Abstract: The invention relates to a device (10) for determining absorption of a sample, comprising an incoherent radiation source (12) for generating a measuring light beam (20), a resonator that is provided with at least two mirrors (30, 32) into which the measuring light beam can be coupled, a sample volume (38) for receiving an absorbing sample within the resonator (14), and a detector (18) for absorbing the radiation that can be decoupled from the resonator (14). The inventive device (10) includes spectrometric or interferometric means (16), provided between the radiation source (12) and the detector (18), for spectrally splitting the measuring light beam. Means may also be provided for generating a signal that represents the amplitude of the measuring light beam independently of the phase.