It is well known in the art to generate a light field by sum frequency generation of two fundamental fields in a nonlinear component. The generated field will have a frequency that is the sum of the frequencies of the two fundamental fields. If the two fundamental fields have the same frequencies, the process is called second harmonic generation. A limiting effect in the process of sum frequency generation is that as the sum frequency field has reached a certain power level conversion will in general be reversed so that power is transferred from the sum frequency field to the fundamental fields. This process is called back-conversion.
A system for sum-frequency generation of 589 nm light by using a periodically poled LiNbO3 ridge wave guide is disclosed in Nishikawa et al., European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference (CLEO Europe—EQEC 2009), IEEE, Piscataway/NJ, USA 14 Jun. 2009, ISBN: 978-1-4244-4079-5. In the disclosed system, light from two Nd:YAG lasers with an output wavelength of 1064 nm and 1319 nm, respectively, is combined and coupled into a periodically poled lithium niobate module for generating laser output at a wavelength of 589 nm.