A laser tracker for continuously tracking a reflective target (25, 81) and for determining distance with respect to the target (25, 81) comprising • a base defining a vertical axis, • a beam directing unit for emitting a measurement radiation and for receiving at least one part of the measurement radiation reflected at the target (25, 81), wherein the beam directing unit is pivotable in motorized fashion about the vertical axis and an inclination axis, which is substantially orthogonal with respect to the vertical axis, relative to the base, • a distance measuring unit embodied as an interferometer and serving for determining a change in distance with respect to the target (25, 81) by means of interferometry, • an interferometer laser beam source for generating the measurement radiation for the interferometer, and • an angle measuring functionality for determining an orientation of the beam directing unit relative to the base, characterized in that the interferometer laser beam source is embodied as a laser diode and the laser diode has a wavelength-selective component arranged in such a way that the measurement radiation can be generated in longitudinally monomode fashion with a defined emission wavelength, which is tunable in a mode-hop-free manner, and has a coherence length of at least 10 m, in particular wherein the coherence length of at least 10 m can be determined by means of the interferometer, and wherein the measurement radiation can be tuned, in terms of wavelength, to a desired absorption line of a wavelength stabilization unit, wherein • the laser diode has a first resonator unit, which defines a number of laser modes which can be generated by the laser diode and which arise jointly, wherein a different mode wavelength is defined by means of each laser mode and it is possible to generate a diode radiation with the different mode wavelengths, • the wavelength-selective component is embodied in such a way that it acts as a second resonator unit and a principal laser mode can be extracted from the number of laser modes by means of an interaction of the wavelength-selective component with the laser diode, and • the diode radiation can be emitted as longitudinally monomode measurement radiation having only the principal laser mode, such that the emission wavelength and the coherence length of the measurement radiation are defined. • a base defining a vertical axis, • a beam directing unit for emitting a measurement radiation and for receiving at least one part of the measurement radiation reflected at the target (25, 81), wherein the beam directing unit is pivotable in motorized fashion about the vertical axis and an inclination axis, which is substantially orthogonal with respect to the vertical axis, relative to the base, • a distance measuring unit embodied as an interferometer and serving for determining a change in distance with respect to the target (25, 81) by means of interferometry, • an interferometer laser beam source for generating the measurement radiation for the interferometer, and • an angle measuring functionality for determining an orientation of the beam directing unit relative to the base, characterized in that the interferometer laser beam source is embodied as a laser diode and the laser diode has a wavelength-selective component arranged in such a way that the measurement radiation can be generated in longitudinally monomode fashion with a defined emission wavelength, which is tunable in a mode-hop-free manner, and has a coherence length of at least 10 m, in particular wherein the coherence length of at least 10 m can be determined by means of the interferometer, and wherein the measurement radiation can be tuned, in terms of wavelength, to a desired absorption line of a wavelength stabilization unit, wherein • the laser diode has a first resonator unit, which defines a number of laser modes which can be generated by the laser diode and which arise jointly, wherein a different mode wavelength is defined by means of each laser mode and it is possible to generate a diode radiation with the different mode wavelengths, • the wavelength-selective component is embodied in such a way that it acts as a second resonator unit and a principal laser mode can be extracted from the number of laser modes by means of an interaction of the wavelength-selective component with the laser diode, and • the diode radiation can be emitted as longitudinally monomode measurement radiation having only the principal laser mode, such that the emission wavelength and the coherence length of the measurement radiation are defined.