Laterally Graded Rugate Filters in Porous Silicon

2003 ◽  
Vol 797 ◽  
Author(s):  
Sean E. Foss ◽  
Terje G. Finstad
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Near Infrared ◽  
Reflectance Spectrum ◽  
Voltage Drop ◽  
Optical Parameters ◽  
Filter Surface ◽  
Strong Reflection ◽  
Discrete Layer ◽  
Reflectance Peak

ABSTRACTRugate optical reflectance filters with position dependent reflectance peaks in the visible to near infrared spectrum were realized in porous silicon (PS). Filters with strong reflection peaks, near 100%, no detectable higher order harmonics and suppressed sidebands compared to discrete layer filters were obtained by varying the current density continuously and periodically during etching. An in-plane voltage up to 1.5 V was used to obtain refractive index and periodicity change along the filter surface resulting in reflectance peak shifts of up to 100 nm/mm in the direction of the voltage drop. The effect of the lateral change in optical parameters on the filter characteristics is studied by varying the gradient and comparing measurements at different positions with measurements on a non-graded filter. We have observed extra features in the reflectance spectrum of these graded filters compared with reflectance from a non-graded filter which is likely caused by the gradient.

DETERMINATION OF THE COMPLEX REFRACTIVE INDEX OF POROUS SILICON LAYERS ON CRYSTALLINE SILICON SUBSTRATES

2010 ◽  
Vol 24 (24) ◽  
pp. 4835-4850 ◽  
Author(s):  
M. C. ARENAS ◽  
HAILIN HU ◽  
R. NAVA ◽  
J. A. DEL RÍO
Keyword(s):  
Thin Film ◽  
Refractive Index ◽  
Porous Silicon ◽  
Extinction Coefficient ◽  
Near Infrared ◽  
Crystalline Silicon ◽  
Complex Refractive Index ◽  
Si Substrate ◽  
Free Standing ◽  
Analytical Relations

In this work, we show an algorithm to calculate the complex refractive index of porous silicon (PS) on its crystalline silicon (c-Si) substrate in UV-NIR range by means of the reflectance spectra only. The algorithm is based on the analytical relations established by Heavens to obtain both complex refractive index and thickness of an absorbing thin film on an absorbing substrate. Based on this model, some simplification is introduced at different wavelengths. We start with the NIR range (1000–2500 nm), where the c-Si substrate has a low extinction coefficient. Then, we continue with the near infrared to the optical range (300–1000 nm), where PS has a strong extinction coefficient and dispersion. The calculated n and k values are in agreement with those reported in the literature obtained from separated measurements of a free standing PS film. We consider that the algorithm can be applied to any thin film on a substrate with similar optical properties.

ANNEALED In2S3 THIN FILMS PREPARED BY SPRAY TECHNIQUE: REPORT ON THE STRUCTURAL, OPTICAL AND DISPERSION ENERGY PARAMETERS

2019 ◽  
Vol 26 (07) ◽  
pp. 1850223
Author(s):  
Y. BCHIRI ◽  
N. BOUGUILA ◽  
M. KRAINI ◽  
S. ALAYA
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Near Infrared ◽  
Spray Pyrolysis Technique ◽  
Dielectric Constants ◽  
Index Formula ◽  
Optical Parameters ◽  
Dispersion Parameters ◽  
Dispersion Energy ◽  
Molar Ratios

