Fig. 4.

(a) CARS image of a live C. parvum oocyst at a Raman shift of 1650 cm⁻¹ corresponding to the amide I vibrational band characteristic of protein taken in 2s. (b) CARS image of the non-resonant contribution at the Raman shift of 1700 cm⁻¹, also obtained with a 2s integration time. (c) and (d) Intensity profile along a line drawn across the CARS image in (a) and (b), respectively, showing peak intensity in (c) arising from the residual body and remaining non-resonant background in (d).