With recent advances in low-loss hollow core optical fibre technology [1], the concept of a flexible electrically pumped gas discharge laser has become a reality. Such a device would be capable of having a very narrow discharge tube, which has been shown to increase gain and output power in neutral noble gas lasers, while eliminating the need for long, rigorously straight glass tubes, a problem that has plagued past attempts to exploit this behaviour [2]. The narrow bore tubes have however made the discharge parameters harder to achieve, but recent work with DC-excited glow discharges provided the first indications of gain on the 3.11 μm, 3.37 μm and 3.51 μm Xenon transmission lines in fibres of over 1 m in length [3]. Here we continue with that work by carrying out a double pass experiment with these discharges, as a step towards a full laser cavity
