短暂时间间隔测量及飞秒技术

回顾了短暂时间间隔测量的历史。条纹概念的引入、电光源和电子仪器的使用、激光的出现使能测量到的短暂时间间隔大大缩短。由于对撞脉冲锁模和啁啾脉冲压缩新概念的提出,人们将脉冲宽度压缩到了几个飞秒。介绍了自锁模钛宝石激光器的锁模、放大和调谐的工作原理以及飞秒技术在物理学、生物学、化学控制反应、光通讯等领域中的应用。     

利用啁啾脉冲光谱滤波和非线性偏振旋转技术实现高稳定性和开机自启动的全光纤掺Yb~(3+)光纤锁模激光器

建立理论模型,讨论了非线性偏振旋转全光纤锁模激光器的锁模过程、谐波过程以及导致激光器锁模运行难以稳定的影响因素.讨论了采用啁啾脉冲光谱滤波产生脉冲自振幅调制、增加激光器锁模稳定性和自启动能力的机理以及非线性偏振旋转与啁啾脉冲光谱滤波相结合实现锁模的物理过程和脉冲演化过程.研制出全光纤结构的超短脉冲掺Yb~(3+)光纤环形激光器,采用非线性偏振旋转和啁啾脉冲光谱滤波相结合的锁模技术,实现了激光器锁模的开机自启动和高稳定运行.对激光器进行了长期运行稳定性、锁模开机自启动能力、锁模输出参数可重复性监测.锁模脉冲中心波长1052.9 nm,谱宽9.1 nm,脉冲能量4.25 nJ,脉冲宽度17.8 ps.运行期间,各参数波动均小于0.3%.开机自启动能力和可重复性测试显示,激光器可实现一键自启动,启动后各参数可重复精度在0.55%以内.     

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。     

基于国产啁啾镜色散补偿的近10fs钛宝石激光器锁模特性的研究

报道了一种基于国产非成对设计的啁啾镜作为腔内色散补偿的钛宝石激光器,在93.7 MHz的重复频率下,得到了平均功率为120 mW的稳定的锁模脉冲输出,经腔外色散补偿,得到了最窄9.7 fs的脉冲宽度。通过调节腔内光楔的插入量,研究了锁模光谱与自相关曲线随腔内净色散的演化过程。基于非线性薛定谔方程的分步傅里叶算法对激光器建立了数值模型,数值模拟的参数选取均与实验中完全一致,利用10阶泰勒展开模拟啁啾镜的色散曲线振荡,获得了谐振腔零色散点附近锁模的动力学过程,并分析了啁啾镜的高阶色散对脉冲宽度压缩的限制。     

可切换多波长全光纤被动锁模光纤激光器

通过在基于碳纳米管的掺铒锁模光纤激光器中加入啁啾光纤光栅,实现了皮秒和飞秒孤子的可切换多波长锁模脉冲输出.通过调节偏振控制器,分别在1530.8,1549.5,1556.5 nm三个波长处实现了多波长可切换锁模脉冲输出,其中锁模脉冲的宽度分别为833 fs,7.43 ps和899 fs.以上三个波长的形成是由掺铒光纤的...     

测量飞秒激光脉冲啁啾的方法

介绍了一种能够直接检测飞秒脉冲啁啾大小的方法。采用共轴结构的迈克尔逊干涉自相关二次谐波检测系统对自制碰撞脉冲锁模循环染料激光器输出的最窄脉冲宽度约为200fs的脉冲进行了测量。测得的飞秒脉冲自相关二次谐波曲线表明：实测曲线的下包络两翼明显隆起，包络外形很不整齐，对称性较差，说明光脉冲含有啁啾。通过比较干涉测量曲线和理论曲线的形状与面积的大小，可以直观地反映出光脉冲所含啁啾的大小。实验结果分析表明，利用满足光相关检测所需精度的光学元件和满足光相关探测基本条件的实验装置，能测得含有相位及啁啾信息的快干涉项信号，是一种能够直观检测光脉冲所含啁啾大小的可行方法。     

