Experimental and theoretical studies of third-harmonic generation in the chalcopyrite CdGeAs2

Experimental and theoretical studies of third-harmonic generation (THG) in the chalcopyrite semiconductor CdGeAs
2
are presented. The phase-matching configurations for THG are analyzed from the irreducible components point of view. A theory of the bound electron and free-carrier contribution to the third-order susceptibility is presented. The experimental results are given. The effective nonlinear coefficient for type-II THG is mainly due to the free-carrier contribution, and for a hole concentration of
5 \times 10^{16}
/cm
³
it is measured to be
(13 \pm 6)10^{-11}
ESU. The practical applications of THG in CdGeAs
2
are discussed.