Cost-efficient and high precision method for the assembly of LN-based photonic crystal slabs on the fiber tip for the implementation of E-field sensors

Lab-on-fiber technology is an emerging topic for sensing cutting-edge technologies due to the high versatility and functionality that it offers when it is combined with different sensitive materials. A particular configuration, which consists of the integration of nanophotonic structures into the tip of a pigtailed fiber, allows the exploitation of light localization performances to produce high-performing sensors. However, integrating such tiny structures into the fiber facet requires complex and expensive procedures. In this work, we report a novel high precision assembly procedure that ensures the parallelism between the photonic chip and the fiber surface, in addition to the alignment with the light injection into the nanostructure. The integrated structure consists of an ultra-compact (19 mu m x 19 mu m) Photonic Crystal Slab (PCS) structure based on a 700 nm thin film of lithium niobate (LN) which is sensitive to external E-fields via the electro-optic effect. Thus, the assembled sensor detects electric fields, presenting great linearity and a sensitivity of 170 V/m. This technique shows a way to assemble compact planar nanostructures into fiber facets keeping high throughput, high precision, and relatively low costs. (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement