Label-free biosensor array comprised of Vernier microring resonator and 3 × 3 optical coupler Parisa Sanati, Amene Shafiee, Mahdi Bahadoran and Elnaz Akbari Eur. Phys. J. Plus, 135 11 (2020) 869 Published online: 30 October 2020 DOI: 10.1140/epjp/s13360-020-00888-6