An experimental study of the effect of pump pulse duration on liquid crystal laser performance

Much work has been done to understand the factors that impact photonic band-edge liquid crystal (LC) laser threshold and slope efficiency; two parameters often stated to quantify performance. Conventionally, LC lasers are optically pumped using Q-switched lasers with a fixed pulse duration, and thus the effect of pump pulse duration on LC laser performance has received little attention. Whilst some studies have been published at different pump pulse durations, these use different laser sources and experimental conditions, making the data incomparable. By exploiting a recent breakthrough in laser diode pumping, our experimental results prove and quantify the detrimental effect of an increase in pump pulse duration on LC laser threshold and slope efficiency. We also show that this conclusion depends upon how threshold is defined, due to an ambiguity in the definition of pulse energy in systems where peak power and pulse duration can be independently controlled. For improved comparison within the literature of LC laser performance, we thus propose an alternative convention whereby threshold can be stated in units of peak power density. This work forms the basis of the paper "An experimental study of the effect of pump pulse duration on liquid crystal laser performance" by Calum M. Brown, Ieva Pakamoryte and Philip J. W. Hands. This paper has been submitted for publication and is currently under review. The data herein pertain to Figures 2, 3, 4 and 5 in our paper.