21 results on '"Thomas Stettner"'
Search Results
2. Direct Coupling of Coherent Emission from Site-Selectively Grown III–V Nanowire Lasers into Proximal Silicon Waveguides
- Author
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Thomas Stettner, Gregor Koblmüller, Daniel Ruhstorfer, Jochen Bissinger, T. Kostenbader, Michael Kaniber, H. Riedl, and Jonathan J. Finley
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010302 applied physics ,Coupling ,Materials science ,business.industry ,Nanowire ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Injection locking ,Semiconductor ,law ,0103 physical sciences ,Optoelectronics ,Direct coupling ,Electrical and Electronic Engineering ,Photonics ,0210 nano-technology ,business ,Lasing threshold ,Biotechnology - Abstract
Semiconductor nanowire (NW) lasers are nanoscale coherent light sources that exhibit a small footprint, low-threshold lasing characteristics, and properties suitable for monolithic and site-selective integration onto Si photonic circuits. An important milestone on the way toward novel on-chip photonic functionalities, such as injection locking of laser emission and all-optical switching mediated by coherent optical coupling and feedback, is the integration of individual, deterministically addressable NW lasers on Si waveguides with efficient coupling and mode propagation in the underlying photonic circuit. Here, we demonstrate the monolithic integration of single GaAs-based NW lasers directly onto lithographically defined Si ridge waveguides (WG) with low threshold power densities of 19.8 μJ/cm2 when optically excited. The lasing mode of individual NW lasers is shown to couple efficiently into propagating modes of the underlying orthogonal Si WG, preserving the lasing characteristics during mode propagati...
- Published
- 2017
3. Tuning Lasing Emission towards Long Wavelengths in GaAs-(In,Al)GaAs Core-Multishell Nanowires
- Author
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Thomas Stettner, Paul Schmiedeke, Andreas Thurn, Markus Döblinger, Jochen Bissinger, Sonja Matich, Daniel Ruhstorfer, Hubert Riedl, Jonathan J. Finley, and Gregor Koblmueller
- Published
- 2019
4. Tuning Lasing Emission towards Long Wavelengths in GaAs-(In, Al)GaAs Core-Multishell Nanowires on Silicon
- Author
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Jochen Bissinger, Paul Schmiedeke, Andreas Thurn, Thomas Stettner, Gregor Koblmueller, Jonathan J. Finley, Daniel Ruhstorfer, and Markus Doeblinger
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Materials science ,Silicon ,business.industry ,Nanowire ,Physics::Optics ,chemistry.chemical_element ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Laser ,7. Clean energy ,law.invention ,Condensed Matter::Materials Science ,Wavelength ,chemistry ,law ,Optoelectronics ,Photonics ,Coaxial ,business ,Waveguide ,Lasing threshold - Abstract
Recent demonstrations of direct integration of GaAs-based nanowire lasers on Si photonic circuits exhibited efficient in-coupling of lasing emission to proximal waveguides - however, transmission in the Si waveguide suffered from high absorption losses. To overcome these issues, we develop here GaAs-(In, Al)GaAs-based nanowire lasers with lasing emission tunable to longer wavelengths ( $> 1.1\ \mu \mathrm{m}$ ) by using coaxial InGaAs/AlGaAs MQW (multi-quantum well) structures as active gain media. We illustrate also the sensitive interplay between design and growth parameters of the MQW structure on the resulting emission wavelength and lasing threshold.
