Scalable wafer-to-fiber transfer method for lab-on-fiber sensing

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We present an efficient and flexible method to realize micro- and nano-optical structures on the tip of optical fibers. We demonstrate this approach for a fiber-tip sensor consisting of a photonic crystal (PhC) structure in a semiconductor membrane on the cleaved facet of a telecom fiber. The PhC structure is fabricated on a wafer by lithography and etching and then transferred to the fiber facet by a simple mechanical pickup process through an opening in the substrate, without the need for adhesives or a micromanipulator. Due to its reliability, scalability, and the use of wafer-scale fabrication methods, this process increases the possibilities for fiber-tip applications at the industrial level. With the fabricated fiber tip sensors, we demonstrate sensing of the refractive index and temperature, with resonance wavelength shifts of 120 nm/RIU and 95 pm/K, respectively.