Abstract. Using 3D test particle simulations, the characteristics and essential conditions under which an electron, in a vacuum laser beam, can undergo a capture and acceleration scenario (CAS). When 0 a 100 the electron can be captured and violently accelerated to energies 1 GeV, with an acceleration gradient 10 GeV/cm, where
Abstract. It has been found that for a focused laser beam propagating in free-space, there exists, surrounding the laser beam axis, a subluminous wave phase velocity region.Relativistic electrons injected into this region can be trapped in the acceleration phase and remain in phase with the laser field for sufficiently long times, thereby receiving considerable energy from the field. Optics placed near the laser focus are not necessary, thus allowing high intensities and large energy gains. Important features of this process are examined via test particle simulations. The resulting energy gains are in agreement with theoretical estimates based on acceleration by the axial laser field.
A scheme for a random number generator based on the intrinsic randomness of quantum mechanics is proposed. A Fresnel multiple prism which can act as a perfect 50∕50 beam splitter is used to realize the random events by choosing single photons from a polarized laser beam. A procedure to get rid of the bias of the raw sequences is discussed in detail together with the random number generation efficiency per light pulse.
The interaction of free electrons with intense laser beams in vacuum is studied using a 3D test particle simulation model that solves the relativistic Newton-Lorentz equations of motion in analytically specified laser fields. Recently, a group of solutions was found for very intense laser fields that show interesting and unusual characteristics. In particular, it was found that an electron can be captured within the high-intensity laser region, rather than expelled from it, and the captured electron can be accelerated to GeV energies with acceleration gradients on the order of tens of GeV/cm. This phenomenon is termed the capture and acceleration scenario (CAS) and is studied in detail in this paper. The maximum net energy exchange by the CAS mechanism is found to be approximately proportional to
Acceleration of neutral particles is of great importance in many areas, such as controlled chemical reactions, atomic nanofabrication, and atom optics. Recent experimental studies have shown that pulsed lasers can be used to push neutral Rydberg atoms forward [Nature 461, 1261 (2009)10.1038/nature08481; Nat. Photonics 6, 386 (2012)10.1038/nphoton.2012.87]. Our simulation shows that pulsed lasers can also be used to pull Rydberg atoms back toward a light source. In particular, we proposed a method of using two laser pulses on a neutral atom, then selective operations on the neutral atom (pushing or pulling) can be performed by adjusting the delay time between the two laser pulses.
By using the superposition of N suitably weighted Laguerre-Gaussian beams, the analytical expressions of all six electromagnetic field components of focused Flattened Gaussian Beams (FGBs) are obtained in the Lorentz gauge. The phase velocity distributions of the field near the focus of FGBs propagating in vacuum are investigated. There exists a subluminous wave phase velocity region surrounding the laser beam axis. We further apply this focused FGB to vacuum laser acceleration. As with the focused Standard Gaussian Beam (SGB), electrons injected into the focused FGB can be captured in the acceleration phase and then violently accelerated.
We analyze two forms of the instantaneous frequency of a linearly chirped laser pulse. Using a 3D test particle simulation, numerical results are presented for electrons accelerated by a chirped laser pulse with these two linearly chirped forms of the instantaneous frequency. We summarize that the linearly chirped frequency, xðtÞ ¼ x 0 1 À aðt À z=cÞ ½ is reasonable, x 0 is laser frequency at z ¼ 0 and t ¼ 0, and a is the frequency chirp parameter.After Shimoda in 1961 had first proposed the use of lasers to accelerate particles was as a clean and simple physical system, 1 vacuum laser acceleration has received much attention in particular. [2][3][4][5][6][7] The key concept in vacuum laser acceleration is breaking the symmetry between acceleration and deceleration so that the former exceeds the latter. 8 Many various schemes have been proposed to achieve just that! Most of these adopt a fixed laser frequency, but what of a time-dependent frequency? Some schemes with chirped laser pulses have been studied in recent years. [9][10][11][12][13][14] The studies that the chirped laser pulses, for which the instantaneous frequency varies with time, could significantly enhance acceleration. Singh introduced the instantaneous frequency xðtÞ ¼ x 0 ð1 À atÞ, where x 0 is the laser frequency at z ¼ 0 and t ¼ 0, and a is the frequency chirp parameter. 10 However, in many other schemes, 11-15 the instantaneous frequency was set as xðtÞ ¼ x 0 1 À aðt À z=cÞ ½ . The question posed is which of the two is reasonable in the end?To begin, we analyze the physical picture of the chirped laser pulses in vacuum for each of these two forms. The latter signifies that the frequency of a fixed point inside a chirped laser pulse will change with time. However, in terms of the moving frame g ¼ t À z=c of the laser pulse, the frequency distribution of a chirped pulse relative to the pulse center will remain unchanged. Thus, the total energy of the chirped laser pulse with the latter form will keep the same, i.e., will not change over time. The former signifies that the frequency in every region inside a chirped laser pulse will uniformly change with time. Then, the total energy of the laser pulse with the former form will change with time. In vacuum, this is unreasonable.We next consider the phase /ðtÞ of the wave which can be written to a Taylor series about the time t,where / 0 is the initial phase and / 1 ¼ x 0 is the instantaneous frequency at t ¼ 0. Thus, the instantaneous frequency isNormally, only the first few terms are typically required to describe well-behaved pulses. If spatial coordinates are considered, a linearly chirped Gaussian pulse of one dimension can be mathematically expressed aswhere g ¼ t À z=c is the retarded time, 5 exp Àðg=sÞ 2 h i the Gaussian profile factor, expðix 0 gÞ the carrier wave, and exp ibg 2 ð Þ the linear chirp part. Normally, the phase term is written aswhere xðtÞ ¼ x 0 þ bg ¼ x 0 ð1 À agÞ, k ¼ xðtÞ=c, and a ¼ Àb=x 0 . Finally, we present some results from our simulations using the above-mentioned two ...
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