Manufacturing process for striae-free multicomponent chalcogenide glasses via multiple fining steps
The present invention provides a method for synthesizing high optical quality multicomponent chalcogenide glasses without refractive index perturbations due to striae, phase separation or crystal formation using a two-zone furnace and multiple fining steps. The top and bottom zones are initially heated to the same temperature, and then a temperature gradient is created between the top zone and the bottom zone. The fining and cooling phase is divided into multiple steps with multiple temperature holds.
1. A method to make striae-free chalcogenide glass, comprising:
loading chalcogenide glass precursors into an ampoule, sealing the ampoule, and placing the ampoule in a rocking furnace, wherein the rocking furnace comprises a top zone and a bottom zone, wherein the top and bottom zones are two independently controllable temperature zones;
heating both the top and bottom zones at a rate of 3° C. per minute to a Step 1 temperature, wherein the Step 1 temperature is the same for both the top and bottom zones;
maintaining the Step 1 temperature in the top and bottom zones while rocking the furnace at an inclination angle of ±45° for about 15 hours;
increasing the temperature of the top zone at a rate of 3° C. per minute to a Step 3 top zone temperature and decreasing the temperature of the bottom zone at a rate of 3° C. per minute to a Step 3 bottom zone temperature while rocking the furnace at an inclination angle of ±45°, wherein there is a temperature gradient of 100° C. between the Step 3 top zone temperature and the Step 3 bottom zone temperature;
setting the furnace to a vertical position and maintaining the Step 3 top zone temperature and the Step 3 bottom zone temperature for about 3 hours;
decreasing the temperature of the top zone at a rate of 10° C. per minute to a Step 5 top zone temperature, decreasing the temperature of the bottom zone at a rate of 10° C. per minute to a Step 5 bottom zone temperature, and maintaining the Step 5 top zone temperature and Step 5 bottom zone temperature for about 3 hours, wherein the Step 5 top zone temperature is about 100° C. lower than the Step 3 top zone temperature, and wherein the Step 5 bottom zone temperature is about 100° C. lower than the Step 3 bottom zone temperature;
decreasing the temperature of the top zone at a rate of 10° C. per minute to a Step 6 top zone temperature, decreasing the temperature of the bottom zone at a rate of 10° C. per minute to a Step 6 bottom zone temperature, and maintaining the Step 6 top zone temperature and Step 6 bottom zone temperature for about 3 hours, wherein the Step 6 top zone temperature is about 100° C. lower than the Step 5 top zone temperature, and wherein the Step 6 bottom zone temperature is about 100° C. lower than the Step 5 bottom zone temperature;
decreasing the temperature of the top zone at a rate of 10° C. per minute to a Step 7 top zone temperature, decreasing the temperature of the bottom zone at a rate of 10° C. per minute to a Step 7 bottom zone temperature, and maintaining the Step 7 top zone temperature and Step 7 bottom zone temperature for about 30 minutes, wherein the Step 7 top zone temperature is at least 100° C. lower than the Step 6 top zone temperature, and wherein the Step 7 bottom zone temperature is at least 100° C. lower than the Step 6 bottom zone temperature; and
removing the ampoule from the furnace and water quenching the glass.
2. The method of claim 1 , wherein the chalcogenide glass precursors comprise germanium, arsenic, sulfur, and selenium.
3. The method of claim 1 , wherein the chalcogenide glass precursors are sufficient to constitute a glass with the composition of x % at. germanium, y % at. arsenic, z % at. selenium, and (100-x-y-z) % at. sulfur, wherein 0≤x≤10, 30≤x+y≤45, and 0≤z≤10.
4. The method of claim 1 , wherein the chalcogenide glass precursors are sufficient to constitute a glass with the composition of x % at. germanium, y % at. arsenic, z % at. selenium, and (100-x-y-z) % at. sulfur, wherein 0≤x≤25, 30≤x+y≤55, and 0≤z≤20.
5. The method of claim 1 , wherein the Step 1 temperature is about 680° C.
6. The method of claim 1 , wherein the Step 1 temperature is about 650° C.
7. The method of claim 1 , wherein the Step 3 top zone temperature is about 750° C. and the Step 3 bottom zone temperature is about 650° C.
8. The method of claim 1 , wherein the Step 7 top zone temperature is about 450° C. and the Step 7 bottom zone temperature is about 350° C.
9. The method of claim 1 , wherein the Step 7 top zone temperature is about 300° C. and the Step 7 bottom zone temperature is about 200° C.