We report values of pseudodielectric functions $〈\ensuremath{\epsilon}〉=〈{\ensuremath{\epsilon}}_{1}〉+i〈{\ensuremath{\epsilon}}_{2}〉$ measured by spectroscopic ellipsometry and refractive indices $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}=n+ik$, reflectivities $R$, and absorption coefficients $\ensuremath{\alpha}$ calculated from these data. Rather than correct ellipsometric results for the presence of overlayers, we have removed these layers as far as possible using the real-time capability of the spectroscopic ellipsometer to assess surface quality during cleaning. Our results are compared with previous data. In general, there is good agreement among optical parameters measured on smooth, clean, and undamaged samples maintained in an inert atmosphere regardless of the technique used to obtain the data. Differences among our data and previous results can generally be understood in terms of inadequate sample preparation, although results obtained by Kramers-Kronig analysis of reflectance measurements often show effects due to improper extrapolations. The present results illustrate the importance of proper sample preparation and of the capability of separately determining both ${\ensuremath{\epsilon}}_{1}$ and ${\ensuremath{\epsilon}}_{2}$ in optical measurements.

Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV

Structural models needed in calculations of properties of substitutionally random ${\mathit{A}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathit{B}}_{\mathit{x}}$ alloys are usually constructed by randomly occupying each of the N sites of a periodic cell by A or B. We show that it is possible to design ``special quasirandom structures'' (SQS's) that mimic for small N (even N=8) the first few, physically most relevant radial correlation functions of an infinite, perfectly random structure far better than the standard technique does. These SQS's are shown to be short-period superlattices of 4--16 atoms/cell whose layers are stacked in rather nonstandard orientations (e.g., [113], [331], and [115]). Since these SQS's mimic well the local atomic structure of the random alloy, their electronic properties, calculable via first-principles techniques, provide a representation of the electronic structure of the alloy. We demonstrate the usefulness of these SQS's by applying them to semiconductor alloys. We calculate their electronic structure, total energy, and equilibrium geometry, and compare the results to experimental data.

Electronic properties of random alloys : special quasirandom structures

The principles and most-recent results of high-power THz generation through optical rectification using a tilted optical pulse front are described. Single-cycle THz pulses of multimicrojoule energies are generated at kHz repetition rates, and average THz power levels exceeding 1 mW can be generated at kHz-MHz repetition rates. Applications in nonlinear THz spectroscopy and THz coherent control are discussed.

Generation of high-power terahertz pulses by tilted-pulse-front excitation and their application possibilities

A method is described for calculation of the optical constants (the refractive index, extinction coefficient, and absorption coefficient) of some III‐V binaries (GaP, GaAs, GaSb, InP, InAs, and InSb), ternaries (AlxGa1−xAs), and quaternaries (In1−xGaxAsyP1−y) in the entire range of photon energies (0–6.0 eV). The imaginary part of the dielectric function [e2(ω)] is derived first from the joint density‐of‐states functions at energies of various critical points (CPs) in the Brillouin zone; then its real part [e1(ω)] is obtained analytically using the Kramers–Kronig relation. The indirect band‐gap transitions are also assumed to provide a gradually increasing e2 spectrum expressed by a power law of (ℏω−EIDg)2, where ℏω is the photon energy and EIDg is the indirect band‐gap energy. The optical dispersion relations are expressed in terms of these model dielectric functions. The present model reveals distinct structures in the optical constants at energies of the E0, E0+Δ0 [three‐dimensional (3‐D) M0 CP], E1, E...

Optical dispersion relations for GaP, GaAs, GaSb, InP, InAs, InSb, AlxGa1−xAs, and In1−xGaxAsyP1−y

Ultrashort terahertz pulses derived from femtosecond table-top sources have become a valuable tool for time-resolved spectroscopy during the last two decades Until recently, the pulse energies and field strengths of these pulses have been generally too low to allow for the use as pump pulses or the study of nonlinear effects in the terahertz range In this review article we will describe methods of generation of intense single cycle terahertz pulses with emphasis on optical rectification using the tilted-pulse-front pumping technique We will also discuss some applications of these intense pulses in the emerging field of nonlinear terahertz spectroscopy

