Excitation of Bloch Surface Waves on an Optical Fiber Tip

Abstract

to the development of extremely sensitive surface plasmon resonance (SPR) biosensors, which can rely on mature fabrication technologies, standard biofunctionalization protocols, and commercial scale production. [1,[3][4][5] In spite of the excellent performance achieved by state-of-the-art SPR platforms, with reported limits of detection (LODs) approaching 10 −7 refractive index units (RIU), [4,6] further improvements are unavoidably limited by the reliance on lossy materials (typically metals). This yields an undesirable resonance broadening, thereby posing an upper bound to the overall figure of merit (FOM). [6] For this reason, there is a strong push to explore alternative, larger-FOM SW implementations. [1,[7][8][9][10][11] As a prominent example, Bloch SWs (BSWs) on truncated 1D photonic crystals (1DPCs) represent an attractive alternative to SPPs, as recently demonstrated in several proof-of-principle studies. [9,[12][13][14][15][16] In spite of sensitivities to local refractive index (RI) changes lower than SPR platforms, the completely dielectric low-loss structure of a BSW sensor yields sensibly sharper resonances, leading to generally larger FOMs. [13][14][15][16][17] This has recently led to the successful development of label-free biosensors exhibiting competitive performance in practical biomolecular detections. [18][19][20][21][22][23][24][25] Moreover, BSW structures offer further benefits with respect to other SW-based counterparts, such as easy realization and experimental observation, and great flexibility in terms of wavelength range of operation, materials choice, and tailoring of the field distribution for specific sensing applications. [1,9,[13][14][15]17,[26][27][28] While most sensing platforms proposed in the literature rely on bulky prism-coupled planar configurations, [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] the integration of BSW structures with optical fibers would bring significant benefits in terms of compactness, light weight, remote sensing capability, biocompatibility, and ease of interrogation. This is especially attractive within the emerging "labon-fiber" technology framework. [29][30][31][32][33][34] The interest in this topic has started growing within the last two years, as witnessed by theoretical studies of BSW sensors based on the use of D-type fibers, [35] and unclad regions of multimode fibers. [36] A first experimental demonstration on a tapered single-mode fiber has also been provided very recently. [37] Within this context, a more intriguing scenario is represented by the integration of the resonant structure directly on the fiber tip. This would allow exploiting fabrication methodologies typically adopted for photonic biochips, thereby enabling the development of probes The integration of structures supporting Bloch surface waves (BSWs) with optical fibers is highly desirable, since it would enable the development of high-figure-of-merit miniaturized all-fiber optrodes, opening new pathways within the "lab-on-fiber" roadmap. Here, the first expe...

Bloch Surface Wave Resonance Based Sensors as an Alternative to Surface Plasmon Resonance Sensors

“…In addition, the angular [ 47 , 48 , 49 , 50 , 51 , 52 , 53 , 60 ] or the wavelength interrogations [ 46 , 61 , 62 , 63 , 64 , 65 , 66 ] have been employed. Similarly to the SPR based fiber optic sensors, fiber sensors with MDSs have been reported [ 67 , 68 , 69 , 70 ], and MDSs have been deposited on a tapered fiber [ 67 ] or on the outer surface of optical fiber [ 68 ]. Moreover, configurations with the MDSs deposited at the tip of a single-mode fiber [ 69 ] or inside of a photonic crystal fiber [ 70 ] have been considered.…”

Lab-On-Fiber Technology: A Roadmap toward Multifunctional Plug and Play Platforms

“…After the identification and assessment of the initial fabrication routes, research attention focused on devices with new functionalities and unparalleled performance. Successful integrations onto the optical fibers of plasmonic nanostructures [ 36 , 37 ], photonic crystals [ 38 ], ring resonators [ 39 ], optomechanical microcavities [ 40 ], metallodielectric nanoarchitectures [ 41 , 42 , 43 ], and dielectric block surface-wave resonators [ 44 ] were recently reported. These first proofs of concept provide the basis for the development of multifunctional LOF platforms, such as plasmonic label-free optical fiber nanosensors [ 43 , 45 , 46 ], SERS nanoprobes [ 33 , 47 ], advanced photonic nanoresonators [ 39 , 44 ], ultrahigh-sensitivity acoustic transducers [ 48 ], optical fiber tweezers [ 49 , 50 ], and optical fiber metatips [ 51 ].…”

Novel Bloch wave excitation platform based on few-layer photonic crystal deposited on D-shaped optical fiber

“…Most devices based on BSW excitation require a 1DPC with a large number of layers–higher than 12 10 , 12 , 17 – 25 . These configurations have been used in 1DPCs consisting of bilayers of materials with refractive index (RI) differences as small as 0.2 refractive index units (RIU) 12 , 17 – 19 up to moderate differences of 0.8 RIU 10 , 20 – 25 . However, there are reported studies that show that it is possible to excite BSWs at the interface of 1DPCs with less than 10 layers 5 , 26 – 31 .…”