At the present time suopicosecond pulses of laser light as short as 0.5·10−12 s have been generated and detected and the possssibility of 50·10−15 s pulses generation as a limit is predicted [1]. Nothing has been said about the fundamental physical reasons that determine this limit. The aim of our work is to throw some light upon the generate mechanisms that govern the generation of ultrashort photon pulses and other pulses of physical fields of limited short duration. It is also obvious that the pulse duration Δt cann't be shorter than the elementary time length Δto if if it exists. So let us search for possicis candidates for Δto and look for methods of their generation. There is only one general method availaole to get automatically snortened pluses of boson fields - the method of boson avalanches [2]. It consists of the following: take an excited particle and put it into a physical resonator for a boson field for getting a boson by means of the sneous boson emission process in the resonator in a time τ. If we put N > 1 equel excited particles into the resonator we shall get a pulse of boson radiation consisting of ∼N bosons in a time (τ/N)·η, where η is an interference factor of the order η (λ2/Ao) for a radiating disk of square section Ao and for bosons of wavelength λ. This law was well established for photons generated by solids for which τ = 10−3 s, Ao = 1 cm2, λ2 = 10−10 cm2 and N = 1019 and Δt = 10−12 s. But these numbers are not the limited ones and we could pose for instance N = 1023 and τ = 10−10s. The result Δ t =10−21 will be wrong because in 10−11 s photons can travel only through a distance Δ1 ∼ 3·10−11 cm and a sphere of diameter Δ1 = 3·10−11 led with ordinary matter cann't contain 1023 particies. It must be said that particles outside of this sphere cann't interact to produce a motor, ava-_anche. So we see thatboson avalancnes can generate pulses as shot as needed if the material is as dense as to fulfill the new condition.
At the present time suopicosecond pulses of laser light as short as 0.5·10−12 s have been generated and detected and the possssibility of 50·10−15 s pulses generation as a limit is predicted [1]. Nothing has been said about the fundamental physical reasons that determine this limit. The aim of our work is to throw some light upon the generate mechanisms that govern the generation of ultrashort photon pulses and other pulses of physical fields of limited short duration. It is also obvious that the pulse duration Δt cann't be shorter than the elementary time length Δto if if it exists. So let us search for possicis candidates for Δto and look for methods of their generation. There is only one general method availaole to get automatically snortened pluses of boson fields - the method of boson avalanches [2]. It consists of the following: take an excited particle and put it into a physical resonator for a boson field for getting a boson by means of the sneous boson emission process in the resonator in a time τ. If we put N > 1 equel excited particles into the resonator we shall get a pulse of boson radiation consisting of ∼N bosons in a time (τ/N)·η, where η is an interference factor of the order η (λ2/Ao) for a radiating disk of square section Ao and for bosons of wavelength λ. This law was well established for photons generated by solids for which τ = 10−3 s, Ao = 1 cm2, λ2 = 10−10 cm2 and N = 1019 and Δt = 10−12 s. But these numbers are not the limited ones and we could pose for instance N = 1023 and τ = 10−10s. The result Δ t =10−21 will be wrong because in 10−11 s photons can travel only through a distance Δ1 ∼ 3·10−11 cm and a sphere of diameter Δ1 = 3·10−11 led with ordinary matter cann't contain 1023 particies. It must be said that particles outside of this sphere cann't interact to produce a motor, ava-_anche. So we see thatboson avalancnes can generate pulses as shot as needed if the material is as dense as to fulfill the new condition.
The development of methods of generation of ultrashort pulses (USP) of femto- and attosecond duration ranges with controlled parameters necessitates the theoretical study of features of their interaction with a matter [1]. Among such features that do not exist in case of “long” pulses should first of all be the nonlinear dependence of the photoprocess probability W on the USP duration (τ) [2] as well as the dependence on the carrier phase with respect to the pulse envelope (φ) [3-4]. It should be noted that if the dependence of the probability W on the phase φ manifests itself either only for very short pulses, when ωτ < 1 (ω is carrier frequency of the pulse), or in case of a nonlinear photoprocess [3], the function W(τ) can differ from a linear function in the limit ωτ> 1 too for fields of moderate strength, when the perturbation theory is applicable [2].
Anomalous quantum processes in the context of spontaneous emission (SpE)1,2 and stimulated emission (StE)3,4, which are closely related to the fundamental dynamics of photon emission and to the related plane-wave quantum photon delocalization process4,5 were studied by our laboratory by use of the optical microcavity. The most efficient method we adopt in our present studies consists of a detailed investigation of the Bose-Einstein (BE) transverse quantum correlation process established within the microcavity active plane between two identical cylindrical microlasers (with diameter δ≈30 μm) excited by two identical focused pump beams (at wavelength λ p = 0.53 μm when working within nanosecond exciting pulse-duration (Δτ) conditions, SHG by an unstable-cavity Nd-YAG laser) and coupled to the same and common microcavity plane-wave, forward k-mode. Our investigation of the quantum coupling process consists of the determination of the thresholdless laser-gain (g) of the overall active device as a function of the radial distance s between the microlasers and determined by the position of the pump focused beams. The solution of the detailed QED intermicrolaser coupling equations leads to the determination of the s-dependence of the relevant dynamical quantity α(s), the degree of BE transverse quantum correlation by assuming the microcavity spacing d = d ¯ N , d ¯ ≡ λ / 2 as a relevant parameter. The overall laser output radiation is detected by a high quantum efficiency, cooled photomultiplier by previous focusing onto a 20-μm pinhole, making a spatial filter that dis criminates efficiently against detection of radiation emitted on FP-cavity modes other than the forward-mode.4
A fresh look at Planck's quantum, h, re-interprets action as the companion of power in a dynamic interplay of energies in a multi particle system of the micro world. An exchange of energy, δE, requires a characteristic duration, δτ, with δE and δτ tied together in a natural way. Action, the product δEδτ, must have a nonzero lower limit, h, as a classical necessity everywhere in physics. Zero h would constitute a singularity. The veritable quantum is action, not energy. Black body radiation formulas (Wien, Planck, and Rayleigh) all require this non zero h. Planck's thermodynamic approach was not consistently developed further. Einstein in his 1905 description of the photo effect chose the single "quantum of light" as statistically independent actor in radiation. The resulting discussions about the wave-particle dualism, the meaning of uncertainty, the collapse of wave packets when observed, self-interference, and related problems can be avoided by the consistent view of the ensemble interpretation. In agreement with action defined as δEδτ only co-operative phenomena produce the effects we observe. In particular, this concerns the photon, directly associated with h, as naturally interactive quantum. Careful experiments on low intensity interference suggest to take the photon out of the isolation, thus changing the general view of quantum physics with surprising consequences. Do photons transport energy or action? To understand where 20th century physics has gone a glance at the historical background is in order.
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.