Collinear versus Non-collinear Autocorrelation between Femtosecond Pulses for Absolute Distance Measurement

Abstract Precise Absolute Distance Measurement (ADM) is of a great importance for several applications such as metrology, large-scale manufacturing and gravitational wave detection. The collinear autocorrelation (CAC) based on the temporal coherence of femtosecond laser pulses has been introduced several times before for ADM. In this paper, the non-collinear autocorrelation (NCAC) between femtosecond pulses is investigated as a replacement for the collinear autocorrelation for precise ADM. A comparison is made between both techniques in terms of precision, accuracy, uncertainty and Signal to Noise Ratio (SNR). In order to perform that, a commercial autocorrelator, which was used normally to measure laser pulse-widths, is exploited here to measure distances up to 21 m using both techniques. Although both techniques showed similar precision, the NCAC technique enables longer distance measurement since it has higher SNR at higher gains without the coherence limitation of the CAC technique.