用于产生亚12fs脉冲的脉冲波前匹配的超宽带光学参量啁啾脉冲放大器

研究和建议了一种用于产生亚12fs脉冲的基于脉冲波前匹配的LBO超宽带光学参量啁啾脉冲放大器。实验结果表明LBO超宽带光学参量啁啾脉冲放大器可以输出大于60nm(FWHM)的增益光谱带宽，为了利用这种放大器产生转换限制的脉冲输出，给出了一种将超宽带光学参量啁啾脉冲放大器与脉冲波前匹配相结合的方法，这种方法等价于信号光脉冲波前无斜置的放大，克服了超宽带参量啁啾脉冲放大器中由于信号光的脉冲波前斜置而导致很难获得最短压缩脉冲输出的缺陷，从而允许产生转换限制的亚12fs脉冲。     

Compact high gain double-pass optical parametric chirped pulse amplifier

A novel double-pass noncollinear optical parametric chirped pulse amplifier based on an Yb³⁺-doped passively mode-locked fiber laser has been demonstrated in this paper. The signal was double-pass amplified in a single nonlinear crystal by a long pump pulse, and the signal and pump pulses of each pass were completely phase matched in the plane of the maximum effective nonlinearity. Net saturated gain of 2×10⁶ was achieved and the superfluorescence was suppressed by increasing the overlap time between the signal and pump pulses.     

Optical parametric chirped pulse amplification based on photonic crystal fibre

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated.A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre (PCF) with femtosecond pulse pumping and then amplified to 2 mJ in an Nd:YAG regenerative amplifier.After the amplified pulses pass through the LBO crystal,the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification (OPA).The 850-nm chirped signal light gain from the stretcher is 1.5×10 4 in the first-stage OPA while it is 120 in the second-stage OPA.The total signal gain of optical parametric chirped pulse amplification (OPCPA) can reach 1.8×10 6.     

Multiterawatt laser system based on optical parametric chirped pulse amplification

A compact multiterawatt laser system based on optical parametric chirped pulse amplification is demonstrated. Chirped pulses are amplified from 20 pJ to 900 mJ by two lithium triborate optical parametric preamplifiers and a final KDP optical parametric power amplifier with a pump energy of 5 J at 532 nm from Nd:YAG-Nd:glass hybrid amplifiers. After compression, we obtained a final output of 570-mJ-155-fs pulses with a peak power of 3.67 TW, which is the highest output power from an optical parametric chirped pulse amplification laser, to the best of our knowledge.     

基于光束偏转的扫描式宽带光参量啁啾脉冲放大

光参量啁啾脉冲放大(OPCPA)是超短激光脉冲领域的重要技术之一,增大增益带宽对提高OPCPA的转换效率、实现宽带光参量放大具有重要的意义.本文将光束偏转和非共线OPCPA有机结合,提出了基于光束偏转的扫描式宽带OPCPA模型.分析了通过光束偏转来时刻改变非共线角,以保证各频率成分的相位匹配,从而增大增益带宽的基本原理.采用提出的扫描式宽带OPCPA,针对800 nm中心波长、带宽约为100 nm信号光的光参量放大进行了数值计算.结果表明:经过扫描式OPCPA后,信号光的带宽与放大之前几乎相同,光谱没有窄化;扫描式OPCPA比固定非共线角方式的放大极大地增加了增益带宽和转换效率,实现了宽带的光参量放大;要满足信号光各频率成分的相位匹配,达到最大的增益带宽和转换效率,需要尽量减小加载到钽铌酸钾(KTa_(1-x) Nb_xO_3, KTN)电光晶体上的电压抖动和电压延时.     

Stacking chirped pulse optical parametric amplification

Stacking chirped pulse optical parametric amplification based on a home-built Yb³⁺-doped mode-locked fiber laser and an all-fiber pulse stacker has been demonstrated. Energic 11 mJ shaped pulses with pulse duration of 2.3 ns and a net total gain of higher than 1.1 × 10⁷ at fluctuation less than 2% rms are achieved by optical parametric amplification pumped by a Q-switched Nd:YAG frequency-doubled laser, which provides a simple and efficient amplification scheme for temporally shaped pulses by stacking chirped pulse.     

