Demonstration of 90° optical hybrid at 2 μm wavelength range based on 4×4 MMI using diluted waveguide

A 4×4 MMI 90°optical hybrid for 2 μm is designed, fabricated and characterized using a monolithically integrated MZI. A phase deviation around ±10°, Common Mode Rejection Ratio > 15.6 dB and an excess loss of 2.2 dB are obtained.