The invention relates to laser beam interleaving. According to the invention, a laser system (511) includes a first source (519/2) and a second source (519/1) for generating a first laser beam (523/2) and a second laser beam (523/1), respectively, and a mirror arrangement (530/1, 567) including a first interleaving laser mirror (531/1) with a high reflecting area configured to reflect the first laser beam (523/2) and a first high transmitting area configured to transmit the second laser beam (523/1).