- Published
- 2019
- Full Text
- View/download PDF
5. Optimized waveguide coupling of an integrated III-V nanowire laser on silicon
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Gregor Koblmüller, Jochen Bissinger, Jonathan J. Finley, Daniel Ruhstorfer, and Thomas Stettner
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010302 applied physics ,Silicon photonics ,Materials science ,Silicon ,business.industry ,Nanowire ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,law.invention ,Semiconductor ,chemistry ,law ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Lasing threshold ,Waveguide ,Refractive index - Abstract
The recent integration of III-V semiconductor nanowire (NW) lasers on silicon waveguides marked a key step toward their usage as coherent light sources for future silicon photonics applications. However, the low index contrast between III-V semiconductors and silicon results in a weak modal reflectivity, calling for improved design structures that enable both low-threshold lasing and good in-coupling efficiency into waveguides. Here, we perform numerical simulations to explore how the alternating refractive index of a silicon waveguide with a thin SiO2 interlayer can be used to significantly improve the reflectivity at the III-V–silicon interface to values of up to 83%. We further investigate the frequency dependencies of the end-facet reflectivity and in-coupling efficiency as a function of the nanowire and waveguide dimensions. Our results are kept general by the normalization to the nanowire radius R and show for a waveguide width of 2.75⋅ R a maximum coupling efficiency of 50%. Variations in waveguide height or SiO2 interlayer thickness by ± 0.1 ⋅ R increase the coupling efficiency by a factor of 2, with little effect on the end-facet reflectivity. Ultimately, a prototypical NW-laser structure consisting of a 1.3-μm emitting InGaAs MQW active region in a core-multishell structure was simulated, showing an optimized low-threshold gain of
- Published
- 2019
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- View/download PDF
6. Tuning Lasing Emission toward Long Wavelengths in GaAs-(In,Al)GaAs Core-Multishell Nanowires
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Andreas Thurn, Gregor Koblmüller, Markus Döblinger, Daniel Ruhstorfer, Megan O. Hill, Thomas Stettner, Lincoln J. Lauhon, T. Kostenbader, H. Riedl, Michael Kaniber, Sonja Matich, Jonathan J. Finley, Jochen Bissinger, and Paul Schmiedeke
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Materials science ,Photoluminescence ,Band gap ,Nanowire ,Physics::Optics ,Bioengineering ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,law ,0103 physical sciences ,General Materials Science ,Quantum well ,010302 applied physics ,business.industry ,Mechanical Engineering ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,Semiconductor ,Quantum dot ,Optoelectronics ,0210 nano-technology ,business ,Lasing threshold - Abstract
Semiconductor nanowire (NW) lasers are attractive as integrated on-chip coherent light sources with strong potential for applications in optical communication and sensing. Realizing lasers from individual bulk-type NWs with emission tunable from the near-infrared to the telecommunications spectral region is, however, challenging and requires low-dimensional active gain regions with an adjustable band gap and quantum confinement. Here, we demonstrate lasing from GaAs-(InGaAs/AlGaAs) core-shell NWs with multiple InGaAs quantum wells (QW) and lasing wavelengths tunable from ∼0.8 to ∼1.1 μm. Our investigation emphasizes particularly the critical interplay between QW design, growth kinetics, and the control of InGaAs composition in the active region needed for effective tuning of the lasing wavelength. A low shell growth temperature and GaAs interlayers at the QW/barrier interfaces enable In molar fractions up to ∼25% without plastic strain relaxation or alloy intermixing in the QWs. Correlated scanning transmission electron microscopy, atom probe tomography, and confocal PL spectroscopy analyses illustrate the high sensitivity of the optically pumped lasing characteristics on microscopic properties, providing useful guidelines for other III-V-based NW laser systems.
- Published
- 2018
7. He-Ion Microscopy as a High-Resolution Probe for Complex Quantum Heterostructures in Core-Shell Nanowires
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Thomas Stettner, Bernhard Loitsch, Lincoln J. Lauhon, Sonja Matich, Jonathan J. Finley, Nari Jeon, J. Becker, Yeanitza Trujillo Gottschalk, Christian Pöpsel, Gregor Koblmüller, Alexander W. Holleitner, Marcus Altzschner, and Markus Döblinger
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010302 applied physics ,Materials science ,Nanostructure ,business.industry ,Mechanical Engineering ,Superlattice ,Resolution (electron density) ,Nanowire ,Bioengineering ,Heterojunction ,02 engineering and technology ,General Chemistry ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Condensed Matter::Materials Science ,Semiconductor ,0103 physical sciences ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Quantum well - Abstract
Core-shell semiconductor nanowires (NW) with internal quantum heterostructures are amongst the most complex nanostructured materials to be explored for assessing the ultimate capabilities of diverse ultrahigh-resolution imaging techniques. To probe the structure and composition of these materials in their native environment with minimal damage and sample preparation calls for high-resolution electron or ion microscopy methods, which have not yet been tested on such classes of ultrasmall quantum nanostructures. Here, we demonstrate that scanning helium ion microscopy (SHeIM) provides a powerful and straightforward method to map quantum heterostructures embedded in complex III-V semiconductor NWs with unique material contrast at ∼1 nm resolution. By probing the cross sections of GaAs-Al(Ga)As core-shell NWs with coaxial GaAs quantum wells as well as short-period GaAs/AlAs superlattice (SL) structures in the shell, the Al-rich and Ga-rich layers are accurately discriminated by their image contrast in excellent agreement with correlated, yet destructive, scanning transmission electron microscopy and atom probe tomography analysis. Most interestingly, quantitative He-ion dose-dependent SHeIM analysis of the ternary AlGaAs shell layers and of compositionally nonuniform GaAs/AlAs SLs reveals distinct alloy composition fluctuations in the form of Al-rich clusters with size distributions between ∼1-10 nm. In the GaAs/AlAs SLs the alloy clustering vanishes with increasing SL-period (5 nm-GaAs/4 nm-AlAs), providing insights into critical size dimensions for atomic intermixing effects in short-period SLs within a NW geometry. The straightforward SHeIM technique therefore provides unique benefits in imaging the tiniest nanoscale features in topography, structure and composition of a multitude of diverse complex semiconductor nanostructures.
