Low-refractive-index materials: A new class of optical thin-film materials

Schubert, E. Fred; Kim, Jong Kyu

doi:10.1109/nusod.2007.4348994

Cited by 7 publications

(6 citation statements)

References 8 publications

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“…For example, low refractive index materials are ideal for the fabrication of optical components such as reflectors, filters, band-passes and photonic crystals. This is in addition to the fabrication of devices such as lasers, LEDs, and solar cells [ 8 ]. On the other hand, high refractive index polymeric materials are reported to be required for anti-refractive coatings, micro-lenses for CMOS image sensors, encapsulants for LEDs, and high-n thermoplastic lens applications [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents

et al. 2020

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The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. The optical constant values were extracted from the absorbance spectra of thin layers of the respective samples. The potential utilization of the materials as the active sensing materials of surface plasmon resonance biosensors has also been assessed in terms of the estimated value of the penetration depth through a dielectric medium. The results show a reasonable dependence of the optical constant parameters on the solvent type. Higher real part refractive index (n) and real part complex dielectric permittivity (ε’) values were observed for the samples prepared using PTSA solution, while higher optical conductivity values were observed for the NMP-based samples due to their relatively higher imaginary part refractive index (k) and imaginary part complex dielectric permittivity (ε″) values. In addition, NMP-based samples show improvement in terms of the penetration depth through a dielectric medium by around 9.5, 1.6, 4.4 and 2.9 times compared to PTSA-based samples for the PANI, PANI-chitosan, PANI-RGO and the ternary composites, respectively. Based on these, it is concluded that preparation of these materials using different dispersion solvents could produce materials of different optical properties. Thus, the variation of the dispersion solvent will allow the flexible utilization of the PANI and the composites for diverse applications.

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Section: Introductionmentioning

confidence: 99%

Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents

et al. 2020

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“…7, the core (lossy) relative permittivity is in line with that exhibited by semiconductors such as silicon, InP, GaP at infrared wavelengths [61], with suitable absorptive dopants. On the other hand, the shell (gain) relative permittivity is obtained from (18), with parameters that are consistent with models of organic dyes [59], [62] embedded in a low-index dielectric [63], [64] available in the literature. For instance, at nearinfrared wavelengths, a realistic parameter configuration could entail ε h = 1.125 and the organic dye LDS798 (by Exciton) featuring ω a = ω c = 2πc/λ a (with λ a = 777 nm), ∆ω a = 2πc∆λ a /λ 2 a (with ∆λ a = 56 nm), σ a = 6πc 3 η/ τ 21 ω 2 a √ ε h (with η = 0.48),N 0 = 6.1·10 18 cm −3 , τ 21 = 50 ps, τ 10 = 100 fs, τ 32 = 100 fs [62], and pumping rate Γ p = 1.536 × 10 9 s −1 compatible with the value considered in [59].…”

Section: Technological Feasibilitymentioning

confidence: 71%

Harnessing Spectral Singularities in Non- Hermitian Cylindrical Structures

Moccia

Castaldi

Alù

et al. 2020

IEEE Trans. Antennas Propagat.

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Non-Hermitian systems characterized by suitable spatial distributions of gain and loss can exhibit "spectral singularities" in the form of zero-width resonances associated to realfrequency poles in the scattering operator. Here, we study this intriguing phenomenon in connection with cylindrical geometries, and explore possible applications to controlling and tailoring in unconventional ways the scattering response of sub-wavelength and wavelength-sized objects. Among the possible implications and applications, we illustrate the additional degrees of freedom available in the scattering-absorption-extinction tradeoff, and address the engineering of zero-forward-scattering, transverse scattering, and gain-controlled reconfigurability of the scattering pattern, also paying attention to stability issues. Our results may open up new vistas in active and reconfigurable nanophotonics platforms.

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“…The absorption coefficient or extinction coefficient of silicon is larger than these of alumina and silicon dioxide, which are approximately zero, within the wavelength of visible light. 29 Therefore, the discoloration of the anodized alloys is the accumulative effect of the two factors. It is difficult to quantitatively determine the contribution of each factor to the discolored appearance since these two factors either go together or interconnect with each other (e.g.…”

Section: Discussionmentioning

confidence: 99%

Discoloration of Anodized AA6063 Aluminum Alloy

Zhou

Wang

et al. 2014

J. Electrochem. Soc.

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The effect of the anodizing process parameters and the influence of β (Mg 2 Si) phase on the appearance of the anodized AA6063 aluminum alloy have been investigated. It was found that β (Mg 2 Si) phase was preferentially oxidized at low anodizing voltages and the selective oxidation of β (Mg 2 Si) phase resulted in the development of a rough alloy/film interface and the incorporation of silicon into the porous anodic film, which led to the discoloration of the anodized alloy. © The Author Discoloration often appears on extruded AA6063 aluminum alloy after anodizing in sulfuric acid solutions and, to date, achieving reproducible and well-controlled surface appearance of anodized AA6063 alloy profiles is still an intractable issue. Discoloration refers to undesirable changes in the appearance of anodized aluminum alloy profiles (usually darker than the normal appearance), either in specific regions or over the macroscopic alloy surface. The effects of precipitation, surface pre-treatments and anodizing process on discoloration of anodized profiles have been explored by previous investigators.1-6 Nakagawa et al.1 suggested that discoloration was caused by rapid cooling of the extrusions on the run-out-table and reheating the extrusions upon removal from the carbon plates. It was believed that such thermal process accelerated the precipitation of β (Mg 2 Si) phase, 2 which subsequently resulted in discoloration of the anodized extrusions. Further, Nakagawa et al. 3 found that the discoloration became more marked with increase of the time and temperature of the desmutting treatment in sulfuric or nitric acid solutions. Additionally, it was found that the discoloration of the anodized alloys was strongly dependent on the pH of the rinsing water after the desmutting procedure. It was further suggested that the discoloration of anodized alloys originated from reactions between β (Mg 2 Si) precipitates and the acid solution during the desmutting and subsequent water-rinsing treatment. Hayashi et al. 5 anodized Al-Mg-Si alloys that had been heat treated under various conditions initially at 15 V and then at 4 V in sulfuric acid solution. The anodized alloys appeared in colors from gray to black and the degree of coloring increased with the amount of β (Mg 2 Si) precipitates formed during heat-treatment. Based on the roughening of the alloy/oxide interfaces, it was suggested that the coloring might result from the formation of a branched-pore morphology due to the local concentration of the anodizing current on the β (Mg 2 Si) precipitates with consequent uneven dissolution of the barrier layer.Although the literature [1][2][3]5 indicates that the discoloration of the anodic films is related to β (Mg 2 Si) precipitates in the alloy matrix, whether the discoloration is introduced in the surface pre-treatment stage or the anodizing stage remains the subject of discussion. Recent work of the authors on an AA6063 aluminum alloy profile with discolored anodic films 7 suggested that the anodizing process parameters and the statu...

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Low-refractive-index materials: A new class of optical thin-film materials

Cited by 7 publications

References 8 publications

Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents

Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents

Harnessing Spectral Singularities in Non- Hermitian Cylindrical Structures

Discoloration of Anodized AA6063 Aluminum Alloy

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