Through the efforts of many students, including Micha, Barbara, and finally, Dylan, we have the capability of fabricating our own microelectromagnetic chips for atom trapping. The chip we are currently using is shown below, after it has been wired up and just before it was put into the vacuum system.
Some features of this chip include:
- Aluminum Nitride substrate for excellent thermal conductivity
- Backside "via" contacts for improved optical access
- Silver conductors for high electrical conductivity, coated with gold to reduce oxidation
- 9 separate current paths, including:
- 1 z-wire (trapping)
- 2 u-wires
- 2 'dimple' wires
- 1 rf antenna
- 1 microwave antenna
- 2 bias field wires
To mount the chip in the vacuum system, we mount it on a copper stack. The chip is glued to the copper stack using a thermally conducting epoxy, and all electrical connections are made by attaching the wires to the backside contact pads with an electrically-conductive, vacuum-compatible epoxy. As can be seen below, this makes for excellent optical access to the atoms trapped near the surface of the chip.
Also in this picture, you can see a number of other elements of the chip set-up. We use vacuum-compatible coaxial cable to transmit the rf and microwave signals to the chip wires (orange Kapton coated wires in picture). The coaxial cable is split and attached to regular copper wires a few cm from the chip contacts, to prevent shorts.
The dispensers can also be seen. The silver-coloured tubes, one of which is easily seen on the front of the stack in this picture, are the Alvatec dispensers. They are placed as close as possible to the chip to allow the best fluence of atoms into the vacuum chamber. Conductors are attached with the brass clamps to the vacuum feedthroughs near the bottom of the stack (not seen).
(Two points for recognising the student in the red t-shirt and attractive hair net in this photo.)
Our original atom chip was provided by the Groupe d'Optique Atomique (Aspect group) at Orsay (now Palaiseau), and was fabricated by Jerome Esteve. The chip is a silicon substrate with electroplated copper wires. This photo was taken after the chip had performed its duty and was removed from vacuum. The white Macor clamps were used to mechanically hold the chip to the stack, as well as providing electrical connections by pressing the copper foils to the chip contact pads. These clamps severely limited our optical access, especially when looking at the atoms along the long axis of the chip.