Drawing Tower
Génération et micro-confinement de plasmas microondes dans des fibres optiques creuses microstructurées
by Benoît Debord
A novel scheme enabling for the first time the generation and confinement of microwave plasma in a hollow-core photonic crystal fibre (HC-PCF) is achieved, thus paving the way to the advent of “Plasma photonics”. This is achieved by combining a non-intrusive and electrode-free microwave excitation with specifically designed HC-PCF. This work includes a theoretical and experimental study to enhance the "inhibited coupling" of a Kagomé cladding lattice HC- PCF. This led to the development of a HC-PCF with a record transmission loss of 17 dB/km at 1 µm, and exhibiting a hollow-core with hypocycloid contour with strong arc curvature. The results show that the enhancing of this core contour negative curvature has three virtues: the propagation losses are strongly reduced, the optical power overlap with silica core-surround is diminished and finally, a better modal content is obtained. Based on these findings, a large core (i.e. a core diameter of ~100 microns) Kagome HC-PCF and guiding around 488 nm is fabricated to facilitate the generation of stable microwave plasma. The generation of the latter is based on an original excitation and is sustained by a microwave surface-wave, which is turn led for the first time, to the generation and confinement of a plasma in the micrometric core of the HC-PCF. Despite the fact that the plasma has a temperature value close to that of the surrounding microstructured glassy material, the latter integrity is preserved. This is explained theoretically by a particular plasma dynamics at this micrometer scale with an important role played by a space charge sheath near the inner wall of the core.
Atomic vapours filled hollow core photonic crystal fibre
for magneto-optical spectroscopy

by Thomas David Bradley
Quantum-fluctuation-initiated coherent Raman comb in hydrogen-filled hollow-core photonic crystal fibre
by Yingying Wang
This thesis explores the generation and the coherence properties of Raman frequency combs that are initiated from vacuum fluctuations using hydrogen-filled hollow-core photonic crystal fibre (HC-PCF). The motivation is to explore a novel route for generating attosecond pulses and waveform synthesis. To this end, work has been undertaken in the design and fabrication of HC-PCF, in the generation of Raman comb with a compact set-up and finally in an experimental demonstration of the mutual coherence between the comb spectral components. Here, the well-established photonic bandgap (PBG) HC-PCF is further developed. Surface mode spectral positions are controlled by chemical etching technique, and a single piece of fibre with two robust bandgaps is fabricated. Furthermore, the second established class of HC-PCF; namely large-pitch Kagome-lattice HC-PCF, has experienced challenging developments. This led to the fabrication of a hypocycloid-core seven-cell Kagome HC-PCF with comparable attenuation value to that of PBG HC-PCF while offering much larger bandwidth. Using the fabricated HC-PCF, different Raman frequency comb systems are developed. In addition to the previously-generated multi-octave Raman frequency comb from a large 1064 nm Nd:YAG Q-switch laser, several more compact version of Raman comb sources have been developed, including one whose lines lay in the visible and UV for applications in forensics and biomedicine. The Raman frequency comb generated inside a length of hydrogen-filled HC-PCF is further investigated by studying the coherence of the Raman lines. Despite of vacuum-fluctuation-initiation, it is demonstrated that the comb has self- and mutualcoherence properties within each single shot, bringing thus the possibility of generating attosecond pulses with non-classical properties.
Photonic microcells for quantum optics applications
by Philip Light
This thesis presents the development of photonic microcells for use as the host for coherent optics phenomena and related applications. A photonic microcell consists of a length of hollow-core photonic crystal fibre (HC-PCF) with a gas-filled core that is spliced to conventional optical fibre at either end to seal the gas within the fibre. Towards the goal of demonstrating and assessing the coherence properties of quantum optical effects in photonic microcells, the fabrication of two types of HC-PCF is presented. The established photonic bandgap HC-PCF offers extremely low transmission loss of ~10 dB/km over kilometre distances. However, the fibre has a limited transmission bandwidth of ~50 THz and exhibits modal coupling unfavourable for many applications. Work is presented on the tailoring of this fibre by control and shaping of the core-surround in order to improve its modal properties. A second type of HC-PCF is based on a large-pitch lattice, whose guidance relies on a new mechanism. This fibre exhibits a much improved bandwidth (>1000 THz) and has a relatively higher but still practical loss of ~1 dB/m. The development of photonic microcells at microbar pressure level and with low optical insertion loss is shown, an important step in the improvement of the technology for coherent optics applications which will take advantage of the extreme gas-laser interaction efficiency achieved in HC-PCF. Finally, quantum optical effects are demonstrated in HC-PCF and photonic microcells loaded with both the molecular gas acetylene and atomic vapour rubidium. The observation of electromagnetically induced transparency (EIT) in acetylene-filled HC-PCF represents the first such observation in a molecular gas, while the use of a photonic microcell allows a comparison of many experimental configurations to explore the coherence properties of coherent optical systems in the core of a HC-PCF. Furthermore, EIT is observed unambiguously in a rubidium loaded HC-PCF for the first time, and the anti-relaxation effects of a polymer coating demonstrated in this configuration.
Photonic solutions towards optical waveform synthesis
by François Couny
This thesis presents the development of photonic tools towards the realisation of an optical intensity waveform synthesiser and of an attosecond pulse synthesiser based on the generation and Fourier synthesis of a continuous-wave coherent spectral comb spanning more than 3 octaves (UV to mid-IR) by use of a gas-filled hollow core photonic crystal fibre (HC-PCF).