Abstract: The invention relates to laser technology and can be used for creating tunable lasers in the near IR region for swept source optical coherence tomography. The developed tunable frequency selector is used for a tunable laser with a shortest possible optical length of the active cavity comprising a frequency selector for operation in the regime of single longitudinal mode generation. The use of the frequency selector as one of the laser mirrors reduces the number of adjustments of laser optical elements and laser costs. To achieve this goal, a waveguide with a mode size of several wavelengths is positioned in front of the Fabry-Perot cavity. The modes of the waveguide and the Fabry-Perot cavity are partially matched. The Fabry-Perot cavity may be tilted relative to the optical axis of the waveguide. The Fabry-Perot cavity may comprise two minors, at least one of which is convex, or two minors, at least one of which has no radial symmetry.