Norman A. Sanford

Simplified Z-propagating DC bias stable TE-TM mode convertor fabricated in Y-cut lithium niobate

A TE-TM mode converter, useful at either 0.632 or 0.840 mu m, has been fabricated on y-cut LiNbO/sub 3/ by Ti indiffusion with the channel waveguide placed parallel to the z-axis. For TE polarized input, the maximum TM modulation depth is 97 percent at 0.632 mu m with a 5-V (pp) drive and 99 percent at 0.840 mu m with a 12-V (pp) drive. A similar device operating at 1.3 mu m displays 98-percent TE-TM switching at 68 V. Operation involves only coplanar electrodes placed alongside the channel acting on the r/sub 61/ electrooptic coefficient. A separately deposited buffer layer is unnecessary. Testing indicates a substantially greater tolerance to electrode misalignment than afforded by similar structures formed in x-cut substrates. Data illustrating immunity to photorefractive drift in the presence of a DC bias voltage is presented for 0.840- mu m wavelength operation. >

Characterization Of Titanium Diffusion During Fabrication Of LiNbO[sub]3[/sub] Optical Waveguides Using Analytical Electron Microscopy

Analytical Electron Microscopy (AEM) has been used to characterize the microstructural evolution of thermally evaporated Ti films on single-crystal LiNbO3 substrates. The microstructural evolution exhibits three primary stages: Ti oxidation which is initially observed at 370°C and is essentially complete by ~500°C; formation of a two-phase microstructure of TiO2 and LiNb3O8 at ~800°C which grows epitaxially with respect to the LiNbO3 substrate; eventual diffusion of both phases occurs at 1000°C to leave only a Ti:LiNbO3 solid solution.