Experimental evaluation of curved polymer waveguides with air trenches and offsets

Excess waveguide bend loss can be minimized through the use of offsets and air trenches. Offsets, used for reducing the junction loss between straight and curved waveguides, and air trenches, which prevent bend radiation loss, were simulated by a three-dimensional, semivectorial beam propagation method. Low loss polymer waveguide bend structures, employing both offsets and trenches, were fabricated. A reduction of the 180 degrees bend insertion loss from 17.7 to 3.0 dB with a bending radius (BR) of 1.5 mm is experimentally confirmed at lambda=1.55 mu m. BR ranging from 5 to 0.5 mm are evaluated with decent match when compared with simulation results. The polarization dependent loss is BR dependent with a maximum value of 0.4 dB when the BR is reduced to 0.5 mm. The experimental results confirm that the joint use of air trenches and junction offsets is effective in reducing the bend radii of low index contrast polymer waveguides in planar lightwave circuits. (c) 2006 American Institute of Physics.