Uno Hisashi, Ishigure Takaaki
Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokoham 223-8522, Japan.
Opt Express. 2011 May 23;19(11):10931-9. doi: 10.1364/OE.19.010931.
Graded-index (GI) polymer parallel optical waveguides with high-absorption, carbon-black-doped cladding are fabricated using the preform method in order to reduce the inter-channel crosstalk. The waveguides exhibit a lower inter-channel crosstalk (<-69.3 dB) than optically-transparent-clad waveguides (~-33.7 dB) and maintain low propagation loss (0.029 dB/cm). We characterize the waveguides with different concentration of carbon black in order to confirm the required concentration (required absorption loss) for keeping the inter-channel crosstalk low enough. In addition, carbon-black-doped waveguides are fabricated directly on a substrate by means of a soft-lithography method. Crosstalk is sufficiently decreased despite the high scattering loss of the core material, while insertion loss is not increased. Furthermore, we fabricate a waveguide with a high-scattering-loss cladding to confirm the origin of low crosstalk in carbon-black-doped waveguides. We confirm that high scattering loss of cladding is not necessarily as effective for crosstalk reduction as high absorption loss of cladding.
为了降低通道间串扰，采用预制棒法制造了具有高吸收、掺炭黑包层的渐变折射率（GI）聚合物平行光波导。与光学透明包层光波导（约-33.7 dB）相比，这些光波导表现出更低的通道间串扰（<-69.3 dB），并保持低传播损耗（0.029 dB/cm）。我们对具有不同炭黑浓度的光波导进行表征，以确定保持通道间串扰足够低所需的浓度（所需吸收损耗）。此外，通过软光刻法在衬底上直接制造掺炭黑光波导。尽管芯材具有高散射损耗，但串扰仍充分降低，而插入损耗并未增加。此外，我们制造了具有高散射损耗包层的光波导，以确认掺炭黑光波导中低串扰的来源。我们证实，包层的高散射损耗对降低串扰的效果不一定与包层的高吸收损耗一样有效。
