Laser Ranging in Air Utilizing Mode-Locking in Laser Cavities

In this letter, a novel and simple technique for precise distance measurement in air is introduced. This technique requires only comprising the measured distance in a passively mode-locked laser cavity while measuring the change in repetition rate of its laser pulses. Consequently, the measured distance can be obtained from the measured change in repetition rate. Distances of up to 14 m are measured with a precision of 19 μm and an expanded uncertainty of 52 μm (k = 2). The measured distance was limited by the available space inside our laboratory; however, it can be extended for hundreds of meters. The main advantage of this method is, in addition to its simplicity and portability, its direct traceability to the SI units.