- Published
- 2018
8. Direct coupling of coherent emission from site-selectively grown III-V nanowire lasers into proximal silicon waveguides (Conference Presentation)
- Author
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Michael Kaniber, Thomas Stettner, H. Riedl, Gregor Koblmueller, Tobias Kostenbader, Jochen Bissinger, Jonathan J. Finley, and Daniel Ruhstorfer
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Active laser medium ,Materials science ,business.industry ,Physics::Optics ,Laser ,law.invention ,Laser linewidth ,Semiconductor ,law ,Optoelectronics ,Stimulated emission ,Photonics ,business ,Lasing threshold ,Quantum well - Abstract
Semiconductor nanowire (NW) lasers are nanoscale coherent light sources that exhibit a small footprint, low-threshold lasing characteristics, and properties suitable for monolithic integration onto Si photonic circuits. An important milestone on the way towards novel on-chip photonic functionalities is the integration of individual, deterministically addressable NW lasers on Si waveguides with efficient coupling and mode propagation in the underlying photonic circuit. Here, we demonstrate the monolithic integration of single GaAs-based NW lasers directly onto lithographically defined Si ridge waveguides (WG). Subject to optical excitation, the observed lasing behavior shows clear “s-shape”-characteristics, linewidth narrowing and threshold values down to 19.8±1 µJ/cm², which is the lowest value reported to date for this kind of integrated lasing structure. The lasing mode of individual NW lasers is shown to couple efficiently into propagating modes of the underlying orthogonal Si WG, preserving the spectral characteristics during mode pro-pagation in the WG, and in good agreement with Finite-Difference Time-Domain (FDTD) simulations. Using a WG structure with a series of mask openings along the central mode propagation axis, we further illustrate the out-coupling properties of both spontaneous and stimulated emission and demonstrate propagation of the lasing mode over distances > 60 µm, despite absorption in the silicon dominating the propagation losses. By replacing the bulk GaAs as the active gain medium by InxGa1-xAs quantum wells, the emission wavelength can be shifted towards telecommunication bands in order to reduce the absorption losses in silicon. These results pave the way for future on-chip monolithic integration of III-V NW lasers onto silicon based optoelectronic circuits.
- Published
- 2018
9. Redshift of lasing modes in time-resolved spectra for GaAs-AlGaAs core-shell nanowires lasers on silicon (Conference Presentation)
- Author
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Juan Salvador Dominguez Morales, Tomasz J. Ochalski, Thomas Stettner, Gregor Koblmueller, Shumithira Gandan, David P. Williams, and Jonathan J. Finley
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Photoluminescence ,Materials science ,business.industry ,Nanolaser ,Nanowire ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,010309 optics ,Semiconductor ,Picosecond ,0103 physical sciences ,Optoelectronics ,Spontaneous emission ,Stimulated emission ,0210 nano-technology ,business ,Lasing threshold - Abstract
III-V semiconductor nanowires (NW) are being considered as future coherent light sources for optoelectronic chips due to their small footprint and high refractive index. The 1D confinement also results in a natural Fabry-Perot resonance cavity. However, the most important feature is the feasibility of direct growth on Si platform. The research carried out in this work consists of time-resolved photoluminescence (TRPL) spectra at different optical excitation powers and temperatures for single GaAs-AlGaAs core-shell nanowire nanolasers on Silicon. The carrier dynamics response for a single nanolaser below and above the threshold is obtained for different sets of temperatures. The lifetime corresponding to the excitation power below the threshold is of the order of hundreds of picoseconds at all low temperature intervals (4K to 60K). With increasing pump power, the decay time gets shorter until the threshold is achieved. At this point, two lifetimes are obtained for the lasing modes, one of the order of tens of picoseconds (stimulated emission) and another of the order of hundreds of picoseconds (spontaneous emission). A redshift in time-resolved spectra (2-3nm in an interval of 700ps) is measured which disappears at higher temperatures (after 60K). This redshift is a result of the change in refractive index caused by a decrease in carrier density with time. This effect disappears at higher temperatures due to the increase of non-radiative recombination.
