Small-particle semiconductors in rigid matrices

An apparatus for producing third-order nonlinear optical effects, comprising an article of manufacture consisting essentially of porous glass, the pores of which contain a polymer and a semiconductor material comprising at least one cation selected from the group consisting of Cd.sup.+2, Zn.sup.+2, Pb.sup.+2, Cu.sup.+2, Ga.sup.+3, In.sup.+3, and Ti.sup.+4, and at least one anion selected from the group consisting of S.sup.-2, Se.sup.-2, Q.sup.-2, I.sup.-, P.sup.-3, Sb.sup.-3, and As.sup.-3, provided that when the cation is In.sup.+3 or GA.sup.+3, the anion is other than P.sup.-3, Sb.sup.-3 or As.sup.-3, and a source of coherent electromagnetic radiation arranged for irradiating said porous glass with said coherent electromagnetic radiation.