/pdf/intense-ultrashort-terahertz-pulses-generation-and-1ewsfynvhb.pdf

Intense ultrashort terahertz pulses: generation and applications

We report high-precision pseudodielectric function spectra ellipsometrically measured from 1.5 to 6.0 eV of ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{As}}_{y}{\mathrm{P}}_{1\ensuremath{-}y}$ alloys lattice-matched to InP. Analysis of third derivatives numerically calculated from these data yields critical-point energies, broadening parameters, phases, and amplitudes for the valence---conduction-band critical points ${E}_{1}$, ${E}_{1}+{\ensuremath{\Delta}}_{1}$, ${E}_{0}^{\ensuremath{'}}$, and ${E}_{0}^{\ensuremath{'}}+{\ensuremath{\Delta}}_{0}^{\ensuremath{'}}$. An observed inversion of the relative strengths of the ${E}_{1}$ and ${E}_{1}+{\ensuremath{\Delta}}_{1}$ transitions as a function of composition is attributed to the $k$-linear interaction. The phases indicate strong Coulomb interactions for ${E}_{1}$ and ${E}_{0}^{\ensuremath{'}}$, without the ambiguities present in the interpretation of electroreflectance spectra. The composition dependence of critical-point energies yields the following bowing parameters for ${E}_{1}$, ${E}_{1}+{\ensuremath{\Delta}}_{1}$, ${\ensuremath{\Delta}}_{1}$, and ${E}_{0}^{\ensuremath{'}}$: 0.33\ifmmode\pm\else\textpm\fi{}0.05, 0.26\ifmmode\pm\else\textpm\fi{}0.04, -0.07\ifmmode\pm\else\textpm\fi{}0.02, and -0.01\ifmmode\pm\else\textpm\fi{}0.05 eV, respectively. We discuss our results with the use of the models of Van Vechten and others for the nonlinear variation of energy gaps and spin-orbit splittings with composition. The ${E}_{0}^{\ensuremath{'}}$ structure may contain contributions from both $\ensuremath{\Gamma}$ and $\ensuremath{\Delta}$, as observed in Ge and GaAs. We reassign the feature previously attributed to ${E}_{2}$ in InP to ${E}_{0}^{\ensuremath{'}}+{\ensuremath{\Delta}}_{0}^{\ensuremath{'}}$, where ${\ensuremath{\Delta}}_{0}^{\ensuremath{'}}$ is the spin-orbit splitting of the second conduction band at $k=0$. Our improved methods of analysis allow spectroscopic ellipsometry to be used as a valuable supplement to modulation spectroscopy for the study of interband transitions in solids.

Optical properties of In 1-x Ga x As y P 1-y from 1.5 to 6.0 eV determined by spectroscopic ellipsometry

Earlier measurements of the three-frequency microwave nonlinear susceptibility coefficient have been extended to include all of the nonzero tensor components of ${d}_{\mathrm{ijk}}^{ m}(\ensuremath{-}{\ensuremath{\omega}}_{3},{\ensuremath{\omega}}_{2},{\ensuremath{\omega}}_{1})$ of LiNb${\mathrm{O}}_{3}$ and LiTa${\mathrm{O}}_{3}$. These results are interpreted, using the formalism developed by Lax and Nelson, to describe nonlinearities associated with electronic and ionic modes of anisotropic crystalline materials. The linear dispersion parameters for each material are first approximated by a single-electronic and a single-ionic normal mode. Nonlinear elements are then added to this normal-mode model. A macroscopic-bond-charge model is developed. With some simplifying asumptions and knowledge of the optical nonlinear coefficient ${d}_{\mathrm{ijk}}^{ o}$ and the electro-optic coefficient ${d}_{\mathrm{ijk}}^{ \mathrm{eo}}$, a good fit with the measured values of ${d}_{\mathrm{ijk}}^{ m}$ can be obtained. The same parameters used to fit ${d}_{\mathrm{ijk}}^{ m}$ are used to calculate the pyroelectric coefficients for LiNb${\mathrm{O}}_{3}$ and LiTa${\mathrm{O}}_{3}$. In both cases, the correct signs and magnitudes within a factor of 2 of experimental values are obtained.

Microwave Nonlinearities in Anisotropic Dielectrics and Their Relation to Optical and Electro-Optical Nonlinearities

Dielectric function spectra in the visible-near uv and energy derivative reflectance spectra in the vacuum uv spectral ranges are reported for In1-xGaxAsyP1-y at compositions between y=0 and 1 lattice-matched to InP. Analysis of these spectra yields bowing parameters for the valence-conduction band critical points E1, E1+Δ1, and E'0, estimates of core exciton binding energies, and the ordering of the lower conduction band minima at L and X.

Band Structure and Optical Properties of In1-xGaxAsyP1-y

The sign of the microwave nonlinear susceptibility has been found for the first time for a number of acentric crystals. The method used determines the absolute sign without recourse to a comparison crystal. Using known signs of piezoelectric coefficients to specify crystal orientation, all of the nonlinear susceptibilities measured are negative. Predictions of signs and magnitudes of some coefficients in pyroelectric crystals are also made.

Determination of Absolute Signs of Microwave Nonlinear Susceptibilities

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

M. A. Pollack

Author Tools

Chat about Author

Papers

Optical properties of In 1-x Ga x As y P 1-y from 1.5 to 6.0 eV determined by spectroscopic ellipsometry

Microwave Nonlinearities in Anisotropic Dielectrics and Their Relation to Optical and Electro-Optical Nonlinearities

Band Structure and Optical Properties of In1-xGaxAsyP1-y

Determination of Absolute Signs of Microwave Nonlinear Susceptibilities