Abstract

Guided-wave nonlinear optical interactions are attractive because of their potential for high conversion efficiency at relatively modest input powers. Achieving this potential requires excellent control over device fabrication process parameters. Interaction between lowest-order guided modes is desirable to maximize overlap integrals and provide a focusable output. Single-crystal fibers of lithium niobate are grown using the laser-heated pedestal growth technique¹ in an orientation suitable for temperature-phase-matched frequency doubling of 1064-nm light. Fiber diameters are maintained to within a few tenths of a percent over tens of millimeter lengths by computer feedback growth control. The crystals are poled by thermoelectric fields generated by temperature gradients applied during or after growth.² This poling technique may enable production of periodically alternating domains for quasiphase-matching interactions using heretofore inaccessible wavelengths or nonlinear coefficients. Magnesium indiffusion is carried out resulting in an approximately parabolic profile graded-index core which will support a 10-20-µm diam fundamental mode.

© 1987 Optical Society of America