Compact InP-based 90° hybrid using a tapered 2×4 MMI and a 2×2 MMI coupler

We proposed a novel 90° hybrid using a paired-interference based linearly tapered 2×4 multimode interference (MMI) coupler and a 2×2 MMI coupler. We theoretically calculated and experimentally demonstrated that the proposed 90° hybrid has very short device length of ~227 μm and is never accompanied by any waveguide intersections for performing balanced detection. The proposed device exhibited quadrature phase response with a relative phase deviation of <;±5° over C-band spectral range.