Institution
Hanscom Air Force Base
Government•Bedford, Massachusetts, United States•
About: Hanscom Air Force Base is a government organization based out in Bedford, Massachusetts, United States. It is known for research contribution in the topics: Ionosphere & Fourier transform. The organization has 561 authors who have published 630 publications receiving 24055 citations.
Topics: Ionosphere, Fourier transform, Photorefractive effect, Filter (signal processing), Spatial filter
Papers published on a yearly basis
Papers
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TL;DR: In this article, a numerical Kramers-Kronig analysis is used to predict the refractive index perturbations produced in crystalline silicon by applied electric fields or by charge carriers.
Abstract: A numerical Kramers-Kronig analysis is used to predict the refractive-index perturbations produced in crystalline silicon by applied electric fields or by charge carriers. Results are obtained over the 1.0-2.0 \mu m optical wavelength range. The analysis makes use of experimental electroabsorption spectra and impurity-doping spectra taken from the literature. For electrorefraction at the indirect gap, we find \Delta n = 1.3 \times 10^{5} at \lambda = 1.07 \mu m when E = 10^{5} V/cm, while the Kerr effect gives \Delta n = 10^{-6} at that field strength. The charge-carrier effects are larger, and a depletion or injection of 1018carriers/cm3produces an index change of \pm1.5 \times 10^{-3} at \lambda = 1.3 \mu m.
2,502 citations
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TL;DR: In this paper, a brief history of near-field antenna measurements with and without probe correction is outlined, beginning with ideal probe scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces.
Abstract: After a brief history of near-field antenna measurements with and without probe correction, the theory of near-field antenna measurements is outlined beginning with ideal probes scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces. Probe correction is introduced for all three measurement geometries as a slight modification to the ideal probe expressions. Sampling theorems are applied to determine the required data-point spacing, and efficient computational methods along with their computer run times are discussed. The major sources of experimental error defining the accuracy of typical planar near-field measurement facilities are reviewed, and present limitations of planar, cylindrical, and spherical near-field scanning are identified.
950 citations
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TL;DR: This work examines the relationship between phase and amplitude in the case of alphanumeric characters, with and without noise, using a computer simulation and compares the phase-only and amplitude-only filters to the classical matched filter using the criteria of discrimination, correlation peak, and optical efficiency.
Abstract: From image processing work, we know that the phase information is significantly more important than amplitude information in preserving the features of a visual scene. Is the same true in the case of a matched filter? From previous work [
J. L.
Horner
,
Appl. Opt.21,
4511(
1982)], we know that a pure phase correlation filter can have an optical efficiency of 100% in an optical correlation system. We examine this relationship between phase and amplitude in the case of alphanumeric characters, with and without noise, using a computer simulation. We compare the phase-only and amplitude-only filters to the classical matched filter using the criteria of discrimination, correlation peak, and optical efficiency. Three-dimensional plots of the autocorrelation and cross-correlation functions are presented and discussed.
939 citations
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TL;DR: A description and summary of the latest edition of the AFGL HITRAN molecular absorption parameters database are presented and a FORTRAN program is now furnished to allow rapid access to the molecular transitions and for the creation of customized output.
Abstract: A description and summary of the latest edition of the AFGL high-resolution transmission molecular absorption database (HITRAN) parameters are presented. This new database combines the information for the seven principal atmospheric absorbers and twenty-one additional molecular species previously contained on the AFGL atmospheric absorption line parameter compilation and on the trace gas compilation. In addition to updating the parameters on earlier editions of the compilation, new parameters have been added to this edition such as the self-broadened half-width, the temperature dependence of the air-broadened half-width, and the transition probability. The database contains 348,043 entries between 0 and 17,900/cm. A FORTRAN program is now furnished to allow rapid access to the molecular transitions and for the creation of customized output. A separate file of molecular cross sections of 11 heavy molecular species, applicable for qualitative simulation of transmission and emission in the atmosphere, has also been provided.
919 citations
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TL;DR: In this paper, the Huang-Rhys theory of multiphonon emission was used to calculate the radiative and non-radiative rates for five luminescing states in fluorozirconate glass.
Abstract: Optical-absorption, -emission, and -excitation spectra are presented for ${\mathrm{Er}}^{3+}$ ions in fluorozirconate glass. Measured oscillator strengths of the transitions between $J$ manifolds at 300 and 15 K are compared with calculated electric and magnetic dipole oscillator strengths. Radiative rates for five luminescing states were calculated. The nonradiative rates from these excited states were determined by calculating the difference between the measured rates and the calculated radiative rates. The low-temperature nonradiative rates are in agreement with the phenomenological energy-gap law followed by rare-earth ions in a number of crystals and glasses. The temperature dependence of the lifetimes was analyzed using the Huang-Rhys theory of multiphonon emission. Values for the $^{4}I_{\frac{11}{2}}$ radiative and nonradiative rates obtained by the above methods are compared with those obtained applying the method Flaherty and DiBartolo used to study Mn${\mathrm{F}}_{2}$: ${\mathrm{Er}}^{3+}$. The multiphonon emission rates in fluorozirconate glass are much lower than the rates for the same levels of ${\mathrm{Er}}^{3+}$ in oxide glasses. Measurements of the bandwidths of the ground and excited states of ${\mathrm{Er}}^{3+}$ and the nearly exponential decay of the emissions indicate a relatively narrow distribution of site symmetries compared to oxide glasses.
573 citations
Authors
Showing all 561 results
Name | H-index | Papers | Citations |
---|---|---|---|
Bahram Javidi | 84 | 937 | 29681 |
G. Dresselhaus | 78 | 325 | 21969 |
Richard A. Soref | 62 | 419 | 19769 |
Yehuda Bock | 62 | 171 | 13236 |
Philip R. Hemmer | 60 | 269 | 22941 |
Laurence S. Rothman | 50 | 133 | 21891 |
John A. Montgomery | 48 | 358 | 33397 |
Shepard A. Clough | 47 | 90 | 17228 |
Donald W. Vasco | 42 | 175 | 5395 |
Frederick J. Rich | 42 | 96 | 5290 |
Brian R. Bennett | 40 | 275 | 10267 |
Joseph Rosen | 39 | 267 | 5252 |
Muralidhar Rangaswamy | 38 | 271 | 5061 |
Mark Cronin-Golomb | 38 | 179 | 5900 |
Jay M. Albert | 38 | 100 | 5586 |