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We utilize singular spectrum analysis (SSA) for post-processing distance measurement data obtained by a dual-comb femtosecond laser rangefinder. Signal denoising technique based on SSA allows detection of low amplitude vibrations from time series of distance data with limited signal-to-noise ratio (SNR). Various one-dimensional vibrations, including harmonic, amplitude modulated harmonic, and sinc-function vibrations, with micrometer amplitude comparable with measurement uncertainty of laser rangefinder, have been imposed on the target mirror by a piezo positioner. These vibrations have been extracted by SSA and the obtained vibration amplitudes agree with that imposed on the target very well. A commercial interferometer is used to evaluate the accuracy of SSA. Standard deviations of residuals between the SSA extractions and interferometer measurements are smaller than 0.6 $\mu$m. This technique is promising for complex moving pattern detection in object tracking and remote sensing.

We demonstrate that third-order dispersion (TOD) precompensation accompanied with nonlinear compensation can improve the pulse quality of high energy pulses in fiber chirped-pulse amplification (FCPA) system. The negative TOD fiber is implemented as the precompensation of TOD mismatch, resulting small required B-integral, which benefits the pulse quality. The conclusion is given by analytical study and numerical simulations. Based on this method, we obtain high-energy pulses up to 10.4 μJ. The quality of the dechirped pulse is high and >90% of pulse energy is contained in the main pulse. The dechirped pulse duration is ~280 fs, which is nearly the same as the transform-limited pulse of the oscillator. The system also shows a wide tunable range of pulse energy from 5 to 10 μJ with the good pulse quality.

Usually, only focused femtosecond (fs) lasers at near-infrared (NIR) range can induce photodamage to transparent cells, making it difficult to treat large amount of cells by such optical methods for photostimulation. In this study, we clarify the mechanism of photodamage to cells that are co-cultured with gold nanorods (GNRs) by fs laser. The pulse duration and repetition rate of the fs laser play a key role in cell damage suggesting that the heat accumulation contributes to the major part for the cell damage rather than the high peak power which mainly determines the efficiency of multiphoton excitation. We further show that cellular Ca2+ can also be released in this scheme, but the process is more sensitive to peak power. Our results can provide a large-scale GNR-mediated photostimulation for cell signaling modulation.

Femtosecond laser ranging has drawn great interest in recent years, particularly based on an asynchronous optical sampling implementation where a pair of femtosecond lasers are used. High precision absolute ranging either relies on tightly-phase-locked optical frequency combs (a dual-comb setup) or multiple averaging of the measurements from two free-running femtosecond lasers. The former technique is too complicated for practical applications, while the latter technique does not apply to moving targets. In this report, we propose a new route to utilizing a powerful singular spectrum analysis (SSA) filtering method to improve femtosecond laser ranging precision for moving targets with acceleration. The SSA method is capable of separating complex patterns in signals without a priori knowledge of the dynamical model. Here, we utilize the basic SSA filter to extract the target trajectory in the presence of measurement noise both in numerical simulation and in the absolute ranging experiment based on a pair of free-running femtosecond lasers. The experimentally-achieved absolute ranging uncertainty of a moving target is well below 110 nm at a 200-Hz update rate by applying the basic SSA filter. This method paves the way to the practical applications of femtosecond absolute ranging for dynamic objects.