Nanometer Precision Time-Stretch Femtosecond Laser Metrology Using Phase Delay Retrieval

Lijie Zhao,Haiyun Xia,Tengfei Wu,Zhen Zhang,Chunbo Zhao,Chuanqing Xia

doi:10.1109/jlt.2021.3079127

Abstract

A femtosecond laser metrology with nanometer precision and dynamic range of centimeter incorporating time-stretch interferometry and phase delay retrieval method is proposed and experimentally demonstrated. Displacement encoded phase-sensitive temporal interferogram is generated when phase stabilized femtosecond laser pulses transmitting through a time-stretch interferometer. To avoid the chirp of temporal interferogram due to high-order dispersion, time-to-frequency mapping is established to transform the temporal interferogram to the spectral interferogram for high-speed detection. The phase delay of spectral interferogram corresponding to specific displacements is retrieved and accumulated for linear fitting. The fitted slope is the time delay between two arms in the interferometer therefore displacement can be calculated. For precision verification, the preset displacements are measured. Mean error and standard deviation are presented after sliding average of measured results in 4 μs.

Highlights

P RECISE and rapid range measurement is vital for high speed target detection and precise industrial manufacturing, especially in recent years[1], [2]
This instability originates from the shift of carrier envelope offset (CEO) frequency of the femtosecond laser
The femtosecond laser is split by a polarization beam splitter (PBS) from the cavity, coupled to a fiber coupler in which one part is used for output and the other part is used for repetition rate locking (RRL)

Summary

INTRODUCTION

P RECISE and rapid range measurement is vital for high speed target detection and precise industrial manufacturing, especially in recent years[1], [2]. Femtosecond laser-based time-stretch technique is another method which has been demonstrated to be feasible, stable and effective in strain measurement [17], [18], ultrafast ranging [19]–[22], imaging [23]-, [25], spectroscopy [26], [27] and microwave photonics applications [28], [29]. The drifted time-domain interferogram on Oscilloscope which indicates the phase shift of the detected signal was observed and this will introduce additional measurement error This instability originates from the shift of carrier envelope offset (CEO) frequency of the femtosecond laser. We demonstrate a time-stretch ultrafast displacement detection method based on phase detection using femtosecond laser with repetition rate and CEO locking system. Fig. 1. shows the technical path that we are pursuing to measure distance and displacement with higher precision and its possible applications

Phase-Stabilized Femtosecond Laser Source

Time-Stretch Interferometry

Time-to-Frequency Mapping and Phase Delay Retrieval

EXPERIMENT AND DISCUSSION

CONCLUSION