Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter at the nanoscale. We do this by exploring ways to shape light and its environment. It's what we call active and passive control. Our current focus is on the interaction of light with biomolecules and nanostructures. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.
We participate in the EU-COST actions MP1102: Coherent Raman microscopy (MicroCor) and CM1202: Supramolecular photocatalytic water splitting (PERSPECT-H2O)


Large bandwidth, highly efficient optical gratings through high index materials

(full pdf)

Helmut Rathgen and H. L. Offerhaus
Optics Express
Vol. 17 Issue 6 p. 4268-4283 march 3 2009

We analyze the diffraction characteristics of dielectric gratings
that feature a high index grating layer, and devise, through rigorous numerical
calculations, large bandwidth, highly efficient, high dispersion dielectric
gratings in reflection, transmission, and immersed transmission geometry.
A dielectric TIR grating is suggested, whose −1dB spectral bandwidth is
doubled as compared to its fused silica equivalent. The short wavelength
diffraction efficiency is additionally improved by allowing for slanted
lamella. The grating surpasses a blazed gold grating over the full octave. An
immersed transmission grating is devised, whose −1dB bandwidth is tripled
as compared to its fused silica equivalent, and that surpasses an equivalent
classical transmission grating over nearly the full octave. A transmission
grating in the classical scattering geometry is suggested, that features a
buried high index layer. This grating provides effectively 100% diffraction
efficiency at its design wavelegth, and surpasses an equivalent fused silica
grating over the full octave.

©2008 Optical Society of America
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