A resonator structure containing an active layer is subdivided into at least two sections in which mode spacings differ from one another by 7 to 10 percent on account of different length dimensions or as a result of grating structures provided therefor. Photonic crystals are integrated as longitudinal and, if appropriate, as lateral boundaries of the resonator structure. Variation of the currents in the sections enables the laser to be tuned in a wide wavelength range.