可编程声光色散滤波器在10 Hz飞秒再生放大系统中的应用

报道了在10 Hz飞秒再生放大超快激光系统中,运用可编程声光色散滤波器(AOPDF)对注入再生放大的种子光进行频谱整形和色散预补偿,使钛宝石激光系统输出光脉冲谱线半峰全宽由原来的38 nm展宽到66 nm,压缩后输出脉冲宽度从35 fs减小到20 fs。实验结果表明,利用可编程声光色散滤波器能够同时独立进行光谱整形和大范围内色散补偿的特性,可以有效抑制啁啾脉冲放大过程中存在的谱线增益窄化效应,补偿钛宝石激光系统中存在的残留色散。这为进一步研制小于20 fs,10 TW量级钛宝石激光系统奠定了基础。     

色散渐减光纤中自相似脉冲传输特性研究

研究了在高阶色散影响下,自相似脉冲在具有正常色散的色散渐减光纤中的演化情况.结果表明:当考虑高阶色散的影响时,脉冲的啁啾仍然具有很强的线性特性,只是中心变得不对称,产生中心漂移.这种啁啾特性使得自相似脉冲在时域中的抛物线形状产生畸形,导致了脉冲峰向一边延迟,并使脉冲的中心位置漂移,同时伴随着脉冲边沿的振荡.但是通过采用色散补偿技术,自相似脉冲强的线性啁啾仍然可以得到高质量的飞秒量级压缩脉冲,与忽略三阶色散影响时得到的压缩脉冲的脉宽近似相等.     

百太瓦级超短超强钛宝石激光装置

100TW级激光装置采用了全钛宝石的啁啾脉冲放大技术路线，可以输出3个不同功率段，以适应不同物理实验需求。前端系统是一个台面TW量级系统，主要包括钛宝石自锁模飞秒振荡器、Offner无像差展宽器、再生放大器、预放大器及主放大器。从前端系统主放输出的脉冲能量高达300mJ。为了克服再生放大器中的增益窄化效应及预补偿放大过程中引入的光谱振幅和位相畸变，在飞秒振荡器后应用一个可编程的声光色散滤波器（AOPDF）。AOPDF可以对脉冲光谱的振幅和位相进行主动的调制，补偿增益窄化效应及高阶色散引起的位相畸变。没有应用AOPDF进行预调制，则再生放大器输出的光谱宽度为25nm；当应用AOPDF进行适当调制后，再生放大输出的光谱宽度为40nm，因而最后的压缩脉冲可以获得更窄的压缩脉宽。     

500 nm带宽啁啾镜对的设计与应用

设计了中心波长在825 nm、有效带宽在600 nm～1100 nm的超宽带啁啾镜对,色散补偿量目标值为-100 fs2。配对设计的啁啾镜对有效抑制了单个啁啾镜的色散振荡,啁啾镜对色散振荡幅度的最大值为50 fs2,用设计制作的啁啾镜对进行色散补偿,用频率分辨光学开关测量装置对脉冲进行测量。将10.3 fs的超短脉冲通过0.5 mm厚的LBO晶体,色散效应导致脉冲展宽,半峰值处的全宽度为39.6 fs,实验结果表明,经过啁啾镜对一次色散补偿后的脉冲形状,半峰值处得全宽度为11.6 fs;脉冲经过2次补偿后,脉冲被压缩到10.7 fs。     

啁啾高斯脉冲光束在正色散介质中的自聚焦特性

 采用分步法结合Hankel变换对修正薛定谔方程进行数值求解，通过数值计算对飞秒脉冲在非线性正色散介质中的自聚焦特性进行了简要分析。在此基础上，针对啁啾脉冲放大系统(CPA)中的啁啾高斯脉冲，对其全光束自聚焦特性进行了计算模拟和分析讨论。研究结果表明，群速度色散(GVD)对大啁啾脉冲的影响很小，谱宽对自聚集的影响可以忽略。因此，具有大啁啾的脉冲在非线性正色散介质中的自聚焦特性不同于飞秒脉冲，而与纳秒脉冲相似。     

