UPNA campus iberus – Academica-e
Study and design of thin-film-deposited optical biosensing devices based on wavelength detection of resonances


Along this thesis, the study and design of several optical waveguide platforms is presented, in order to check their viability when used as biosensors based on either optical fiber or other photonic substrates. In this work, some fiberoptic-based structures such as cladding removed multimode structures, tapered single-mode fibers and single-mode – multimode – single-mode fibers are  deposited with thin-films of materials, using nanotechnology-based methods such as layer-by-layer assembly (LbL-assembly) or sputtering. Moreover, a brief chapter is focused on the study of toroidal microring resonators deposited by spin-coating.
The final objective is to generate or enhance the parameters of the resonant phenomena obtained in these structures, in terms of resolution and sensitivity. Then, a biological detection is addressed and characterized, to see if they are able to perform a future early diagnosis for illnesses.

Experimental results

… Regarding the T-CRMMFs (named as TCRMMF), a similar device to that presented in Fig. 3.5a was also fabricated, using a Nadetech Innovations S.L. tapering system (see Fig. 3.6). This equipment is capable of fabricating tapered structures by heating the optical fiber and pulling it from both sides until the desired structure is obtained. The software used to fabricate the tapers was based on the equations and theory suggested in [6]. The tapering system, consisted of a butane flux (1), two step-by-step motorized guides to pull the fibers (2), a third guide to move the heating flame side-by-side (3) and the corresponding digital electronics and power supply to control the tapering process ((4) and (5)). The software is based on a previous design of the desired taper and the corresponding controls to start, pause or stop the process


Immunosensor based on LMRs generated with a polymeric thin-film deposited on a T-CRMMF

… To this purpose, and using the same kind of multimode fiber than in the previous sensor, a 30 mm uncladded segment was tapered using the tapering system by Nadetech Innovations S.L. until a waist diameter of 100 m and a waist length of 10 mm were reached. This tapered uncladded multimode fiber (T-UMF, the same as T-CRMMF) was subjected to a sputtering process to deposit a silver mirror on its tip, so that a simple reflective set-up could be prepared, similar to Fig. 3.10. 

Optimization of T-SMF parameters to generate LMRs

… A tapered single-mode optical fiber (T-SMF) is usually fabricated by pulling an SMF fiber from both sides at the same speed while it is heated to its softening temperature, reducing the diameter until desired. A design of a taper puller prototype by Nadetech Innovations S.L.

… To prove this, a pair of experiments based on the deposition of a [PAH+NR/PAA] thin-film (where NR is Neutral Red) by LbL-assembly were performed [4]. Here, NR is used to make sure that the fiber is correctly deposited because of the purple color it dyes the substrate, although it does not affect the generation of the LMR [4]. Two T-SMF structures were fabricated from a SMF-28 single-mode optical fiber from Telnet Inc. Their transition lengths were Lt = 3 mm, their waist lengths were Lw = 10 mm and their waist diameters were around 50 and 40 m respectively. They were stripped and cleaned with ethanol before subjecting them to the tapering machine designed by Nadetech Innovations S.L. and obtaining the corresponding T-SMFs. 

Subjects: Optical biosensing devices; Thin films