Robert S. Feigelson

Second harmonic generation and accurate index of refraction measurements in flux-grown KTiOPO 4

Accurate index of refraction measurements have been performed in flux-grown KTiOPO(4). These measurements give good agreement between experiment and theory for angle phase matching in Type II second harmonic generation at 1.064 microm. These refractive-index data have allowed us to calculate the propagation angles for second harmonic generation at wavelengths of interest other than 1.064 microm such as 1.34 microm. Type II second harmonic energy conversion efficiency of 1.064 micro m of up to 59% in this material has also been demonstrated with higher efficiencies possible. Limits to conversion efficiency are discussed.

Pulling optical fibers

Abstract Single crystal fibers have potential for a variety of optical applications both as active and passive elements. They can be produced by a variety of methods; the most versatile of which is the laser-heated pedestal growth technique. Laser heating provides a clean heat source which can be tightly focussed directly onto the sample with a beam size which is comparable with the fiber dimensions of a few μm to several mm. Contamination problems arising from crucibles and furnace components are virtually eliminated in the pedestal growth method, and the amount of material required is minimal. Very steep temperature gradients are possible which permit more rapid growth rates ( ≈ mm/min) than conventional growth methods, and can lead to increased dopant incorporation and the formation of potentially interesting metastable compounds. Crystals of both congruently and incongruently melting compounds can be grown. This method has been found to be a fast, simple, and inexpensive means to produce single crystals for property evaluation, making it an extremely valuable tool for surveying new materials. In addition, small diameter single crystal fibers will usually contain fewer defects than comparable bulk crystals.

Growth and investigation of new non-linear optical crystals of LAP family

Abstract The possibility of preparing new analogs of L-arginine phosphate monohydrate, (LAP), has been investigated. Single crystals of the compound L-Arg·HCOOH, which had earlier been obtained in powdered form, were successfully grown during the course of this investigation. In addition, we have found that there is a class of compounds having the Arg·2Ax composition, (where Ax is one of several inorganic or organic acids). Such compounds (Arg·2HIO 3 , Arg·2HNO 3 , Arg·2H 3 PO 4 , Arg·2HF, Arg·2HCl·H 2 O, and Arg·2HBr·H 2 O) have been synthesized and single crystals grown. The crystals grown in this investigation were studied by IR and X-ray diffraction methods. The influence of the different amino acid groups on crystal symmetry and the influence of this symmetry on non-linear optical properties are discussed.

CdGeAs2—A New Nonlinear Crystal Phasematchable at 10.6 μm

In this paper, we present the optical and nonlinear optical properties of a new nonlinear crystal CdGeAs2. The chalcopyrite structure (42 m) crystal is positive birefringent with Δn equal to 0.1. It is phasematchable for second harmonic generation (SHG) and parametric interactions over most of its transparency range from 2.4 to 18 μm. In addition, it has the largest known nonlinear coefficient for a phasematchable crystal with the exception of tellurium. The measured nonlinear coefficient is 3.4 times GaAs. The calculated doubling efficiency for SHG of a CO2 laser is 10 times that of tellurium. The crystal promises to be a very useful nonlinear material for parametric interactions between 3 and 18 μm.

AgGaS2 infrared parametric oscillator

We report the first operation of an optical parametric oscillator in a chalcopyrite crystal, AgGaS2. Tuning from 1.4 to 4.0 μm is demonstrated for 1.06‐μm Nd:yttrium aluminum garnet pumping. The potential tuning range extends to the 12‐μm transparency limit of the crystal.

Superconducting Bi-Ca-Sr-Cu-O Fibers Grown by the Laser-Heated Pedestal Growth Method

Superconducting fibers of several compositions including the nominal composition Bi2CaSrCu2O8 have been grown by means of the laser-heated pedestal growth method. The influence of starting composition and growth conditions on structure and superconducting properties is discussed. The a-b planes of the material are parallel to the fiber axis (along the growth direction), providing the ideal condition for conduction along the copper-oxygen planes.

Growth of High‐Quality LiNbO3 Crystals from the Congruent Melt

The use of LiNbO3 crystals in nonlinear optical experiments has been limited by the lack of long, high‐quality crystals. We have shown that crystals grown from a congruent composition melt are significantly less susceptible to birefringence variations which in the past have limited the useful phase‐matchable lengths of LiNbO3 crystals. Both a birefringence test which directly measures the spatial birefringence of the crystal and a second harmonic generation test were used to evaluate crystals grown from melts of various compositions. Crystals with less than 10−5 variation in birefringence over a length of 4 cm have been obtained repeatably when grown from congruent melts.

II‐VI solid‐solution films by spray pyrolysis

A complete range of solid‐solution films has been prepared by spray pyrolysis for the CdSxSe1−x and ZnxCd1−xS systems. The composition of the sprayed film is compared with the composition of the spraying solution and correspondence plots are given. The large variation in resistivity with x in the ZnxCd1−xS system appears to be only incidentally dependent on the method of preparation.

High-Throughput Combinatorial Database of Electronic Band Structures for Inorganic Scintillator Materials

For the purpose of creating a database of electronic structures of all the known inorganic compounds, we have developed a computational framework based on high-throughput ab initio calculations (AFLOW) and an online repository (www.aflowlib.org). In this article, we report the first step of this task: the calculation of band structures for 7439 compounds intended for the research of scintillator materials for γ-ray radiation detection. Data-mining is performed to select the candidates from 193,456 compounds compiled in the Inorganic Crystal Structure Database. Light yield and scintillation nonproportionality are predicted based on semiempirical band gaps and effective masses. We present a list of materials, potentially bright and proportional, and focus on those exhibiting small effective masses and effective mass ratios.

Ferroelectric domain structures in LiNbO3 single-crystal fibers

The ferroelectric domain structures of small diameter LiNbO3 single crystal fibers were found to be different from those usually observed in large LiNbO3 crystals. c-Axis grown fibers with diameters up to 800 μm were found to be virtually single domain with +c end facing the melt during growth. Fibers grown along the a-axis had a bi-domain configuration with the domain boundary along the a-axis and parallel to the c-face. A model is proposed, based on the thermoelectric potential generated by axial and radial temperature gradients, to explain the domain structures observed in these fibers.