Tunable Flat Lenses in the Mid-Infrared

Jon R Pugh, Alissa Silva, Jamie L Stokes, Craig Stacey, Geoff Nash, John Rarity, Ian D Lindsay, Martin J Cryan

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

Abstract

We present a stand-alone beam focusing flat lens for use in the mid-infrared wavelength range. An aperture and second-order grating structure in a thin gold layer is used to excite and then scatter a propagating surface plasmon polariton (SPP) to constructively interfere in the far-field to produce a narrow beam. A rapidly tunable optical parametric oscillator source is used to demonstrate how changing the wavelength of the incident light from 3.8-4.2µm produces two interfering beams in the far-field caused by the scattering of the propagating SPP interfering with the incident light diffracted by the narrow (sub λ/2) aperture. We identify measured far-field patterns for varying wavelengths using the razor blade edge beam profiling method. The agreement between Finite-Difference Time-Domain (FDTD) modelled and measured results will allow the aperture/grating structures to be integrated directly onto the facets of edge-emitting lasers to dramatically reduce their beam divergence. As edge-emitting lasers have a fixed wavelength, the addition of a thin layer of material such as Silicon or Barium Strontium Titanate to the facets allows tuning by altering the SPP wavelength.
Original languageEnglish
Title of host publicationTransparent Optical Networks (ICTON), 2013 15th International Conference on
Publication statusPublished - 23 Jun 2013

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