Abstract: This application is generally related to methods, apparatuses and systems for rapid, sensitive detection of biological agents. One aspect is directed to a system including an infrared optical source configured to output an optical beam at a pulse repetition rate greater than or equal to 1 MHz. The system also includes a medium configured to receive the optical beam in first and second locations of the medium, where each of the first and second locations is separated by a barrier, the first location includes a solvent, and the second location includes a biological agent in the solvent. The system also includes a detector configured to receive the outputted optical beam from the medium and detect infrared spectra therefrom.