In2S3 thin films with different S/In molar ratios (from 1.5 to 3.5) were deposited via a spray pyrolysis technique on glass substrates at 340∘C. Then, the obtained films were annealed at the same temperature 400∘C for 2[Formula: see text]h. X-ray diffraction study reveals the formation of cubic [Formula: see text]-In2S3 phase with (400) as preferred orientation. The crystallite size varies in the range 64–97[Formula: see text]nm. Optical analysis exhibits that transmittance in visible and near infrared regions is higher than 65% for all films. The optical band gap varied from 2.58[Formula: see text]eV to 2.67[Formula: see text]eV. The optical parameters (refractive index, extinction coefficient, dielectric constants) were calculated through the transmittance ([Formula: see text]) and reflectance ([Formula: see text]). Dispersion parameters ([Formula: see text], [Formula: see text]), high frequency dielectric constant ([Formula: see text]), refractive index ([Formula: see text]), oscillator length strength ([Formula: see text]), average oscillator wavelength ([Formula: see text]) and optical moments ([Formula: see text]) were determined by Wemple–DiDomenico model. The surface and volume energy losses with photon energy were also calculated. The optical and electrical conductivities were estimated. These properties of In2S3 films are important for photovoltaic applications.

POLYNOMIAL FITTING APPROACH FOR THE KRAMERS–KRONIG METHOD FOR OPTICAL PROPERTIES COMPUTING FOR Bi2O3 FABRIC

2012 ◽  
Vol 26 (07) ◽  
pp. 1250049 ◽  
Author(s):  
GABRIEL MURARIU ◽  
SIMONA CONDURACHE-BOTA ◽  
NICOLAE TIGAU
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Optical Properties ◽  
Reflectance Spectrum ◽  
Optical Parameters ◽  
Thermal Vacuum ◽  
Data Set ◽  
Glass Substrates ◽  
Different Temperatures ◽  
Good Agreement

The optical reflectance of Bi 2 O 3 was measured, and the optical properties were estimated by Kramers–Kronig analysis. The novelty of the present study is due to the implementation of a MAPLE software approach to the complex computations implied by this extrapolation. The analytical fit of the reflectance spectrum is applied, accompanied by a careful extrapolation, which is necessary within the Kramers–Kronig method. In this way starting from the reflectance samples data, using this transformation, a very good agreement is obtained between the main optical parameters, namely the refractive index and the absorbtion coefficient. The study is implemented for Bi 2 O 3 films deposited by thermal vacuum evaporation at different temperatures of the glass substrates and the comparison with the experimental data set being made using the transmission and the reflection optical spectra.

scholarly journals Synthesis of PVA/CeO2 Based Nanocomposites with Tuned Refractive Index and Reduced Absorption Edge: Structural and Optical Studies

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1570
Author(s):  
Shujahadeen B. Aziz ◽  
Elham M. A. Dannoun ◽  
Dana A. Tahir ◽  
Sarkawt A. Hussen ◽  
Rebar T. Abdulwahid ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Absorption Edge ◽  
Ceo2 Nanoparticles ◽  
Poly Vinyl Alcohol ◽  
Optical Parameters ◽  
Single Oscillator Model ◽  
Vis Spectroscopy ◽  
The Impact ◽  
Host Polymer

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO2 on optical properties of PVA. On the insertion of CeO2 nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO2 nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO2 content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ɛ” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.

scholarly journals Polymer Composites with 0.98 Transparencies and Small Optical Energy Band Gap Using a Promising Green Methodology: Structural and Optical Properties

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1648
Author(s):  
Muaffaq M. Nofal ◽  
Shujahadeen B. Aziz ◽  
Jihad M. Hadi ◽  
Wrya O. Karim ◽  
Elham M. A. Dannoun ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Polymer Composites ◽  
Amorphous Phase ◽  
Absorption Edge ◽  
Complex Form ◽  
Bandgap Energy ◽  
Optical Parameters ◽  
Visible Spectroscopy ◽  
Uv Visible

