Focusing of in-plane hyperbolic polaritons in van der Waals crystals with tailored infrared nanoantennas

Javier Martín-Sánchez^*, Jiahua Duan, Javier Taboada-Gutiérrez, Gonzalo Álvarez-Pérez, Kirill V. Voronin, Iván Prieto, Weiliang Ma, Qiaoliang Bao, Valentyn S. Volkov, Rainer Hillenbrand, Alexey Y. Nikitin, Pablo Alonso-González^*