Optically induced currents in dielectrics and semiconductors as a nonlinear optical effect

Abstract

We demonstrate theoretically that when well-below-the-bandgap femtosecond optical pulses propagate through a dielectric or semiconductor, DC current and charges are produced even though no real carriers are excited in the bands. The photo-induced current is a new ultra-fast nonlinear optical effect based on multi-photon quantum interference and creation of an asymmetric distribution of virtual carriers in the conduction and valence bands. We establish an unambiguous connection between the nonlinear optical conductivity responsible for the photo-induced DC currents and charges and the odd-order nonlinear optical susceptibilities of the material. We then apply our results to the recent experiments [1] in which photo-induced charges have been observed in SiO2 irradiated by belowthe-gap ultra-short optical pulses. Using a single well known measured value of the third order susceptibility (nonlinear index) of SiO2 we obtain excellent agreement with all the experimental data of [1]. A clear physical picture of the origin of the photo-induced currents and charges shows that the versatility of ultrafast (virtual) nonlinear optical phenomena extends even further than had been previously thought.

Colloquium : Strong-field phenomena in periodic systems

“…An example of such a theory is the analytical approach to strong-field ionization of atoms and interband transitions in solids developed by Keldysh in his seminal paper (Keldysh, 1965), which was followed by many related works (Bychkov and Dykhne, 1970;Faisal, 1973;Gruzdev, 2007;Hawkins and Ivanov, 2013;Kovarskii and Perlin, 1971;Minasian and Avetisian, 1986;Mishima et al, 2002;Reiss, 1980;Shcheblanov et al, 2017;Vanne and Saenz, 2007). The key approximation of this theory is the neglect of the Coulomb interaction between an electron excited to the conduction band and the positively charged hole left behind in the valence band.…”

“…For a monochromatic field, the integral in Eq. (19) can be evaluated analytically using the saddle-point approximation (Keldysh, 1965) or the residue theorem (Mishima et al, 2002;Vanne and Saenz, 2007). In his original paper, Keldysh used analytical expressions of energy bands and optical matrix element from the second order of the two-band k· p-perturbation theory (Kane, 1960;Yu and Cardona, 2010).…”

“…is called the nonperturbative intensity parameter (Reiss, 1992) because it naturally appears in a perturbative expansion of strong-field theories (Faisal, 1973;Keldysh, 1965;Reiss, 1980). At the same time, this parameter describes the number of additional photons that must be involved in the excitation of an electron-hole pair to overcome the increase of the band gap due to intraband motion [see Eq.…”

“…The description of a particle in a periodic potential has been one of the greatest successes of quantum mechanics, revolutionizing solid-state physics and triggering the evolution of modern electronics, which forms the basis of our life. First works on band theory (Bethe, 1928;Bloch, 1929;Kronig and Penney, 1931), localized electronic states (Wannier, 1960(Wannier, , 1962, and electron dynamics in the presence of an external field (Houston, 1940;Kane, 1960;Keldysh, 1965;Zener, 1934) contributed to the foundations of strong-field semiconductors physics and its numerous industrial applications.…”

Few-cycle lightwave-driven currents in a semiconductor at high repetition rate

“…To observe lightwave-driven currents, the driving laser pulse has to be short enough so that the symmetry between positive and negative half-cycles can be broken by means of tuning the CEP. Several models explaining the underlying physical mechanism behind this phenomenon have been proposed [18][19][20][21]. Similarities to coherent control experiments of interfering multiphoton transitions driven in semiconductors by two-color fields [22][23][24][25][26][27][28][29][30] have also been pointed out.…”