Striae-Free Chalcogenide Glasses

Abstract

A striae-free chalcogenide glass with uniform refractive index.

What we claim is: 
     
         1 . A product of the process comprising the steps of:
 melting chalcogenide glass inside a sealed silica ampoule;   providing a 2-zone furnace comprising an upper zone and a lower zone wherein the upper zone is at a higher temperature than the lower zone and wherein the zones are independently controllable temperature zones;   mixing by rocking the sealed silica ampoule inside the 2-zone furnace;   placing the sealed silica ampoule in a vertical position;   forming a glass melt as the upper zone is at a higher temperature than the lower zone;   positioning the glass melt such that the glass melt is within the lower zone; and   cooling slowly and quenching the temperature;   reducing the temperature of the upper zone at a rate of 0.6° C./min to 370° C.;   reducing the temperatures of the lower zone at a rate of 0.6° C./min to 260° C.;   holding these temperatures for 12 hours; and thereby   forming the striae-free chalcogenide glass.   
     
     
         2 . The product of the process of  claim 1  further comprising the step of preventing convection currents within the glass melt as the glass melt solidifies forming the chalcogenide glass. 
     
     
         3 . The product of the process of  claim 2  further comprising the step of preventing condensation of glass on the ampoule as the glass melt cools. 
     
     
         4 . The product of the process of  claim 1  further comprising the steps of:
 allowing for an initial melting of the chalcogenide glass prior to the step of mixing by rocking; and 
 allowing for homogenization of the chalcogenide glass. 
 
     
     
         5 . The product of the process of  claim 4  further comprising the step of avoiding abrasion of the ampoule during the rocking step. 
     
     
         6 . The product of the process of  claim 1  further comprising the steps of:
 maintaining the temperature of the lower zone at a temperature of about 700° C. for about 24 hours; and 
 maintaining the temperature of the upper zone at a temperature of about 100° C. greater than the temperature of the lower zone for about 24 hours. 
 
     
     
         7 . A product of the process comprising the steps of:
 loading arsenic and sulfur precursors sufficient to constitute a 120 gram batch of glass with the composition of 39% at. arsenic (As) and 61% at. sulphur (S) or about 71.88 grams As and 48.12 grams S into a silica ampoule under an inert gas atmosphere;   connecting the ampoule to a vacuum pump;   evacuating the ampoule for 4 hours at 1×10 −5  Torr;   sealing the ampoule;   placing the ampoule inside a rocking furnace with a ±45° angle of inclination wherein the furnace has a top zone and a bottom zone and wherein the zones are independently controllable temperature zones;   heating and rocking the ampoule;   heating the top zone and the bottom zone of the furnace at a rate of 3° C./min from room temperature;   heating the top zone to 850° C.;   heating the bottom zone to 750° C.;   holding constant the temperature of the top zone (850° C.) and bottom zone (750° C.) for 10 hours;   rocking the furnace at an inclination angle of ±45° to facilitate mixing and homogenization of the elemental components;   stopping the furnace motion;   setting the furnace to a vertical position or 90° fixed angle;   decreasing the temperature of the top zone at a rate of 1° C./min to 800° C.;   decreasing the temperature of the bottom zone at a rate of 1° C./min to 700° C.;   holding the furnace position and temperature profile for 24 hours to facilitate fining and settling of the glass melt;   reducing the temperature of the top zone at a rate of 0.6° C./min to 370° C.;   reducing the temperatures of the bottom zone at a rate of 0.6° C./min to 260° C.;   holding these temperatures for 12 hours;   forming a chalcogenide glass;   removing the ampoule from the furnace;   submerging the ampoule in a room temperature water bath for 10 seconds to quench the chalcogenide glass;   annealing the chalcogenide glass by placing the ampoule in another furnace at 180° C. for 10 hours; and   forming a striae-free chalcogenide glass.   
     
     
         8 . A chalcogenide glass comprising a striae-free and high optical quality chalcogenide glass that is uniform and homogeneous. 
     
     
         9 . The chalcogenide glass of  claim 8  wherein the striae-free chalcogenide glass has no refractive index perturbations. 
     
     
         10 . The product of the method to synthesize striae-free chalcogenide glass using melt processing comprising melting chalcogenide glass inside a sealed silica ampoule, providing a 2-zone furnace comprising an upper zone and a lower zone wherein the upper zone is at a higher temperature than the lower zone, mixing by rocking the sealed silica ampoule inside the 2-zone furnace, placing the sealed silica ampoule in a vertical position, forming a boule as the upper zone is at a higher temperature than the lower zone, positioning the boule such that the chalcogenide glass is within the lower zone, and cooling slowly and quenching the temperature and thereby forming the striae-free chalcogenide glass.