Patent ID: 7792006

Claim:
An optical head for converting an incident light to a subwavelength-scale light beam, said optical head comprising: a transparent substrate; a thin film having a first surface attached to said transparent substrate, a second surface opposite to said first surface, an inner surrounding wall extending from said first surface to said second surface and a passage with a subwavelength aperture confined by said inner surrounding wall, said passage enabling said incident light propagating from said transparent substrate toward said thin film to generate surface waves on said inner surrounding wall, wherein said thin film is formed of a material having a relative dielectric constant ranging between −4.5 and −6.5; and a surface subwavelength structure having a relative dielectric constant that is different from a relative dielectric constant of said thin film, said surface subwavelength structure being formed on said second surface of said thin film for modulating the generated surface waves.