Optical lattice generation using vertically embedded multimode-interference square-core polymer waveguides on a silicon chip

We demonstrate two-dimensional optical lattice generation at 1064nm wavelength using vertically embedded multimode-interference (MMI) square-core polymer waveguides on a silicon chip. We demonstrate tuning of the effective waveguide length by longitudinally offsetting the waveguide input end-face from the input beam waist. Our measurement results of the waveguides with different cross-sectional dimensions at different effective waveguide lengths exhibit lattice patterns spanning from 4 × 4 to 10 × 10 arrays at the waveguide output end-face. Our theoretical analysis reveals that the offset causes additional mode-dependent phase changes. Our numerical modeling results using the three-dimensional beam-propagation method are consistent with our experimental results and theory.