Systematic variation of parametrically shaped sub-pulse sequences after transmission through a photonic crystal fiber

We present an analytical concept for generating shaped femtosecond laser pulses at the distal end of a microstructured hollow core photonic crystal fiber. The properties of the fiber are analyzed and included in the shaping procedure. A parametric pulse shaping method allows for tailoring a sequence of sub-pulses. In this method, each sub-pulse can be individually controlled by its physically intuitive parameters distance in time, energy, phase and chirps as well as the state of polarization including ellipticity, orientation, and helicity. This is demonstrated with a series of double pulses, in which a single parameter is systematically varied, and additionally with more complex example pulses. Further, we investigate the impact of mechanical distortions of the fiber on the pulse shape. The presented method could be beneficially used in endoscopic applications in life sciences.     

Photonic generation of microwave arbitrary waveforms

In this paper, techniques to generate microwave arbitrary waveforms based on all-fiber solutions are reviewed, with an emphasis on the system architectures based on direct space-to-time pulse shaping, spectral-shaping and wavelength-to-time mapping, temporal pulse shaping, and photonic microwave delay-line filtering. The generation of phase-coded and frequency-chirped microwave waveforms is discussed. The challenges in the implementation of the systems for practical applications are also discussed.     

Femtosecond pulse shaping with space-to-time conversion based on planar optics

We propose a novel structure of planar optical configuration for implementation of the space-to-time conversion for femtosecond pulse shaping. The previous apparatuses of femtosecond pulse shaping are 4f Fourier-transforming type system that is usually large, expensive, difficult to align. The planar integration of free-space optical systems on solid substrates is an optical module with the attractive advantages of compact, reliable and robust. This apparatus is analyzed in details and the design of the particular lens for femtosecond pulse shaping based on planar optics is presented.     

Diffraction properties of multi-layer volume holographic gratings under an ultrashort pulsed beam with arbitrary temporal profiles

The diffraction properties of a system of multi-layer volume holographic gratings under an ultrashort pulsed beam with arbitrary temporal profiles are investigated using the multi-layer coupled wave theory. The dependence of the pulse profiles of the diffracted beams, diffraction bandwidth and the total diffraction efficiency of the multi-layer system on the temporal profiles of the input ultrashort pulse are investigated. The calculated results indicate that the temporal shape of the input pulsed beams is an important factor in the analysis of the propagation characteristics. The analysis of this paper will be valuable for the applications of pulse shaping, processing and filter.     

飞秒激光脉冲整形技术及其应用

通过频域上控制飞秒激光脉冲幅度、相位和偏振在时域上可以获得几乎任意形状的飞秒激光脉冲,这种飞秒激光脉冲整形技术可为研究光与原子分子非线性相互作用提供一种全新实验技术手段.本文介绍飞秒激光脉冲整形发展历史、技术方法、控制方式及其相关应用,并展望飞秒激光脉冲整形技术未来的发展方向.     

高功率钕玻璃啁啾脉冲放大系统光谱整形

增益窄化效应限制了啁啾脉冲放大系统输出的最短脉冲宽度,需要对注入放大系统的种子啁啾脉冲进行光谱整形,以保证放大后的啁啾脉冲光具有足够的带宽并满足特定的光谱分布.理论上假定放大后啁啾脉冲的光谱分布为高斯分布或超高斯分布,对"百焦耳级钕玻璃啁啾脉冲放大系统"进行逆运算.研究发现,所需种子啁啾光的能量、带宽以及压缩后脉冲的信噪比都与该分布密切相关.通过光谱整形,使放大后的啁啾脉冲光的光谱分布为二阶超高斯分布.能够获得小于400 fs高信噪比的超短脉冲输出,此时所需种子啁啾脉冲能量仅为33μJ,带宽14 nm,在装置前级注入能力的范围之内.为百焦耳装置光谱整形实验的开展提供了理论指导.     

Enhanced Dispersive Waves Generation via Sinusoidally Spectral Phase-Modulated Pulses

The dispersive waves (DWs) emitted from a Gaussian pulse with an initial sinusoidally spectral phase (SSP) modulation are investigated. By tailoring the modulation depth and frequency, the SSP results in complex pulses shape with a multipulses structure ranging from Airy-like to pulse sequences having controllable delay and phase. These salient features are able to control and enhance the radiation frequency and energy conversion efficiency of the DWs. The resonant frequencies based on a modified phase-matching condition are given, which agree with the numerical results obtained by solving the nonlinear Schrödinger equation directly. The results not only further extend the application of the pulse shaping technology in fiber optics, but also provide an alternative approach to manipulate the process of DWs emission which is relevant to the generation broadband supercontinuum as well as frequency comb.     