In this work, a green approach was implemented to prepare polymer composites using polyvinyl alcohol polymer and the extract of black tea leaves (polyphenols) in a complex form with Co2+ ions. A range of techniques was used to characterize the Co2+ complex and polymer composite, such as Ultraviolet–visible (UV-Visible) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The optical parameters of absorption edge, refractive index (n), dielectric properties including real and imaginary parts (εr, and εi) were also investigated. The FRIR and XRD spectra were used to examine the compatibility between the PVA polymer and Co2+-polyphenol complex. The extent of interaction was evidenced from the shifts and change in the intensity of the peaks. The relatively wide amorphous phase in PVA polymer increased upon insertion of the Co2+-polyphenol complex. The amorphous character of the Co2+ complex was emphasized with the appearance of a hump in the XRD pattern. From UV-Visible spectroscopy, the optical properties, such as absorption edge, refractive index (n), (εr), (εi), and bandgap energy (Eg) of parent PVA and composite films were specified. The Eg of PVA was lowered from 5.8 to 1.82 eV upon addition of 45 mL of Co2+-polyphenol complex. The N/m* was calculated from the optical dielectric function. Ultimately, various types of electronic transitions within the polymer composites were specified using Tauc’s method. The direct bandgap (DBG) treatment of polymer composites with a developed amorphous phase is fundamental for commercialization in optoelectronic devices.

scholarly journals Flexible Methyl Cellulose/Polyaniline/Silver Composite Films with Enhanced Linear and Nonlinear Optical Properties

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1225
Author(s):  
Ali Atta ◽  
Mostufa M. Abdelhamied ◽  
Ahmed M. Abdelreheem ◽  
Mohamed R. Berber
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Nonlinear Optical ◽  
Composite Films ◽  
Methyl Cellulose ◽  
Carbon Cluster ◽  
Nonlinear Susceptibility ◽  
Optical Parameters ◽  
Flexible Polymer

In order to potentiate implementations in optical energy applications, flexible polymer composite films comprising methyl cellulose (MC), polyaniline (PANI) and silver nanoparticles (AgNPs) were successfully fabricated through a cast preparation method. The composite structure of the fabricated film was confirmed by X-ray diffraction and infrared spectroscopy, indicating a successful incorporation of AgNPs into the MC/PANI blend. The scanning electron microscope (SEM) images have indicated a homogenous loading and dispersion of AgNPs into the MC/PANI blend. The optical parameters such as band gap (Eg), absorption edge (Ed), number of carbon cluster (N) and Urbach energy (Eu) of pure MC polymer, MC/PANI blend and MC/PANI/Ag films were determined using the UV optical absorbance. The effects of AgNPs and PANI on MC polymer linear optical (LO) and nonlinear optical (NLO) parameters including reflection extinction coefficient, refractive index, dielectric constant, nonlinear refractive index, and nonlinear susceptibility are studied. The results showed a decrease in the band gap of MC/PANI/AgNPs compared to the pure MC film. Meanwhile, the estimated carbon cluster number enhanced with the incorporation of the AgNPs. The inclusion of AgNPs and PANI has enhanced the optical properties of the MC polymer, providing a new composite suitable for energy conversion systems, solar cells, biosensors, and nonlinear optical applications.

Simplified coupling power model for fibers fusion

2009 ◽  
Vol 17 (3) ◽  
Author(s):  
J. Saktioto ◽  
J. Ali ◽  
M. Fadhali
Keyword(s):  
Refractive Index ◽  
Propagation Constant ◽  
Tunable Filter ◽  
Experimental Result ◽  
Total Power ◽  
Optical Parameters ◽  
Coupling Region ◽  
Ratio Distribution ◽  
Hydrogen Flow ◽  
Wide Range

AbstractFiber coupler fabrication used for an optical waveguide requires lossless power for an optimal application. The previous research coupled fibers were successfully fabricated by injecting hydrogen flow at 1 bar and fused slightly by unstable torch flame in the range of 800–1350°C. Optical parameters may vary significantly over wide range physical properties. Coupling coefficient and refractive index are estimated from the experimental result of the coupling ratio distribution from 1% to 75%. The change of geometrical fiber affects the normalized frequency V even for single mode fibers. V is derived and some parametric variations are performed on the left and right hand side of the coupling region. A partial power is modelled and derived using V, normalized lateral phase constant u, and normalized lateral attenuation constant, w through the second kind of modified Bessel function of the l order, which obeys the normal mode and normalized propagation constant b. Total power is maintained constant in order to comply with the energy conservation law. The power is integrated through V, u, and w over the pulling length of 7500 µm for 1-D. The core radius of a fiber significantly affects V and power partially at coupling region rather than wavelength and refractive index of core and cladding. This model has power phenomena in transmission and reflection for an optical switch and tunable filter.

