Simple devices for measuring complex ultrashort pulses

We describe experimentally simple, accurate, and reliable methods for measuring from very simple to potentially very complex ultrashort laser pulses. With only a few easily aligned components, these methods allow the measurement of a wide range of pulses, including those with time‐bandwidth products greater than 1000 and those with energies of only a few hundred photons. In addition, two new, very simple methods allow the measurement of the complete spatio‐temporal intensity and phase of even complex pulses on a single shot or at a tight focus.     

A novel method of measuring coherent ultrashort light pulses using diffraction by a grating

We propose a novel method of measuring coherent ultrashort light pulses in a single shot by monitoring the ratio of the energy of a pulse, diffracted by a grating, to the energy of the incident pulse. In the case of a gaussian pulse we present numerical calculations which allow easy determination of the pulse width. The proposed method is extremely versatile with respect to wavelength regions and pulse duration.     

A new method of measuring ultra-short coherent light pulses

A new method of pulse width measurement based on the total energy response of an etalon is presented. The theory is developed and results for several pulse shapes are given. The method is unique because no fast response detector is required and there are practically no spectral region limitations.     

Interferometric technique for measuring broadband ultrashort pulses at the sampling limit

We present a new technique for measuring ultrashort optical pulses by use of spectral phase interferometry for direct electric-field reconstruction that is suitable for large bandwidth pulses. The method does not require generation of a replica of the pulse to be measured and encodes the spectral phase information in a spatial interference pattern. A major advantage of this method is that the spectral sampling saturates the Whittaker-Shannon bound. Moreover, the technique allows for the characterization of some types of space-time coupling. An experimental demonstration of the technique is presented.     

A new method for measuring the pulse-front distortion of arbitrary shapes in high-power ultrashort laser systems

We present a new method that can be used to calculate pulse-front distortion by measuring the spectral interference of two point-diffraction fields in their overlapped district. We demonstrate, for the first time, the measurement of the pulse-front distortion of the pulse from a complex multi-pass amplification system, which exists in almost all high-power laser systems, and obtain the irregular pulse-front distribution. The method presented does not need any reference light or assumption about the pulse-front distribution, and has an accuracy of several femtoseconds.     

A new method for measuring the pulse-front distortion of arbitrary shapes in high-power ultrashort laser systems

We present a new method that can be used to calculate pulse-front distortion by measuring the spectral interference of two point-diffraction fields in their overlapped district.We demonstrate,for the first time,the measurement of the pulse-front distortion of the pulse from a complex multi-pass amplification system,which exists in almost all high-power laser systems,and obtain the irregular pulse-front distribution.The method presented does not need any reference light or assumption about the pulse-front distribution,and has an accuracy of several femtoseconds.     

超短脉冲激光与钾原子的相互作用

采有耦合和非耦合表象,描述了超短脉冲激光与钾原子的相互作用。分析了进一步 激发光电离的过程,导出了跃迁终态随激光偏振组合的密切关键。     

Sliding pump method for generation and amplification of ultrashort light pulses

A method for the generation of an ultrashort Raman pulse train with peak power considerably in excess of the pumping one is proposed and theoretically developed. It is shown that it can be used for obtaining tunable picosecond pulses in Raman fiber laser.     

A nonlinear correlation method using multiphoton ionization for the measurement of uv ultrashort pulses

A new nonlinear correlation method which makes it possible to measure the duration of uv ultrashort pulses has been proposed. In this method the multiphoton ionization of gases is used as a nonlinear process and the ion current caused by the process is detected. We have also experimentally demonstrated its usefulness in the uv region by observing the second- and the third-order auto-correlation profiles of picosecond pulses at 2661 Å (the fourth harmonic of a mode-locked YAG laser), using NO and Xe gases, respectively.     

Epsilon-near-zero metamaterials for tailoring ultrashort pulses

Interaction between epsilon-near-zero (ENZ) metamaterials and optical pulses is investigated theoretically. A transform between total transmission and total reflection is revealed for the ultrashort pulses incident onto an ENZ slab, which can be controlled by changing the thickness of the slab. Furthermore, the resonance of the ENZ materials leads to a cutoff frequency in spectroscopic response, where longer wavelengths have no chance to propagate through the ENZ materials and are totally reflected. These characteristics enable the ENZ materials to be applied in ultrashort pulse shapers, cutoff filters, and Fabry–Pérot resonators.     

Reconfigurable wavefront sensor for ultrashort pulses

A highly flexible Shack-Hartmann wavefront sensor for ultrashort pulse diagnostics is presented. The temporal system performance is studied in detail. Reflective operation is enabled by programming tilt-tolerant microaxicons into a liquid-crystal-on-silicon spatial light modulator. Nearly undistorted pulse transfer is obtained by generating nondiffracting needle beams as subbeams. Reproducible wavefront analysis and spatially resolved second-order autocorrelation are demonstrated at incident angles up to 50° and pulse durations down to 6 fs.     

Molecular wakes for ultrashort laser pulses

The molecular wake-assisted interaction between two collinear femotosecond laser pulses is investigated in air,which leads to the generation of a controllable 1.8 mJ super-continuum pulse with an elongated self-guided channel due to the cross-phase modulation of the impulsively aligned diatomic molecules in air. For two parallel launched femtosecond laser pulses with a certain spatial separation,controllable attraction and repulsion of the pulses are observed due to the counter-balance among molecular wakes,Kerr and plasma effects,where the molecular wakes show a longer interaction distance than the others to control the propagation of the intense ultrashort laser pulses.     

机械阻抗测量的一种新方法

本文介绍了一种新的机械阻抗测量方法－声强法，由定义出发将机械阻抗表为功率流和加速度响应谱的函数，应用结构声强技术测量功率流，声强法不需要测量作用力信号，可以用于测量任意结构中的各类机械阻抗，实验结果表明，声强获得的测量值与直接获得的测量值相近，声强法能较准确地测量一维和二维匀质结构中机械阻抗。     

A instrument for measuring solution concentration

Optical Review - In this paper, a set of devices, including hardware and software systems, is designed based on the basic principle of Michelson interferometry to measure solution concentration,...     

Real-time chirp diagnostic for ultrashort laser pulses

Using a real-time Fourier-transform algorithm, we present a simple technique for measuring the chirp of femtosecond laser pulses. We demonstrate significantly enhanced sensitivity compared with standard autocorrelation measurements.     

Hybrid optics for focusing ultrashort laser pulses

We present a specially designed hybrid optics comprising refraction and diffraction effects for tight spatial and temporal focusing of ultrashort laser pulses. Both aims can be put into practice by having a high numerical aperture (NA=0.45) and low internal dispersion at the same time. We are presenting what we believe is the first experimental realization of such a hybrid short plus focusing optics. The focusing properties are compared with a commonly used microscope objective (20 X, NA = 0.45) in theory and experimentally.     

Mode-locked lasers and ultrashort light pulses

This article reviews some aspects of the generation of very short optical pulses using mode-locked lasers, with the emphasis laid on pulsed laser systems. Active and passive mode-locking is discussed, and the problem of measuring ultrashort light pulses is considered. A survey of some commonly used sources and techniques for the generation of ultrashort light pulses follows. The paper concludes with a short account of limitations in the generation and propagation of these pulses.