A head slider for flying above a rotating magneto-optic or optical disk and an optical mechanical assembly with a fixed height above a rotating magneto-optic or optical disk contains magnetic coils and a lens plate with a diffractive optic structure for focusing laser light into a small spot on the disk. The diffractive optic structure may be a zone plate, a phase zone plate or a blazed phase zone plate or other diffractive focusing optical element. The diffractive optic structure does not require curved transparent material such as glass or a high index of refraction. The diffractive optic structure is easily manufactured using lithographic or other techniques.