Quantum beats in absorption

Mark P. Silverman

Phedon Palinginis, Hailin Wang

We report experimental studies of absorption quantum beats induced by electron spin coherence in GaAs quantum wells. Absorption quantum beats occur for strongly localized excitons, but nearly vanish for mobile excitons in the third order nonlinear optical response. Pronounced quantum beats for mobile excitons emerge in an unusual fifth order process. These results, along with a qualitative analysis based on the use of N-exciton eigenstates, elucidate how the manifestation of electron spin coherence in the excitonic nonlinear optical response can differ fundamentally from that in an atomic system.

Dmitry V. Kolomoitsev, S. Yu. Nikitin

Shunsuke Nakanishi, Hiroshi Itoh

Subpicosecond photon echo quantum beats were studied in a dye, Rhodamine 800, doped in a polymer (polyvinyl alcohol) by using an incoherent photon echo technique. At the long-wavelength tail of absorption, photon echo quantum beats were observed as the sinusoidal modulation with the frequency of about 100 cm-1, which resulted from the interference between a single vibronic line and the zero-phonon line. The dephasing time of the vibronic line and its temperature dependence were briefly studied. At nearly the peak of absorption, the quantum beats appeared as more complicated modulation, indicating the contribution from multiple vibronic lines.

M. D. Levenson

Two-photon absorption can produce a coherent oscillating atomic polarizability in a macroscopic vapor. If this vapor contains an ensemble of atoms having different transition frequencies, the beat frequencies between the polarizabilities of the two species can be detected in the time domain. Energy-level splittings can be determined which are too small to resolve in the frequency domain and are not accessible to quantum beats.

P. Johansson, I. E. Mazets, Oleg S. Vasyutinskii +1 more