The invention relates to a photoacoustic detector including an acoustically open measuring area which is not completely surrounded by a housing. The detector includes an arrangement for introducing excitation light into the measuring area, such that the excitation light can be absorbed by absorbent materials which are located in the measuring area and which are used to produce acoustic energy. The invention also relates to a detector which includes at least one acoustic sensor and an arrangement is provided in order to concentrate the acoustic energy, in order to reach a local maximum of the acoustic pressure on at least one position. The at least one sensor is arranged in the vicinity of the at least one position, whereon the local maximum of the produced acoustic pressure is present or can be produced. The invention also relates to an associated method.