Lab-on-fiber using fs-laser technologyThe “lab-on-fiber” concept essentially envisages fabrication of micro- and nano-structures within a single mode optical fiber. This can also involve integration with other materials such as metals for both communication and sensing applications. Most of the work reported in this field involves writing structures in the side of the fiber. This is quite a cumbersome approach due to the curved surface of fiber and aligning to the core of the fiber is a very challenging task in itself. Writing directly onto the fiber tip addresses all these problems. Plus the procedures used for planar surfaces can be easily adapted for this approach.
The main target of this project is inscription of gratings on the tip of the single mode fiber using femtosecond laser. The advantages and applications of this flexible "fiber tool" are immense. For example, it can be used to couple light into a slab/ rib waveguide without the need of a grating coupler and prism coupling set-up. Further, using two such fibers could enable measuring losses in the slab/rib waveguide. It provides huge advantages over the existing expensive and destructive standard techniques such as prism coupling and cut-back. Apart from this the other advantages that this tool offers are flexibility, robustness, versatility and cost-effectiveness. To achieve higher index contrast gratings femtosecond laser- assisted etching can be utilized.
Figure: SEM images of a) micro-grating, b) micro-lens and c) micro-prism fabricated using fs laser direct writing technology on an optical fiber tip.
During the course of this thesis the following aspects will be covered:
1) Simulations to determine the grating parameters
2) Optimize the key laser parameters for inscribing gratings
3) Characterization of the inscribed gratings
Time permitting, other application domains such as plasmonic sensors by laser-printing metal nano-dots on top of the gratings can also be explored.
Ardoyen CMST + technicum + at home.