Demonstration of a novel laser-driven light source for broadband spectroscopy between 170 nm and 2.1 mm Meez Islam, * a Luca Ciaffoni, b Gus Hancock b and Grant A. D. Ritchie b Combining broadband light sources with optical cavities is a well established approach to sensitive monitoring of trace species in both gas and liquid phases. Here we investigate for the first time the potential of a novel source based on laser-driven xenon plasma technology for spectroscopic studies of gaseous species over the 170–2100 nm spectral range. Over the past decade, the use of broadband light sources in combination with optical cavities has increased considerably, 1–4 largely due to the growing interest in targeting multi-compo- nent mixtures or species with broad spectral signatures. In particular, broadband cavity enhanced absorption spectroscopy (BBCEAS) has been widely investigated, and successfully applied to the detection of trace species both in the gas phase, 5–7 and liquid phase. 8–12 The ideal light source for this technique is one which combines broad wavelength coverage with high spectral radiance, and which can be efficiently coupled into the optical cavity. In addition, high intensity stability, long oper- ating lifetime and low cost are also desirable characteristics. For measurements in the UV-VIS region previous studies have used either xenon arc lamps, 2 high intensity light emitting diodes (LEDs), 6,9,11–14 or supercontinuum (SC) light sour- ces. 10,15,16 Xenon arc lamps are able to provide moderate levels of spectral radiance across the UV-VIS range and require collima- tion optics to couple the output into the cavity. Their intensity stability over long periods of time is good but their lifetime is short (500–1000 h) and their cost is moderately high (>£5000). In comparison, LEDs have can have powers of several Watts in the visible but only moderate to low levels of spectral irradiance in the deep UV (<300 nm). Their output is astigmatic which requires signicant additional optics, which further reduces the output radiance, before being coupled into the optical cavity. However, their intensity stability is very good, their lifetime can exceed 20 000 h and they can be very low cost (<£5). True broadband coverage is restricted to white LEDs, but devices which output over short wavelength ranges can be obtained for UV wavelengths down to 240 nm. SC light sources offer laser like output properties (highly collimated output) with broad wave- length coverage typically from 400–2100 nm. This leads to very high spectral radiant uxes of >1 mW nm 1 , which are easy to efficiently couple into an optical cavity with minimal additional optics. The lifetimes of SC light sources can exceed 20 000 h, however, their cost is high (>£30 000) and the spectral stability of their output over a period of a few minutes has been found to be relatively poor compared to LEDs. 17 Recently a new type of broadband light source, termed a laser driven light source (LDLS), has become commercially available. 18 This source uses a continuous wave (cw) laser to directly heat a xenon plasma to high temperatures, up to 20 000 K, which can then emit broadband radiation. In traditional xenon arc lamps, the brightness, UV power, and lamp lifetime are limited by the use of electrodes to couple power to the plasma. The electrode- less LDLS technology results in a small, stable, high brightness plasma, with emission over a broad spectral range from 170 nm to 2100 nm and which can be efficiently coupled into optical systems. The lamp lifetime is also extended to >10 000 h, whilst the current price is £10k. These specications indicate that LDLSs should be investigated as a potential light source for BBCEAS applications as they could address some of the limita- tions of currently used light sources. The aim of this work is therefore to characterize the perfor- mance of a bre-pigtailed LDLS source (Energetiq EQ-99FC) at discrete spectral windows of its emission spectrum, namely the 280 nm, 760 nm, and 1.2–2.1 mm regions, and thus assess for the rst time its potential as broadband source for analytical spec- troscopy in the gas phase. The sensitivity levels achieved by employing the LDLS as an excitation source for BBCEAS measurements over the rst two discrete wavelength ranges were evaluated by conducting a comparative analysis with a UV-LED and a SC source in the 280 nm and 760 nm regions, respectively. a School of Science and Engineering, Teesside University, Borough Road, Middlesbrough, TS1 3BA, UK. E-mail: m.islam@tees.ac.uk b Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK Cite this: DOI: 10.1039/c3an01020a Received 21st May 2013 Accepted 28th June 2013 DOI: 10.1039/c3an01020a www.rsc.org/analyst This journal is ª The Royal Society of Chemistry 2013 Analyst Analyst COMMUNICATION Published on 28 June 2013. Downloaded by University of Oxford on 08/07/2013 08:56:03. View Article Online View Journal