ZnO nanorods with controlled-surface density have been successfully obtained by simply varying the concentration of the growth solution. It was found that the variation in the growth solution concentration may vary the surface density of the ZnO nanorods arrays grown on the surface. The lowest concentration produces the lowest nanorods surface density. The photoinduced second harmonic generation was studied for the nanosecond Er: glass lasers at wavelength 1540 nm and induced by bicolour treatment at 1540/770 nm wavelengths. The nonlinear dependence on the Ag NP presence was observed. And it s was substantially higher than for the pure ZnO nanoparticles.