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Jeremy Witzens

Publications and source records attributed to Jeremy Witzens.

5 recordsLinked to original sources
PubMed2005

Hybrid superprism with low insertion losses and suppressed cross-talk.

We demonstrate with the two-dimensional finite-difference time-domain method that an adiabatic transition in a superprism with an interface along the [1 2 ] direction enhances the transmission through the superprism to more than 90% (-0.5 dB) over the wavelength range 1.47-1.68 mum , including the telecommunication C and L bands. We also show that diffraction governed by a quasinegative index of refraction inside the superprism can be used to obtain nearly transform-limited beam widths at the output of the superprism. The reduction of the beam width at the output suppresses cross-talk and greatly enhances the achievable frequency resolution of the superprism.

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PubMed2004

Mode matching interface for efficient coupling of light into planar photonic crystals.

In order to integrate superdispersive elements based on photonic crystals, such as the superprism, with conventional integrated optics, insertion losses at the interface to the photonic crystal need to be reduced to an acceptable level. We describe a mode matching interface composed of cascaded diffraction gratings that generates the field profile of the photonic crystal Bloch mode from a slab mode. We calculate with three-dimensional finite-difference time-domain computation that by interposing such a multilayered grating between an unpatterned slab and a planar photonic crystal, the insertion efficiency is enhanced from 9% to 84%. Each diffraction grating consists of a row of holes and does not require any additional process steps from those used to fabricate the planar photonic crystal. In order to optimize the efficiency of the mode matching interface, constructive interference conditions are imposed between successive gratings and reflections from individual gratings are suppressed. We fabricate devices in silicon on insulator material and show experimental evidence of the Bloch mode structure and of the mode matching mechanism.

Journal Article↗
PubMed2003

Efficient excitation of self-collimated beams and single Bloch modes in planar photonic crystals.

Using finite-difference time-domain calculations, we investigate out-of-plane coupling between a square-lattice planar photonic crystal and a conventional waveguide located above the photonic crystal. We couple a waveguide oriented in the gamma(chi) direction to a photonic crystal mode in the second band and show that anticrossing takes place. In this way, a self-collimated beam is launched in the planar photonic crystal, with full power transfer. Furthermore, we investigate the coupling between a waveguide oriented in the gamma(mu) direction and a photonic crystal and show that single photonic crystal modes can be selectively excited.

Journal Article↗
PubMed2003

Photonic crystal waveguide-mode orthogonality conditions and computation of intrinsic waveguide losses.

We simulate the propagation of light in a W1 planar photonic crystal waveguide with the three-dimensional finite-difference time-domain method and apply an inner product against previously calculated mode profiles to the simulated field cross sections. We show that this inner product satisfies mode orthogonality for both photonic crystal waveguides and segmented waveguides and use the obtained data to evaluate waveguide losses.

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