The invention concerns a wavelength tunable semiconductor laser comprising a laser gain section (510) optically coupled to an underlying optical waveguide (520). According to an embodiment of the invention, a first and a second passive microring resonators (530, 560) having a whistle geometry, are arranged on both sides of the laser gain section and evanescently coupled with the optical waveguide (520). Highly reflective broadband mirrors (541, 571) are provided at the free ends of optical waveguide branches (240, 270) tangentially connected to the microring resonators. The first and second passive microrings resonators provide an optical feedback to the laser gain section and allow to select the desired wavelength. The laser structure can be implemented according to a III-V/Si technology.