40 Gb/s窄脉冲预啁啾归零码色散管理传输

通过数值计算的方法，对40Gb/s带有预啁啾和无啁啾的窄脉冲归零码在色散管理光纤链路中的传输特性进行了比较，计算发现，脉冲的预啁啾会与光纤的高阶色散共同作用，并增强高阶色散对传输的影响，只有在高阶色散得到很好补偿以后，窄脉冲带啁啾的归零码（CRZ）的传输特性才会好于无啁啾的归零码。对不同的入射脉冲条件和传输链路参量存在相应的预啁啾最佳值。     

基于多层膜系传输矩阵理论的双啁啾镜设计与实验

把光在多层膜中传输的矩阵理论应用于双啁啾镜的设计。理论分析结果表明设计的双啁啾镜可以对波长从600 nm到1 100 nm波段范围的色散进行补偿,每次可以实现-100 fs2的色散补偿量,而且双啁啾镜可以有效降低单镜色散补偿中的寄生振荡。用设计制造的双啁啾镜进行了实验测试,用双啁啾镜对畸变脉冲进行色散补偿,实验结果表明:经过两次色散补偿可以将脉冲还原至初始状态,而过量的负色散又将脉冲重新展宽。     

飞秒激光脉冲压缩用啁啾镜新设计方法

对配对啁啾镜传统的优化过程进行了改进,并且尝试了新的多个啁啾镜匹配的方法。理论上实现了在700～1050 nm光谱范围内,两个啁啾镜配对色散总和振荡小于±10 fs2,三个啁啾镜配对色散总和振荡小于±15 fs2。此配对啁啾镜所实现的精确补偿色散,是获得极短光脉冲的基础,可以用于飞秒激光的脉冲压缩。     

色散缓变光纤啁啾演变特性

从理论上分析了色散缓变单模光纤中啁啾演变特性。采用储里叶变换法得到了只有群速度色散效应或自相位调制效应时皮秒脉立足点啁啾的解析解，利用数值法模拟了色散缓变光纤中皮秒脉立足点秋演变过程。结果表明：色散缓变光纤中的啁啾比常规光纤中的啁啾小，而且，合理选择光纤色散参数可实现脉冲波形无畸变传输。     

亚10飞秒脉冲的诊断与压缩

采用二次谐波-频谱分辨光闸法对克尔透镜锁模钛宝石激光器输出的飞秒脉冲的振幅和相位 进行诊断，测得其脉冲包络是双曲正割型的，而相位则近似为时间的三次幂形式. 通过对脉 冲频域相位的拟合，诊断出二阶群速度色散是造成脉冲啁啾、导致脉冲展宽的主要原因. 利 用棱镜对补偿二阶群速度色散，进一步将17 fs啁啾脉冲压缩至半高全宽为8.5 fs的近似转 换极限脉冲. 关键词： 飞秒脉冲 二次谐波-频谱分辨光闸法 群速度色散     

Generation of 17-TW 23-fs Pulses with a Two-Stage Ti：Sapphire Amplifier at Repetition Rate 10 Hz

We have developed a two-stage Ti：sapphire amplifier system which can produce 17- TW/23-fs pulses at a repetition rate 10Hz. A birefringent plate is used in the regenerative amplifier to alleviate gain narrowing, while an all- reflective cylindrical-mirror-based pulse stretcher and an acousto-optic programmable dispersive filter （AOPDF） are used to compensate for the higher order dispersion of the system.     

用于色散补偿的反射型棱栅的色散分析

利用角色散和材料色散得到了反射型棱栅的二阶、三阶色散完整的解析表达式,与光线追迹法的结果能很好地符合,利于工程中棱栅的设计.系统分析了温度、棱栅结构参数对其色散的影响.结果表明,温度、棱镜材料折射率、插入量、棱栅间距对棱栅色散影响很小.而入射角、光栅常数、棱镜项角等对色散的影响很大,可以调节上述参数来改变棱栅的色散,从而补偿放大介质等材料色散.     

