An apparatus, comprising: a laser arrangement which is configured to provide a laser radiation, and including an optical cavity which comprises: - a first dispersive element which is configured to receive and disperse at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation, - a first optical phase modulator which is configured to receive and modulate the at least one second radiation so as to provide at least one third electro-magnetic radiation, and - a second dispersive element which is configured to receive and disperse the at least one third electro-magnetic radiation so as to provide at least one fourth electro-magnetic radiation, - a second optical phase modulator which is configured to receive and modulate the at least one fourth radiation so as to provide at least one fifth electro-magnetic radiation, the optical cavity further comprising - a Fabry Perot etalon which spectrally filters the at least one fifth electro-magnetic radiation relative to the at least one first electro-magnetic radiation, wherein the laser radiation is associated with the at least one fifth radiation, - wherein the apparatus is configured such that the first optical phase modulator is driven by a first electrical signal and the second optical phase modulator is driven by a second electrical signal, and - such that the first and second electrical signals (761, 762) are modulated such that the laser arrangement switches wavelengths among the transmission modes of the Fabry Perot etalon, thereby achieving a wavelength-varying output. a laser arrangement which is configured to provide a laser radiation, and including an optical cavity which comprises: - a first dispersive element which is configured to receive and disperse at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation, - a first optical phase modulator which is configured to receive and modulate the at least one second radiation so as to provide at least one third electro-magnetic radiation, and - a second dispersive element which is configured to receive and disperse the at least one third electro-magnetic radiation so as to provide at least one fourth electro-magnetic radiation, - a second optical phase modulator which is configured to receive and modulate the at least one fourth radiation so as to provide at least one fifth electro-magnetic radiation, the optical cavity further comprising - a Fabry Perot etalon which spectrally filters the at least one fifth electro-magnetic radiation relative to the at least one first electro-magnetic radiation, - a first dispersive element which is configured to receive and disperse at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation, - a first optical phase modulator which is configured to receive and modulate the at least one second radiation so as to provide at least one third electro-magnetic radiation, and - a second dispersive element which is configured to receive and disperse the at least one third electro-magnetic radiation so as to provide at least one fourth electro-magnetic radiation, - a second optical phase modulator which is configured to receive and modulate the at least one fourth radiation so as to provide at least one fifth electro-magnetic radiation, the optical cavity further comprising - a Fabry Perot etalon which spectrally filters the at least one fifth electro-magnetic radiation relative to the at least one first electro-magnetic radiation, wherein the laser radiation is associated with the at least one fifth radiation, - wherein the apparatus is configured such that the first optical phase modulator is driven by a first electrical signal and the second optical phase modulator is driven by a second electrical signal, and - such that the first and second electrical signals (761, 762) are modulated such that the laser arrangement switches wavelengths among the transmission modes of the Fabry Perot etalon, thereby achieving a wavelength-varying output. - wherein the apparatus is configured such that the first optical phase modulator is driven by a first electrical signal and the second optical phase modulator is driven by a second electrical signal, and - such that the first and second electrical signals (761, 762) are modulated such that the laser arrangement switches wavelengths among the transmission modes of the Fabry Perot etalon, thereby achieving a wavelength-varying output.