A laser assembly (1) comprising: a semiconductor laser (2) with a fast gain medium, wherein the gain relaxation time of the gain medium is smaller than the round-trip time in the standing wave cavity, in particular a quantum cascade laser or an interband cascade laser, and a standing wave cavity (3); a DC source (9) coupled to the standing wave cavity (3) for pumping the laser (2); and an AC injection device (10) for injecting an electrical AC signal into the standing wave cavity (3) to stabilize an optical frequency comb, the AC injection device being suitable for producing an electrical AC signal within a range and/or within an integer multiple of the range, wherein the range is within ±1% of the natural round-trip frequency in the standing wave cavity, comprising at least a first and a second electric contact section (5, 6) extending along a first longitudinal side of the longitudinal extension of the standing wave cavity (3), wherein the AC injection device (10) is coupled to the first and/or to the second electric contact section (5, 6) such that the complex amplitude of the injected electrical AC signal differs for the first and the second longitudinal electric contact section (5, 6).