The recent emergence of efficient high-power lasers in the visible-UV region has led to their serious consideration for a number of applications. However, for some of these applications, while the lasers' output power and efficiency are quite adequate, their output wavelengths are inappropriate. In these instances, then, means of shifting the laser wavelengths without undue sacrifices, in the overall efficiency of the system and the spatial quality of the beam must be found. Two properties that any wavelength conversion scheme in this connection must have are simplicity and scalability.
N. Djeu, N. Djeu,
"Frequency Conversion Of Visible Lasers", Proc. SPIE 0138, Advances in Laser Technology III: Emphasizing Gaseous Lasers, (17 August 1978); doi: 10.1117/12.956223; https://doi.org/10.1117/12.956223