- Published
- 2018
- Full Text
- View/download PDF
10. Silicon Waveguide Coupled III-V Nanowire Lasers with Epitaxial Gain Control
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Jonathan J. Finley, Thomas Stettner, Andreas Thurn, Daniel Ruhstorfer, H. Riedl, Gregor Koblmüller, T. Kostenbader, Michael Kaniber, and Jochen Bissinger
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Coupling ,Materials science ,Silicon ,business.industry ,Nanowire ,Physics::Optics ,chemistry.chemical_element ,Epitaxy ,Laser ,Waveguide (optics) ,law.invention ,chemistry ,law ,Automatic gain control ,Optoelectronics ,business ,Lasing threshold - Abstract
We demonstrate lasing from individual GaAs-based NWs integrated onto Si ridge waveguides. In addition, proof-of-principle coupling emission to the Si WG is shown, with propagation distances of the lasing mode exceeding > 60 pm
- Published
- 2018
11. Long-term mutual phase locking of picosecond pulse pairs generated by a semiconductor nanowire laser
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Thomas Stettner, Kathy Lüdge, Gregor Koblmüller, Jonathan J. Finley, Michael Kaniber, A. Regler, S. Sterzl, Benjamin Lingnau, and Benedikt Mayer
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Materials science ,Active laser medium ,Science ,FOS: Physical sciences ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,law.invention ,Optics ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Ultrafast laser spectroscopy ,Laser power scaling ,010306 general physics ,Distributed feedback laser ,Multidisciplinary ,Condensed Matter - Mesoscale and Nanoscale Physics ,business.industry ,General Chemistry ,021001 nanoscience & nanotechnology ,Laser ,ddc ,Picosecond ,Photonics ,0210 nano-technology ,business ,Ultrashort pulse ,Optics (physics.optics) ,Physics - Optics - Abstract
The ability to generate phase-stabilized trains of ultrafast laser pulses by mode-locking underpins photonics research in fields, such as precision metrology and spectroscopy. However, the complexity of conventional mode-locked laser systems has hindered their realization at the nanoscale. Here we demonstrate that GaAs-AlGaAs nanowire lasers are capable of emitting pairs of phase-locked picosecond laser pulses with a repetition frequency up to 200 GHz when subject to incoherent pulsed optical excitation. By probing the two-pulse interference spectra, we show that pulse pairs remain mutually coherent over timescales extending to 30 ps, much longer than the emitted laser pulse duration (≤3 ps). Simulations performed by solving the optical Bloch equations produce good quantitative agreement with experiments, revealing how the phase information is stored in the gain medium close to transparency. Our results open the way to phase locking of nanowires integrated onto photonic circuits, optical injection locking and applications, such as on-chip Ramsey comb spectroscopy., Although nanolasers have been an active field of research for over a decade, mode-locking on the nanoscale has not been achieved yet. Here, Mayer et al. show that semiconductor nanowire lasers can emit pairs of phase-locked picosecond pulses when the nanowires are incoherently pumped.
