Precise pulse shaping for quantum control of strong optical transitions

Optical pulse-shaping for internal cooling of molecules

We consider the use of pulse-shaped broadband femtosecond lasers to optically cool rotational and vibrational degrees of freedom of molecules. Since this approach relies on cooling rotational and vibrational quanta by exciting an electronic transition, it is most easily applicable to molecules with similar ground and excited potential energy surfaces, such that the vibrational state is usually unchanged during electronic relaxation. Compared with schemes that cool rotations by exciting vibrations, this approach achieves internal cooling on the orders-of- magnitude faster electronic decay times…

Attosecond Pulse-shaping using a seeded free-electron laser

Attosecond pulses are fundamental for the investigation of valence and core-electron dynamics on their natural timescale. At present the reproducible generation and characterisation of attosecond waveforms has been demonstrated only through the process of high-order harmonic generation. Several methods for the shaping of attosecond waveforms have been proposed, including metallic filters, multilayer mirrors and manipulation of the driving field. However, none of these approaches allow for the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer fro…

Improving the phase response of an atom interferometer by means of temporal pulse shaping

We study theoretically and experimentally the influence of temporally shaping the light pulses in an atom interferometer, with a focus on the phase response of the interferometer. We show that smooth light pulse shapes allow rejecting high frequency phase fluctuations (above the Rabi frequency) and thus relax the requirements on the phase noise or frequency noise of the interrogation lasers driving the interferometer. The light pulse shape is also shown to modify the scale factor of the interferometer, which has to be taken into account in the evaluation of its accuracy budget. We discuss the …

Temporal shaping of entangled photons

We experimentally demonstrate shaping of the two-photon wavefunction of entangled photon-pairs, utilizing coherent pulse-shaping techniques. By performing spectral-phase manipulations we tailor the two-photon wavefunction exactly like a coherent ultrashort pulse. To observe the shaping we perform sum-frequency generation (SFG) with an ultrahigh flux of entangled photons. At the appropriate conditions, SFG performs as a coincidence detector with an ultrashort response time (~100 fs), enabling a direct observation of the two-photon wavefunction. This property also enables us to demonstrate backg…

Attosecond pulse shaping around a Cooper minimum

High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straight-forward interpretation as an emission time, in c…

自制37-keV束流线中高电流脉冲电子束的阿秒整形

Attosecond shaping of high-current pulsed electron beams in a home-built 37-keV beamline

本研究利用自制装置中的薄膜对亚相对论电子束进行阿秒整形，实现了高平均电流（样品上每脉冲>2个电子）且空间电荷效应可忽略，通过优化薄膜排列将电子-光延迟展宽控制在飞秒内，清晰观察到阿秒条纹谱图，估计聚束电子持续时间为1.3 fs（FWHM）和0.5 fs（RMS），并展示了具有大能量展宽的脉冲束的阿秒调制，为实现含一个或多个电子的阿秒脉冲生成迈出重要一步。

Polarization shaping of high-order harmonics in laser-aligned molecules

The present work reports on the generation of short-pulse coherent extreme ultraviolet radiation of controlled polarization. The proposed strategy is based on high-order harmonics generated in pre-aligned molecules. Field-free molecular alignment produced by a short linearly-polarized infrared laser pulse is used to break the isotropy of a gas medium. Driving the aligned molecules by a circularly-polarized infrared pulse allows to transfer the anisotropy of the medium to the polarization of the generated harmonic light. The ellipticity of the latter is controlled by adjusting the angular distr…

光谱相脉冲成型改变光电离时间

Spectral Phase Pulse Shaping Alters Photoionization Time

研究通过改变光谱相位影响光电离时间延迟，揭示了相位依赖的内在光电离动力学，为操控离子化时间提供新方法。

Cold molecules formation by shaping with light the short-range interaction between cold atoms: photoassociation with strong laser pulses

The paper investigates cold molecules formation in the photoassociation of two cold atoms by a strong laser pulse applied at short interatomic distances, which lead to a molecular dynamics taking place in the light-induced (adiabatic) potentials. A two electronic states model in the cesium dimer is used to analyse the effects of this strong coupling regime and to show specific results: i) acceleration of the ground state population to the inner zone due to a non-impulsive regime of coupling at short and intermediate interatomic distances; ii) formation of cold molecules in strongly bound level…

利用脉冲整形实现极紫外波段的强场量子控制

Strong-field quantum control in the extreme ultraviolet using pulse shaping

针对短波长强场量子控制缺乏脉冲整形技术的问题，本研究利用FERMI种子型自由电子激光的脉冲整形，实现氦原子超快拉比动力学的高保真强场量子控制，揭示电离连续谱强修饰效应并实现电离速率调控，为芯电子过程等的实时操控开辟新途径。

Doppler-free coherent-control spectroscopy with a colliding pair of shaped pulses

We demonstrate the use of the ultrafast spatial coherent-control method to resolve the fine-structure two-photon transitions of atomic rubidium. Counter-propagating ultrafast optical pulses with spectral phase and amplitude programmed with our optimized solutions successfully induced the two-photon transitions through $5S_{1/2}$-$5P_{1/2}$-$5D$ and $5S_{1/2}$-$5P_{3/2}$-$5D$ pathways, both simultaneously and at distinct spatial locations. Three different pulse-shaping solutions are introduced that combine amplitude shaping, which avoids direct intermediate resonances, and phase programming, wh…