UV-imprinting of single-mode polymeric waveguides

Polymers are important materials in fabrication of photonics devices due to their good optical properties, such as, high transmittivity, versatile processability also at low temperatures allowing potential for low-cost fabrication. A critical requirement in the fabrication of integrated optical devices has been selecting a most suitable method for patterning the ridge bounding the optical mode in the waveguide. In this paper, we discuss a UV-imprint fabrication of polymeric single-mode waveguides with different configurations: ridge type, inverted rib type and layered composite waveguides. A ridge waveguide type consists of a strip waveguide superimposed onto a slab waveguide made of the same material. When patterning a ridge by imprinting technique, a residual layer is formed underneath the imprinted ridges. A too thick residual layer might cause a loss of propagation mode due to power leakage to the slab guide, which might require a subsequent etching step. In inverted rib waveguide structure, a groove of cladding material is patterned by imprinting. This is followed by the filling of the groove with a core material. From the imprint fabrication point of view, the fabrication tolerances can be relaxed because the residual slab layer underneath the waveguide can have arbitrary thickness. Besides fabrication of above mentioned waveguide structures, we also investigate the possibility to produce composite waveguide devices by depositing inorganic thin films with high-refractive index on UV-imprinted polymeric structures with low-refractive. The purpose to use composite structures is to manipulate the optical field distribution in waveguides.