Ultra-Sharp and Highly Tolerant Waveguide Bends for InP Photonic Membrane Circuits

In this letter, we present a sharp bend design for the InP-based photonic membrane, which shows low loss and high tolerance. The traditional arc bends on InP membranes face high loss when the bending radii reduce below 2 $\mu \text{m}$ . In addition, their performance deteriorates even more dramatically at the presence of waveguide footings. The proposed design has the advantages of low loss, high compactness, wide spectral response, and ease of fabrication. It is also verified to be much more resilient to design and fabrication variations, such as waveguide footings. The sharp bend is fabricated together with traditional arc bends. Experimental results confirm its potential as a basic building block for InP photonic membrane platforms.