Toward an Optofluidic gene Sensor based on Fluorescence Enhancement in a Hollow Bottle Microresonator

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Introduction 
My thesis work was carried out at the Optoelectronic Research Centre (ORC) in the 
United Kingdom. Founded in 1989, the ORC is situated within the Faculty of Physics 
and Applied Science of the University of Southampton and is considered, in the interna-
tional scientific community, as one of the leading institution in the field of photonics 
and optoelectronics. Its facilities include the EPSRC (Engineering and Physical Scienc-
es Research Council) Centre for Innovative Manufacturing in photonics, which offers 
the opportunity to the institute to develop fibres and materials that can meet market 
needs, and to identify commercially viable ways of manufacturing them. New genera-
tion of fibres are the main key of research, used for every application such as communi-
cations, laser manufacturing, sensing, infrared fibres and defence countermeasures. For 
this reason, it supports the growth of companies, not only in the UK (as for SPI Laser 
company of Southampton), but all over Europe and even in Italy as for Selex Galileo 
and Pirelli, at least before the telecommunication bubble. 
The project was started in the Optical Biosensors and Biophotonics Group that is more 
oriented to the area of micro and nanofabricated devices, for bio-analyses or for bio-
medical applications, either based on optics, microfluidics or self-assembled techniques. 
The project, due to its multidisciplinary characteristic, was continued within the Inte-
grated Photonic Devices Group that traditionally exploited mainly planar photonic de-
vices, for various applications included diagnostics in medicine, but, more recently, also 
integrated microsphere resonators fabricated with fibre technologies. The project meets 
the demand of small integrated biological sensors which could eliminate the lengthy and 
hard laboratory work traditionally required to perform gene detection. For these devices, 
the biochemical functionalization of the device is the first aspect to consider, which con-
fer to the optical device its specificity, i.e., the way to interact with biological entities. 
For optical methods the sensitivity and speed is considerably enhanced respect to elec-
trochemical approaches; moreover, optical detection can be integrated with a capillary 
fabricated with fibre technology that provides the advantages of microfluidics. For bio-
logical measurements, optics offers different approaches. In particular, label-free meth-
ods are very interesting since do not require the use of any marker and achieve among 
the best sensitivity in biosensing. Unfortunately, the label-free technique was found not 
suitable for the fluidic device considered and it was necessary to consider the use of flu-