Goto N, Yip G L
Appl Opt. 1989 Jan 1;28(1):60-5. doi: 10.1364/AO.28.000060.
Low-loss optical waveguides in Z-cut LiNbO(3) made by proton-exchange with pyrophosphoric acid are investigated. The index increase of 0.131 can be reduced by thermal annealing, which provides a low mismatch of optical fields between a Ti-diffused waveguide and a proton-exchange one. Fabrication conditions of single-mode waveguides are presented. Single-mode slab waveguides without and with annealing show low propagation losses at 0.25 and 0.15 dB/cm with an effective index of 2.2932 and 2.2068, respectively. These waveguides are designed to be just below the cutoff of the next higher-order mode. The diffusion coefficient resulting from both proton-exchange and annealing is also discussed. The fabrication conditions and the prescribed parameters give useful information for designing and fabricating waveguides by proton-exchange and annealing.
研究了通过与焦磷酸进行质子交换在Z切割铌酸锂（LiNbO₃）中制备的低损耗光波导。通过热退火可以降低0.131的折射率增加，这使得钛扩散光波导和质子交换光波导之间的光场失配较低。给出了单模光波导的制备条件。未经退火和经过退火的单模平板光波导分别在0.25 dB/cm和0.15 dB/cm处具有低传播损耗，有效折射率分别为2.2932和2.2068。这些光波导被设计为刚好低于下一个高阶模的截止值。还讨论了质子交换和退火产生的扩散系数。制备条件和规定参数为通过质子交换和退火设计和制造光波导提供了有用信息。
