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Kinoshita T, Matsuda T, Takahashi T, Ichimiya M, Ashida M, Furukawa Y, Nakayama M, Ishihara H. Synergetic Enhancement of Light-Matter Interaction by Nonlocality and Band Degeneracy in ZnO Thin Films. PHYSICAL REVIEW LETTERS 2019; 122:157401. [PMID: 31050541 DOI: 10.1103/physrevlett.122.157401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 03/08/2019] [Indexed: 06/09/2023]
Abstract
This study aims to reveal the full potential of ZnO as an ultrafast photofunctional material. Based on nonlocal response theory to incorporate the spatially inhomogeneous quality of the samples coupled with experimental observations of linear and nonlinear optical responses, we establish the ultrafast radiative decay of excitons in ZnO thin films that reaches the speed of excitonic dephasing at room temperature in typical semiconductors at a couple tens of femtoseconds. The consistency between the observed delay-time dependence of the transient-grating signals and the theoretical prediction reveals that the ultrafast radiative decay is due to the synergetic effects of the giant light-exciton interaction volume and the radiative coupling between multicomponent excitons.
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Affiliation(s)
- Takashi Kinoshita
- Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | - Takuya Matsuda
- Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | - Takuya Takahashi
- Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Masayoshi Ichimiya
- Department of Electronic Systems Engineering, The University of Shiga Prefecture, Hikone, Shiga 522-8533, Japan
| | - Masaaki Ashida
- Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yoshiaki Furukawa
- Department of Applied Physics, Osaka City University, Osaka, Osaka 558-8585, Japan
| | - Masaaki Nakayama
- Department of Applied Physics, Osaka City University, Osaka, Osaka 558-8585, Japan
| | - Hajime Ishihara
- Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
- Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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Bamba M, Ishihara H. Entangled-photon generation in nano-to-bulk crossover regime. PHYSICAL REVIEW LETTERS 2010; 105:123906. [PMID: 20867645 DOI: 10.1103/physrevlett.105.123906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Indexed: 05/29/2023]
Abstract
We have theoretically investigated the generation of entangled photons from biexcitons in a semiconductor film with a thickness in the nano-to-bulk crossover regime. In contrast with the cases of quantum dots and bulk materials, we can highly control the generated state of entangled photons through the design of a peculiar energy structure of exciton-photon coupled modes in the thickness range between nanometers and micrometers. Owing to the enhancement of the radiative decay rate of excitons (exciton superradiance), the statistical accuracy of generated photons can be increased beyond the trade-off problem with signal intensity. By implementing an optical cavity structure in the strong-coupling regime, the generation efficiency can be enhanced while maintaining the high statistical accuracy.
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Affiliation(s)
- Motoaki Bamba
- Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
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Ichimiya M, Ashida M, Yasuda H, Ishihara H, Itoh T. Observation of superradiance by nonlocal wave coupling of light and excitons in CuCl thin films. PHYSICAL REVIEW LETTERS 2009; 103:257401. [PMID: 20366280 DOI: 10.1103/physrevlett.103.257401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 05/29/2023]
Abstract
We report the observation of a remarkably strong coupling between light and a multinode-type exciton. The observed radiative decay time reaches the order of 100 fs, which is much faster than the dephasing process of nonradiative scattering. In this high-speed superradiance, the light wave and the excitonic wave in a high-quality thin film form a harmonized wave-wave coupling over a range of multiple wavelengths. This mechanism contradicts the conventional physical description of light-matter interaction based on the long-wavelength approximation.
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Hohenester U, Goldoni G, Molinari E. Dark-state luminescence of macroatoms at the near field. PHYSICAL REVIEW LETTERS 2005; 95:216802. [PMID: 16384169 DOI: 10.1103/physrevlett.95.216802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Indexed: 05/05/2023]
Abstract
We theoretically analyze the optical near-field response of a semiconductor macroatom induced by local monolayer fluctuations in the thickness of a semiconductor quantum well, where the large active volume results in a strong enhancement of the light-matter coupling. We find that in the near-field regime bright and dark excitonic states become mixed, opening new channels for the coupling to the electromagnetic field. As a consequence, ultranarrow luminescence lines appear in the simulated two-photon experiments, corresponding to very long lived excitonic states, which undergo Stark shift and Rabi splitting at relatively small field intensities.
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Affiliation(s)
- Ulrich Hohenester
- Institut für Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, 8010 Graz, Austria.
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