Compact Polymeric Optical Attenuator Using Laser Writing Asymmetric Y-Junction

We have proposed and demonstrated a wide-angle thermooptic variable optical attenuator using a new type of truncated asymmetric Y-branch waveguide in polymers. The asymmetric parameters in the truncated zone and also the asymmetric waveguide widths of the branch depend on its cross-talk (CT), attenuation efficiency and the length of the device or the packing density. An analysis for the optimum phase matching at the branching zone is performed to improve the transmission efficiency. The attenuation efficiency of this structure with variation of the device parameters is studied. In the passive state the simulated cross-talk is obtained ~ –38dB at branching angle 2A=1. It is shown that the length of each attenuator is ~ 1.3 mm which is about 6.5 times less than that of the attenuator using a normal Y-junction. The structure also shows that the wanted power in the wider output arm can be made maximum at the phase matching between the inner and the outer paths of bending and also considering the optimum parameters of the structure. A focused argon-ion laser beam (O=351nm) was used to polymerize acrylate monomer for patterning the core waveguide. The Gaussian shaped core with uniform refractive index profile produces an equivalent rib structure with a single-mode channel waveguide even for high-index difference core and the cladding. The experimental results of relative output power in the wider arm of the proposed structure without trench versus electrical power consumption of the heater and the corresponding simulated results are shown. The simulated result of the structure with a trench shows the improvement of electric power consumption.