Dual-comb spectroscopy

A dual comb spectroscopy device for spectroscopically detecting a sample substance, comprising:

• a first slave laser light source configured to generate a first optical output, the optical spectrum of which comprises a first frequency comb having a first comb free spectral range;
• a second slave laser light source configured to generate a second optical output, the optical spectrum of which comprises a second frequency comb having a second comb free spectral range which is different from the first comb free spectral range;
• a master laser light source configured to inject seed light in to both the first slave laser light source and the second slave laser light source therewith to injection lock said generation of both the first optical output and the second optical output;
• a photodetector part arranged to combine the first optical output and the second optical output and to detect a beat signal the spectrum of which comprises a third frequency comb including beat tones produced by interference between the combined first and second optical outputs;
• wherein the device comprises a sample detection area configured for receiving the sample for detection and for directing at least one of the first optical output and the second optical output to the photodetector part via the sample detection area.