Looking at common practice in cold atom laboratories, where the experimental setup is dominated by a vibration isolation table full of lasers and optical components, the optical system surrounding cold atoms is easily identified as the key technology with high potential for shrinking. In principle an example to follow is the huge effort in the telecom sector to integrate various optical devices using AlGaAs technology resulting in commercially available components such as multiplexers, intensity modulators and more complex systems. However, in general these devices are only available in the telecommunication wavelength range, i.e. 1310nm and 1550nm, and in this range no practical atomic transitions are available. Rb as the most commonly employed atom needs laser light at 780nm for cooling, which is very close to the bandgap in AlGaAs, requiring careful design to avoid losses and only few relatively simple devices have been tested.
One attempt to circumvent this issue and still make use of telecom technology for cold atom applications is the ICE project (CNRS-IOGS), which uses standard telecom devices at 1560nm and doubles the frequency of the light before using it with the atoms. Only relatively simple integrated optics devices have been used here and the doubling adds complexity if high efficiency is needed.
Other attempts to shrink optics for mobile cold atom applications rely on small “standard” optics, which are to some extent available from commercial companies like Thorlabs-OfR, Schaefter & Kirchhoff or Ingeneric. In order to maximize stability small custom optics designs have been realised in the German QUANTUS and LASUS, the European SAI and SOC projects as well as at JPL and Yale/Stanford University. These attempts have however come close to the practical limits of shrinkage for this standard technology and a technology leap is needed to go further.
iSense will for the first time create a set of integrated optics devices for cold atom applications at 780nm using GaAs technology and explore its further extension to the full visible range using GaN technology. For this crucial breakthrough for cold atom applications iSense combines the expertise from all the above approaches and will achieve a technology leap in optical systems similar to the replacement of discrete circuits by integrated circuits in electronics.
Research progress in the 1st year
Nottingham has taken over the tasks assigned to QinetiQ in the original Annex-I and has successfully started modelling work for integrated devices. First samples shall be produced in autumn 2011. The work on an alternative free-space optical delivery module has started ahead of schedule with a preliminary system design and some component tests.