ADVANCED ABSOLUTE LENGTH METROLOGY BASED ON PULSE TRAINS' CONSTRUCTIVE INTERFERENCE - TOWARDS MEASUREMENTS OF METER ORDER WITH AN ACCURACY OF NANO ORDER

摘要

Measurements of lengths are strongly demanded for not only science purposes but also industry requirements. Because of the great potential for a technological revolution in high precision distance measurement and related areas, femtosecond mode-locked optical frequency combs (FOFCs) have attracted many attentions from researchers and engineers. Due to theirs the improved frequency-stability and the very broad frequency-band, the FOFCs have led to new applications in several precision metrology areas such as high precision optical frequency metrology, spectroscopy, and distance measurements. The interferometric measurement using the FOFC is in progress at present. We had analyzed the temporal coherence function of the FOFC since it is the fundamental description of interference phenomenon. As a result, it has been understood that the coherence peak exists during the time which is equal to the repetitions interval in the travelling direction of the FOFC. In order to make the best use of the temporal coherence characteristic, we proposed a high precision length measurement method by the multi-interaction between different pulse train beams. As one demonstration, the concept of the use of a femtosecond optical frequency comb for high precision length measurement based on phase controlled pulse trains' constructive interference is proposed in this paper. The theoretical derivation shows that the present technique offers a significantly different approach to high precision length measurement. Preliminary experimental results of the constructive interference with different pairs of pulse trains show many applications possibility of the proposal method.