- Published
- 2017
12. Advances in semiconductor nanowire lasers
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Bernhard Loitsch, Gerhard Abstreiter, Jonathan J. Finley, Gregor Koblmüller, Benedikt Mayer, Michael Kaniber, and Thomas Stettner
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010302 applied physics ,Amplified spontaneous emission ,Materials science ,business.industry ,Ti:sapphire laser ,Physics::Optics ,02 engineering and technology ,Laser pumping ,021001 nanoscience & nanotechnology ,01 natural sciences ,Semiconductor laser theory ,Condensed Matter::Materials Science ,Quantum dot laser ,0103 physical sciences ,Optoelectronics ,Semiconductor optical gain ,0210 nano-technology ,business ,Quantum well ,Tunable laser - Abstract
We present recent advances on monolithically integrated GaAs-nanowire lasers on silicon, and further demonstrate epitaxial gain control to tune threshold power density and lasing wavelength using low-dimensional systems. Ultimately, we also show schemes for ultrafast emission and unique phase coherence properties for future phase-locked lasers.
- Published
- 2016
13. Monolithic integration and epitaxial gain control of GaAs-based nanowire lasers on Si
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Gerhard Abstreiter, Gregor Koblmüller, Thomas Stettner, Benedikt Mayer, Bernhard Loitsch, Michael Kaniber, and Jonathan J. Finley
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Amplified spontaneous emission ,Materials science ,business.industry ,Physics::Optics ,Laser pumping ,Gain-switching ,Condensed Matter::Materials Science ,Quantum dot laser ,Optoelectronics ,Semiconductor optical gain ,Laser power scaling ,business ,Lasing threshold ,Tunable laser - Abstract
Here, we present our recent highlights on monolithically integrated GaAs-nanowire lasers on silicon and further demonstrate capabilities in epitaxial gain control to tune threshold power density and lasing wavelength. Importantly, the investigated NW lasers reveal high spontaneous emission coupling factors (beta-factor) of 0.2, and ultrafast temporal emission down to 250 GHz. Introduction of coaxial multiple-quantum wells in the NW lasers allows to tune threshold power density, opening a gateway for advanced epitaxial gain control. Ultimately, we also demonstrate continuous-wave lasing under optical excitation of the GaAs-nanowire lasers with very sharp emission linewidths, lower required pump power and negligible heating effects.
- Published
- 2016
14. Laser intensity effects in carrier-envelope phase-tagged time of flight-photoemission electron microscopy
- Author
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H. Bian, S. Nobis, Ulf Kleineberg, Hassan Ouacha, C. Späth, Thomas Stettner, Y. Y. Yang, Bernhard Loitsch, J. Schmidt, F. Schertz, Jonathan J. Finley, Matthias Kübel, Soo Hoon Chew, Abdallah M. Azzeer, and Alexander Gliserin
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Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Attosecond ,Carrier-envelope phase ,General Engineering ,Phase (waves) ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,Electron ,Physics and Astronomy(all) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Condensed Matter::Materials Science ,Time of flight ,Photoemission electron microscopy ,Optics ,Ionization ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,business ,Phase modulation - Abstract
A time of flight-photoemission electron microscope is combined with a single-shot stereographic above-threshold ionization phase meter for studying attosecond control of electrons in tailored plasmonic nanostructures spatially and energetically via a carrier-envelope phase tagging technique. First carrier-envelope phase-resolved measurements of gold nanoparticles on gold plane and surface roughness from a gold film show an apparent carrier-envelope phase modulation with a period of π. This modulation is found to originate from an intensity dependence of the photoelectron spectra and the carrier-envelope phase measurement rather than from an intrinsic carrier-envelope phase dependence, which is confirmed by simulations. This useful finding suggests that intensity tagging should be considered for phase tagging experiments on plasmonic nanostructures with low carrier-envelope phase sensitivity in order to correct for the intensity-related carrier-envelope phase artifact.