Femtosecond shaping of transverse and longitudinal light polarization

Femtosecond laser pulse shaping techniques have been restricted to propagating transverse electromagnetic waves. We present a scheme for pulse shaping of optical near fields based on the excitation of longitudinal electromagnetic fields with polarization-shaped light pulses. By solving Maxwell's equations for a model nanostructure, i.e., a scanning tunneling microscope tip, with help from the boundary-element method, we demonstrate that the electric field vector oscillates in a complex yet controllable fashion in three dimensions. Many applications are envisioned because literally another dimension in the optimal control of light-matter interaction is accessible.     

薄膜靶整形强激光脉冲的理论分析和数值模拟

超强超短脉冲激光广泛应用于粒子加速以及新型X射线辐射源产生。较长的激光脉冲上升前沿直接影响激光应用效果。等离子体薄膜靶作为新型光学介质开关,可以有效降低超强激光脉冲前沿上升时间,优化激光等离子体相互作用参数。采用一维理论分析和粒子模拟方法研究了等离子体薄膜靶实现超强激光脉冲整形的机制。研究结果表明,薄膜靶通过对激光脉冲的非线性调制,可有效实现脉宽缩短和脉冲陡化;对比单层靶调制结果,选择参数优化的双层靶,可进一步优化脉冲整形效果,获得更短脉宽和更高振幅的激光脉冲;对于峰值振幅高于薄膜靶击穿阈值的超强激光,脉冲上升前沿可得到明显陡化,薄膜靶的击穿是产生这种脉冲整形效果的直接原因。     

Spectral phase control and temporal superresolution toward the single-cycle pulse

The concept of temporal superresolution is applied to optical few-cycle laser pulses for the first time to our knowledge. Pulse durations of as little as to 3.7 fs, well below the Fourier limit, are achieved by pulse shaping of an octave-spanning Ti:sapphire oscillator spectrum. Our prism-based pulse shaper also enables us to generate a manifold of well-controlled pulse sequences that are important for coherent control applications on a femtosecond time scale.     

波包动力学-飞秒激光操纵波包过程

本文介绍了波包动力学的基本理论和数值模拟方法,尤其是在飞秒激光与分子相互作用领域中的应用,探讨了飞秒激光引起的波包过程（包括波包的制备、波包的干涉）,以及利用调频脉冲、脉冲串和优化脉冲形状控制波包动力学的方案。     

波包动力学-飞秒激光操纵波包过程

本文介绍了波包动力学的基本理论和数值模拟方法,尤其是在飞秒激光与分子相互作用领域中的应用,探讨了飞秒激光引起的波包过程（包括波包的制备、波包的干涉）,以及利用调频脉冲、脉冲串和优化脉冲形状控制波包动力学的方案。     

啁啾脉冲堆积用于光脉冲整形

报道了一种利用100 ps啁啾脉冲堆积产生2．2 ns任意整形脉冲的脉冲整形系统。采用掺Yb~(3 )光纤锁模振荡器得到稳定的锁模光脉冲序列,将该锁模脉冲通过啁啾光纤光栅展宽并通过1 nm带宽的高斯形光谱滤波器滤波,得到标准的100 ps高斯形啁啾脉冲序列,将此脉冲选单经过光纤延迟线组成的32路脉冲堆积器,得到了精度为32 bit的重复频率为1 Hz的2．2 ns任意整形光脉冲。研究了堆积脉冲的特性,分析了宽带啁啾堆积整形脉冲的光谱时间扫描特性对激光驱动惯性约束聚变打靶束匀滑的优化作用。实验测得了该系统输出的2．2 ns整形光脉冲具有小于50 ps的上升沿,与100 ps啁啾脉冲的时间抖动小于4 ps。     

时域超短脉冲光栅记录和读取的研究

为实现超短脉冲信号的重现或整形,从理论上推导了时域超短脉冲光栅的记录和读取,并结合高斯型脉冲分布,讨论了信号脉冲、参考脉冲和读出脉冲宽度不同时的衍射结果,提出了利用超短脉冲全息实现超短脉冲信号的重现或整形等功能的方法.结果发现,长信号脉冲和短参考脉冲干涉记录全息后,如果用足够短的脉冲读取,衍射完全再现了原输入信号脉冲.但是在读出脉冲带宽接近于信号带宽时,衍射波频谱宽度有一定程度减小.     

