Towards InP-based QD-VCSELs emitting at 633 nm

The helium-neon (HeNe) laser with its characteristic wavelength of 633 nm is one of the most well-known and successful laser systems. Although it was already invented in 1961 [1], the HeNe laser is still the basis for many optical metrology techniques and has found many applications in the fields of manufacturing, medicine and quantum optics. However, the range of implementations for emission at this specific wavelength could be expanded by exploiting the advantages of semiconductor systems in terms of miniaturization and level of integration. A promising approach is given by an InP-based quantum dot (QD) vertical-cavity surface-emitting laser (VCSEL). In addition to the compact size and the easy integration, the potentially low fabrication costs, good beam quality, low lasing threshold and power consumption are some of the advantages of a VCSEL [2, 3]. Compared to quantum well based VCSELs, VCSELs with quantum dots as gain medium exhibit decreased threshold currents [4] without any temperature dependency [5], an improved gain [6] and the possibility to tune the wavelength.