Research Fellows Directory
Dr Natalie Wheeler MPhys PhD
University of Southampton
The mid-infrared (IR) wavelength region (2.5-12 um) is critically important due to the overlap with atmospheric windows (3-5 um and 7-12 um) and the presence of strong absorption lines of important gas molecules. Gas sensors operating in the mid-IR could offer unprecedented sensitivities and response times, orders of magnitude higher than near-IR devices. Recent developments in new optical sources and detectors for this spectral region are driving new activity in mid-IR applications, including diagnostics, surgery and industrial sensing. To meet the needs of these applications, mid-IR fibres are required which can rival the performance that conventional, silica-based fibres offer in the near-IR, providing ultralow loss, low bend sensitivity and outstanding thermal, chemical and mechanical properties.
In this project I will lead fabrication of hollow core-photonic crystal fibres (HC-PCFs) which can meet this growing demand. These specialty fibres consist of an air core surrounded by a periodic array of air holes defined by a glass web and as more than 99.8% of the transmitted light is guided in air, they can have low attenuation even in spectral regions where the loss of the glass defining the fibre structure is high. The high overlap of the guided modes with air also makes HC-PCFs exceptional hosts for ultra-high peak power delivery due to their inherent low nonlinearity and also to exploit gas-light interactions, as a gas-filled HC-PCF can offer an unprecedented interaction length between the confined gas and the optical mode. This opens up the potential to achieve a compact, fibre-based gas sensing device with the ultrahigh sensitivity (p.p.t-p.p.b range) that an application such as breath analysis requires; this technique could revolutionise point of care patient diagnostics.
Recently, I fabricated hollow core-photonic bandgap fibres, a type of HC-PCF, with losses an order of magnitude lower than previous examples in the mid-IR. In this project I will build on this breakthrough, fabricating silica and non-silica HC-PCFs with new designs to achieve further loss reduction and to provide optical guidance towards or even beyond 12 um. These HC-PCFs will fulfil the rising demand for low loss, flexible, bend insensitive and durable fibres in the mid-IR for gas sensing and high power beam delivery, e.g. for new optical sources, and device applications.