Flat and ultra-broadband two-pump fiber optical parametric amplifiers based on photonic crystal fibers

A two-pump fiber optical parametric amplifier (FOPA) based on the photonic crystal fiber (PCF) in the telecommunication region is investigated numerically. The fiber loss and pump depletion are considered. The influences of the fiber length, input signal power, input pump power, and the center pump wavelength on the gain bandwidth, flatness, and peak gain are discussed. The 6-wave model-based analysis of two-pump FOPA is also achieved and compared with that based on the 4-wave model; furthermore, the gain properties of the FOPA based on the 6-wave model are optimized and investigated. The comparison results show that the PCF-based two-pump FOPA achieves flatter and wider gain spectra with less fiber length and input pump power compared to the two-pump FOPA based on the normal highly nonlinear fiber, where the obtained results show the great potential of the FOPA for the optical communication system.     

Progress in chirped pulse optical parametric amplifiers

We discuss the main issues of optical parametric chirped pulse amplification and overview recent progress in the field. Although we distinguish between the two operating modes of modern chirped pulse parametric amplifiers, OPCPA and NOPA, we reveal that both represent the same technique and share a common concept. PACS 42.65.Yj; 42.65.Re     

光参量啁啾脉冲放大过程中脉冲特性理论研究

 通过数值求解非线性三波耦合方程组,并利用色散致啁啾引起的瞬时频率与时间的关系,模拟了啁啾脉冲在光参量放大过程中的脉冲波形和频谱形状的变化关系,以及通过压缩器的脉冲形状。模拟结果表明：啁啾脉冲在光参量放大过程中的时域宽度和频谱有很小程度的加宽,但基本上不影响放大后脉冲的压缩及信噪比。     

光参量啁啾脉冲放大过程中脉冲特性理论研究

通过数值求解非线性三波耦合方程组,并利用色散致啁啾引起的瞬时频率与时间的关系,模拟了啁啾脉冲在光参量放大过程中的脉冲波形和频谱形状的变化关系,以及通过压缩器的脉冲形状。模拟结果表明：啁啾脉冲在光参量放大过程中的时域宽度和频谱有很小程度的加宽,但基本上不影响放大后脉冲的压缩及信噪比。     

光参量啁啾脉冲放大的逆问题

针对光参量啁啾脉冲放大的逆问题,即如何在给定输出信号光脉冲波形的前提下,通过计算得到输入信号光脉冲波形,提出了相应的计算模型和方法.以分步傅里叶变换和四阶龙格-库塔法为基础,通过数值拟合等方法,建立了输入-输出信号光强之间的定量关系.分别以预期输出信号光脉冲为啁啾高斯脉冲以及具有特定形状的整形脉冲为例,通过逆算得到了相应的输入信号光脉冲波形.研究结果表明,该逆算方法具有原理简单、计算快速准确等优点,可为激光脉冲整形设计提供参考. 关键词： 光参量啁啾脉冲放大 逆问题 啁啾脉冲 脉冲整形     

Numerical studies of optical parametric chirped pulse amplification

Based on the coupled wave equations, optical chirped-pulse parametric amplification (OPCPA) is simulated and its characteristics are investigated under the conditions of small-signal and pump depletion. The influence of the group-velocity mismatch and the phase mismatch among the three waves on the process of the amplification are discussed, respectively. Compared with the conventional chirped-pulse amplification system, synchronization between pump and signal-pulses is a crucial issue in OPCPA. The requirement on Δτ_p–s as well as the stability of the system is investigated.     

Narrowband optical parametric amplifier for efficient conversion of high-energy pulse with high beam quality

In a two-stage optical parametric amplifier based on KTiOAO4 crystals, we apply beam-overlapping technique to nanosecond signal pulse amplification, which results in high conversion efficiency and good beam quality. A signal pulse energy of 66 mJ at 1.572 μm wavelength is generated with 220 mJ of pump pulse input. A maximum gain of 66 and a maximum pump depletion of as high as 44% are determined. The spectral linewidth of the amplified signal pulse is around 50 MHz, and the beam quality factor of M 2 is less than 2.3.     

