A system, method and apparatus for taking a Raman spectrum of a sample is disclosed. In one embodiment, for example, an integrated Raman spectrometer is provided. In another embodiment, a portable Raman spectrometer is provided. In another embodiment, a Raman spectrometer is provided comprising a collimated beam tube for transmitting excitation radiation to an external optical system, such as a microscope, a telescope or a camera lens. In another embodiment, a method for correcting a Raman spectrum for background interference is provided. In yet another embodiment, a method for rejecting fluorescence in a Raman spectrometer is provided. A chemical reactor comprising a built-in Raman detector for monitoring a chemical reaction in a reaction chamber of the reactor is also provided.