Two-wave sum-frequency light generation in optical fibers

The generation of phase-matched two-wave sum-frequency light has been observed in optical fibers. A Nd:YAG laser by simultaneous mode-locking and
Q
-switching or only
Q
-switching operation is used as a pump laser. The input power dependence and fiber length dependence of the sum-frequency light are investigated in the two pumping methods. The observed coherence length for the sum-frequency light generation is about 200 m.