高效三通光参量啁啾脉冲放大器

为了提高信号光与抽运光在时域上的匹配,提高放大系统的增益,提出了三通光参量啁啾脉冲放大的方法。实验中,信号光在一块晶体内被一抽运光在完全相位匹配的条件下放大了三次,总放大增益为3.7×107,能量晃动小于3%rms,放大后的信号光谱宽为30nm,压缩后的信号光脉宽为82fs。实验结果表明:采用三通光参量啁啾脉冲放大方法,有效地抑制了放大过程中参量荧光对放大过程的影响,在抽运光强为350MW/cm2时,参量荧光仅占输出总能量的1%。     

Competing processes in optical parametric chirped pulse amplification

Optical parametric chirped pulse amplification (OPCPA) has the potential to revolutionise the generation of high power ultrashort optical pulses. In this paper, we present the results of a numerical investigation into processes that potentially compete with OPCPA. Specifically, we examine group velocity dispersion, non-degenerate operation, background noise, pump pulse fluctuations, and compressor error. We also discuss the “local approximation” and show that, in the case of OPCPA, it offers a substantial advantage in computational speed for minimal cost in accuracy. The overall conclusion is that OPCPA is fundamentally robust, and that the processes studied pose a less serious problem than might have been expected.     

Phase matched scanning optical parametric chirped pulse amplification based on pump beam deflection

Combined with the optical beam deflection, a novel approach of phase matched broadband scanning optical parametric chirped pulse amplification(OPCPA) was proposed. For this scheme, there was no superfluous operations to the chirped signal pulse which propagated in a changeless direction straightforward, but the pump beam were deflected in space with time by passing through a KTN crystal, which was applied with varied driving voltage. The theories of phase matching of each chirped signal frequency based on pump beam deflection was analyzed detailedly. And the type-I amplification of chirped signal with 800 nm central wavelength and 20 nm bandwidth pumped by 532 nm in BBO crystal was simulated as a case in point. The simulation results showed that the spectral distribution of chirped signal pulse was almost the same as the initial form, i.e., there was nearly no narrowing on the amplified spectrum by using of the scanning OPCPA based on pump beam deflection. In addition, the simulations demonstrated that it was worth minimizing the voltage deviation applied to KTN crystal as much as possible for the sake of better waveform, larger bandwidth and higher conversion efficiency of amplified signal pulse in the proposed scanning OPCPA.     

High-power and high-contrast optical parametric chirped pulse amplification in beta-BaB2O4 crystal

We have developed a high-power laser system based on optical parametric chirped-pulse amplification in a beta-BaB2O4 crystal. The system provides gain of 10(8), a conversion efficiency of approximately 23%, an output energy of -65 mJ, and good amplified beam quality. The prepulse ratio has been measured to be 1.5 x 10(-8) or less. The spectral width was as broad as 16.5 nm centered at 1053 nm.     

光参量啁啾脉冲放大增益特性研究

 通过对非线性三波耦合方程组进行数值求解，研究了光参量放大的增益特性及饱和放大特性。给出了泵浦光、信号光参数对参量增益的影响及其与晶体饱和长度的关系。且OPA具有传统CPA系统所不具有的优点，将有可能取代传统的CPA系统而作为超短超强激光系统的新型前端。     

光参量啁啾脉冲放大系统非线性晶体长度确定及调谐方法研究

首先介绍了模拟光参量啁啾脉冲放大（OPCPA）过程的多种计算模型,在此基础上提出了三步走逐步逼近算法,以确定OPCPA过程中最稳输出时所需的非线性晶体长度.这种算法综合利用了上述计算模型,随着计算模型越来越精确,非线性晶体长度的计算范围越来越小.因而利用这种算法能高效、精确地确定最佳非线性晶体长度.最后提出在OPCPA过程引入一定的相位失配量,来调谐最稳输出时所需晶体长度,从而能突破晶体加工精度不够的局限,在实际OPCPA过程中获得稳定输出. 关键词： 光参量啁啾脉冲放大 最稳输出 相位失配 非线性晶体长度     

光参量啁啾脉冲放大系统非线性晶体长度确定及调谐方法研究

首先介绍了模拟光参量啁啾脉冲放大（OPCPA）过程的多种计算模型,在此基础上提出了三步走逐步逼近算法,以确定OPCPA过程中最稳输出时所需的非线性晶体长度.这种算法综合利用了上述计算模型,随着计算模型越来越精确,非线性晶体长度的计算范围越来越小.因而利用这种算法能高效、精确地确定最佳非线性晶体长度.最后提出在OPCPA过程引入一定的相位失配量,来调谐最稳输出时所需晶体长度,从而能突破晶体加工精度不够的局限,在实际OPCPA过程中获得稳定输出.