Thesis
During my PhD, I have studied optical microfibres, their fabrication, their properties and their potenial uses in optics, especially in non linear optics. My memoir is available here but you can find some info on my PhD's works on this page.
Scanning Electron Microscop image of two optical microfibres.
Microfibres
Microfibres are optical fibres with diameters around or below 1 µm (1 thousandth of millimeter, 5 times smaller than a red blood cell, 50 times thinner than a hair). With such diameters, the light is no longer guided by the interface between the core and the cladding, as is the case in standard optical fibers, but by the interface between the air and the glass. Actually, the surrounding medium (the air in general) is behaving as a cladding. This gives microfibres some very interesting properties.
Optical microscope image of a tellurite microfibre doped with erbium ions. The green light comes from the luminescence of the erbium ions excited by an infrared beam.
Optical properties
Owing to their small diameters, the electromagnetic field is very confined in microfibres. The local intensity of the beam is therefore much larger than in standard telecom fibres. The core diameter of a standard fiber (SMF) is about 10 µm, making an effective area of 100 µm², whereas for a microfibre the effective area is typically 1 µm². Then, the optical intensity in the microfibre is multiplied by 100 compared to a single mode fibre.
This property is very compelling for non linear optics, since high intensities are required to obtain interesting effects on short distances and with low input power.
Light is so confined in microfibres that it extends beyond the glass, in the surrouding medium. The field propagating outside the fibre is called evanescent field and can be used for a variety of applications:
- analyse the optical properties of the surrounding medium, allowing for the detection of some gases for instance,
- displace nanoparticules in a solvent through optical forces,
- excite the luminescence of particules on the surface of the microfibres and capture this light,
- couple light from one microfibre to an other waveguide,
- ...
We try to use these properties to build new optical devices with potential applications in all-optical processing, and on a more fundamental point of view, to study the propagation of light in those micro-guides.
Additional info
Here are some more detailled documents on my thesis (in french):
- My memoir,
- My master 2 thesis,
- the full description of my PhD subject,
- Some historical background of this field.
Please refer to the publication section for further details in english.
I am preparing my thesis at the Laboratoire Interdisciplinaire Carnot de Bourgogne, in the university of Bourgogne, under the direction of Philippe Grelu.