Slow-light enhancement of Beer-Lambert-Bouguer absorption

Optical techniques are finding widespread use in chemical and bio-chemical analysis, and Beer–Lambert– Bouguer (BLB) absorption in particular has become one of the classical workhorses in analytical chemistry [1]. During the past decade, there has been an increasing emphasize on miniaturization of chemical analysis systems [2] and naturally this has stimulated a large effort in integrating microfluidics [3, 4] and optics in labon-a-chip microsystems [5], partly defining the emerging field of optofluidics [6, 7]. At the same time, there is an increasing attention to slow-light phenomena as well as the fundamentals and applications of light-matter interactions in electromagnetically strongly dispersive environments [8, 9, 10, 11, 12]. In this Letter we consider the classical problem of BLB absorption. As with the phenomenon of photonic band-edge lasing [13], we show how slow light in an optofluidic environment facilitates enhanced light-matter interactions, by orders of magnitude, with strong opportunities for improving existing miniaturized chemical absorbance cells.