Generation of Ultra Low Phase Noise Microwave Local Oscillators from Optical Frequency Standards Using Femtosecond Laser Synthesis

The development of ultra stable femtosecond laser comb generators is resulting in the emergence of a method to transfer the fundamentally higher stability of optical frequency standards and oscillators to microwave frequency outputs. This is important for applications where coherent signal generation and reception is used e.g. Radar or Electronic Defence. The stability and accuracy of calcium and mercury ion standards are at the 2x10 and 1x10 levels respectively. The most recent results from the National Institute for Standards and Technology demonstrate that the stability of the laser comb generators, which can link the optical standards to the microwave, at the 1x10 level; a level, which could lead to a means, to track the evolution of the fine structure constant . This precursor project has reviewed this emerging technology which has its basis in providing optical outputs from the microwave domain. Although currently a technique based upon a controlled laboratory environment and the use of powerful solid state lasers, indications are provided which provide a path to integration and miniaturisation. A comparison with other emerging technology is made and a first UK measurement of the particular technique has been instigated at the National Physical Laboratories.