are dealt with.

The appearance of the bulk plasmon in thin silver overlayers monitored by electrochemical modulation spectroscopy

Electroreflectance spectra of thin Ag films from the submonolayer range up to about 20 monolayers, electrodeposited onto Cu(111) electrodes have been studied in the photon energy range between 1.6 and 5.3 eV in an optical thin layer cell. We find that the excitation of volume plasmons in the Ag overlayer is indicated in the electroreflectance spectra already at coverages around 2.5 monolayers, but the resonance is displaced to slightly higher values with respect to the volume plasmon frequency in bulk Ag. This shift can be explained by taking spatial dispersion into account which considers the presence of longitudinal waves in the Ag overlayer as well as in the substrate. In addition, differential reflectance spectra were recorded and compared to model calculations with and without the inclusion of spatial dispersion. For p-polarization we again find agreement between experiment and theory only when non-local effects are taken into account.