- Published
- 2016
15. Lattice-Matched InGaAs-InAlAs Core-Shell Nanowires with Improved Luminescence and Photoresponse Properties
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Julian, Treu, Thomas, Stettner, Marc, Watzinger, Stefanie, Morkötter, Markus, Döblinger, Sonja, Matich, Kai, Saller, Max, Bichler, Gerhard, Abstreiter, Jonathan J, Finley, Julian, Stangl, and Gregor, Koblmüller
- Subjects
energy conversion efficiency ,Letter ,strain ,InGaAs nanowires ,photoluminescence ,catalyst-free selective area growth ,HRXRD - Abstract
Core–shell nanowires (NW) have become very prominent systems for band engineered NW heterostructures that effectively suppress detrimental surface states and improve performance of related devices. This concept is particularly attractive for material systems with high intrinsic surface state densities, such as the low-bandgap In-containing group-III arsenides, however selection of inappropriate, lattice-mismatched shell materials have frequently caused undesired strain accumulation, defect formation, and modifications of the electronic band structure. Here, we demonstrate the realization of closely lattice-matched radial InGaAs–InAlAs core–shell NWs tunable over large compositional ranges [x(Ga)∼y(Al) = 0.2–0.65] via completely catalyst-free selective-area molecular beam epitaxy. On the basis of high-resolution X-ray reciprocal space maps the strain in the NW core is found to be insignificant (ε < 0.1%), which is further reflected by the absence of strain-induced spectral shifts in luminescence spectra and nearly unmodified band structure. Remarkably, the lattice-matched InAlAs shell strongly enhances the optical efficiency by up to 2 orders of magnitude, where the efficiency enhancement scales directly with increasing band offset as both Ga- and Al-contents increase. Ultimately, we fabricated vertical InGaAs−InAlAs NW/Si photovoltaic cells and show that the enhanced internal quantum efficiency is directly translated to an energy conversion efficiency that is ∼3–4 times larger as compared to an unpassivated cell. These results highlight the promising performance of lattice-matched III–V core–shell NW heterostructures with significant impact on future development of related nanophotonic and electronic devices.
- Published
- 2015
16. GaAs–AlGaAs core–shell nanowire lasers on silicon: invited review
- Author
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Thomas Stettner, Benedikt Mayer, Gerhard Abstreiter, Gregor Koblmüller, and Jonathan J. Finley
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010302 applied physics ,business.industry ,Nanowire ,Single-mode optical fiber ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Optical pumping ,Semiconductor ,law ,0103 physical sciences ,Materials Chemistry ,Optoelectronics ,Spontaneous emission ,Electrical and Electronic Engineering ,Photonics ,0210 nano-technology ,business ,Lasing threshold - Abstract
Semiconductor nanowire (NW) lasers provide significant potential to create a new generation of lasers and on-chip coherent light sources by virtue of their ability to operate as single mode optical waveguides at the nanoscale. Due to their unique geometry, a major benefit lies also in the feasibility for direct integration on silicon (Si), enabling III–V-on-Si NW lasers that could fuel applications in optical interconnects and data communication. In this review, we describe the state-of-the-art and recent progress in GaAs–AlGaAs based NW lasers emitting in the near infrared (NIR) spectral region, with a specific emphasis on integration on a Si platform. First, we explore design rules for the photonic properties in GaAs NW waveguides based on finite difference time domain calculations. The lasing characteristics of GaAs–AlGaAs core–shell NW lasers are then investigated under various different optical pumping schemes ranging from pulsed to continuous wave excitation. We further review recent activities on the realization of low-dimensional quantum heterostructures inside NW cavities as a means to tune lasing wavelength, gain and threshold properties. Ultimately, we describe schemes for monolithic integration of GaAs-based NW lasers directly on Si and show how such vertical nanocavity lasers are excellent candidates for low-threshold lasing, high spontaneous emission coupling (high β-factor lasers), and ultrafast emission characteristics.
- Published
- 2017
17. Coaxial GaAs-AlGaAs core-multishell nanowire lasers with epitaxial gain control
- Author
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Julia Winnerl, Philipp Zimmermann, Gregor Koblmüller, Gerhard Abstreiter, Sonja Matich, Markus Döblinger, Thomas Stettner, Benedikt Mayer, Jonathan J. Finley, Michael Kaniber, Bernhard Loitsch, H. Riedl, and A. Regler
- Subjects
010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Nanowire ,Physics::Optics ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,law.invention ,Gallium arsenide ,Optical pumping ,chemistry.chemical_compound ,Laser linewidth ,chemistry ,law ,0103 physical sciences ,Optoelectronics ,Coaxial ,0210 nano-technology ,business ,Lasing threshold ,Quantum well - Abstract
We demonstrate the growth and single-mode lasing operation of GaAs-AlGaAs core-multishell nanowires (NW) with radial single and multiple GaAs quantum wells (QWs) as active gain media. When subject to optical pumping lasing emission with distinct s-shaped input-output characteristics, linewidth narrowing and emission energies associated with the confined QWs are observed. Comparing the low temperature performance of QW NW laser structures having 7 coaxial QWs with a nominally identical structure having only a single QW shows that the threshold power density reduces several-fold, down to values as low as ∼2.4 kW/cm2 for the multiple QW NW laser. This confirms that the individual radial QWs are electronically weakly coupled and that epitaxial design can be used to optimize the gain characteristics of the devices. Temperature-dependent investigations show that lasing prevails up to 300 K, opening promising new avenues for efficient III–V semiconductor NW lasers with embedded low-dimensional gain media.
