Victor Callegari

Optimized fabrication of curved surfaces by a FIB for direct focusing with glass fibres

A focused ion beam (FIB) was used to fabricate Fresnel phase lenses on optical fibre tips. The influence of dwell time and the scanning strategy to produce parabolic structures in silicon was investigated, because these parameters have a strong influence on the shape of the fabricated structures. The lens shape was characterized by atomic force microscopy and it was shown that the FIB does not roughen the surfaces. The optical performance of the lenses was characterized by scanning near field optical microscopy (SNOM) and the results were compared to simulations taking into account fabrication imperfections of the Fresnel lenses. At a wavelength of 840 nm a spot size of 740 nm FWHM was achieved.

Focused ion beam induced synthesis of a porous antimony nanowire network

We present a focused ion beam-based approach for the synthesis of an antimony nanofiber network. The nanofibers, with a homogeneous distribution of diameters of about 25 nm and lengths up to several microns, are synthesized in a self-assembling process without any additional material source at room temperature. It is possible to recrystallize the as-grown amorphous nanofibers by moderate rapid thermal annealing at 473 K. These results have been verified by means of scanning electron microscopy, Auger electron spectroscopy, high-resolution transmission electron microscopy, selected area electron diffraction, and energy dispersive x-ray analysis. As this approach is not limited solely to the material discussed here, other substrates (e.g., GaSb and Ge) and ion sources should extend this method to other materials, which offers a great potential for future nanoscale devices and applications.

Engineering gold nano-antennae to enhance the emission of quantum emitters

We study the fluorescence enhancement of a single emitter coupled to two spherical gold nanoparticles and discuss the differences with respect to coupling to a single one. We also show that by changing the aspect ratio of the nanoparticles we can easily tune the plasmon-mediated enhancement from the infrared to the visible range. We present the fabrication of our nanoantennae by two alternative methods, namely X-ray interference lithography followed by focused ion beam milling and electron beam lithography. The manufactured structures are characterized individually by confocal microscopy.

FIB Precise Prototyping and Simulation

We present a closed approach towards direct microstructuring and high precision prototyping with focused ion beams (FIB). The approach uses the simulation of the involved physical effects and the modeling of geometry/topography during milling while the ion beam is steered over the surface. Experimental examples are given including the milling of single spots, trenches, rectangles, and Fresnel lenses. Good agreements between simulations and experiments were obtained. The developed procedures can also be applied to other FIB prototyping examples.

Fabrication and Modification of Photonic Structures with Focused Ion Beam

Photonic crystals (PhC) are structures consisting of alternating domains with different indexes of refraction. They can be designed to posses an optical bandgap and act as filters or mirrors for light [2]. FIB (30 keV Ga + , FEI Strata 235 with a scanning electron microscope (SEM)) was used to directly fabricate PhC structures, to fabricate PhC-masks for use with reactive ion etching (RIE) or to mill holes in a pre-fabricated PhC for rapid prototyping [3]. For direct structuring of InP, the challenge lies in fabricating large aspect ratio holes (AR>10). The diameter and positions of the holes are defined by the wanted wavelength λ (1550 nm for InP, corresponding to the absorption minimum of optical glass fibers) and are calculated by Maxwell-equations-solving finiteelement simulation programs. Fabrication and Modification of Photonic Structures with Focused Ion Beam