Hollow core antiresonant fibres for fibre laser applications

• Main Author: Huang, Xiaosheng
• Other Authors: Yoo Seongwoo
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: http://hdl.handle.net/10356/73926
• Institution: Nanyang Technological University

Hollow core photonic crystal fibres (HC-PCFs) have promising applications in high power beam delivery, chemical sensing and gas-based nonlinear optics. According to the waveguide mechanisms they based on, HC-PCFs are typically classified into two kinds. One kind guide light via a two dimensional photonic bandgap while the other through anti-resonant reflection. The former one is so-called hollow core photonic bandgap fibres (HC-PBGFs) while the latter is commonly named hollow core anti-resonant fibres (HAFs).Compared to HC-PBGFs, HAFs can have much broader transmission windows and more flexible fibre designs. As a result, HAFs are currently more popular than HC-PBGFs. Hence the topic of this thesis is focused on HAFs. HAFs have already been demonstrated to have potential on the application of gas filled fibre lasers. As early as 2002, the first demonstration of the Raman scattering emission had been observed with an H2 filled HAF. During the past decades, a lot of efforts have been devoted into the gas filled HAF lasers. However, so far there is no demonstration of any all HAF based fibre laser because there exist two restrictions. The first restriction is that hollow core fibres are favoured in long wavelength regions where solid core glass fibres suffer high material loss, besides, a small cavity cross section (i.e., fibre core size) is preferred to reduce the lasing threshold. However, the confinement loss of a HAF (i.e., cavity loss) increases fastly when core size gets smaller or wavelength gets longer. The second restriction is there is no hollow core fibre based fibre coupler to build an all hollow core fibre based laser ring cavity. Therefore, the task of this thesis is to get rid of these two restrictions to make our contributions to all HAF based fibre lasers. Firstly, I develop the hollow core fibre fabrication technique based on our local facilities. Secondly, I design, fabricate, and characterize a HAF which can have relatively low transmission loss in small core and long wavelength conditions. Thirdly, I design, fabricate, and characterize a HAF based fibre coupler whose power splitting ratio is tunable by adjusting the fibre strain. Thirdly, I use the HAF based fibre coupler to build a ring cavity in a fibre laser system, where the tunable feature of the fibre coupler helps to optimize the conversion efficiency. Moreover, the HAF based fibre coupler is experimentally proved to be able to split and deliver the ultra fast laser pulse without degradation.