Masters in Photonics and Optical Science - Student Projects Showcase

The first batch of Masters in Photonics and Optical Science students completed their projects in the first semester of 2011, achieving great results in a very short time. The projects lasts three months (full-time) during semester 1, over which the students perform a literature review of their topic area, independent and original work on their project, and complete a 30-minute presentation and a 40-page thesis. Some information on the completed projects is presented below.

Charithra Rajapakse

Student: Charithra Rajapakse

Supervisors: Alexander Argyros and Sergio Leon-Saval

Abstract: Hollow core microstructured polymer optical fibres were specifically designed and fabricated for trapping particles in the core of the fibre using an optical trap. Three dimensional trapping of 5 μm polystyrene spheres was demonstrated by focusing the trapping beam laterally into the fibre, and the spheres could be moved and positioned over the full range of the fibre core. Trapping of 1 μm particles was also demonstrated, but in the cladding holes of the fibre. The optical trap was characterized by using trap stiffness in different places in the fibre as well as by conducting flow measurements using 5 μm particles.

Fabrication of hollow core optical fibre for optical trapping

Rong Li

Student: Rong Li

Supervisors: Stuart Jackson

Abstract: We constructed a fibre laser at 2.1 µm with Ho-doped double-clad fibres (DCF) pumped by semiconductor laser diodes at 1.95 μm. We collimated the diode laser beam with two collimating lenses after characterising of the beam profile of the diodes. According to the measured launched efficiency from the cutback measurements of the Fujikura DCF and the Ho-doped DCF using different focusing lenses, we determined the optical focusing lens for free space to fibre pump light coupling. We studied the relationship between the fibre diameter and the launch efficiency. Using the cutback measurements, the attenuation co-efficient of Fujikura DCF and the Ho-doped DCF was measured to be approximately 1 dB/m and 2.34 dB/m respectively. The contribution to the absorption at 1.95 μm from the polymer second cladding of the two types of DCF was isolated from the attenuation of the whole fibre. The measured absorption co-efficient of the polymer cladding was approximately 0.3 dB/m. Based on the measured launch efficiency and the attenuation co-efficient of the Ho-doped DCF, we designed a dual diode pump arrangement and double pump light path laser cavity.

Exciting Ho-doped silicate glass fibre lasers using high power diode lasers operating at 1.95 µm

Pat Blown

Student:Pat Blown

Supervisors: Martijn de Sterke, Nadav Gutman, and Felix Lawrence.

Abstract: The physical processes underlying slow light within photonic crystal waveguides are investigated through consideration of the waveguide mirror properties. The photonic crystal waveguide is conceptually broken down to consist of a core region surrounded by two mirrors. The reflective properties of mirrors are treated numerically, while the core is treated analytically. Two different classes of photonic crystal waveguides are considered: one with a core containing only one propagating plane wave order, and one with a core containing two propagating plane wave orders. For each class of waveguide, the phase condition for the even fundamental mode is found and used to derive an expression for group velocity. The expression for group velocity is analysed to gain insight into the physical mechanisms behind slow light in terms of Goos Hanschen shift and group delay. This treatment is shown to offer improvements over current dispersion engineering techniques by simultaneuosly obtaining dispersion relations for photonic crystal waveguides of arbitrary waveguide core thickness. Numerical results are found and used to find a photonic crystal waveguide with a quartic band-edge.

Peering into the Mirror: Slow Light in Photonic Crystals

Tomonori Hu

Student: Tomonori Hu

Supervisors: Dr. Jochen Schröder and Prof. Ben Eggleton

Abstract:Dissipative soliton dynamics describe the nature of many fascinating waves, such as optical pulses produced inside mode-locked lasers. Lasers based on dissipative soliton dynamics exhibit interesting phenomena, and enhance the performance of conventional fibre lasers. We numerically investigate a new technique of complex spectral filtering on the dissipative optical soliton dynamics, to further improve these lasers. For a specific disipative soliton laser, we have discovered an elegant method to control and optimise the pulse widths and energies produced by these lasers, which have advantages over currently existing methods. Further, recent work has presented a new attractive Soliton-similariton laser, and a question has been proposed whether higher order soliton excitations are possible. Simulations have confirmed that higher order soliton dynamics in these new lasers are limited by stimulated Raman effects. However, for the first time, second order solitons were found to exist in these lasers. In this process the incredible stability of these lasers was realised. These findings lay foundations for next generation all-fibre lasers, which are beginning to reach the pulse energies provided by the record holding bulk lasers

Complex filtering in dissipative optical soliton lasers