Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter. Our current focus is on detection and sensing/imaging with an emphasis on the development of integrated photonics. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.


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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