Abstract

Semiconductor core optical fibres are a relatively nascent technology that is highly desirable for fibre-based photonic applications [1,2]. They have the capacity to combine strong optical nonlinearities, tight light confinement, broadband transmission, and electronic functionality within a single fibre platform. Recently perovskites have emerged as exciting materials for semiconductor photonics as they have strong optical nonlinearities and tunable optoelectronic properties. However, the lead-based perovskites comprise toxic elements making them en-vironmentally unfriendly materials. Furthermore, the inverse temperature crystallization process used to produce the fibres limits the core size to a minimum of 50 µm, rendering them unsuitable for nonlinear optics and applications that require single-mode guidance, such as telecommunications [3]. In this paper, we introduce a metal-free perovskite core optical fibre where lead has been substituted for an ammonium cation in the perovskite structure. The core material, MDNI, has a wide band gap greater than 5 eV and a core diameter that can be produced as small as 5 µm. The fibre supports just six modes at this core size, and the fundamental mode can readily be excited and isolated. In contrast to archetypal lead-based perovskites and many other semiconductor core materials, such as silicon and germanium, the metal-free perovskite core material lacks centrosymmetric and has a second-order susceptibility. The second-order susceptibility is important for many important nonlinear optics applications such as second-harmonic generation and quantum optics.

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