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.