Feedback System Automation/Modeling for Crystal
Optical Fiber Growth
Recent interests in developing miniature fiber laser, couplers, and integration of those with fiber optic communications, demand high quality defect free single crystal fibers of materials with fine core-cladding structure to be compatible with single mode propagation. To achieve the required geometry and fiber diameter, the laser heated pedestal growth (LHPG) technique is one of the most promising approach. A state-of-the-art laser growth facility has been developed in Dr. Guo’s lab in the last decade, with its numerous advantages (high growth speed, crucible free growth, growth of very high melting point materials), the technique is capable of rendering crystals of high purity, excellent stoichiometry, and high optical quality with orientation control. The uniformity of a fiber diameter along the length of the growth is affected by laser power and its mode distribution, and also by the pulling and feeding mechanism in the LHPG set up. In the past we have employed successfully this system for growing fibers of various ferroelectric, nonlinear optic, photorefractive and high melting point materials, for both materials studies and fiber device applications in federal funded programs. An automation system is envisioned to facilitate special growth conditions, including ferroelectric crystals with periodically poled structures, tapered crystal fiber growth with single mode core-cladding configurations, etc.. Melt-growth modeling may be also built in with the automatic control systems, coupled with CCD camera, and digital optical pyrometers. Undergraduate student will work on this project to construct an automatic control system, integrating laser gas pressure, discharge current, pulling and feeding parameter controls, into a complete real time computer controlled system, develop LabView software, and conduct testing and tuning of the system, with assistance from a postdoctoral personnel.. MathCAD 3D modeling for liquid-solid growth surface under laser heated pedestal growth condition may be also performed.