Tunable photonic differentiator via Bloch surface waves Jian Shi, Jun Li, Cuicui Li, Yuqiu Zhang, Jiangnan Lv, Yan Zhan, Xianping Wang, Yibin Huang and Jian Wu Eur. Phys. J. D, 78 8 (2024) 109 Published online: 22 August 2024 DOI: 10.1140/epjd/s10053-024-00867-x