The invention generally relates to detecting biological substances. In certain aspects, the invention is directed to a method directing one or more wavelengths of light within a deep ultraviolet (UV) spectrum into a medium to excite a biological substance in the medium, detect emission from the excited biological substance via a plurality of semiconductor photodetectors, and analyze the deep UV emission data for presence of a deep UV spectral signature indicative of the biological substance, wherein presence of the deep UV spectral signature indicates that the medium comprises a biological substance. The invention is also directed to identifying a pathogen in a medium comprising a pathogen and a non-pathogen biological substance.