An injection-locked laser system (1, 25) comprising: a master laser that generates a continuous-wave output field having a frequency (f 0); one or more optical modulators (5, 5a, 5d) employed to produce from the continuous-wave output field a first seed optical field having a first frequency (f 1) and a second seed optical field having a second frequency (f 2); wherein the first seed optical field provides an input to injection lock one or more optical amplifiers (8a-c) at the first frequency (f 1), the one or more optical amplifiers comprising a cavity arranged to be resonant at the first frequency (f 1), the one or more optical amplifiers (8a-c) producing one or more continuous-wave output fields (12a- c) for the injection-locked laser system (1, 25) at the first frequency (f 1) and the second seed optical field provides an input to injection lock one or more optical amplifiers (8d-f) at the second frequency (f 2), the one or more optical amplifiers comprising a cavity arranged to be resonant at the second frequency (f 2), the one or more optical amplifiers (8d-f) producing one or more continuous-wave output fields (12d-f) for the injection-locked laser system (1, 25) at the second frequency (f 2); characterised in that - the injection-locked laser system (1, 25) further comprising a first phase lock control loop that provide a first feedback signal to one of the one or more optical modulators (5, 5a) to phase lock the continuous-wave output field, produced at the first frequency (f 1), of a first optical amplifier to the continuous-wave output field and; - the injection-locked laser system (1, 25) further comprising a second phase lock control loop that provides a second feedback signal to one of the one or more optical modulators (5, 5d) to phase lock the continuous-wave output field, produced at the second frequency (f 2), of a second optical amplifier to the continuous-wave output field. a master laser that generates a continuous-wave output field having a frequency (f 0); one or more optical modulators (5, 5a, 5d) employed to produce from the continuous-wave output field a first seed optical field having a first frequency (f 1) and a second seed optical field having a second frequency (f 2); wherein the first seed optical field provides an input to injection lock one or more optical amplifiers (8a-c) at the first frequency (f 1), the one or more optical amplifiers comprising a cavity arranged to be resonant at the first frequency (f 1), the one or more optical amplifiers (8a-c) producing one or more continuous-wave output fields (12a- c) for the injection-locked laser system (1, 25) at the first frequency (f 1) and the second seed optical field provides an input to injection lock one or more optical amplifiers (8d-f) at the second frequency (f 2), the one or more optical amplifiers comprising a cavity arranged to be resonant at the second frequency (f 2), the one or more optical amplifiers (8d-f) producing one or more continuous-wave output fields (12d-f) for the injection-locked laser system (1, 25) at the second frequency (f 2); characterised in that - the injection-locked laser system (1, 25) further comprising a first phase lock control loop that provide a first feedback signal to one of the one or more optical modulators (5, 5a) to phase lock the continuous-wave output field, produced at the first frequency (f 1), of a first optical amplifier to the continuous-wave output field and; - the injection-locked laser system (1, 25) further comprising a second phase lock control loop that provides a second feedback signal to one of the one or more optical modulators (5, 5d) to phase lock the continuous-wave output field, produced at the second frequency (f 2), of a second optical amplifier to the continuous-wave output field. - the injection-locked laser system (1, 25) further comprising a first phase lock control loop that provide a first feedback signal to one of the one or more optical modulators (5, 5a) to phase lock the continuous-wave output field, produced at the first frequency (f 1), of a first optical amplifier to the continuous-wave output field and; - the injection-locked laser system (1, 25) further comprising a second phase lock control loop that provides a second feedback signal to one of the one or more optical modulators (5, 5d) to phase lock the continuous-wave output field, produced at the second frequency (f 2), of a second optical amplifier to the continuous-wave output field.