Electrochemical etching techniques were used to fabricate semiconductor sieves of gallium phosphide, i.e., two-dimensionally nanostructured membranes exhibiting an enhanced optical second harmonic generation (SHG) in comparison with the bulk material. The SHG rotational and fundamental polarization dependencies studied under sample excitation by a 1064-nm Nd-YAG laser beam indicate optical homogeneity and uniaxial symmetry of the membranes. The artificial anisotropy and the enhanced nonlinear optical response induced by nanotexturization make semiconductor sieves very promising for use in all-optical devices.

Electrochemical etching is shown to represent a unique approach for tailoring linear and nonlinear optical properties of III-V compounds. We demonstrate that under defined etching conditions uniformly distributed pores with transverse dimensions less than 100 nm are formed. The presence of pores modifies the refractive index of the materials and, with parallel orientation, induces an artificial optical anisotropy, as evidenced by optical transmission studies. Small dimensions of both pore and skeleton entities are shown to provide the optical homogeneity of the porous specimens. The enhanced optical second harmonic generation (SHG) inherent to porous membranes of GaP containing triangular-prism like pores is attributed to giant third order electric field fluctuations. The dependence of the SHG phase matching angle upon the degree of porosity is deduced.

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