Experimental Demonstration of Birefringence Compensation Using Angled Star Couplers in Silica-Based Arrayed Waveguide Grating

A birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) is experimentally investigated in silica-on-silicon waveguide with B-Ge codoped upper cladding. A 16-channel AWG with 100-GHz channel spacing is designed and fabricated. The star couplers are designed according to Rowland circle construction with an oblique incident/diffraction angle. Five different polarization compensation parameters corresponding to different incident/diffraction angles are employed to investigate the stress-induced birefringence. The experimental results confirm that the polarization-dependent wavelength shift (PDλ) can be tuned by varying the incident/diffraction angle at the star couplers, and a birefringence-free AWG can be achieved without any additional fabrication process.