Synchronously Pumped and Continuous Wave Mid-IR Hollow Core Fibre Gas Lasers

Abstract

The mid-infrared (mid-IR) spectral range between 3 and 8 m is an area of growing interest for a range of applications, mainly in the fields of aerospace and sensing. This thesis describes the demonstration of a new form of the mid-infrared fibre laser, based on the use of acetylene in high-performance silica hollow core fibre. The first results of this work describe the fabrication and characterization of hollow core fibre that used in our laser system. The hollow-core fibre has the lowest-loss optical fibre in the 3 µm spectral band. The fibre attenuation of 0.025±0.005 dB/m was recorded. This enables us to demonstrate that this type of hollow core fibre can be used to make a novel form of a laser for the mid-infrared. Our laser consists of a hollow core fibre filled with an active gas – in our case, acetylene – and excited using a widely-available diode laser at 1.5 m wavelength. We have demonstrated lasing on a number of transitions in the spectral band 3.1 – 3.2 m. It lases either continuous wave or synchronously pumped when pumped by telecoms-wavelength diode lasers. The system is highly stable over long periods, in both CW and synchronously-pumped configurations. Studies of the generated mid-infrared output power, pump power threshold, and slope efficiency as functions of the input pump power and gas pressure have been performed and show an optimisation condition where the maximum laser output power is achieved for a given fibre length. This laser system could be extended to other selected molecular species to generate output in the spectral band up to 5 μm, and it has excellent potential for power scaling.

Date of Award	16 Jan 2017
Original language	English
Awarding Institution	University of Bath
Supervisor	Jonathan Knight (Supervisor)