Gain spectroscopy and plasma recombination in CdS

Bohnert, K.; Schmieder, G.; El-Dessouki, S.; Klingshirn, C.

doi:10.1016/0038-1098(78)90039-x

Cited by 25 publications

(17 citation statements)

References 13 publications

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“…The disappearance of the excitonic reflection structures with increasing I,, has already been observed by different authors [7,21 to 241, and is generally regarded as an argument for t>he existence of an EHP [7, 23, 261. We shall t'ry to analyse here the whole reflection spectra for different I,,, since we have realized that parameters deduced only from the modulation of reflectivity AR = Rmax -Rmin and the corresponding photon energies Ahw = hwminhwmax sometimes give a rather poor overall agreement between experiment and theory.…”

Section: Reflectionmentioning

confidence: 87%

Gain and Reflection Spectroscopy and the Present Understanding of the Electron–Hole Plasma in II–VI Compounds

Bohnert¹,

Schmieder²,

Klingshirn³

1980

Physica Status Solidi (b)

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111

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The reflection and gain spectra of CdS and ZnO are investigated as a function of excitation intensity and temperature. For the gain spectroscopy the two beam method and the variation of the excitation strip length are used. The results indicate, that an electron-hole plasma is formed under high excitation, preferentially if small excitation spots are used. The electron-hole plasma comes close to its thermal equilibrium only in especially favourable cases. Excitonic recombination processes are predominant, if larger excitation spots are used.Die Spektren der Reflexion und der optischen Verstarkung werdcn an CdS und ZnO in Abhangigkeit von der Anregungsintensitat und der Temperatur untersucht. Fur die Messung der optischen Verstarkung werden die Zweistrahl-und die Strichlangenmethode eingesetzt. Die Ergebnisse zeigen, daB sich bei hoher Anregung ein Elektron-Loch-Plasma bildet, besonders bei Verwendung kleiner angeregter Gebiete. Es nahert sich aber nur in besonders gunstigen Fallen dem thermischen Gleichgewicht an. Bei groBeren angeregten Gebieten uberwiegen exzitonische Rekombinationsprozesse.

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Section: Reflectionmentioning

confidence: 87%

Gain and Reflection Spectroscopy and the Present Understanding of the Electron–Hole Plasma in II–VI Compounds

Bohnert¹,

Schmieder²,

Klingshirn³

1980

Physica Status Solidi (b)

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111

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“…The CdS material is a highly advantageous model system for our proof of principle experiments, as it emits in the important green spectral range while providing extraordinarily high gain values. 28 We prove dynamical tuning of the NW laser spectra by exploiting the inherent resonator morphology of the NW in combination with the strain induced bandgap modification of the semiconductor material. Results and Discussion.…”

mentioning

confidence: 97%

Dynamical Tuning of Nanowire Lasing Spectra

Zapf¹,

Röder²,

Winkler

et al. 2017

Nano Lett.

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Realizing visionary concepts of integrated photonic circuits, nanospectroscopy, and nanosensing will tremendously benefit from dynamically tunable coherent light sources with lateral dimensions on the subwavelength scale. Therefore, we demonstrate an individual nanowire laser based device which can be gradually tuned by reversible length changes of the nanowire such that uniaxial tensile stress is applied to the respective semiconductor gain material. By straining the device, the spontaneous excitonic emission of the nanowire shifts to lower energies caused by the bandgap reduction of the semiconductor. Moreover, the optical gain spectrum of the nanolaser can be precisely strain-tuned in the high excitation regime. The tuning of the emission does not affect the laser threshold of the device, which is very beneficial for practical applications. The applied length change furthermore adjusts the laser resonances inducing a redshift of the longitudinal modes. Thus, this concept of gradually and dynamically tunable nanolasers enables controlling and modulating the coherent emission on the nanoscale without changing macroscopic ambient conditions. This concept holds therefore huge impact on nanophotonic switches and photonic circuit technology.

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“…Moreover, we apply suitable experimental methods to directly image which transverse modes operate in single nanolasers and determine their influence over laser dynamics within the semiconductor material. Zinc oxide (ZnO) NWs generate robust ultraviolet laser emission at room temperature due to their high optical gain supplied by the formation of an electron–hole plasma. ,,, Here, the intensity of laser emission from individual ZnO NWs with diameters below and above single mode cutoff of ∼180 nm is sampled using a back-focal plane polarization imaging technique, as schematically shown in Figure a (and Supporting Information, Figure S1a; this technique is usually applied to NW arrays in spontaneous emission regime , ). Although fundamental mode lasing was believed to be hardly possible in ZnO NWs thinner than ∼180 nm due insufficient modal-gain and feedback at room temperature, we observe a transverse mode switching from the dominant TE 01 mode to the fundamental HE 11 mode near this cutoff condition (for field plots of the basic modes see the Supporting Information).…”

mentioning

confidence: 99%

Mode Switching and Filtering in Nanowire Lasers

Röder¹,

Sidiropoulos

Buschlinger³

et al. 2016

Nano Lett.

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Coherent light sources confining the light below the vacuum wavelength barrier will drive future concepts of nanosensing, nanospectroscopy, and photonic circuits. Here, we directly image the angular emission of such a light source based on single semiconductor nanowire lasers. It is confirmed that the lasing switches from the fundamental mode in a thin ZnO nanowire to an admixture of several transverse modes in thicker nanowires approximately at the multimode cutoff. The mode competition with higher order modes substantially slows down the laser dynamics. We show that efficient photonic mode filtering in tapered nanowires selects the desired fundamental mode for lasing with improved performance including power, efficiency, and directionality important for an optimal coupling between adjacent nanophotonic waveguides.

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Gain spectroscopy and plasma recombination in CdS

Cited by 25 publications

References 13 publications

Gain and Reflection Spectroscopy and the Present Understanding of the Electron–Hole Plasma in II–VI Compounds

Gain and Reflection Spectroscopy and the Present Understanding of the Electron–Hole Plasma in II–VI Compounds

Dynamical Tuning of Nanowire Lasing Spectra

Mode Switching and Filtering in Nanowire Lasers

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