Bell Telephone Laboratories

Heinz Paul Weber

Edwin Arthur Chandross

Walter J Tomlinson, Iii

Bruce Cedric Tofield

Paul Foo-Hung Liao

Coralie Anne Pryde

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

A photopolymerization process is adapted for the production of various optical devices by means of a modified process which serves to increase the index change obtainable in a variable pattern of index of refraction. The process comprises the steps of flowing into place in a supporting structure a mixture of two components of differing reactivity and polarizability, partially polymerizing the mixture, writing a pattern of varying index of refraction in the partially polymerized mixture by further polymerizing it by suitable optical radiation in a corresponding pattern, and fixing the mixture against subsequent changes in polymerization. Typical components used in the process include a mixture of the monomers cyclohexyl methacrylate and N-vinylcarbazole together with benzoin methyl ether as a photosensitive initiator of polymerization, which proceeds by free radical reactions. In the limit of our technique, one of the components can have zero reactivity. This photopolymerization process is applicable to production of volume gratings in closed cavities having parts with constricted clearances therebetween, in which application it is impossible to evaporate unreacted components after the mixture has been flowed into place. The volume gratings are useful in distributed feedback lasers, in frequency sensitive optical filters and in channel-dropping arrangements for optical communication systems. Submerging the apparatus in which polymerization is to occur in an index-matching fluid between flat glass plates is an aid to producing uniform volume gratings in a cylindrical device.

Photopolymerization process and related devices

A technique for the fabrication of integrated optical circuits is described wherein a transparent polymer film, which is doped with a polynuclear aromatic thiol having higher index of refraction than the polymer, is deposited from a liquid solution on a smooth substrate. Upon selective exposure to radiation there is a substantial reduction or elimination of the mobility and volatility of the dopant in the polymer matrix, a phenomenon known as 'photolocking'. The described class of dopant permits the attainment of higher resolution than previously reported, as well as the preparation of optical direction couplers having higher coupling strengths than those of the prior art.

Producing integrated optical circuits

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.+).

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Middletown, NJ, United States of America

Heinz Paul Weber