Polymeric Single-Mode Step and Gaussian Refractive Index Profile Directional Couplers

We fabricated polymeric single-mode step and Gau]ssian core refractive index profile optical waveguides. We used polymethylmethacrylate (PMMA) and mixture of two monomers for the cladding and core of the waveguide, respectively. The thickness of the core guiding layer was controlled by the spinning speed and viscosity of the polymeric solution. Cores of the Gau]ssian profile waveguide are fabricated by using an argon ion laser beam for UV-light irradiation on the two blended monomers. The advantages of using laser beam in fabricating core of the polymeric waveguides are discussed. Step profile waveguides arc fabricated by the conventional mask-based photolithographic technique. The losses of waveguides are measured ~0.05 dB/cm at 780 nm and 1.3 μm wavelengths. We fabricated the directional couplers of different coupling lenguSs as well as the different waveguide dimensions. Experiments for the directional couplers are carried out using a laser diode light source of wavelength λ =780 nm. We performed theoretical analysis for the directional couplers using coupled-mode and beam propagation theory, and observed good agreement with the experimental results.