Selective two-photon excitation of a vibronic state by correlated photons

Abstract

We theoretically investigate the two-photon excitation of a molecular vibronic state by correlated photons with energy anticorrelation. A Morse oscillator having three sets of vibronic states is used, as an example, to evaluate the selectivity and efficiency of two-photon excitation. We show that a vibrational mode can be selectively excited with high efficiency by the correlated photons, without phase manipulation or pulse-shaping techniques. This can be achieved by controlling the quantum correlation so that the photon pair concurrently has two pulse widths, namely, a temporally narrow width and a spectrally narrow width. Though this concurrence is seemingly contradictory, we can create such a photon pair by tailoring the quantum correlation between two photons.

Two-photon process via internal conversion by correlated photon pairs

“…5(c)] when , the vibrational eigenmode with v = 13 is selectively excited enough to count the nodes of the eigenmode owing to the negative energy correlation between two photons, as is the case with the two-photon absorption in Ref. [19]. However, the negative correlation means that TB photons have the nature of coincidence, and this coincidence leads to saturation of |m .…”

“…(16) with where r c = (r 0 + r 0 )/2. Equation (19) means that two photons in a pair distribute at a distance symmetrically on the center of a wave packet, r c , and the photon pair distributes within the wave packet, changing the distance between two photons [ Fig. 3(b)].…”

“…Generally, two-photon processes are classified into two types, namely, two-photon absorption via a virtual state and two-step excitation via a real excitation of an intermediate state. For two-photon absorption by short pulses, it has already been shown that correlated photons can enhance the excitation efficiency and realize selective excitation of a vibronic state, with limited influence of molecular vibration [19]. However, since vibronic energy levels of molecules are often dense, two-step two-photon excitation via nonradiative processes, such as internal conversion or intersystem crossing, would be important in controlling chemical reactions.…”

Two-photon spectroscopy of excitons with entangled photons

“…This favorable intensity scaling [15][16][17][18] has been demonstrated experimentally in various systems, and allows to perform measurements at low intensities, avoiding damage to the sample. Moreover, the non-classical time-bandwidth properties of entangled photon pairs [19][20][21] provide unconventional observation windows, and can be used to selectively excite specific two-exciton states 21 or specific vibrational states, 22,23 and control population transport. 24 New control parameters of quantum light can be varied to create novel twodimensional correlation plots.…”

Matter correlations induced by coupling to quantum light

“…Moreover, the possible exploitation of strong correlations in nonlinear spectroscopy with quantum light promises new routes to probe complex quantum systems [5][6][7][8][9]. Quantum spectroscopy offers increased signal strength at low photon fluxes [10][11][12], new control parameters to disentangle complex spectra [13][14][15][16], the control of exciton distributions [17][18][19][20], and the suppression of exciton transport [21] thanks to the unusual combination of high temporal and spectral resolution. However, whether all of these effects are genuine quantum effects in the sense that they may not be mimicked-at least in principle-by properly shaped pulses with classical correlations [22][23][24] remains an open topic.…”