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

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.

All-fiber real time ultrafast ranging Lidar for motion management of patients during stereotactic radiotherapy

“…The distance changes affect the frequency of the detected pulse and can be retrieved through accumulated phase profiles by applying time-to-frequency mapping due to the sensitivity of phase change to the distance variation. This technique has nanometer precision which requires a high-speed oscilloscope in its data acquisition system 10 . Since the head motion under the thermoplastic mask is limited to a millimeter at most, an ultrafast time-stretch Lidar system is adapted for this experiment with MHz detection speed, sub-mm precision, and a simple direct all-optical measurement with dual pulse detection capability is the most appropriate for the head motion detection application.…”

Differential and phase-diverse electrooptic modulators

“…This class of real-time measurement systems have been exceptionally successful in capturing single shot phenomena such as optical rogue waves [24], relativistic electron dynamics [25][26][27], chemical transients in combustion [28], shock waves [29], internal dynamics of soliton molecules [30], birth of laser mode-locking [31], and single-shot spectroscopy of chemical bonds [32,33]. They have also evolved into high throughput microscopy [34] of biological cells [35], label-free classification of cells [36][37][38], gyroscope [39], mid-infrared spectroscopy [40] and many other applications [41][42][43][44][45][46]. This paper shows the efficacy of the new modulator in canceling the dispersion penalty in optical fibers with emphasize on time-stretch systems.…”

Laser-induced electron dynamics and surface modification in ruthenium thin films

“…Ultrashort lasers are used for surface nanostructuring [1] and nanofabrication [2,3,4], as well as for reversible switching of material structure between crystal and amorphous phases for applications in data storage [5]. Alternatively to these high intensity laser applications, ultrashort lasers with relatively low intensity are used in various metrology and probing techniques [6,7,8]. In this context, contrarily to the previous examples, laser-induced damage must be avoided.…”