快速与慢速饱和吸收体被动锁模掺铒光纤激光器的理论分析

利用半导体饱和吸收波导作为慢速饱和吸收体与非线性快速饱和吸收体相结合，建立了共同被动锁模掺铒光纤激光器的理论模型-分析了半导体饱和吸收波导、光纤自相位调制和自振幅调制对锁模脉冲宽度和脉冲啁啾的影响- 关键词：     

啁啾光脉冲在类时间透镜介质中的传播

利用空间－时间类似和光线光学方法得到啁啾高斯光脉冲在类时间透镜介质中传播的解析解，讨论了光脉冲宽度和啁啾参数随传播距离的演变，并与光脉冲在克尔介质中传播的特征作了比较。     

国产啁啾布拉格光纤光栅在飞秒激光系统中的应用

利用自行研制的啁啾布拉格光纤光栅(CFBG)刻写系统完成CFBG样品制作,成功应用于光纤锁模振荡器和啁啾脉冲放大(CPA)系统中。振荡器可输出19.4 nm带宽、18 mW平均功率激光,并可压缩至143 fs,经时域展宽、功率放大、时域压缩后,脉冲宽度可至264 fs。实验结果初步证明了国产CFBG在飞秒激光系统应用的可行性。     

10 GHz可调谐主动锁模光纤环形激光器研究

采用主动锁模技术 ,在光纤环形激光器中实现了脉冲重复率为 10GHz、脉冲宽度为 10ps、线宽为 0 171nm的激光输出 ,波长调谐范围达 37 8nm。实验结果表明 ,主动锁模光纤激光器由于其输出脉冲窄、脉冲啁啾小、波长调谐方便及与光纤系统兼容等优点 ,有望成为未来超高速光通信系统中的理想光源。     

Effect of pulse duration on generation of attosecond pulse with coherent wake emission

High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase (CEP) of few-cycle laser pulse. We find that short pulse duration will cause the negative chirp for the high harmonics. When the laser pulse is shortened to a few cycles, the influence of the laser CEP on the chirp of the harmonics will also become more prominent.     

Generation of chirp-free picosecond pulses

The frequency spectrum of moderately chirped laser pulses depends upon the portion of the beam which is accepted by the spectrometer. Observation of the development of the chirp in a mode-locked pulse train allows to determine the small incipient chirp of early pulses. A product, bandwidth times pulse duration, of 0.47 ± 0.03 is consistently observed for single pulses switched from a passively mode-locked Nd-glass system.     

不同波形脉冲激光的时域误差对相干合成的影响

相干合成技术是实现高功率、高亮度光纤激光系统的重要技术途径.然而, 脉冲激光阵列中常常存在时域误差,这将影响脉冲激光的相干合成效果. 建立了脉冲激光存在时域误差时的相干合成理论模型,并在不同波形(方波、三角波、正弦波) 的脉冲激光存在时域误差时,对相干合成光束在远场的脉冲波形、峰值功率、 光强分布和桶中功率(PIB)等特性进行了数值计算和对比分析.计算结果表明: 方波脉冲激光相干合成光束的脉冲波形受时域误差影响严重,光强分布和PIB随着时域误差 的增大发生线性变化;三角波脉冲激光相干合成光束的脉冲波形和峰值功率受时域误差 影响严重,光强分布和PIB在时域误差较大时随着时域误差的增大发生较为剧烈的变化; 正弦波脉冲激光相干合成光束具有较好的输出特性,在两路正弦波脉冲激光相干合成中, 将两脉冲之间的时延控制在脉冲持续时间的10%以内,就能取得良好的合成效果.     

