Ultrafast exciton dynamics in ZnO: Excitonic versus electron-hole plasma lasing

Shih, Tina; Mazur, Eric; Richters, Jan‐Peter; Gutowski, J.; Voss, T.

doi:10.1063/1.3549614

Cited by 28 publications

(19 citation statements)

References 27 publications

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“…The difference, , for photonic lasers suggest much broader output pulses. The pulse widths of 4-5 ps for 200 nm are consistent with the EHP decay time for ZnO 31 . Interestingly for larger photonic nanowire diameters, a change in output polarization indicates that a different transverse mode lases, and the value of suggests a different gain mechanism to the EHP one occurs, which should be explored in future work.…”

supporting

confidence: 49%

“…5b). The initial decay is faster as two output pulses compete for gain, whereas the slower decay corresponds only to the second pulse's use of residual excited carriers, , which is indicative of the EHP recombination time 31 . We emphasize that the transition from fast to slow decay corresponds directly to the maximum in the double-pump response, , observed…”

mentioning

confidence: 99%

“…1b). Under weak optical pumping, spontaneous photoluminescence and gain occur below the band-edge near 3.24 eV through either exciton-exciton scattering or via optical phonon scattering ( 72 meV) 31,32 . Meanwhile, under strong excitation above the Mott density, carrier screening causes exciton dissociation into an electron hole plasma (EHP), which together with band-gap renormalization, provides gain as far below the band-edge as ~3.19 eV 33 .…”

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confidence: 99%

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Ultrafast plasmonic nanowire lasers near the surface plasmon frequency

et al. 2014

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Lasers that use metallic cavities have emerged recently as a new class of light source [1][2][3] . Plasmonic lasers achieve optical confinement and feedback using surface plasmon polaritons (SPPs), quasiparticles of photons and electrons at metal-dielectric interfaces, which can be amplified by suitable optical gain media 4 . The high gain of inorganic crystalline semiconductors is typically necessary to overcome fast electron scattering in metals (~10 fs), which leaves plasmonic lasers with high parasitic cavity loss. Nevertheless, SPPs offer the capability to reduce optical mode sizes far below the scale of the vacuum wavelength 3,5-8 leading to compact lasers that can generate extremely focussed optical excitations on potentially ultrafast time scales 1,9 with applications in Raman sensing

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Ultrafast plasmonic nanowire lasers near the surface plasmon frequency

et al. 2014

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“…With the pumping power increase, the peak intensity of the main band becomes stronger and stronger and the full width at half maximum (FWHM) of the band becomes narrower and narrower. As the pumping power density increases to 7.28 MW cm −2 , a new sharp emission (524.8 nm) appears at the low energy side of the main band, with a narrower FWHM of 0.53 nm, meaning the occurrence of the exciton–exciton scattering [ 33 ] and the highly coherent resonance lasing oscillation in the cavity. As the inset exhibits in Figure 2b, the intensity of the PL peak at 524.8 nm increases nonlinearly with the pumping power density and the threshold of the junction is around 5.02 MW cm −2 .…”

Section: Resultsmentioning

confidence: 99%

Multipoint Nanolaser Array in an Individual Core–Shell CdS Branched Nanostructure

Huang

Ding

et al. 2020

Advanced Optical Materials

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Nanoscale laser arrays are attractive for their potential applications in highly integrated nanodevices, which are always obtained by nanowire arrays with complicated fabrication techniques. Here, a quite different nanolaser array is successfully realized based on a highly ordered core–shell CdS branched nanostructure with implanted Sn nanoparticles in junctions that split the individual multichannel nanostructures to various microcavities with effective light confinement and oscillation, thus to achieve a multipoint nanolaser array. Under the excitation of an ultraviolet laser, the strong band‐edge emission can be well reflected between Sn nanoparticles at junctions and effectively scattered into branch segments due to Sn nanoparticles existence in junctions, furthermore oscillating in various microcavities along trunks or branches to form multipoint lasing from Fabry‐Pérot (F‐P) mode with a quality factor up to 990 and the low threshold at around 3.78 MW cm−2. The corresponding fluorescent microscope images further demonstrate the formation of multipoint F‐P lasing at various segments. The theoretical simulation indicates that implanted Sn nanoparticles work as hot point to enhance the confinement of light around the Sn centers. The existence of surface plasmon from the Sn metal particles is further confirmed by the polarization dependent photoluminescence measurement. The results provide a new way to realize nanolaser arrays.

