Additional Waves and Polariton Dispersion in CdS Crystals

Makarenko, I. V.; Uraltsev, I. N.; Киселев, В. А.

doi:10.1002/pssb.2220980243

Cited by 62 publications

(8 citation statements)

References 11 publications

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“…exciton-polaritons. 20,60,84,85,87,[109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128] The new quasi-particles are represented in the energy vs. wave-vector dispersion by the lower and upper polariton branch, respectively. There is a similarity with the bonding and anti-bonding molecular levels that arise from the interaction of resonant orbitals of two atoms.…”

Section: Exciton-polaritons In Macroscopic Crystals Of Znomentioning

confidence: 99%

ZnO nanowire lasers

2011

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The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review.

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Section: Exciton-polaritons In Macroscopic Crystals Of Znomentioning

confidence: 99%

ZnO nanowire lasers

2011

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“…Dispersion curves of the transverse exciton (dotted curve) and the polariton (thin solid curves) were derived using parameters of the exciton translational mass M7-=2.3mo and the LT splitting EL ~"£ , r == 5.7 meV [11]. The open circles correspond to the quantized exciton states of CdS, CdSe [12,13], and CuCl [14]. In their reflection and transmission spectra, both even and odd n states were observed in the energy region of E < EL, and double spacing appeared only when E > E^.…”

Section: Optical Selection Rule and Oscillator Strength Of Confined Ementioning

confidence: 99%

Optical selection rule and oscillator strength of confined exciton system in CuCl thin films

et al. 1993

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Transmission and absorption spectra of CuCl epitaxial films are studied. Many structures are observed over the Z3 exciton region, corresponding to the quantization condition K" ^nnlL with odd n (K n : wave number). The absence of the states with even n is interpreted in terms of the parity selection rule in the confined exciton system. The value of the oscillator strength for the nth exciton is found to be proportional to Lin 1 for odd n and zero for even «, in accordance with theoretical expectation. As a polariton system, this belongs to a simple regime of long wavelength approximation.PACS numbers: 73.20.Dx, 68.55.Bd, 71.35,+z, 71.36.+C Quantum confinement effects of excitons in semiconductor systems with reduced dimensions have attracted considerable attention because of their potential application to nonlinear optical devices, and as a means of exploring the basic physics of the quantized excitonic states. The qualitative behavior of the exciton in confined systems can be characterized by the ratio of a film thickness L to the Bohr radius as of the exciton. In a quantum well with Lias ^ 1, the electron and hole levels are separately quantized in discrete subbands, leading to increases in both the binding energy and the oscillator strength of the exciton. In this confinement regime, the oscillator strength is independent of the electron and the hole quantum numbers (n e ,n n ), and the excitonic transitions obey the selection rule of An s=: n e -nh = 0.These properties of the exciton in quantum wells have been extensively studied in III-V compound systems both in theory and experiment [l]. For thin films outside the quantum well regime, the center-of-mass (cm.) motion of the exciton is quantized, while the relative motion is essentially identical to that in the bulk except for a possible distortion near the surfaces [2]. When long wavelength approximation (LWA) holds, L<£X (X: photon wavelength), this confined system can be regarded as an assembly of local oscillators characterized by the quantized exciton energy E n and its ^-dependent oscillator strength f n , where n is the quantum number of the exciton. Optical transitions are expected to obey the parity selection rule that only the transitions with odd quantum number n are allowed. The properties of cm. confinement have been studied in heterostructures of II-VI [3-6] and III-V [2,7] compounds. Alternating strengths of the resonant structures have been observed in luminescence excitation spectra [3-6] and luminescence spectra [7]. These spectra were analyzed in terms of the interference between the upper and lower polaritons (UP, LP) [8,9], but an analysis in terms of {/"} has not been done, probably because of the ambiguity in obtaining {f n } from luminescence measurements.Compared to the III-V and II-VI compounds, CuCl has a large binding energy (-190 meV) and a small Bohr radius (~7 A) of the exciton. The electron-hole Coulomb interaction will be strong enough to maintain the bulklike electron-hole relative motion, down to surprisingly small film thic...

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“…At the same time, the data presented by different authors differ very much in the near band edge region were the lasing modes are observed. At these short wavelengths the measurements are markedly affected by strong absorption, exciton resonances and the interference of additional waves 19,20 resulting in an interference fringe structure significantly different from the classical Fabry-Pérot one.…”

Section: Refractive Index Dispersion Deduced From Lasing Modes In Znomentioning

confidence: 97%

Refractive index dispersion deduced from lasing modes in ZnO microtetrapods

Ursaki

Zalamai

Tiginyanu

et al. 2009

Applied Physics Letters

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High optical quality, well end leg faceted ZnO microtetrapods sustaining lasing modes with quality factors of 2500–3000 have been grown by carbothermal chemical vapor deposition. It is shown that lasing is due to longitudinal Fabry–Pérot modes in individual tetrapod legs and the analysis of the wavelength position of these modes is an effective instrument for the investigation of temperature dependence of the refractive index dispersion in the region of exciton resonances. The dispersion of the ZnO refractive index is experimentally determined in the temperature interval from 10 to 300 K and is compared with available literature data.

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Additional Waves and Polariton Dispersion in CdS Crystals

Cited by 62 publications

References 11 publications

ZnO nanowire lasers

ZnO nanowire lasers

Optical selection rule and oscillator strength of confined exciton system in CuCl thin films

Refractive index dispersion deduced from lasing modes in ZnO microtetrapods

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