【作者】 吴昆；

【导师】 曾和平；

【作者基本信息】 华东师范大学 ， 光学， 2007， 博士

【摘要】 周期量级超短脉冲的载波包络相位(CEP)对与瞬时电场强度相关的非线性实验具有决定性的影响，尤为突出的是它在阿秒科学和光频标测量学领域发挥着举足轻重的作用。随着阿秒激光脉冲的不断窄化和相关应用研究的不断深入，测量并控制飞秒激光脉冲CEP，已经成为当今最前沿的研究内容之一。本工作致力于稳定周期量级超短脉冲CEP的研究，目标是探索控制超短激光脉冲载波包络相位的新方案与新技术，发展CEP稳定的周期量级超短脉冲系统。在稳定和控制超短激光脉冲CEP方面，我们主要着力于发展控制CEP的新方案。为此我们首先提出了基于级联光学参量放大(OPA)的CEP稳定方案。该方案巧妙地利用不同类型OPA的组合使用，实现了大能量、超宽频谱、CEP稳定的超短脉冲，同时还避免了白光注入类型的OPA方案中由于白光中剩余泵浦光对信号脉冲CEP影响严重的问题。该方案是目前实现超短脉冲CEP稳定的有效手段之一。我们首次在实验中发现了时空耦合调制不稳定性产生的多色锥状辐射现象。发现时空耦合调制不稳定性作用使基波与二次谐波发生强非线性相位锁定，平衡了二者之间的群速度色散和衍射，有效地提高了非线性转换效率。在此基础上，我们提出了利用时空耦合调制不稳定性参与的参量过程实现超短脉冲CEP自稳定的方案。该方案有效地利用了时空耦合调制不稳定性参与的参量过程具有指数增益的优点，可以实现极宽频谱范围内连续可调、高能量、CEP稳定的超短脉冲。使用这种极具潜力的新方案，我们在简单的OPA装置上实现了超短激光脉冲CEP的自稳定。本论文还提出并实现了利用调制上转换放大和泵浦光之间的差频实现超短脉冲CEP自稳定的方案。在该方案中，由于调制上转换放大的CEP在放大过程中保持不变并且具有能量高、光斑质量好以及宽频谱宽度等优点，所以其与泵浦光之间的差频信号具有CEP自稳定的特性，同时调节调制上转换放大的中心波长能够实现CEP稳定的差频信号在极宽频谱范围内连续可调。围绕着CEP稳定的周期量级超短脉冲系统的研究，我们发展了一系列关键性的技术。提出了利用全光方法获得CEP稳定的超短脉冲，随后利用光学参量啁啾脉冲放大(OPCPA)实现了构建CEP稳定的周期量级超短脉冲系统的新方案。全光方法可以获得CEP精确稳定的超短脉冲。OPCPA不仅能够有效地放大激光脉冲的能量，而且研究表明OPCPA过程不会影响信号光的CEP信息。该方案能够实现CEP稳定的周期量级强激光脉冲输出，这是目前获得CEP稳定的周期量级强激光源的有效方案之一。提出并证明了获得用于800nm钛宝石激光器OPCPA的精确同步的泵浦源的新技术。这项技术是基于连续光注入的非共线OPA技术。在参量作用时间内，连续光能够提供足够的光子有效抑制了荧光的参量放大从而获得大能量、光斑质量较好的信号输出。在此基础上，我们分别发展了基于1064nm的连续光、632.8nm连续光以及氦氖激光腔内放大等新技术。这些新技术能够有效地产生与800nm钛宝石激光器精确同步的泵浦光脉冲，二者之间的时间抖动不超过10fs。实验获得的无连续光背景的1064nm超短脉冲能量可以通过再生放大或者多通放大的手段获得进一步的提高，其532nm的倍频光可以为同源钛宝石激光器的OPCPA装置提供精确同步的高强度泵浦源。更多还原

【Abstract】 The phase of the carrier frequency with respect to the pulse envelope in few-cycle laser pulses, which can be described by the concept of carrier-envelope phase (CEP) plays a crucial role in many nonlinear experiments correlated with electric field intensity, such as attosecond science and optical frequency metrology. As attosecond laser pulses become more and more narrow and its challenging applications, controlling and measuring the CEP of femtosecond laser pulses have now turn to one of the most fascinated research.The main purpose of this work is to explore novel schemes and techniques for stabilizing the CEP of ultrashort laser pulses. And the experimental work is concentrated on building up a CEP-stabilized intense few-cycle laser system.In order to stabilize the CEP of ultrashort laser pulses, we have proposed several innovative setups. The first one is based on cascaded optical parametric amplifier (OPA). The combination of different type OPAs not only realize the output of intense, broadband spectrum, CEP-stabilized ultrashort laser pulses, but also avoid the detrimental effects on the CEP of signal pulses in white-light seeded OPA. It is one of the effective methods for stabilizing the CEP of ultrashort laser pulses.We have observed for the first time colored conical emission due to the spatiotemporal modulational instability in second harmonic generation of ultrashort laser puses. As a consequence, the strong nonlinearity between fundamental waves and second harmonic has balanced their group velocity dispersion and diffraction, which lead to the great improvement of energy conversion. Therefore, we have proposed stabilizing the CEP of ultrashort pulses by use of modulational instability assisted OPA. This method take full advantage of modulational instability assisted OPA, facilitating the generation of widely tunable, CEP-stabilized intense ultrashort pulses.And we also proposed CEP self-stabilization by use of difference frequency generation between mudulational up-conversion amplification and pump pulses. Due to the white-light seeded amplification of colored conical emission, mudulational up-conversion amplification has very good beam quality and broadband spectrum with the same CEP as pump pulses. By tuning the central wavelength of mudulational up-conversion amplification, widely tunable of the CEP-stabilized difference frequency signal is realized.When stepping toward the goal of building up a CEP-stabilized intense few-cycle laser system, we have developed many key techniques for it.We have proposed a novel scheme for building CEP-stabilized intense few-cycle laser system by use of all-optical CEP-stabilizer and optical parametric chirped pulse amplifier (OPCPA). All-optical CEP-stabilizer achieved absolute stabilize of CEP of ultrasgort pulses. OPCPA can not only boost the energy of laser pulses, but also preserve its CEP in the whole process. It is one of the most effective methods for uilding CEP-stabilized intense few-cycle laser system.And we have also proposed generation of accurate synchronized pump pulses for OPCPA operated on 800 nm Ti:sapphire lasers by use of continues-wave (CW) seeded NOPA. The continues-wave provides sufficient photons in the parametric interaction time, which greatly restrain the fluorescence amplification. Due to the good beam quality of the CW laser beam, the output signal exhibits large single pulse energy and good beam quality. We have developed 1064 nm CW laser, 632.8 nm laser and intracavity of He-Ne laser as the seed pulse for NOPA, respectively. These scheme can generate accurate synchronized pump pulses with 800 nm Ti:sapphire lasers. The time jitter of the generated pump pulse with respect to the 800 nm pulse was measured about 10 fs in a few seconds. The generated background-free 1064 nm pulse can be further amplificted and the frequency doubled to produce an accurately synchronized pump source for OPCPA for the same Ti:sapphire laser.更多还原