Advances in mid-infrared spectroscopy enabled by supercontinuum laser sources

Abstract

Supercontinuum sources are all-fiber pulsed laser-driven systems that provide high power spectral densities within ultra-broadband spectral ranges. The tailored process of generating broadband, bright, and spectrally flat supercontinua—through a complex interplay of linear and non-linear processes—has been recently pushed further towards longer wavelengths and has evolved enough to enter the field of mid-infrared (mid-IR) spectroscopy. In this work, we review the current state and perspectives of this technology that offers laser-like emission properties and instantaneous broadband spectral coverage comparable to thermal emitters. We aim to go beyond a literature review. Thus, we first discuss the basic principles of supercontinuum sources and then provide an experimental part focusing on the quantification and analysis of intrinsic emission properties such as typical power spectral densities, brightness levels, spectral stability, and beam quality (to the best of the authors’ knowledge, the M2 factor for a mid-IR supercontinuum source is characterized for the first time). On this basis, we identify key competitive advantages of these alternative emitters for mid-IR spectroscopy over state-of-the-art technologies such as thermal sources or quantum cascade lasers. The specific features of supercontinuum radiation open up prospects of improving well-established techniques in mid-IR spectroscopy and trigger developments of novel analytical methods and instrumentation. The review concludes with a structured summary of recent advances and applications in various routine mid-IR spectroscopy scenarios that have benefited from the use of supercontinuum sources.

Mid-infrared supercontinuum-based Fourier transform spectroscopy for plasma analysis

“…Currently, the relative intensity noise of the MIR SC source limits the sensitivity of the spectrometer, although this is not essential for the demonstrated application, in identification and quantification of the products of a plasma reaction. Moreover, with the current rapid developments in MIR SC sources, it is anticipated that the intensity noise of these sources will be reduced further in the near future 29 , 34 . Finally, the spatial coherence of the MIR SC beam could also be exploited for other applications, such as for accurate in-situ probing in plasmas, to monitor the plasma dynamics, as well as to detect intermediate products in the plasma.…”

“…Several applications for these type of SC sources have been demonstrated, such as absorption spectroscopy with high sensitivity and selectivity for simultaneous measurement of multiple compounds 30 , spectroscopic standoff detection 31 , or optical coherence tomography in the MIR range providing real-time and high-resolution images 32 , 33 . Current developments in MIR SC sources extend the spectral range of the source beyond 4 μm to cover a larger part of the MIR fingerprint region 34 . Applications in absorption spectroscopy 35 and hyperspectral imaging 36 , 37 have been demonstrated for these highly experimental, new sources.…”

Mid-infrared Supercontinuum-based Fourier Transform Spectroscopy for plasma analysis

“…In conclusion, the reaction products were quanti ed for a discharge plasma with a varying ratio of CO Currently, the relative intensity noise of the MIR SC source limits the sensitivity of the spectrometer, although this is not essential for the demonstrated application, in identi cation and quanti cation of the products of a plasma reaction. Moreover, with the current rapid developments in MIR SC sources, it is anticipated that the intensity noise of these sources will be reduced further in the near future 29,32 . Finally, the spatial coherence of the MIR SC beam could also be exploited for other applications, such as for accurate in-situ probing in plasmas, to monitor the plasma dynamics, as well as to detect intermediate products in the plasma.…”

“…Several applications for these type of SC sources have been demonstrated, such as absorption spectroscopy with high sensitivity and selectivity for simultaneous measurement of multiple compounds 30 , or optical coherence tomography in the MIR range providing real-time and high-resolution images 31 . Current developments in MIR SC sources extend the spectral range of the source beyond 4 μm to cover a larger part of the MIR ngerprint region 32 . Applications in absorption spectroscopy 33 and hyperspectral imaging 34 have been demonstrated for these highly experimental, new sources.…”

Mid- and Far-Infrared Supercontinuum Generation in Bulk Tellurium Spanning from 5.3 $μ$m to 32 $μ$m

“…Abundant applications of SC sources exist, including spectroscopy (e.g. in the MIR molecular fingerprint region) [1,2], interferometry [3], pulse compression [4], and seeding of tunable optical parametric amplifiers [5].…”