Heikki J Hyvärinen

Publications (3)8.91 Total impact

• Article: Limitations of superoscillation filters in microscopy applications.

  Heikki J Hyvärinen, Shakil Rehman, Jani Tervo, Jari Turunen, Colin J R Sheppard
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  ABSTRACT: The idea of superresolving pupil filters comes from the concept of superoscillations that may occur in regions of a band-limited signal with small amplitude having oscillations faster than the fastest Fourier component of the signal. In optical microscopy, superresolution can be achieved by appropriate design of pupil functions where the angular aperture determines the ultimate focal spot smaller than the Abbe diffraction limit outside the evanescent field region. The angular aperture cannot be increased indefinitely and the huge sidelobes cannot be avoided that are present in superresolving filters. The limitations of using such kind of filters in microscopy applications are discussed through computational examples.
  Optics Letters 03/2012; 37(5):903-5. · 3.40 Impact Factor
• Article: Polarization insensitive resonance-domain blazed binary gratings.

  Heikki J Hyvärinen, Petri Karvinen, Jari Turunen
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  ABSTRACT: Three variants of binary blazed gratings with subwavelength features are considered, which have high first-order efficiencies in the non-paraxial domain for arbitrarily polarized light. A combination of effective medium theory and further parametric optimization with the Fourier modal method are used in design. Experimental demonstration is provided by electron beam lithography on a structure etched in a Si3N4 layer on top of a SiO2 substrate, with period approximately 3.5lambda at lambda = 633 nm. The measured efficiency (81% for TE and 85% for TM polarization) agrees well with the calculated value, 84%.
  Optics Express 06/2010; 18(13):13444-50. · 3.59 Impact Factor
• Article: Efficiency optimization of blazed effective-medium gratings in the resonance domain

  Heikki J Hyvärinen, Jari Turunen, Pasi Saarikko
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  ABSTRACT: Three types of subwavelength-structured grating for efficient beam deflection in the non-paraxial domain are considered. The first-order efficiency is optimized by first designing an index-modulated grating and then encoding the optimized values of refractive index in the form of surface-relief profiles using effective-medium theory. Comparison with direct parametric optimization shows the feasibility of the approach in finding nearly optimum designs with greatly reduced computational effort.
  Journal of Optics A Pure and Applied Optics 04/2008; 10(5):055005. · 1.92 Impact Factor