Infrared supercontinuum generation with solid-state lasers

Infrared spectral continuum is of high interest for numerous applications such as precision frequency metrology, femtosecond pulse phase stabilization, ultrashort pulse compression, optical coherence tomography, high-resolution spectroscopy, etc. Until recently production of the infrared supercontinuum beyond 2 m involved using the rather complex and costly nonlinear conversion schemes. This project aims at the development of the compact and low cost infrared spectral continuum sources with controllable parameters. The latter promises a break-through in the field of the infrared laser technique and nonlinear optics. To achieve this ambitious aim we plan to employ novel infrared microstructured and liquid-cladded tapered fibers, nanocrystalline-doped fibers, and fibers made of strongly nonlinear crystalline materials, as well as semiconductor bulk media. In combination with the novel all-solid-state lasers based on the diode-pumped mode-locked Cr4+:YAG (1.4-1.6 m) and Cr2+:Zinc-chalcogenide (2-3 m) oscillators, this will provide an extension of the supercontinuum technique into the important mid-infrared region beyond 2 m and will open up the new prospects for precision metrology, nonlinear optics and medicine. As a result of the project, compact transportable frequency comb sources spanning the range from atomic frequency standards in the near-infrared to molecular frequency standards in the mid-infrared will become a reality.

We live in the world of molecules: we consist of them, we are surrounded by them, we breathe them. Optics provides means to analyze all the molecules in our environment with very high precision just by measuring the molecular absorption spectra. To do this with sufficient sensitivity it is important, that the spectra are analyzed in the middle-infrared wavelength range (roughly between 2 and 20 microns), where all relevant molecules absorb the most. For correct quantitative measurement, high resolution is also a must. The results of this project have made critical improvements into the middle-infrared optical spectroscopy by providing new light sources, based on ultrashort-pulsed lasers. These lasers have unique property of generating a large number of wavelengths at once (thus allowing simultaneous measurement of many molecules) and having a very high brightness, many orders of magnitude better than other sources. The high brightness allows radical shortening of the time, necessary to measure the spectra - from hours to seconds and even to hundreds of spectra per second. Lasers also enable very sensitive measurement: it is possible to observe gas concentrations of just 1 part per billion and even less. In the long term, the developed techniques allow creating compact and transportable devices for gas analysis that would record all relevant molecules at once, be it industrial pollutants or natural biomolecules. The speed of such analysis can be so high as to perform online monitoring of fast gas flows in industrial setups or measuring human breath on disease markers during the exhale.