Semiconductor Optics

Klingshirn, C.

doi:10.1007/b138175

Cited by 322 publications

(379 citation statements)

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“…Since laser oscillations are likely caused by the formation of an electron-hole plasma (EHP) at high pumping intensities in single CdS (and ZnO NWs as a comparable NW laser system) [14,16,27,17], the approximately 1.24 times higher absorption for parallel polarization supplies the semiconductor more efficiently with charge carriers. This is further accompanied by a red-shift of the gain profile at the same pumping powers due to band gap renormalization effects in the EHP [28]. The red-shift of the gain profile, which in our case is achieved by changing the polarization from α = ± 90° to α = 0° and proven by the high polarization ratio for the low energy mode B, is usually obtained for an increase in pumping intensity under constant polarization [14,17].…”

Section: Resultssupporting

confidence: 51%

Polarization features of optically pumped CdS nanowire lasers

Röder¹,

Ploss²,

Kriesch³

et al. 2014

J. Phys. D: Appl. Phys.

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Abstract. High quality CdS nanowires suspended in air were optically pumped both below and above the lasing threshold. The polarization of the pump laser was varied while the nanowire emission was monitored in a 'head-on' measurement geometry. Highest pump-efficiency and most efficient absorption of the pump radiation are demonstrated for an incident electric field being polarized parallel to the nanowire axis. This polarization dependence was observed both above the lasing threshold and in the regime of amplified spontaneous emission. Measured Stokes parameters of the nanowire emission reveal that due to the onset of lasing the degree of polarization rapidly increases from approximately 15% to 85 %. Both, Stokes parameters and degree of polarization of the nanowire lasing emission are independent of the excitation polarization.

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Section: Resultssupporting

confidence: 51%

Polarization features of optically pumped CdS nanowire lasers

Röder¹,

Ploss²,

Kriesch³

et al. 2014

J. Phys. D: Appl. Phys.

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“…This feature is neither reproduced by theory nor assigned to vibronic replicas (51), as the latter would be strongly polarization dependent. We tentatively assign this feature to a polaritonic stopband (59,60): a strong, characteristic reflection found between the transversal and the longitudinal exciton-polariton branches. Similar features are observed in quasione-dimensional polymer crystals and TCNQ crystals (61)(62)(63)(64).…”

Section: Resultsmentioning

confidence: 87%

Low-lying excited states in crystalline perylene

Rangel

Rinn

Sharifzadeh

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Organic materials are promising candidates for advanced optoelectronics and are used in light-emitting diodes and photovoltaics. However, the underlying mechanisms allowing the formation of excited states responsible for device functionality, such as exciton generation and charge separation, are insufficiently understood. This is partly due to the wide range of existing crystalline polymorphs depending on sample preparation conditions. Here, we determine the linear optical response of thin-film single-crystal perylene samples of distinct polymorphs in transmission and reflection geometries. The sample quality allows for unprecedented high-resolution spectroscopy, which offers an ideal opportunity for judicious comparison between theory and experiment. Excellent agreement with firstprinciples calculations for the absorption based on the GW plus Bethe-Salpeter equation (GW-BSE) approach of many-body perturbation theory (MBPT) is obtained, from which a clear picture of the low-lying excitations in perylene emerges, including evidence of an exciton-polariton stopband, as well as an assessment of the commonly used Tamm-Dancoff approximation to the GW-BSE approach. Our findings on this well-controlled system can guide understanding and development of advanced molecular solids and functionalization for applications. molecular crystals | many-body perturbation theory | excited states | spectroscopy

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“…Among them, the substitutional Cu 2+ model proposed first by Dingle 9 has received much attention due to the distinct spectral features of a sharp zero-phonon line (ZPL) and a broad longitudinal optical (LO) phonon sideband at low temperature. [13][14][15] Taking into account only the coupling between one LO phonon mode and one electronic transition, Kuhnert and Helbig 13 employed a Poission distribution, I n ) S n e -S /n!, to fit the line shape of the green emission band and then obtained a Huang-Rhys factor of S ) 6.5. It is well-known that the Poission distribution simply gives only a backbone of the absorption or luminescence line shape of the electron-LO phonon coupling system.…”

mentioning

confidence: 99%

Green Luminescence Band in ZnO: Fine Structures, Electron−Phonon Coupling, and Temperature Effect

Shi

et al. 2006

J. Phys. Chem. B

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The green emission band of ZnO has been investigated by both experimental and theoretical means. Two sets of equally separated fine structures with the same periodicity (close to the longitudinal optical (LO) phonon energy of ZnO) are well resolved in the low-temperature broad green emission spectra. As the temperature increases, the fine structures gradually fade out and the whole green emission band becomes smooth at room temperature. An attempt to quantitatively reproduce the variable-temperature green emission spectra using the underdamped multimode Brownian oscillator model taking into account the quantum dissipation effect of the phonon bath is done. Results show that the two electronic transitions strongly coupled to lattice vibrations of ZnO lead to the observed broad emission band with fine structures. Excellent agreement between theory and experiment for the entire temperature range enables us to determine the dimensionless Huang-Rhys factor characterizing the strength of electron-LO phonon coupling and the coupling coefficient of the LO and bath modes.Historically, zinc oxide (ZnO) is a technologically important material thanks to its piezoelectric characteristics and other unique properties such as its transparency up to the near ultraviolet (UV). It is also known that ZnO is a semiconductor with a wide band gap (∼3.37 eV) and an extremely large exciton binding energy (as high as 60 meV). 1 Recently, it has attracted renewed research interest due to its newly-found application potential in exciton-type short-wavelength optoelectronic devices that are functional at room temperature or above. 1-3 Despite a long history of industrial applications, a clear understanding of some fundamental properties of ZnO still remains elusive. 1,2,4-7 For example, contention still surrounds the microstructural origin. 4,8 To date, very different defect origins, such as the substitutional Cu 2+ on the zinc site, 9 oxygen vacancy (V O ), 10 zinc vacancy (V Zn ), 11 and interstitial zinc (Zn i ), 12 have been suggested to be responsible for the green band of ZnO. Among them, the substitutional Cu 2+ model proposed first by Dingle 9 has received much attention due to the distinct spectral features of a sharp zero-phonon line (ZPL) and a broad longitudinal optical (LO) phonon sideband at low temperature. [13][14][15] Taking into account only the coupling between one LO phonon mode and one electronic transition, Kuhnert and Helbig 13 employed a Poission distribution, I n ) S n e -S /n!, to fit the line shape of the green emission band and then obtained a Huang-Rhys factor of S ) 6.5. It is well-known that the Poission distribution simply gives only a backbone of the absorption or luminescence line shape of the electron-LO phonon coupling system. Broadening due to acoustic-phonon-bath dissipation and the temperature effect cannot be accounted for in the model. Moreover, in addition to the first set of structures, the second set of structures with the same periodicity was also observed but its origin is not yet understood. 9,...

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Semiconductor Optics

Cited by 322 publications

References 0 publications

Polarization features of optically pumped CdS nanowire lasers

Polarization features of optically pumped CdS nanowire lasers

Low-lying excited states in crystalline perylene

Green Luminescence Band in ZnO: Fine Structures, Electron−Phonon Coupling, and Temperature Effect

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