Frequency standards based on hollow core fibres and micro-fabricated opto-electronic components

Atomic clock and other frequency standards are behind-the-scenes technologies that enable many familiar systems fundamental to modern living standards such as the Global Positioning System (GPS) and mobile communications. Presently we depend on large scale instruments to provide these standards. This proposal is about developing miniature versions of these instruments - ideally, the miniaturisation could go down to chip-scale.The chip-scale standards would use a version of the optical fibres already used in long haul communications - the new version has the glass central core of the fibre hollowed out and replaced with atomic gas vapour such caesium atomic vapour or molecular gases such as acetylene. These are called hollow core fibres and the gases at the centre of these fibres provide the basis of the new frequency and clock standards. The hollow core fibres are vital but they are only one part of the system and new mircoscale components are being developed as part of this proposal that will mean that the whole standard will be compact, reliable robust and low powered.These reliable, compact and low powered chip-scale standards will not only greatly improve GPS and mobile communications but will also allow new applications to come into existence. For example, highly sensitive magnetometers based on these standards can be used in imaging the electrical activity of the brain and heart and will replace the large cumbersome technology presently employed -to the point where in 10 years time brain and heart imaging could be available in a GP's surgery.

The impact of the proposed research on this novel frequency standards technology will be spread across several sectors that include atomic and molecular spectroscopy, mobile, military and long haul communications, global positioning systems and medical imaging. Therefore the developers and users of these systems will benefit from this research. The developers of equipment for atomic and molecular spectroscopy will have compact low powered systems that can be easily incorporated in their equipment to provide calibration that can be traced back to fundamental standards. The users will have lower cost calibrated equipment that will give reproducible results. The developers of the communications equipment will have field deployable systems that will provide both microwave and frequency standard calibrated against international unit standards -ensuring reproduce results in variety of operating conditions. They will also have access to new commercial supplies of microfabricated optoelectronic components that will allow them to configure the standards in manner most convenient for their systems. The users will benefit from improved systems at lower cost. Already chip-scale atomic clocks are being developed for deployment in GPS receivers as this improves the system by reducing the amount satellites required to fix a position because the receiver as its own on-board time reference, it reduces the time required to fix a position and the accuracy of the fix. The hollow core fibre technology promises to further reduce the size and accuracy of these compact atomic clocks. Closely related to the hollow core fibre atomic clock technology is work on room temperature optical magnetometers as sensitive as cryogenic magnetometers (SQUIDs) currently used in Magnetocardiography (MCG) and Magnetoencephalography (MEG). The developers of these imaging instruments will find that their market expands hugely if they can offer the same performance but without the cryogenics. The users will benefit from much reduced capital and operational expenditure. In addition the proposal has a knowledge transfer element - to UK based chip manufacturers and wafer growers - this will help generate UK employment.