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Frequency Standards and Dissemination

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We are currently collaborating with a defence organisation. The team are evaluating the use of our cryogenic sapphire oscillator (CSO) and frequency synthesisers in their applications

We are developing optical and microwave sources having extremely high frequency stability for high impact experiments. These include direct measurement of Einstein’s time dilation effect, as well as frequency references for: leading-edge atomic clocks, optical and radio astronomy and radar applications.

We are also developing a fibre dissemination network to allow fast and precise frequency comparison between frequency standards within different laboratories. This can be extended to time dissemination over large scales for applications such as the square kilometre array (SKA) radio telescope.








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Cryogenic Sapphire Oscillator

cylindrical Sapphire oscillator

A highly stabilised frequency sources can be made by linking the frequency of electromagnetic radiation of a microwave field to the physical dimension of a cryogenically cooled mechanical resonator. In this project a cylindrical Sapphire oscillator is used (pictured) in which the microwave field bounces around the cylinders circumference in a “whispering gallery mode” configuration.

The oscillator is cooled to near 4 Kelvin to reduce the frequency standards dependence on temperature through utilising a minimum in the Sapphire’s thermal expansion coefficient. Our goal is to achieve a relative frequency instability of 10-17 during at 1s observation time, a factor of 10 better than any previous demonstration. This expected frequency stability corresponds to 0.1uHz at the optical frequency of 11GHz.

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Cryogenic Optical Cavity

Optical Cavity

A highly stabilised frequency sources can be made by linking the frequency of a lasers electromagnetic radiation to the physical dimension of a cryogenically cooled mechanical resonator. In this project a silicon cube mounted in a vibration insensitive configuration will be the cooled mechanical resonator reference for a laser source.

At temperatures just above absolute zero, the thermal vibrations of the resonator are significantly reduced, therefore lowering variations in the frequency. Our goal is to achieve a relative frequency instability of 10-17 during at 1s observation time, a factor of 10 better than any previous demonstration. This expected frequency stability corresponds to 2mHz at the optical frequency of 200THz.

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Stabilized Fibre Link

A major challenge in measuring the stability of a frequency standard is in transporting the stabilised signal between various locations to make the comparison. Lengths of optical fibre or electronic transmission lines all act in such a way that the stabilised signal deteriorates. This can be circumnavigated by stabilising the length of the link that is transporting the frequency standard signal.

Using state-of-the-art noise cancellation techniques we will deliver the high spectral purity of our laser and microwave sources and allow precision measurements between remote locations. This can be extended beyond the laboratory enabling end-users who require precise timing to benefit from the frequency standard developed within the laboratory. One such end-users would be the square kilometre array (SKA) radio telescope.

Institute for Photonics and Advanced Sensing
Address

North Terrace Campus
The Braggs Building
The University of Adelaide
SA 5005
Australia

Contact

T: +61 8 8313 0589 
F: +61 8 8313 4380
ipasadelaide@adelaide.edu.au

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