Second harmonic generation in orderedGa1−xInxP

Reflection second harmonic generation (SHG) has been used to measure the rotation/reflection properties of spontaneously ordered ${\mathrm{Ga}}_{1-x}{\mathrm{In}}_x\mathrm{P}.$ Particular conditions are identified in which the SHG signal arises solely from the order-induced symmetry breaking of the 4¯ operation in zinc blende. By extending the usual experimental techniques to the epilayer edges, the point group of ordered ${\mathrm{Ga}}_{1-x}{\mathrm{In}}_x\mathrm{P}$ was completely determined from optical methods, and the four components of the nonlinear susceptibility were measured. The case of double-variant samples is also discussed.