Fifth-Order Frequency Mixing

In the past fifth harmonic generation has been investigated with powerful fixed frequency solid state (Nd-YAG or Nd-Glass) and gas (XeCl, KrF) lasers . In one of these experiments input powers of more than 300 MW (mode-locked Nd-YAG fourth harmonic, X=266.1 nm) provide, for example, conversion efficiencies of 10 to 10 . Since the pulse power of most dye laser systems is lower by one or two orders of magnitude nonresonant fifth-order frequency mixing of this radiation would produce intensities below a useful level. 

Fifth- and higher-order harmonic and frequency mixing UV (216 nm) XUV (106-35.3 nm) Nd, harmonics of Nd, excimer Rare gases, metal vapors... 

More recently, Schmid et al. [12] have shown that a separation of the different contributions to the degenerate four-wave mixing signal can be obtained by a modulation technique two of the incoming laser beams are chopped at different frequencies /, and /2 and the detection occurs at special combination frequencies of /, and /2- This technique was applied to the measurements of the third- and fifth-order autocorrelation functions of a picosecond laser using a polydiacetylene single crystal. 

---