Résumé
Applications working with continuous light wave need specific properties concerning the light that is emitted by the source. Most applications need to exist “out‐of‐the lab” in real conditions and thus need to be embedded in a compact and integrated package, with good power efficiency. This chapter focuses on the design parameters of a vertical external‐cavity surface‐emitting lasers (VECSELs) that demonstrates tunability, compactness, and high coherence. The VeCSEL is composed of a semiconductor chip, an output coupler, and in most cases an optical pump. Well‐designed VeCSELs can reach the single‐mode operation at large power without any intracavity filter, which is very unusual in the state of the art of lasers. The chapter examines how a laser can select a single mode, which is a key point for high‐coherence emission. The VeCSEL can be understood like a traditional solid‐state laser relying on the modern semiconductor technology for gain medium.