A laser device for outputting filtered light pulses for inducing coherent Raman scattering in a sample, the laser device comprising: a first optical cavity comprising a first gain medium; and a second optical cavity comprising a second gain medium different to the first gain medium, wherein the first gain medium and the second gain medium are each excitable by a pump light source (22a,22b) to generate light at respective different ranges of wavelengths; a synchronizer optically coupled to both the first optical cavity and the second optical cavity, wherein the synchronizer is configured to synchronize and mode-lock light from the first optical cavity and the second optical cavity; a first optical filter and a second optical filter, wherein the first optical filter and the second optical filter are configured to filter the light from the first optical cavity and the second optical cavity respectively in order to output first filtered light pulses at a first predetermined range of wavelengths and second filtered light pulses at a second predetermined range of wavelengths; and a first fiber amplifier doped with a gain element corresponding to the first gain medium at the first optical outlet and a second fiber amplifier doped with a gain element corresponding to the second gain medium at the second optical outlet for amplifying the light; wherein at least one of the first optical filter or second optical filter is a tunable optical filter and configured to vary the first predetermined range of wavelengths or the second predetermined range of wavelengths respectively; and wherein the synchronizer comprises a saturable absorber and is configured to carry out synchronization and passive mode locking of the light pulses from the first optical cavity and the second optical cavity; and wherein the first optical filter and the second optical filter are positioned externally to the first optical cavity and second optical cavity, respectively, and in that the first optical filter and the second optical filter are positioned between the corresponding optical outlet (26a,26b) and the corresponding optical amplifier (36a,36b). a first optical cavity comprising a first gain medium; and a second optical cavity comprising a second gain medium different to the first gain medium, wherein the first gain medium and the second gain medium are each excitable by a pump light source (22a,22b) to generate light at respective different ranges of wavelengths; a synchronizer optically coupled to both the first optical cavity and the second optical cavity, wherein the synchronizer is configured to synchronize and mode-lock light from the first optical cavity and the second optical cavity; a first optical filter and a second optical filter, wherein the first optical filter and the second optical filter are configured to filter the light from the first optical cavity and the second optical cavity respectively in order to output first filtered light pulses at a first predetermined range of wavelengths and second filtered light pulses at a second predetermined range of wavelengths; and a first fiber amplifier doped with a gain element corresponding to the first gain medium at the first optical outlet and a second fiber amplifier doped with a gain element corresponding to the second gain medium at the second optical outlet for amplifying the light; wherein at least one of the first optical filter or second optical filter is a tunable optical filter and configured to vary the first predetermined range of wavelengths or the second predetermined range of wavelengths respectively; and wherein the synchronizer comprises a saturable absorber and is configured to carry out synchronization and passive mode locking of the light pulses from the first optical cavity and the second optical cavity; and wherein the first optical filter and the second optical filter are positioned externally to the first optical cavity and second optical cavity, respectively, and in that the first optical filter and the second optical filter are positioned between the corresponding optical outlet (26a,26b) and the corresponding optical amplifier (36a,36b).