Application Of Attosecond Pulses Research Articles

Jeszcze szybsza lampa błyskowa czyli Nagroda Nobla z fizyki 2023

Nobel Prize in Physics in 2023 was awarded for generation of attosecond (1 as=10−18 s) pulses of electromagnetic radiation and application of attosecond pulses in studies of electrons in condensedmatter. I show basic physicalmechanisms leading to generation of such pulses and methods to measure them. I also show an exemplary application of attosecond pulses - studies dynamic of photo effect.

Generation and control of attosecond laser pulse

Time-resolved measurement enables us to reveal the dynamical evolution of the system. The ultrashort laser and pump-probe method provide a powerful tool for achieving the time resolved measurement. With the development of laser technology, e.g., Q -switching, mode-locking, chirped pulse amplification and the application of the Ti:Sapphire crystal, the pulse width of laser is getting shorter and shorter, and the pulse energy is getting higher and higher. It has brought tremendous changes to the field of optics and photonics. For example, in the 1980s, femtosecond (1 fs =10–15 s) lasers have been used to study the evolution of molecular intermediate states during chemical reactions, which revealed the dynamics of chemical reactions at the molecular level. Nevertheless, the electron inside atoms and molecules moves even faster on a timescale of “attosecond” (1 as =10–18 s). At the dawn of the 21st century, attosecond pulses were produced from the high harmonics generated in the interaction between intense femtosecond laser and novel atoms. In 2001, an isolated attosecond pulse with a duration of 650 as was produced in the experiment via a 7 fs few-cycle driving laser. In the same year, an attosecond pulse train with a duration of 250 as for single pulse was produced by a multicycle driving laser. These results marked that the pulse width of the laser broke through the femtosecond timescale, and opened the door to attosecond science. In the next decades, lots of ultrafast processes inside atoms and molecules, e.g., tunneling ionization, Auger decay of atoms and electron localization and internal charge transfer of molecules, have been invested by pump-probe measurement combining the attosecond pulses and few-cycle near infrared laser pulses. In addition, the applications of attosecond pulses have been gradually extended from gas to solid materials. By using the attosecond pulse, it is possible to manipulate the electron motion in the attosecond time scale, which corresponds to an extremely high frequency rate of petahertz. Such manipulation is considered to be the basis for developing the photoelectric information processing at petahertz. Attosecond science has become one of the most important achievements in the field of ultrafast optics in the past two decades. The crucial issue is the generation and control of attosecond laser pulses. Many schemes have been demonstrated to produce the isolated attosecond pulses. The most popular scheme is few-cycle driving laser, which requires carrier-envelope phase stabilized ultrashort laser pulse. On the other hand, since the generation efficiency of the attosecond pulse depends on the driving laser ellipticity, a polarization gating scheme has also been developed, which was later generalized to double optical gating. Another scheme is the two-color field scheme, which synthesizes the laser pulses with different wavelengths. The advantage of this method is that multi-cycle driving laser pulse can be used to produce isolated attosecond pulse. Recently, this method has been extended to the three-color cases. In addition, ionization gating and lighthouse schemes are also demonstrated in experiment. With these methods, the pulse duration of the attosecond pulse decreases gradually. At present, the shortest pulse width has reached 43 as and high power isolated attosecond pulse with a peak power of 2.6 GW has been produced. But how to improve the attosecond pulse energy and generation of circularly polarized attosecond pulses are still the hot topics currently.

Strong-field control and attosecond probing of multielectron dynamics

The past thirty years witnessed rapid developing of strong field physics that leads to the first generation of attosecond (10−18 s) pulses. The duration of available pulses has recently been reduced to less than 100 as, approaching the Kepler period of a classical electron revolving around the nucleus. For the first time, electron motions inside atoms, molecules and solids can be traced, probed and even steered in real time. It pushed the study on ultrafast dynamic processes into a new frontier, giving birth to attosecond physics. The development of attosecond pulses provides unprecedented coherent ultrashort XUV (extreme ultra-violet) of soft X-ray sources that enable imaging the atomic structure and resolving the related quantum dynamics for matter science. In particular, it allows the probing and monitoring of electron dynamics in the natural time scale of attoseconds with atomic spatial resolution. The generation and applications of attosecond pulses are directly related to the control and manipulation of the sub-cycle electron dynamics. Recent studies on the correlated multielectron dynamics have provided insight into the optical and dynamical properties of matter in the perspectives of time, phase and entanglement. It deepens our understanding on some of the fundamental questions, e.g., how the single or multiple photons are absorbed and how short are the quantum processes such as photoionization, tunneling ionization and charge migration. Although currently attosecond pulses are limited by the flux and pulse duration, the combination of attosecond pulses with intense infrared laser pulses paves new ways of controlling and probing electron dynamics in the domains of energy, time and space that lays the foundation for petahertz optoelectronics and attosecond pulse based transient spectroscopy. In this review, we will first briefly summarize the advancement of strong field and ultrafast physics including the relevant experimental findings, the theoretical explorations, the related technologies and the possible applications. Then we focus on the sub-cycle electron or multielectron dynamics and their manifestation on the ionization and coherent radiation properties. We start with the time behavior of Fano resonance and how it can be probed in time domain. In section 2, the correlated electron dynamics is discussed in term of anti-screening effect and Pauli effect that influence strong field ionization and high harmonic generation processes. In section 3, the coherent emission with frequency from terahertz to soft XUV and their joint measurement are discussed by emphasizing the generation mechanism of terahertz wave in two-color laser pulses. The developed high-harmonic and terahertz wave spectroscopy (HATS) is shown capable of imaging the molecular structure and dynamics. In section 4, the time-resolving of electron and hole dynamics and their coherence is proposed based on attosecond transient absorption technique. The coherence of ionization and the correlated electron dynamics is hinted crucial for electron-hole interaction. The topics are very limited and mainly selected from the perspectives of our group.

