Timo Hakkarainen

Publications (4)1.56 Total impact

• Article: Electromagnetic near-field interactions of a dipolar emitter with metal and metamaterial nanoslabs

  Timo Hakkarainen, Tero Setälä, Ari T. Friberg
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  ABSTRACT: We investigate the emission properties of a polarizable point dipole placed within a subwavelength distance from a silver or a slightly absorbing, negative-index metamaterial nanoslab. Using electromagnetic theory we show that in the immediate vicinity of the slab the dipole-slab interaction prevents the dipole from radiating. For the metamaterial slab close to the perfect-lens arrangement, the interaction is relatively weak and of short range. In particular, a region exists in the near zone of the metamaterial slab where the dipole emission is not disturbed by the interaction, and a bright intensity distribution of subwavelength width is created on the opposite side of the slab. This suggests that a low-loss metamaterial slab can act as a near-field imaging device which does not disturb the object. For the silver slab the interaction is stronger and it reaches over the near-field zone, adversely influencing the imaging capabilities in terms of brightness and resolution. The results are important for the development of metal and metamaterial superlenses.
  Phys. Rev. A. 09/2011; 84(3).
• Source

  Available from: metamorphose-vi.org

  Article: Subwavelength electromagnetic near-field imaging of point dipole with metamaterial nanoslab.

  Timo Hakkarainen, Tero Setälä, Ari T Friberg
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  ABSTRACT: We investigate near-field imaging of a point dipole by a lossy, nanoscale metamaterial slab. Making use of the electromagnetic angular-spectrum representation, we derive the Green tensor for the field transmission through the metamaterial slab, duly considering multiple reflections, polarizations, and wave-vector signs. With this general formalism, we calculate the point-spread function of the imaging system, which enables us to assess, for instance, resolution and image brightness. Our results demonstrate that with the metamaterial-slab lens one achieves resolution beyond the conventional diffraction limit of half the wavelength. In general, the resolution and image brightness are degraded when the slab thickness and absorption increase, but we show that in some cases the resolution is rather insensitive to the magnitude of the losses in the metamaterial.
  Journal of the Optical Society of America A 10/2009; 26(10):2226-34. · 1.56 Impact Factor
• Source

  Available from: Bernhard J Hoenders

  Article: Invisibility cloaking in weak scattering

  Tero Setälä, Timo Hakkarainen, Ari T Friberg, Bernhard J. Hoenders
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  ABSTRACT: We consider invisibility cloaking of a slab object in scalar wave theory within the first-order Born approximation. We show that in the forward direction cloaking is achieved for any object slab and incident field, whereas in the backward direction cloaking is possible at least for self-imaging fields. In both cases the scattering potential of the cloak slab depends on that of the object slab. The method of object-dependent cloaking using weak slab scatterers can be a useful addition to existing cloaking methods, for instance, in atmospheric optics and biophotonics.
• Source

  Available from: Bernhard J Hoenders

  Article: Object-dependent cloaking in the first-order Born approximation

  Tero Setälä, Timo Hakkarainen, Ari T Friberg, Bernhard J. Hoenders
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  ABSTRACT: We consider the cloaking of a slab object in scalar wave theory within the first-order Born approximation. We show that in the forward direction cloaking is achieved for any transversally invariant, positively refracting, and absorbing object by using a lossy, negative-index metamaterial cloak. Cloaking is perfect and occurs for incident fields having any spatial structure and bandwidth. In the backward direction cloaking is found to be possible for self-imaging fields. In both cases the refractive-index distribution and dispersive properties of the cloak slab resemble those of the object slab. The method of object-dependent cloaking with weak scatterers may find useful applications.