Low-Loss Y-Branch Waveguides Designed by Wavefront Matching Method

In this paper, we describe the procedure for designing low-loss Y-branch waveguides by the wavefront matching (WFM) method, and report experimental results as proof of concept. The designed Y-branches were fabricated using silica-based planar lightwave circuit (PLC) technology. A Y-branch fabricated with a 0.45%-$\Delta$ waveguide exhibited a low excess loss of less than 0.2 dB over a wide wavelength range of 1250 to 1650 nm. In addition, we demonstrate that the WFM-designed Y-branches enable us to provide compact 1 $\times$ 32 splitters with an average insertion loss of 16.0 dB at a wavelength of 1550 nm. In addition, we present some experimental results obtained using samples with different $\Delta$ values, and show that our design method is more efficient for a higher $\Delta$ waveguide suitable for functional PLC devices.