Abstract
We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a subwavelength hole; and (iv) the simulation that shows the light transmission through subwavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal. We believe these finding should have broad and significant impacts and applications to optical systems in many fields.
Highlights
Many optical systems today, such as those in sensing, nanolithography, and many others [1,2,3,4], are built on a general belief: An optically opaque metal film would block light transmission even if the film has small holes, as long as the holes are covered with opaque metals which geometrically block the light path through the holes
We report the details of our experiments, observations, simulations and potential applications of enhancing and tuning the light transmission through subwavelength holes by blocking them with metal disks
We report the study of the enhanced optical transmission through a periodically perforated metallic film with each subwavelength hole blocked by an opaque metal disk
Summary
Many optical systems today, such as those in sensing, nanolithography, and many others [1,2,3,4], are built on a general belief: An optically opaque metal film would block light transmission even if the film has small holes, as long as the holes are covered with opaque metals which geometrically block the light path through the holes. Numerical simulations have predicted that covering the subwavelength holes or slits by cavity antennas [11] can enhance the optical transmission; and that by properly placing periodic structures on both sides of a continuous metal film without any holes, the light can transmit through the film [8]. These predications are yet to be confirmed experimentally. Received 6 Sep 2011; revised Sep 2011; accepted Sep 2011; published 7 Oct 2011 10 October 2011 / Vol 19, No 21 / OPTICS EXPRESS 21099
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