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“…The lasers under study consist of single‐crystal, wurtzite ZnO nanowires lying on a silver film with a 10 nm thick magnesium fluoride (MgF 2 ) spacer layer, as shown in Figure . The wide‐bandgap semiconductor ZnO ( E g ≈ 3.37 eV) emits in the ultraviolet regime (≈380 nm), which is close to the surface plasmon frequency of a silver/air interface . For optimizing the epitaxial growth of silver films, C ‐axis mica is chosen as a substrate due to its extremely clean and atomically flat surface, low cost, and well lattice‐matched crystalline structure with silver .…”

Section: Introductionmentioning

confidence: 99%

Influence of Silver Film Quality on the Threshold of Plasmonic Nanowire Lasers

Sidiropoulos

Liu

et al. 2017

Advanced Optical Materials

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Such lasers enable the investigation of enhanced light-matter interactions and can have large impact on applications in the fields of nonlinear optics, sensing, and optical communications. [7][8][9][10][11][12] However, metal-based lasers suffer from high losses, caused by the inherent electron scattering in metals, which leads to an increased lasing threshold and limits their use in applications. To minimize losses and thus improve their performance, it has been suggested to use metal films of high quality which ideally have an ultraflat surface with a high crystalline perfection. [1,[13][14][15][16] Typically, metal films are deposited by thermal evaporation or sputtering. However, the quality of thin metal films is strongly dependent on the growth conditions [17,18] and without careful optimization they are polycrystalline with a surface roughness on the order of a few nanometers. [19,20] Alternatively, the template-stripping method can be used to obtain ultraflat metal films, [21,22] however stripped films are usually still polycrystalline. Optimally, the metal films should be a single crystal with an atomically flat surface over a large area. Epitaxial growth and chemical synthesis have been demonstrated as an effective way to obtain monocrystalline metal films for reducing the metal losses. [13,17,[23][24][25][26] It is known that a high deposition rate and high substrate temperature are essential to obtain epitaxial growth of continuous and flat monocrystalline metal films based on a general deposition system (thermal evaporator or sputtering system). [17,19] In this work, first the film fabrication process for both template-stripping and epitaxial growth based on a thermal evaporator was optimized. Subsequently, the performance of room temperature hybrid plasmonic ZnO nanowire lasers with different silver films (general polycrystalline silver films, template-stripped silver films, and monocrystalline silver films) was characterized.The lasers under study consist of single-crystal, wurtzite ZnO nanowires lying on a silver film with a 10 nm thick magnesium fluoride (MgF 2 ) spacer layer, as shown in Figure 1. [27] The widebandgap semiconductor ZnO (E g ≈ 3.37 eV) emits in the ultraviolet regime (≈380 nm), which is close to the surface plasmon frequency of a silver/air interface. [6,[28][29][30][31] For optimizing the epitaxial growth of silver films, C-axis mica is chosen as a substrate due to its extremely clean and atomically flat surface, low cost, and well lattice-matched crystalline structure with In recent years, the field of plasmonics has become dependent on the ability to maximize the quality of metal films. In particular, plasmonic lasers will require a metal loss as low as possible in order to minimize their operational threshold if they are to find applications. In this article, the findings of recent studies, which report reduced thresholds in plasmonic lasers incorporating high quality metal films with both ultraflat surfaces and high crystallinity, are reassessed. In particular, the role of d...

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Ultrafast exciton dynamics in ZnO: Excitonic versus electron-hole plasma lasing

Cited by 28 publications

References 27 publications

Ultrafast plasmonic nanowire lasers near the surface plasmon frequency

Ultrafast plasmonic nanowire lasers near the surface plasmon frequency

Multipoint Nanolaser Array in an Individual Core–Shell CdS Branched Nanostructure

Influence of Silver Film Quality on the Threshold of Plasmonic Nanowire Lasers

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