Self-Assembled Colloidal Photonic Crystal on the Fiber Optic Tip as a Sensing Probe

• Main Authors: Pasquale Di Palma, Chiara Taddei, Anna Borriello, Giovanna De Luca, Michele Giordano, Agostino Iadicicco, Stefania Campopiano, Lucia Sansone
• Format: Article
• Language: English
• Published: IEEE 2017-01-01
• Series: IEEE Photonics Journal
• Subjects: Fiber optic sensor; photonic crystal; colloidal crystal; self assembly.
• Online Access: https://ieeexplore.ieee.org/document/7888923/

This paper presents an effective and efficient method to fabricate novel fiber optic sensing probes. The new, simple, and low cost approach is based on a 3-D photonic crystal dielectric structure directly deposited on the tip of a multimode optical fiber through the self-assembly of colloidal crystals (CCs) via a vertical deposition technique. Here, the CC is made of polystyrene nanospheres with 200 nm diameter, and the optical fiber is a UV-vis fiber with a core diameter of 200 μm. The obtained fiber probes exhibit a resonant peak at 480 nm and an amplitude enhancement of 3.7 with respect to the bare fiber; these results are highly repeatable. A numerical tool based on a finite element method analysis has been developed to study and analyze the 3-D subwavelength structures. Numerical results are in good agreement with the observed experimental spectra. Moreover, refractive index measurements have been carried out, revealing a sensitivity of up to 445 nm/RIU in the 1.33-1.36 values range. The achieved performances, which have been obtained by using very small active areas and an easy and reliable fabrication procedure, demonstrate the future perspectives of these fiber-optic probes for chemical and biological sensing applications.