The source issue in infrared microspectroscopy

Infrared spectroscopy using a Fourier Transform Infrared (FTIR) spectrometer is routine. These instruments are sophisticated and mature, and generally use a blackbody radiator as their infrared source. However, because the brightness of a thermal source is limited, the signal-to-noise ratio of these instruments begins to degrade at spatial resolutions not much better than 1 mm and they are rarely useful at resolutions smaller than 20 μm. Synchrotrons provide much brighter infrared beams than thermal sources, and Free-Electron Lasers (FELs) provide even brighter beams than synchrotrons. We will discuss the limitations of thermal sources, and show that a synchrotron is an excellent source for infrared spectroscopy at spatial resolutions on the order of the wavelength (λ). Even better spatial resolution, about λ/10, can be expected if an FEL is used as a source.