Attosecond science

Scientists have been developing sources of light with ever-shorter pulse durations, in order to study motion in systems ranging from a golfer’s swing to the motion of atoms within molecules. The shortest pulses produced to date are under 60 attoseconds, i.e. s. One attosecond is to one second as one second is to the age of the universe. For comparison, the classical orbital period of an electron in a hydrogen atom is 150 attoseconds. Attosecond pulses were first produced in 2001. This article describes how attosecond pulses are generated and how they are measured. Some applications of attosecond pulses are described, such as measuring the delay in photoionisation, or observing molecular dissociation dynamics.

Compensation of high order harmonic long quantum-path attosecond chirp

We propose a method to compensate for the extreme ultra violet (XUV) attosecond chirp associated with the long quantum-path in the high harmonic generation process. Our method employs an isolated attosecond pulse (IAP) issued from the short trajectory contribution in a primary target to assist the infrared driving field to produce high harmonics from the long trajectory in a secondary target. In our simulations based on the resolution of the time-dependent Schrödinger equation, the resulting high harmornics present a clear phase compensation of the long quantum-path contribution, near to Fourier transform limited attosecond XUV pulse. Employing time–frequency analysis of the high harmonic dipole, we found that the compensation is not a simple far-field photonic interference between the IAP and the long-path harmonic emission, but a coherent phase transfer from the weak IAP to the long quantum-path electronic wavepacket. Our approach opens the route to utilizing the long quantum-path for the production and applications of attosecond pulses.

Importance of intensity-to-phase coupling for water-window high-order-harmonic generation with few-cycle pulses

We present half-cycle cutoff features in the water window using high-order-harmonic generation (HHG) with two-cycle, carrier-envelope-phase-controlled pulses at 1.85 μm in a high-pressure neon target. A relative carrier-envelope-phase (CEP) shift of the acquired spectra at different pressures is related to an in situ slip of the CEP in the HHG target. A simple model based on the pressure-dependent dispersion of the target gas reveals the importance of the free electrons for this effect. Our analysis also reveals that the effect is relaxed at high target pressures due to plasma defocusing of the driving pulse. We show that as a consequence of the CEP slip mediated by free electrons, moderate-intensity fluctuations can have a detrimental influence on the generation and application of attosecond pulses. Our findings emphasize the potential of combining high target pressures and long driver wavelengths to reveal subtle details of the complex light-matter interaction of HHG.

How to focus an attosecond pulse

Attosecond experiments involving focusing of attosecond light pulses can suffer from a spread of the attosecond radiation both in space and time due to optical aberrations. We present a detailed numerical study of the distortions induced in the most common focusing geometries that make use of parabolic, spherical, toroidal and ellipsoidal mirrors. We deduce the consequences on the pulse duration and possible issues that could arise in applications of attosecond pulses. This should serve as a guideline for setting up attosecond focusing optics.

Attosecond Technology and Science

The generation of attosecond pulses has been the result of tremendous efforts and advances in the field of the interaction of ultrashort intense laser pulses with matter. Nowadays, the electric field waveform of femtosecond pulses can be precisely controlled and used to synthesize and measure the evolution in time of attosecond pulses. The quest for increasing photon fluxes in the extreme-ultraviolet region (XUV) and the requirement of a complete characterization of complex attosecond waveforms are stimulating the development of new technological approaches that should make feasible XUV sources combining attosecond pulse duration, high energy, and high repetition rate. The use of such sources with state-of-the-art techniques for the measurement of the momentum of charged particles will allow a detailed description of photoionization and photodissociation processes. Advances in selection of the initial quantum state and structure of molecules will open the way for the extension of attosecond spectroscopy to complex molecules. The first applications of attosecond pulses allowed the investigation of electron dynamics with a resolution close to the atomic unit of time. Simple systems such as helium and noble gases were investigated using trains and isolated pulses. These experiments represent benchmarks to elucidate the response of atoms on the typical electron timescale.

Theory of Attosecond Phenomena

Attosecond extreme ultraviolet and soft X-ray pulses are generated through high-order harmonic generation, a highly non-linear and non-perturbative phenomenon. Nonlinear optical effects and electron-electron interaction play an essential role in various applications of attosecond pulses. The best way to study atomic dynamics under such circumstances theoretically is direct numerical simulation of the time-dependent Schrödinger equation (TDSE). The present article introduces how to model the high-field and ultrafast phenomena on the basis of TDSE, and reviews recent theoretical findings on attosecond pulse generation and attosecond phenomena, peculiar to the time scale of electronic motion inside an atom.