W. H. Grodkiewicz

1.5‐μm infrared excitation of visible luminescent in Y1−xErxF3 and Y1−x−yErxTmyF3 via resonant‐energy transfer

Intense visible emission in the red, green, and blue has been observed from infrared to visible multiphoton Y1−xErxF3 upconversion phosphors pumped with 1.5‐μm radiation from InGaAsP‐laser sources. With 0.01<x<0.2, the dominant emission is in the green corresponding to transitions from the 4S3/2 level of Er3+. The addition of Tm3+ in the 0.001–0.02 range preferentially quenches the emission from the higher‐energy Er3+ levels resulting in a red visible emission originating on the Er3+ 4F9/2 level. The phosphors are useful visible monitors of focused 1.5‐μm semiconductor laser and unfocused F‐center laser radiation. The unexpectedly high brightness in the visible may be attributed to thermal equilibration, where the excitation is trapped in the higher lying states after each upconversion step.

The growth of K0.6Li0.4NbO3 crystals for electro-optic and non-linear applications

Single crystals of ferroelectric K0.6Li0.4NbO3 can be grown from the melt by slow cooling or by the Czochralski technique. A preferred form is obtained when an excess of alkali metal is present. This material has good optical properties, is desirable for electro-optic and non-linear applications and is stable to 0.488 μm radiation at least to the 0.3 W level.

Borosilicate glasses for fiber optical waveguides

Abstract Of the existing optical glasses, pure fused silica is known to have the lowest optical attenuation in the red and near infrared portion of the spectrum where optical communications appears most promising. However, to approach the low attenuations afforded by pure fused silica in a waveguide structure requires that a core of fused silica be clad with a glass of slightly lower index refraction. This paper describes an investigation of the binary borosilicate glass system which has led to the realization of a promising cladding material for pure fused silica core fibers.

SOME CHARACTERISTICS OF Ba, Sr, Na NIOBATES.

Abstract Curie temperature (T C ) and spontaneous polarization (P S ), dielectric constant (e), and voltage for half-wave retardation (V π ) of 0.6328μ radiation, all at room temperature, are given for single crystals of a Ba, Sr, Na niobate series which have tetragonal tungsten bronze-like structures. P s is a relatively constant 0.38 ± 0.02 C/m 2 for most of the series while T c varies between 560°C and 200°C. V π declines approximately linearly with increasing Sr-content and the product eV π tends to remain constant for poled crystals. Resistivity data are also given.

EFFICIENT INFRARED‐TO‐VISIBLE CONVERSION BY RARE‐EARTH OXYCHLORIDES

When pumped by radiation from a Si–GaAs diode, the luminous efficiency of Y3OCl7:Yb3+, Er3+ is comparable to that of visible emitting GaP diodes. By varying the Yb3+ concentration, phosphors have been made which produce a red or yellow visual response.

Iron garnet crystals for magneto‐optic light modulators at 1.064 μm

Faraday rotation and optical absorption measurements are reported for several magnetic iron garnets. The results show that certain compositions containing praseodymium (or possibly neodymium) should allow the operation of magneto‐optic modulators at 1.064 μm, having less than 3 dB of optical loss and requiring less drive power per unit bandwidth than the best available diffraction‐limited electro‐optic modulators.

Growth‐induced anisotropy of some mixed rare‐earth iron garnets

We have measured the growth‐induced noncubic magnetic anisotropy under (110) facets of flux‐grown garnet crystals at 300°K. The garnets studied have the general formula RM2Fe5O12, where R represents Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and M represents Y, Lu, or Gd. Measurements were made at room temperature in the (110) plane. The contribution of Gd and of all ions heavier than Tb is found to be small. The growth‐induced anisotropy of all garnets containing Pr, Sm, Eu, or Tb is consistent with a model in which site preferences on the rare‐earth sublattice are smooth functions of the ionic radius mismatch, and the single‐ion magnetic anisotropy is due to anisotropic exchange. The anisotropy of the exchange appears to have the same sign and order of magnitude for all four ions. The behavior of Nd is anomalous and can be attributed to crystal field effects.

Garnets for bubble domain devices

Abstract Large crystals of rare earth iron garnets having magnetically uniaxial regions under 211 faces may be grown from a PbO·PbF 2 ·B 2 O 3 flux. Bubble size and uniformity over large areas can be particularly good for plates cut from crystals with low moment and negligible magnetostriction. Garnets containing four to six metals appear to be most useful; two to form a low moment garnet, one or two more to obtain a small temperature coefficient and an additional one or two to minimize magnetostriction (e.g. Eu 2 GdAl .3 Fe 4.7 O 12 and Y 1.85 Eu .18 Gd .50 Tb .47 Ga .6 Fe 4.4 O 12 ).

Infra-red stimulable rare earth oxy-halide phosphors; their synthesis, properties and applications

Abstract Rare earth compounds containing C1 that are activated by Er, Ho and/or Tm and sensitized by Yb can emit visible radiation with considerable efficiency when excited by 0.93μ radiation from a GaAs: Si diode. Further, color “tunability” from green to red is realized for Er or Er plus Ho activation when oxygen is present. The growth of oxychlorides out of trichlorides, the preparation of fluorochlorides, their properties and their applications are discussed.

Investigation of the soda aluminosilicate glass system for application to fiber optical waveguides

Abstract An extensive investigation of the soda aluminosilicate glass systems has been conducted to determine the suitability of this material for low loss fiber optical waveguides. Based on measurements of scattering loss energy gap, and glass transition temperature we conclude that certain compositions of soda aluminosilicate glass have substantially lower measured scattering loss and less estimated absorption loss than pure fused silica, the best of the present waveguide materials. Scattering losses less than 1 4 that of pure fused silica have been observed.