“…BPP modes are nonradiative with infinitely large momentum and can only be excited using a momentum coupler, such as a prism, or grating, such as surface plasmon polaritons. BPP modes of both type I and type II ( ) can be excited using either coupling technique, showing a high-quality factor (Q) resonance ideal for developing ultrasensitive multimode biosensor [ 2 , 5 , 6 , 9 , 12 , 13 , 14 , 15 , 16 , 17 ].…”