Bell Telephone Laboratories

Bruce Cedric Tofield

Heinz Paul Weber

Paul Foo-Hung Liao

Paul Michael Bridenbaugh

Acicula of rare earth pentaphosphates, of a diameter and length ideal for waveguiding laser-type applications, are grown by controlling the rate of metaphosphoric acid conversion by introducing water vapor into an inert gas atmosphere continuously flowed through the reaction zone. The required amount of water vapor in the reaction zone has to be within the range between approximately 14 grams per cubic meter and 290 grams per cubic meter of the flowing atmosphere. This control is implemented by bubbling the inert gas atmosphere through a water bath at temperatures between 15.degree. and 80.degree. C. It is believed that the control of the water vapor eliminates problems of supersaturation in the forming of pentaphosphoric crystals in the growth solution and thereby promotes their natural tendency to form purely chainlike polymer structures.

Process for growing acicula of rare earth pentaphosphates

New lasers employ a halide crystal including alkali metals and rare earths with a very high concentration of the active ions that are arranged to have largest possible separation between themselves. Such laser crystals provide very high energy storage that is finally released in the form of optical radiation. The high energy storage is attributable to a relatively low gain per unit length. The halide crystal is of the perovskite type and typically includes two alkali metals, one of which, for example, sodium, has a much smaller ionic charge than the rare earths and, therefore, will be ordered on the octahedral sites of the perovskite crystal with respect to the rare earth atoms. The stoichiometry of the materials facilitates the high concentration of the rare earth active ions; and the ordering or strict sequencing of alkali and rare earth ions facilitates the large separation of the rare earth active ions which is necessary to minimize non-radiative decay via rare earth pair interaction. If other rare earths are employed other than the active ion, they can serve as diluents or energy transferring elements but are typically not ordered with respect to the active ions, even though on the octahedral sites, unless they are sufficiently different in size from the active ion. In addition, transition metal ions such as chromium can be included and will appear on the octahedral sites and serve to transfer energy to the active ion. When erbium (Er), ytterbium (Yb) or thulium (Tm) are included in suitable combinations, energy conversion of the emission from the infrared to the visible can be obtained. A typical crystal is dicesium sodium neodymium hexachloride (Cs.sub.2 NaNdCl.sub.6), in which Nd.sup.3.sup.+ is the active ion. It is likely that the alkali metals may be replaced by other monovalent ions such as thallium (T1.sup.+), (Cu.sup.+), and silver (Ag.sup.+).

Growing community of inventors

Eatontown, NJ, United States of America

Bruce Cedric Tofield