Visible cw solid-state lasers

This chapter focuses on generating visible coherent radiation through intracavity frequency doubling and mixing and by in-coherent up-conversion. Compact and efficient cw all-solid-state lasers emitting in the visible spectral region are of interest for many applications in fields such as medicine, biology, printing technology, metrology, optical storage, and display. Blue, green, and red cw semiconductor lasers with high cw output power are expected in the near future. Frequency doubling of near infrared semiconductor lasers is a very difficult task due to the poor beam quality of such devices. The magnitude of the nonlinearity required for optimum second-harmonic generation is proportional to the loss, inversely proportional to the saturation intensity and independent of the gain. The mixing resonator consists of two plane-parallel lasers that are stabilised by their thermal lenses. Both resonators are built as short as possible to guarantee the highest intracavity powers.