Effect Of Pulse Chirp Research Articles

Absolute delay calibration by analytical fitting of attosecond streaking measurements

An accurate temporal characterization of both pump and probe pulses is essential for the correct interpretation of any pump-probe experiment. This is particularly true for attosecond spectroscopy, where the pulses are too short to be directly measured with electronic devices. However, when measuring the absolute timing between a light waveform and the related photoinduced physical phenomenon, such characterization does not suffice. Here, we introduce a new method called rACE (refined Analytical Chirp Evaluation), which retrieves both pump and probe pulses while establishing a direct relation between the reconstructed time axis and the experimental delay. This feature is particularly relevant for the extraction of absolute time delays, a growing field in attosecond spectroscopy. In this work, we prove the robustness of rACE with simulated datasets involving the effect of pulse chirp, distinctive target attributes, and non-isolated attosecond pulses, which normally constitute challenging situations for standard methods. For all the cases reported here, rACE achieves a precise absolute delay calibration with an accuracy better than the atomic unit of time. Its successful application to attosecond experimental measurements makes it a fundamental tool for attaining sub-cycle absolute temporal resolution, enabling new investigations of lightwave-driven ultrafast phenomena.

Effects of pulse chirp on laser-driven proton acceleration

Optimisation and reproducibility of beams of protons accelerated from laser-solid interactions require accurate control of a wide set of variables, concerning both the laser pulse and the target. Among the former ones, the chirp and temporal shape of the pulse reaching the experimental area may vary because of spectral phase modulations acquired along the laser system and beam transport. Here, we present an experimental study where we investigate the influence of the laser pulse chirp on proton acceleration from ultrathin flat foils (10 and 100 nm thickness), while minimising any asymmetry in the pulse temporal shape. The results show a pm 10% change in the maximum proton energy depending on the sign of the chirp. This effect is most noticeable from 10 nm-thick target foils, suggesting a chirp-dependent influence of relativistic transparency.

System-theoretical modeling of terahertz time-domain spectroscopy with ultra-high repetition rate mode-locked lasers.

Terahertz time-domain spectroscopy (THz-TDS) systems based on ultra-high repetition rate mode-locked laser diodes (MLLDs) and semiconductor photomixers show great potential in terms of a wide bandwidth, fast acquisition speed, compactness, and robustness. They come at a much lower total cost than systems using femtosecond fiber lasers. However, to date, there is no adequate mathematical description of THz-TDS using a MLLD. In this paper, we provide a simple formula based on a system-theoretical model that accurately describes the detected terahertz spectrum as a function of the optical amplitude and phase spectrum of the MLLD and the transfer function of the terahertz system. Furthermore, we give a simple yet exact relationship between the optical intensity autocorrelation and the detected terahertz spectrum. We theoretically analyze these results for typical optical spectra of MLLDs to quantify the effect of pulse chirp on the terahertz spectrum. Finally, we confirm the validity of the model with comprehensive experimental results using a single-section and a two-section MLLD in a conventional THz-TDS system.

Carrier-envelope phase shift of few-cycle pulses along the focus of lenses and mirrors beyond the nonreshaping pulse approximation: the effect of pulse chirp

The carrier-envelope phase (CEP) shift of few-cycle pulses along a focal region is evaluated without neglecting the pulse reshaping inherent to any focusing process. The CEP shift is then found to strongly depend on the chirp of the focused pulse. Based on this effect, realistic optical systems for focusing few-cycle pulses are proposed to control their focal CEP shift for their phase-sensitive interactions with matter.

Effects of pulse chirp on supercontinuum produced in dispersion decreasing fibre

The supercontinuum (SC) source plays a key role in wavelength division multiplexing over the optical time division multiplexing (WDM/OTDM) transmission system. The SC produced in dispersion decreasing fibre (DDF) is wider and flatter than that produced in dispersion shifted fibre (DSF). In this paper, a SC producing process in DDF is numerically simulated, the effects of pump pulse chirp on the SC width and flatness are initially studied and the corresponding theoretical explanations are given. Particularly, we have analysed and compared the evolutions of the SC along DDF pumped by different chirp pulses. Several valuable conclusions are obtained.

Study on Effect of Pulse Chirp on Interference Correlation Measurement

The usual second harmonic correlation technique is effectively used for the measurement of pico-and subpico-second light pulses. But with the development of CPM and pulse compress technique, the pulse width range has reached tens, even several femtoseconds. Much attention must be paid to the question if the usual method possessed enough precision in the fs range. After the realization of 30 ft pulses and the obtainment of interference correlation curve (IFCC) first in China, we proposed that higher precision can be obtained using IFCC for fs pulses. Further evolution of