Vector-dispersion compensation and pulse pedestal cancellation in a femtosecond nonlinear amplification fiber laser system

We report on a femtosecond nonlinear amplification fiber laser system using a vector-dispersion compressor, which consists of a transmission grating pair and multipass cell based Gires-Tournois interferometer mirrors. The mirror is designed with nearly zero group-delay dispersion and large negative third-order dispersion. As a result, the third-order dispersion of the compressor can be adjusted independently to compensate the nonlinear phase shift of amplified pulses to reduce the pulse pedestal. With this scheme, the system outputs 44 fs laser pulses with little wing at 26.6 W output average power and 531 nJ pulse energy, corresponding to 10.8 MW peak power.     

Dispersion compensation by microstructured optical devices in ultrafast optics

Dispersion compensation is a ubiquitous problem for the generation and application of ultrashort optical pulses. Early approaches to compensate for the spectral group-delay dependence in materials used prism and grating sequences for this purpose, but are limited in bandwidth. Microstructuring dielectric optical materials on the scale of the optical wavelength have developed as an alternative for inducing a desired spectral group-delay dependence. With this approach a nearly arbitrary dependence of group delay vs. wavelength can be compensated for. We will discuss different approaches to microstructured dispersion compensation, namely chirped Bragg gratings, different generations of chirped mirrors, quasi-phase-matching gratings, and arrayed-waveguide gratings. We will outline common limitations and discuss ideas to expand further the utility of these approaches. PACS 42.65 Re; 42.79 Wc; 42.81 Wg     

Group-delay Dispersion in Double-prism Pair and Limitation in Broadband Laser Pulses

A general expression of group-delay dispersion is obtained without any approximation for a pair of double prisms with an arbitrary apex angle. This expression also includes the change of dispersion resulting from change in insertion of the prism material into the beam by translating prism-pairs. The high-order dispersion can be calculated by means of this expression. The limitation for generation of negative group-delay dispersion by use of prism-pairs is presented for ultrashort laser pulses with broadband spectrum.     

Gires-Tournois干涉镜补偿色散的自启动飞秒Cr4+:YAG激光器实验研究

利用一片GTI镜补偿腔内色散,并使用宽带半导体可饱和吸收片,实现了锁模自启动的飞秒Cr⁴⁺:YAG激光输出.在9W平均功率的1030nm激光抽运下,获得输出脉冲功率为95 mW,光谱半高全宽45 nm,中心波长1508 nm,实测脉冲宽度为65 fs.     

Amplitude and phase control of ultrashort pulses by use of an acousto-optic programmable dispersive filter: pulse compression and shaping

We demonstrate experimentally that an arbitrary phase and amplitude profile can be applied to an ultrashort pulse by use of an acousto-optic programmable dispersive filter (AOPDF). Our filter has a large group-delay range that extends over 3 ps and a 30% diffraction efficiency over 150 THz. Experiments were conducted on a kilohertz chirped-pulse amplification laser chain capable of generating 30-fs pulses without additional pulse shaping. Compensating for gain narrowing and residual phase errors with an AOPDF in place of the stretcher results in 17-fs transform-limited pulses. Arbitrary shaping of these 17-fs pulses is also demonstrated in both the temporal and the spectral domains.     

Spectral phase shift and residual angular dispersion of an acousto-optic programmable dispersive filter

Spectral phase shift and both types of wavelength dependent angular deviation introduced by an acousto-optic programmable dispersive filter (AOPDF) into a femtosecond laser beam at 800 nm have been measured with high precision. With the use of spectrally and spatially resolved interferometry, we have proved experimentally that the AOPDF controls the group delay dispersion (GDD) and third-order dispersion (TOD) with an accuracy of better than 1% and 3% of the preset values within the range of 10–1000 fs² and 1000–40,000 fs³, respectively. The values of angular deviation and angular dispersion are primarily dependent on the set absolute value of GDD of the AOPDF when it is operating in continuous mode. Besides of a small offset value, there is no added angular dispersion at 0 fs², while it can increase up to 0.2 μrad/nm at 10,000 fs².     

Effect of group-delay ripples on dispersion-managed soliton communication systems with chirped fiber gratings

The effect of group-delay ripples in dispersion-managed soliton communication systems that use chirped fiber gratings for dispersion compensation is studied. Using both a reduced model and direct numerical simulation, we find that dispersion-managed solitons exist even in the presence of large dispersion variation caused by group-delay ripples. The dispersion-managed solitons suppress the growth of intersymbol interference induced by the group-delay ripples.