K. B. Chang

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Error rates for a narrow-band digital FM system with discriminator detection in a land mobile radio channel characterized hy fading and Doppler frequency shift are obtained using a new analytical method. The fading rate is assumed to be much slower than the bit rate so that signal distortion through a narrow bandpass filter can he analyzed via a quasistatic(More)
The efficiency of third-harmonic generation in cuprous oxide was measured. Intensities followed a noncubic power law that indicates nonperturbative behavior. Polarization anisotropy of the harmonic generation was demonstrated and related to the third-order susceptibility. The results will influence the understanding of harmonic generation in centrosymmetric(More)
Laszlo Frazer,1,* Kelvin B. Chang,2 Kenneth R. Poeppelmeier,2,3 and John B. Ketterson1,4 1Department of Physics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3112, USA 2Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3112, USA 3Chemical Sciences and Engineering Division, Argonne(More)
The various decay mechanisms of excitons in cuprous oxide (Cu2O) are highly sensitive to defects which can relax selection rules. Here we report cryogenic hyperspectral imaging of exciton luminescence from cuprous oxide crystals grown via the floating zone method showing that the samples have few defects. Some locations, however, show strain splitting of(More)
The role of charge density matching was investigated in the formation of templated vanadium tellurites under mild hydrothermal conditions. Reactions were conducted using a fixed NaVTeO(5):amine ratio in an ethanol/water solution to isolate the effects of amine structure. The use of 1,4-diaminobutane, 1,3-diaminopropane, and piperazine resulted in three(More)
Mid-IR nonlinear optical (NLO) materials are of great importance in modern laser frequency conversion technology and optical parametric oscillator processes. However, the commercially available IR NLO crystals (e.g., AgGaQ2 (Q = S, Se) and ZnGeP2) suffer from two obstacles, low laser damage thresholds (LDTs) and the difficulty of obtaining high-quality(More)
Phase-pure cuprous oxide (Cu2O) crystals are difficult to grow since cupric oxide can form within the crystal as the crystal is cooled to ambient conditions. Vacancies are the solute which causes precipitation of macroscopic defects. Therefore, even when a mostly phase-pure single crystal is used as a feed rod, cupric oxide inclusions persist in the(More)
The title compound, {(C6H21N4)[V3O9]·H2O} n , crystallizes as a salt with [trenH3](3+) cations [tren is tris-(2-amino-eth-yl)amine], and one-dimensional anionic {[V(V)O3](-)} n (metavanadate) chains along the c-axis direction. Three crystallographically distinct V(V) sites and one occluded water mol-ecule are present for every [trenH3](3+) cation in the(More)
In oxyfluoride chemistry, the [MO(x)F(6-x)](2-) anions (M = transition metal) are interesting polar building units that may be used to design polar materials, but their polar vs antipolar orientations in the solid state, which directly depend on the interactions between O(2-)/F(-) ligands and the extended structure, remain difficult to control. To improve(More)
The valence matching principle is used to explain the loss of inversion symmetry in the noncentrosymmetric (NCS) polymorph of KNaNbOF5 in comparison to its centrosymmetric (CS) polymorph. The [NbOF5](2-) anion has five contacts to both potassium and sodium in the NCS polymorph, whereas in the CS polymorph there are only four contacts to potassium and six(More)