- Published
- 2016
18. Trade-off between morphology, extended defects, and compositional fluctuation induced carrier localization in high In-content InGaN films
- Author
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James Zi-Jian Ju, Fabian Schuster, Gregor Koblmüller, Martin Stutzmann, Bernhard Loitsch, and Thomas Stettner
- Subjects
Diffraction ,Materials science ,Photoluminescence ,Condensed matter physics ,Homogeneity (physics) ,X-ray crystallography ,Wide-bandgap semiconductor ,Analytical chemistry ,General Physics and Astronomy ,Spectroscopy ,Flux ratio ,Molecular beam epitaxy - Abstract
We elucidate the role of growth parameters (III/N flux ratio, temperature TG) on the morphological and structural properties, as well as compositional homogeneity and carrier localization effects of high In-content (x(In) > 0.75) In–polar InGaN films grown by plasma–assisted molecular beam epitaxy (PAMBE). Variations in III/N flux ratio evidence that higher excess of In yields higher threading dislocation densities as well as larger compositional inhomogeneity as measured by x-ray diffraction. Most interestingly, by variation of growth temperature TG we find a significant trade-off between improved morphological quality and compositional homogeneity at low–TG (∼450–550 °C) versus improved threading dislocation densities at high–TG (∼600–630 °C), as exemplified for InGaN films with x(In) = 0.9. The enhanced compositional homogeneity mediated by low–TG growth is confirmed by systematic temperature-dependent photoluminescence (PL) spectroscopy data, such as lower PL peakwidths, >5× higher PL efficiency (less...
- Published
- 2014
19. 4. Cassiodors Name
- Author
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Thomas Stettner
- Subjects
Linguistics and Language ,History ,Literature and Literary Theory ,Classics ,Language and Linguistics - Published
- 1926
20. Waveguide Coupling of an Integrated Nanowire Laser on Silicon with Enhanced End-Facet Reflectivity
- Author
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Jochen Bissinger, Daniel Ruhstorfer, Thomas Stettner, Gregor Koblmueller, and Jonathan J. Finley
- Subjects
010309 optics ,0103 physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences - Full Text
- View/download PDF
21. GaAs–AlGaAs core–shell nanowire lasers on silicon: invited review.
- Author
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Gregor Koblmüller, Benedikt Mayer, Thomas Stettner, Gerhard Abstreiter, and Jonathan J Finley
- Subjects
GALLIUM arsenide ,ALUMINUM compounds ,SEMICONDUCTOR nanowires ,STRUCTURAL shells ,LASER beams ,SILICON - Abstract
Semiconductor nanowire (NW) lasers provide significant potential to create a new generation of lasers and on-chip coherent light sources by virtue of their ability to operate as single mode optical waveguides at the nanoscale. Due to their unique geometry, a major benefit lies also in the feasibility for direct integration on silicon (Si), enabling III–V-on-Si NW lasers that could fuel applications in optical interconnects and data communication. In this review, we describe the state-of-the-art and recent progress in GaAs–AlGaAs based NW lasers emitting in the near infrared (NIR) spectral region, with a specific emphasis on integration on a Si platform. First, we explore design rules for the photonic properties in GaAs NW waveguides based on finite difference time domain calculations. The lasing characteristics of GaAs–AlGaAs core–shell NW lasers are then investigated under various different optical pumping schemes ranging from pulsed to continuous wave excitation. We further review recent activities on the realization of low-dimensional quantum heterostructures inside NW cavities as a means to tune lasing wavelength, gain and threshold properties. Ultimately, we describe schemes for monolithic integration of GaAs-based NW lasers directly on Si and show how such vertical nanocavity lasers are excellent candidates for low-threshold lasing, high spontaneous emission coupling (high β-factor lasers), and ultrafast emission characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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