The first aim of iSense is to develop a set of tools and technologies that can be used as basic blocks to build a robust and portable device based on ultracold atoms.
In the picture you see a preliminary model of an apparatus that could be used for gravimetry. It consists of several high-tech components that have to be developed to match the demanding requirements of iSense.
Below you can find some general information about the technology used and developed in iSense with links to the corresponding research sections to get an inside view about the detailed research and the progress achieved so far.
Ultracold atoms are so cold that they need to be insulated from the rest of the world by a very good vacuum in order to stay cold. Therefore they are trapped and cooled down inside a vacuum chamber.
The vacuum chamber is in general made out of steel and has a number of viewport to allow the laser beams to get in. It is connected to one or several pumps that ensure a high quality vacuum. If necessary, feedthroughs let electric cables in to power electromagnets or other devices. This results in a bulky apparatus which is incompatible with a portable device.
The iSense project seeks to develop technologies that will reduce the volume and weight of the necessary connections between glass and steel, using speciality glues or new bonding techniques.
Miniaturized Laser Systems
Laser cooling requires high-quality lasers, that is to say lasers with an extremely well defined frequency (colour). Regular lasers, such as the ones found in DVD players are not good enough in terms of stability. Their design, based on a semiconductor chip, is well suited to a compact apparatus but the extra optics required to stabilize them tends to cancel this advantage. iSense will develop miniature, fully stabilised lasers based on semiconductor technology and micro-bench optics which combine small size, high power and great stability.
Having good lasers is not enough. To cool atoms with lasers, beams of several frequencies have to be overlapped, and the resulting beam should be split into 6 beams converging toward the region where the atoms are trapped. Moreover, in the course of an experiment, where the atoms are successively trapped, cooled, released and probed, the intensities and frequencies of the lasers need to be adjusted with switches and modulators. All this results in a rather intricate optical set up which can fill up an optical table.
The iSense project seeks to drastically reduce the footprint of the optical system by combining the optical elements on a single semiconductor chip. At first, we will integrate the guiding, splitting and combining of the beams, and the switches. The second time, we will also try to integrate the modulators.
The active components of the set up, such as the lasers and their stabilisation, the frequency shifters, the optical switches, the electromagnets, etc., must be finely controlled by a range of electronic drivers which in turn are made to work in unison with a computer. In the iSense project, the whole system, which traditionally spans many racks and consumes kilowatts of power, is tightly integrated following the industry standard PC-104. The drivers for all the active optical components are custom-made extension boards of a small-factor PC.
Low Power Atom Chip
The trapping of ultracold atoms requires a magnetic field in addition to the laser beams. The magnetic field can be created by electric coils placed outside the vacuum chamber. A more modern approach consists in generating the magnetic field with copper tracks running on a small substrate, a so-called "atom chip". The atom chip is much smaller than the traditional coils and can be placed inside the vacuum, much closer to the atoms. The iSense project will develop an atom chip tailored for atom interferometry that operates at low electrical power.