Ultrafast, sub-nanometre-precision and multifunctional time-of-flight detection

Abstract

Displacement measurement is a fundamental functionality in modern science and technology. Although there has been remarkable progress in the precision of such measurements with various laser ranging methods1–8, they are incapable of capturing fast and complex mechanical displacements. Here, we have established a displacement measurement method using time-of-flight detection9 with femtosecond optical pulses and frequency-locked electrical waveforms. This method uniquely combines ultrafast measurement speed, sub-nanometre precision and non-ambiguity range of more than several millimetres. The achieved performance features unprecedented detection speed and precision. Starting from 24 nm precision for 4 ns acquisition time, the precision can reach 180 pm for 5 ms acquisition time. Using this method, we show real-time detection of single-event, fast and high-dynamic-range mechanical displacements. This capability can lead to the realization of new measurement and analysis platforms for studying broadband, transient and nonlinear mechanical dynamics in real time, which will be useful for directly probing optomechanics10, the onset of cracks11, dynamic deformations12, nonlinear vibrations13, ultrasonic phenomena14 and cell-generated forces15. Using a femtosecond mode-locked laser and a frequency-locked electric signal, a displacement measurement method that offers a >MHz measurement speed, sub-nanometre precision and a measurement range of more than several millimetres is achieved, facilitating the study of broadband, transient and nonlinear mechanical dynamics in real time.