Non-uniform electric and magnetic fields provide a versatile tool to manipulate and control the motional states of polarizable and magnetizable particles in a remote and non-destructive fashion. However, as the field force falls dramatically with the particle size, the manipulation of sub-micron particles against their Brownian motion at room temperature is challenging. This requires the use of strong field gradients and high intensities which makes the miniaturization of the field-producing structures preferable. Other motivations to develop miniaturized trapping structures are the improved positional control and reduced power consumption provided by them. The objective of this thesis is to pursue the realization of two novel miniaturized manipulation tools based on static electric and magnetic fields by modeling the trapping potentials, and fabricating the trapping structures. In particular, a method to fabricate a three-dimensional periodic nanoelectrode array for nanoparticle manipulation is described. The method is based on tapering a microstructured photonic crystal fiber and filling the contracted capillaries with a conductive material. Based on numerical simulations, such nanoelectrodes can be used to produce electric-field patterns with nanometer scale features for control and assembly of nanoparticles at room temperature. The other miniaturized device considered in this thesis is a permanent-magnet chip for atom and nanoparticle manipulation. Microscopic magnetic-domain patterns recorded in a ferrite-garnet (FG) film can be used to create microscopic traps for nanoparticles at room temperature and for atoms cooled to AK-range temperatures. The magnetic-domain patterns can be created by using a conventional magneto-optical recording technique. In addition, we have developed a novel technique to record the domain patterns all-optically. These techniques allow one to record and reconfigure the domain patterns in situ. In essence, arbitrary two-dimensional trapping structures can be readily produced. Our FG chip has many advantages over the conventionally used current-carrying wire structures. Most important of them are optical transparency, reconfigurability, and the ability to produce nearly noiseless and strong magnetic fields without any electric-power consumption. In our laboratory, this kind of microscopic magnetic atom traps have been demonstrated experimentally using 85Rb atoms. In all-optical recording the local magnetization direction in the FG film is controlled purely optically by adjusting the beam parameters of the recording laser. This magnetization-reversal phenomenon is intriguing from both fundamental and technological points of view and can be used not only in the magnetic chip technology, but also in other magnetic and optical device applications in which the use of electricity is undesirable. As an example, a novel concept of all-optical memory elements that allow writing and erasing of information in three dimensions, is introduced in this thesis. Both the nanoelectrode array and magnetic FG chip could be integrated with other nano- and microfabricated components to built multifunctional devices on a single substrate. With this respect, the work introduced in this thesis constitutes one more step forwards the "lab on a chip" technology.

Jan 1, 20080 citations

Trapping atoms on a transparent permanent-magnet atom chip

Andriy Shevchenko, M. Heiliö, Thomas Lindvall +4 more

We describe experiments on the trapping of atoms in microscopic magneto-optical traps on an optically transparent permanent-magnet atom chip. The chip is made of magnetically hard ferrite-garnet material deposited on a dielectric substrate. The confining magnetic fields are produced by miniature magnetized patterns recorded in the film by magneto-optical techniques. We trap Rb atoms on these structures by applying three crossed pairs of counterpropagating laser beams in the conventional magneto-optical trapping geometry. We demonstrate the flexibility of the concept in creation and in situ modification of the trapping geometries through several experiments.

arXiv:quant-ph/0601163Physical Review AMay 5, 200616 citations