Planar polymer waveguides with a graded-index profile resulting from intermixing of methacrylates in closed microchannels

• Published in: Optical materials Vol. 76; pp. 210 - 215
• Main Authors: Missinne, Jeroen, Misseeuw, Lara, Liu, Xiang, Salter, Patrick S., Van Steenberge, Geert, Adesanya, Kehinde, Van Vlierberghe, Sandra, Booth, Martin J., Dubruel, Peter
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2018
• Subjects: Capillary filling; Graded-index; Intermixing; Microchannel; Polymer waveguide; Capillary filling; Graded-index; Microchannel; Polymer waveguide; Intermixing
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2017.12.039

Graded-index waveguides are known to exhibit lower losses and considerably larger bandwidths compared to step-index waveguides. The present work reports on a new concept for realizing such waveguides on a planar substrate by capillary filling microchannels (cladding) with monomer solution (core). A graded-index profile is obtained by intermixing between the core and cladding material at the microchannel interface. To this end, various ratios of methyl methacrylate (MMA) and octafluoropentyl methacrylate (OFPMA) were evaluated as starting monomers and the results showed that the polymers P50:50 (50:50 MMA:OFPMA) and P0:100 (100% OFPMA) were suitable to be applied as waveguide core and cladding material respectively. Light guiding in the resulting P50:50/P0:100 waveguides was demonstrated and the refractive-index profile was quantified and compared with that of conventional step-index waveguides. The results for both cases were clearly different and a gradual refractive index transition between the core and cladding was found for the newly developed waveguides. Although the concept has been demonstrated in a research environment, it also has potential for upscaling by employing drop-on-demand dispensing of polymer waveguide material in pre-patterned microchannels, for example in a roll-to-roll environment. [Display omitted] •A new concept for obtaining graded-index polymer waveguides on a planar substrate is presented and evaluated.•The gradual index transition is obtained by mixing between polymer core and cladding materials at a microchannel interface.•Non-destructive and quantitative techniques (THG microscopy and QPM) are used for mapping the refractive index distribution.