A wavelength swept light source (21, 100, 200, 300) in which an output wavelength temporally and periodically varies, comprising: an oscillator part including an electro-optic deflector (103, 201, 301), the oscillator part comprises a resonator with a gain medium and a diffraction grating, the electro-optic deflector is disposed between the gain medium and the diffraction grating in an optical path formed by the resonator; and a controlled voltage generator part (104, 202, 302) configured to generate a controlled voltage, the controlled voltage being applied to the electro-optic deflector; the electro-optic deflector further includes an electro-optic crystal, and the electro-optic deflector and the controlled voltage generator part are configured such that, by application of the controlled voltage, charges are injected into the electro-optic crystal in accordance with an electric field generated by the application of the controlled voltage, whereby, based on a gradient of a refractive index evoked within the electro-optic deflector by the electric field a light ray path is bended perpendicular to the gradient, a non-uniform electric field distribution attributed to the charge distribution evokes the gradient of the refractive index, characterized in that the controlled voltage generator part (104,202,302) is configured to generate the controlled voltage V that defines a modified sawtooth waveform according to the formula V(t) = V 0 t + V 1 t 2 + V 2 t 3 with coefficients V 0, V 1, V 2 and where t is equal to time; the coefficients V 1, V 2 being chosen so that the wavenumber of the output of the light source varies linearly with time; and the electro-optic crystal has potassium tantalate niobate or potassium tantalate niobate doped with lithium. an oscillator part including an electro-optic deflector (103, 201, 301), the oscillator part comprises a resonator with a gain medium and a diffraction grating, the electro-optic deflector is disposed between the gain medium and the diffraction grating in an optical path formed by the resonator; and a controlled voltage generator part (104, 202, 302) configured to generate a controlled voltage, the controlled voltage being applied to the electro-optic deflector; the electro-optic deflector further includes an electro-optic crystal, and the electro-optic deflector and the controlled voltage generator part are configured such that, by application of the controlled voltage, charges are injected into the electro-optic crystal in accordance with an electric field generated by the application of the controlled voltage, whereby, based on a gradient of a refractive index evoked within the electro-optic deflector by the electric field a light ray path is bended perpendicular to the gradient, a non-uniform electric field distribution attributed to the charge distribution evokes the gradient of the refractive index, characterized in that the controlled voltage generator part (104,202,302) is configured to generate the controlled voltage V that defines a modified sawtooth waveform according to the formula V(t) = V 0 t + V 1 t 2 + V 2 t 3 with coefficients V 0, V 1, V 2 and where t is equal to time; the coefficients V 1, V 2 being chosen so that the wavenumber of the output of the light source varies linearly with time; and the electro-optic crystal has potassium tantalate niobate or potassium tantalate niobate doped with lithium.