Pulse shaping and diffraction properties of multi-layers reflection volume holographic gratings

The multi-layers coupled-wave theory is extended to systematically investigate the pulse shaping and diffraction properties of a system of multi-layers reflection volume holographic gratings (MRVHG) under ultrashort laser pulse (ULP) readout. The combined effects that the grating parameters such as the number and thickness of layers and gaps between them and the pulse duration of the input ULP have on the pulse shaping properties are considered. The pulse profiles of the diffracted and transmitted beams, the diffraction bandwidth, and the total diffraction efficiency are presented. The calculated results we have derived permit an optimal choice of grating parameters for the pulse shaping and process applications.     

Acousto-optical shaping of ultraviolet femtosecond pulses

This work demonstrates a simple method for ultraviolet (UV) acousto-optical pulse shaping of both spectral amplitude and phase. A fused-silica acousto-optical modulator is used to ensure high transmission and a high damage threshold at 400-nm center wavelength. The technique eliminates complications associated with the parametric transfer of the spectral phase of near-infrared pulses through a nonlinear process out to UV wavelengths, by separating the frequency doubling and shaping processes. Three illustrative applications of phase control are presented: the compensation of material dispersion, the generation of multiple pulse trains, and the generation of arbitrarily shaped pulse trains. Self-diffraction frequency-resolved optical gating is used to characterize the success of the technique.     

Two-dimensional materials-decorated microfiber devices for pulse generation and shaping in fiber lasers

Two-dimensional(2D) materials have been regarded as a promising nonlinear optical medium for fabricating versatile optical and optoelectronic devices. Among the various photonic applications, the employment of 2D materials as nonlinear optical devices such as saturable absorbers for ultrashort pulse generation and shaping in ultrafast lasers is one of the most striking aspects in recent years. In this paper, we review the recent progress of 2D materials based pulse generation and soliton shaping in ultrafast fiber lasers, and particularly in the context of 2D materials-decorated microfiber photonic devices. The fabrication of 2D materials-decorated microfiber photonic devices, high performance mode-locked pulse generation, and the nonlinear soliton dynamics based on pulse shaping method are discussed. Finally, the challenges and the perspective of the 2D materials-based photonic devices as well as their applications are also discussed.     

Design and fabrication of diffractive elements for laser material processing applications

Diffractive optical elements have an important role to play in the provision of process adapted beam shaping for laser-materials processing applications. The design techniques and dominant methods of fabrication are described for intra-cavity and external beam shaping diffractive elements fabricated in a variety of dielectric and metallic materials for use with a wide range of laser sources. Theoretical and experimental examples are given in each section.     

Investigation of adaptive laser pulse shaping by direct estimation of group delay profile

We investigate the benefits of estimating the group delay spectrum (as opposed to the phase spectrum) on the performance of an adaptive laser pulse shaping experiment. We use both numerical and experimental approaches, and consider different figures of merit such as efficiency, noise robustness, convergence speed, repeatability, fitness sensitivity, and parameter insensitivity. While primarily focused on the process of broadband second harmonic generation, we also study a resonant third order nonlinear process. Our results show an overall superiority of delay-based formulation in the cases under study (compared to a conventional phase-based formulation) for adaptive laser pulse shaping.     

Ultrafast control of coherent population transfer with a train of femtosecond pulse pairs

We investigate the ultrafast control of coherent population transfer in a Λ-type three-level system with a train of pump-Stokes femtosecond pulse pairs, where the pulse sequences can be produced either by optical delay line or by pulse shaping with sinusoidal phase modulation. It is shown that when the pump and Stokes pulses in each pair are applied in the counterintuitive order, similar to that in the stimulated Raman adiabatic passage technique, due to temporal quantum interference (besides optical interference in the case of overlapped subpulses), ultrafast control of coherent population transfer can be achieved by scanning the inter-pair time delay or by changing the sinusoidal phase modulation parameters. This method has potential applications in ultrafast control of chemical reactions and quantum information processing.