Population transfer via adiabatic passage in the Rydberg potassium atom

Using the time-dependent multilevel approach, we have calculated the coherent population transfer between the quantum states of potassium atom by a single frequency-chirped laser pulse. The result shows that a pair of sequential `broadband' frequency-chirped laser pulses can efficiently transfer population from the initial state of the ladder system to the target state. It is also found that the population can be efficiently transferred to a target state and trapped there by using an `intuitive' or a `counterintuitive' frequency sweep laser pulse in the case of `narrowband' frequency-chirped laser pulse. Our research shows that the complete population transfer is related to the pulse duration, chirp rate, and amplitude of the laser pulse.     

Fiber optical parametric oscillator for sub-50 fs pulse generation: optimization of fiber length

We demonstrate generation of 48fs pulses with linear chirp using a short (27mm) fiber optical parametric oscillator (FOPO), which is synchronously pumped by a mode-locked ytterbium-doped fiber laser. We also study the pulse quality for both the short- and long-wavelength operation where the fiber length inside of the oscillator varies from 17 to 61mm. The optimal pulse duration is observed only in the short-wavelength operation. Furthermore, we model the FOPO system as a single-pass parametric amplifier including dispersive pulse broadening and walk-off between the pump and output. The optimal condition arises from the minimization of the walk-off and dispersion. When walk-off is large, the parametric amplification process is most efficient over some reduced effective fiber length, leading to an upper limit in the amount of the observed pulse broadening.     

Limiting temporal and spectral resolution in spectroscopy and microscopy of coherent Raman scattering with chirped ultrashort laser pulses

Chirped ultrashort light pulses offer new options for coherent nonlinear spectroscopy and microscopy. We show here that the temporal resolution of spectroscopy and microscopy based on coherent anti-Stokes Raman scattering (CARS) can be smoothly tuned within a broad range, with upper and lower bounds of this range controlled by the pump and probe pulse durations. The spectral resolution of CARS spectroscopy and microscopy is analyzed as a function of the duration and chirp of the pump pulses. Pulses with a periodic phase modulation can provide the limiting spectral resolution of the CARS technique, corresponding to the lower bound of uncertainty in spectral measurements, dictated by the uncertainty principle.     

同步泵浦染料激光中的频率啁啾计算

利用光场的自洽模型，将同步泵浦染料激光器的输出光脉冲的频率啁啾β作为光波场的位相参数，推导出适合于同步泵浦染料激光器的锁模方程．由此方程出发，求出输出光脉冲频率啁啾β的解析表达式，为实验上减小脉冲的频率啁啾，获得符合变换极限的短脉冲提供依据．     

Scattering-induced changes in the temporal coherence length and the pulse duration of a partially coherent plane-wave pulse

The scattering of a partially coherent plane-wave pulse on a Gaussian-correlated, quasi-homogeneous random medium is investigated. The analytical expressions for the temporal coherence length and the pulse duration of the scattered field are derived. We demonstrate that the scattering-induced changes in the temporal coherence length and the pulse duration may be used to determine the correlation function of the scattering potential of the medium.     

Timing Jitter Induced by White Noise in Mode-locked Solid-state Lasers

A new method is proposed to analyze and calculate the jitters in a modelocked solid-state laser with chirp. A set of motion equations for amplitude, inverse pulse width, chirp, frequency, pulse central position and phase in a femtosecond mode-locked solid-state laser are derived, and then the jitter induced by white noise is obtained. In a Ti-sapphire mode-locked laser, the jitter is theoretically estimated, and the result is well consistent with the experimental value.     

All-optical square-pulse generation and multiplication at 1.5 mum by use of a novel class of fiber Bragg gratings

A new class of linearly chirped fiber Bragg gratings, suitable for all-fiber optical multiplication and reshaping of picosecond pulse trains, is proposed and experimentally demonstrated. Repetition-rate multiplication, based on the temporal Talbot effect, is achieved by accurate control of the grating chirp, and a suitable design of the index-modulation depth profile allows for simultaneous square-pulse shaping. A 50-ps squarelike optical pulse train at 10-GHz repetition rate is obtained, starting from a 2.5-GHz Gaussian pulse train emitted by a mode-locked Er-Yb laser.