Long-wavelength lattice vibrations of Ag3In5Se9 and Ag3In5Te9 single crystals — An inversion of LO- and TO-mode frequencies

2016 ◽  
Vol 30 (18) ◽  
pp. 1650229 ◽  
Author(s):  
Nizami Mamed Gasanly
Keyword(s):  
Refractive Index ◽  
Single Crystals ◽  
Longitudinal Optical ◽  
Absorption Index ◽  
Energy Losses ◽  
Optical Parameters ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Long Wavelength ◽  
Optical Modes

Infrared (IR) reflectivities are registered in the frequency range of 50–2000 cm[Formula: see text] for Ag3In5Se9 and Ag3In5Te9 single crystals grown by Bridgman method. Three infrared-active modes are detected in spectra. The optical parameters, real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes (TO and LO modes) and oscillator strength were also determined. The bands detected in infrared spectra were tentatively attributed to various vibration types (valence and valence-deformation). The inversion of LO- and TO-mode frequencies of the sandwiched pair was observed for studied crystals.

scholarly journals Characteristics of Poly(vinyl Alcohol) (PVA) Based Composites Integrated with Green Synthesized Al3+-Metal Complex: Structural, Optical, and Localized Density of State Analysis

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1316
Author(s):  
Shujahadeen B. Aziz ◽  
Muaffaq M. Nofal ◽  
Hewa O. Ghareeb ◽  
Elham M. A. Dannoun ◽  
Sarkawt A. Hussen ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Metal Complex ◽  
Band Gap ◽  
Optical Band Gap ◽  
Complex Dielectric Constant ◽  
Poly Vinyl Alcohol ◽  
Optical Parameters ◽  
Dispersion Energy ◽  
Casting Technique

The influence of dispersing Al-metal complex on the optical properties of PVA was investigated using UV–visible spectroscopy. Polymer composite films with various Al3+-complex amounts in the PVA matrix were arranged by solution casting technique by means of distilled water as a widespread solvent. The formation of Al3+-metal complex was verified through Ultraviolet–visible (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) examinations. The addition of Al-complex into the polymer matrix led to the recovery of the optical parameters such as dielectric constant (εr and εi) and refractive index (n). The variations of real and imaginary parts of complex dielectric constant as a function of photon wavelength were studied to calculate localized charge density values (N/m*), high-frequency dielectric constant, relaxation time, optical mobility, optical resistivity, and plasma angular frequency (ωp) of electrons. In proportion with Al3+-complex content, the N/m* values were amplified from 3.68 × 1055 kg−1 m−3 to 109 × 1055 kg−1 m−3. The study of optical parameters may find applications within optical instrument manufacturing. The optical band gap was determined from Tauc’s equation, and the type of electronic transition was specified. A remarkable drop in the optical band gap was observed. The dispersion of static refractive index (no) of the prepared composites was analyzed using the theoretical Wemple–DiDomenico single oscillator model. The average oscillator energy (Eo) and oscillator dispersion energy (Ed) parameters were estimated.

Single‐Material, Near‐Infrared Selective Absorber Based on Refractive Index‐Tunable Tamm Plasmon Structure

2022 ◽  
pp. 2102388
Author(s):  
So Hee Kim ◽  
Joo Hwan Ko ◽  
Young Jin Yoo ◽  
Min Seok Kim ◽  
Gil Ju Lee ◽  
...  
Keyword(s):  
Refractive Index ◽  
Near Infrared ◽  
Single Material
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