Compact and Low-Loss Coherent Mixer Based on High Δ ZrO2-SiO2 PLC

In this paper, we report design and characteristics of a compact coherent mixer based on high Δ planar lightwave circuit (PLC) which consists of ZrO
₂
-doped silica glass. The PLC with 5% or more Δ is realized by employing ZrO
₂
as a dopant. Propagation loss of the fabricated 5.5%-Δ ZrO
₂
-SiO
₂
PLC is reduced to 0.02 dB/cm by an optimized fabrication process. A coherent mixer is designed and fabricated by using ZrO
₂
-SiO
₂
PLC and size of the mixer chip is reduced to 4 mm × 2 mm. Coupling loss between standard single-mode fiber and ZrO
₂
-SiO
₂
PLC is reduced to less than 0.31 dB/facet by an optimized spot-size converter.