A system for optically scanning a region comprising a sample of which a chemical composition is to be determined, comprising: a pulsed laser source for emitting a pulsed laser beam; a focusing device for adjusting the position of the waist of the laser beam along an optical path of the laser beam; a deflector for adjusting a propagation direction of the laser beam to a given direction; a controller for varying, via the beam deflector, the propagation direction of the pulsed laser beam according to a predefined beam path and varying, via the focusing device, the given position of the waist of the laser beam along the optical path; and a photodetector for detecting light emitted by a plasma created when a given one of laser pulses has an irradiance is greater than a breakdown threshold, the detected light being indicative of the chemical composition of the sample.