An optical article is disclosed comprised of a support including a portion adjacent one major surface which is transparent to the electromagnetic radiation sought to be propagated, an organic layer unit capable of converting a portion of polarized electromagnetic radiation of a selected wavelength to its second harmonic wavelength, means for optically coupling into said organic layer unit polarized electromagnetic radiation of a selected wavelength in its zero order transverse magnetic mode, and means for receiving from the layer unit a portion of the electromagnetic radiation in the form of a first order transverse magnetic mode. The organic layer unit has a thickness which is at least 70 percent of the wavelength of the zero order transverse magnetic mode and differs by less than 100.ANG. from the thickness required for identical propagation constants of the zero and first order transverse magnetic modes. The organic layer unit is comprised of a Y-type Langmuir-Blodgett assembly of amphiphiles forming a first Langmuir-Blodgett layer unit containing noncentrosymmetric organic molecular dipoles of a first orientation providing a second order polarization susceptibility to the first layer unit in excess of 10.sup.-9 electrostatic units, and a Y-type Langmuir-Blodgett assembly of amphiphiles forming a second Langmuir-Blodgett layer unit adapted to be coated on the first Langmuir-Blodgett layer unit containing noncentro-symmetric organic molecular dipoles of a second orientation providing a second order polarization susceptibility to the second layer unit in excess of 10.sup.-9 electrostatic units, but of opposite sign to that of the first layer unit.