Single mode field analysis and adjustment on polymer waveguides understanding the reasons for coupling losses

Abstract

Integrated optic single mode waveguides in polymer substrates are of interest for several applications especially in the visible wavelength range e.g. to build waveguide components for biophotonic, sensors or passive splitters. The manufacturing process contains DUV or UV lithography and some different pre or post exposure bakes depending on the used type of polymer. Chromium masks offer facile and controllable processing and rapid exposure times. Surface waveguides can be covered with an index matched cladding substrate on top to get buried light guiding. The end faces and also the over all thickness of about 1 mm of the component packages gives the possibility for a stable coupling between fiber arrays and planar waveguide substrates.The paper describes the results of a single mode field analysis and the experimental adjustment of polymer waveguides for wavelengths within the visible range of light to achieve low coupling losses. Some different manufacturing process steps are compared depending on the used polymer material. A comparison between the measured waveguides and fiber mode near field diameters and the nominal calculated numerical apertures are presented. The different insertion loss is measured and illustrated as well.

Investigation of birefringence in PMMA channel waveguides inscribed with DUV radiation

“…where n is the maximum change of the refractive index at the top of the substrate and a represents the decay constant of the refractive index change. As was shown in [6,7], the parameter n increases nonlinearly with increasing exposure dose, while the decay constant a does not depend on the dose. The values of n and a were determined using the inverse WKB method that allows us to reconstruct an arbitrary profile of the refractive index in the planar waveguide from the measured effective indices of higher order modes [6,8].…”