23 December 2016 Length measurement in absolute scale via low-dispersion optical cavity
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Proceedings Volume 10142, 20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics; 101420T (2016) https://doi.org/10.1117/12.2264452
Event: 20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 2016, Jasna, Slovakia
Abstract
We report on the length measuring instrument with the absolute scale that was based on the combination of an optical frequency comb and a passive optical cavity. The time spacing of short femtosecond pulses, generated by the optical frequency comb, is optically phase locked onto the cavity free spectral range with a derivative spectroscopy technique so that the value of the repetition frequency of the femtosecond laser is tied to and determines the measured displacement. The instantaneous value of the femtosecond pulse train frequency is counted by a frequency counter. This counted value corresponds to the length given by the spacing between the two mirrors of the passive cavity. The phase lock between the femtosecond pulsed beam and the passive cavity is possible due to the low-dispersion of the cavity mirrors, where the silver coating on the mirrors was used to provide the low dispersion for the broadband radiation of the comb. Every reflection on the output mirror feeds a portion of the beam back to the cavity so that the output beam is a result of multiple interfering components. The parameters of the output beam are given not only by the parameters of the mirrors but mainly by the absolute distance between the mirror surfaces. Thus, one cavity mirror can be considered as the reference starting point of the distance to be measured and the other mirror is the measuring probe surveying the unknown distance. The measuring mirror of the experimental setup of the low-dispersion cavity is mounted on a piezoelectric actuator which provides small changes in the cavity length we used to test the length measurement method. For the verification of the measurement accuracy a reference incremental interferometer was integrated into our system so that the displacement of the piezoelectric actuator could be obtained with both measuring methods simultaneously.
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Lenka Pravdova, Lenka Pravdova, Adam Lesundak, Adam Lesundak, Radek Smid, Radek Smid, Jan Hrabina, Jan Hrabina, Simon Rerucha, Simon Rerucha, Ondrej Cip, Ondrej Cip, } "Length measurement in absolute scale via low-dispersion optical cavity", Proc. SPIE 10142, 20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 101420T (23 December 2016); doi: 10.1117/12.2264452; https://doi.org/10.1117/12.2264452
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