Unipolar light: existence, generation, propagation, and impact on microobjects

Abstract

A review is presented of recent works on optical unipolar pulses, whose electric area (integral of the electric field strength over time) is nonzero, which determines the predominant direction of the electric field strength. It is shown that the existence of unipolar pulses does not contradict Maxwell’s equations, and that unipolar pulses can propagate in waveguides. It is emphasised that, along with the spectral, energy, and polarisation parameters, the electric area of short light pulses is also an important characteristic. The unidirectional action of these pulses on microobjects indicates that it is promising to develop methods for generating radiation with such properties. We disciuss methods for the generation, propagation, and interaction of unipolar light with classical and quantum systems, as well as methods for recording the electric area of light pulses.

Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses

“…The latter allows using THz pulses experimentally available to date, and field strengths, significantly lower than in the optical range. It worth to note that practically available subcycle THz pulses often contain a burst of single polarity and a big tail of opposite polarity and small amplitude [1][2][3][4][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] . Action of such quasi-unipolar pulses is nearly the same as the true unipolar ones 38 .…”

“…Generation of unipolar and quasi-unipolar pulses and their applications in optics is a subject of active discussions [22][23][24][25][26][27][28][29][30] , see also recent review 31 and references therein. These pulses, due to their unipolar character, effectively transfer their energy to charged particles, resulting in novel applications, including highly effective ionization and control of Rydberg atoms [32][33][34] , effective attosecond pulse generation 35 , effective excitation and ultra-fast control of electron wave packets dynamics 23,[36][37][38] , charge acceleration 39 , holographic recording 40 and others.…”

Energy-band echoes: Time-reversed light emission from optically driven quasiparticle wavepackets

“…( 4), with the CEP being 𝜃 d = 0, which leaves a finite vector potential 𝐴 f ∝ cos 𝜃 d after 𝐸 d (𝜏) decays. While the existence of such a unipolar (i.e., 𝐴 f ≠ 0) pulse is controversial [109][110][111][112], here by introducing a CEP-controlled mono-cycle driving pulse we show that energy-band echoes can be obtained even for 𝐴 f = 0.…”

“…Hereafter, we discuss the energy-band echo with 𝜃 d = 0, which facilitates the analysis. We note that the existence of such a unipolar pulse with 𝐴 f ≠ 0 is controversial [109][110][111][112]; we demonstrate in Sec. III E that the echoes can be generated even by a driving pulse with 𝜃 d = 𝜋/2; i.e., 𝐴 f = 0.…”

2D splash mode

“…However, there is no contradiction in this: the double improper integral of function (3) over the variables t and x is not absolutely convergent, therefore the conditions of the Fubini theorem [25] are not satisfied, and therefore the values of the iterated integrals over the indicated variables may depend on the order of integration. Note that solutions of the wave equation, the time integral of which within infinite limits is nonzero, are called unipolar [26][27][28][29].…”