EPHQUAMHalbleiterepitaxie
Wavelength tunable ultraviolet laser emission via intra-cavity frequency doubling of an AlGaInP vertical external-cavity surface-emitting laser down to 328 nm
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We demonstrate an optically pumped vertical external-cavity surface-emitting laser in a compact v-shaped cavity configuration for frequency doubling to the ultraviolet (UV) spectral range at ∼330 nm. The fundamental red laser emission is realized with a metal-organic vapor-phase epitaxy grown (Ga xIn 1−x) 0.5P 0.5/[(Al xGa 1−x) yIn 1−y] 0.5P 0.5 multi-quantum-well structure. Second harmonic generation is accomplished by using a beta barium borate non-linear crystal to generate maximum UV output powers exceeding 100 mW. By using a birefringent filter, we are able to tune the fundamental laser resonance to realize a maximum tuning range of 7.5 nm of the second harmonic.
Publication:
Wavelength tunable ultraviolet laser emission via intra-cavity frequency doubling of an AlGaInP
vertical external-cavity surface-emitting laser down to 328 nm
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Halbleiterscheibenlaser für Spektroskopieanwendungen im roten und ultravioletten Spektralbereich
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Für die Spektroskopie im roten Spektralbereich sowie im UV stellen AlGaInP-Halbleiterscheibenlaser eine effiziente Ergänzung zu Titan:Saphir-Lasern dar. Die Verwendung eines externen Resonators ermöglicht eine hohe Ausgangsleistung im Dauerstrichbetrieb bei höchster Strahlqualität. Die offene Geometrie erlaubt im Gegensatz zu gewöhnlichen kanten- oder oberflächenemittierenden Halbleiterlasern eine breitbandige Wellenlängendurchstimmung und eine Frequenzverdopplung durch optische Elemente im Resonator. Wir präsentieren im Folgenden die Ergebnisse eines VECSEL-Entwicklungsprojekts.
Publication:
Halbleiterscheibenlaser für Spektroskopieanwendungen im roten und ultravioletten
Spektralbereich
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Transverse-Mode Analysis of Red-Emitting Highly Polarized Vertical-Cavity Surface-Emitting Lasers
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We present experimental investigations of the transverse beam profile and polarization characteristics of GaInP-based oxide-confined vertical-cavity surface-emitting lasers in dependence on the oxide aperture size, mesa size, current, and temperature. We demonstrate that these lasers with aperture diameters of less than 6 µm are required for stable fundamental-mode operation. The influence of operation current and external temperature on the mode shape is investigated. We experimentally present a highly stable linearly polarized GaInP-based microcavity laser emitting at around 655 nm, where the polarization characteristics originate from intrinsic material properties.
Publication:
Transverse-Mode Analysis of Red-Emitting Highly Polarized Vertical-Cavity Surface-Emitting
Lasers
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Short wavelength red-emitting AlGaInP-VECSEL exceeds 1.2 W continuous-wave output power
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We present a vertical external cavity surface-emitting laser system based on a multi-quantum-well structure with 20 compressively strained GaInP quantum wells for an operation wavelength of around 665 nm with a monolithic integrated distributed Bragg reflector. With the help of an intra-cavity diamond heatspreader the laser operates in continuous-wave mode. Operation with a TEM 00 Gaussian beam profile and a beam propagation factor of M² <= 1.05 is shown as well as a high resolution spectrum of the laser line, which shows the etalon effect of the diamond. The laser can be operated at a maximum output power exceeding 1.2 W with a slope efficiency of eta diff = 18%. At maximum output power the wavelength of the laser resonance is at 670 nm, which is shortest reported until now at powers exceeding 1 W. By rotating a birefringent filter in an extended folded cavity arrangement a wavelength tuning of 21 nm was attained.
Publication:
Short wavelength red-emitting AlGaInP-VECSEL exceeds 1.2 W continuous-wave output power
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Low-density InP quantum dots embedded in Ga0.51In0.49P with high optical quality realized by a strain inducing layer
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We present a method to reduce the intrinsically high InP quantum dot density embedded in a Ga 0.51In 0.49P barrier by introducing an InGaAs quantum dot seed layer. The additional strain reduces the total InP quantum dot density by around one order of magnitude from 2x10 10 to 3x10 9 cm -2 but only ~1% of the InP nanostructures seem to be optically active (10 7 cm -2). Therefore, microphotoluminescence measurements could be accomplished without masks. We found resolution-limited photoluminescence linewidths (<100 µeV), good signal-to-noise ratios ( ~ 65), single-photon emission behavior (g (2)((t = 0) = 0.3), and excitonic decay times of typically between 1 and 2 ns. Furthermore the structural quantum dot properties were investigated.
Publication:
Low-density InP quantum dots embedded in Ga
0.51In
0.49P with high optical quality realized by a strain inducing layer
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Optical properties of red emitting self-assembled InP/(Al0.20Ga0.80)0.51In0.49P quantum dot based micropillars
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Using focused ion beam etching techniques, micropillar cavities were fabricated from a high reflective AlAs/AlGaAs distributed Bragg reflector planar cavity containing self-assembled InP quantum dots in (Al 0.20Ga 0.80) 0.51In 0.49P barrier layers. The mode spectra of pillars with different diameters were investigated using micro-photoluminescence, showing excellent agreement with theory. Quality factors of the pillar cavities up to 3650 were observed. Furthermore, for a microcavity pillar with 1.26 um diameter, single-photon emission is demonstrated by performing photon correlation measurements under pulsed excitation. Publication: Optical properties of red emitting self-assembled InP/(Al 0.20Ga 0.80) 0.51In 0.49P quantum dot based micropillars Wolfgang-Michael Schulz, Tim Thomay, Marcus Eichfelder, Moritz Bommer, Michael Wiesner, Robert Roßbach, Michael Jetter, Rudolf Bratschitsch, Alfred Leitenstorfer, and Peter Michler 07 June 2010 / Vol. 18, No. 12 / OPTICS EXPRESS 12543
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Low density MOVPE grown InGaAs QDs exhibiting ultra-narrow single exciton linewidths
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Low density (~10 7 cm -2), small sized InGaAs quantum dots were grown on a GaAs substrate by metal–organic vapor-phase epitaxy and a special annealing technique. The structural quantum dot properties and the influence of the annealing technique was investigated by atomic force microscope measurements. High-resolution micro-photoluminescence spectra reveal narrow photoluminescence lines, with linewidths down to 11 µeV and fine structure splittings of 25 µeV. High signal to noise ratios (~140) and a nearly background free autocorrelation measurement indicate an excellent optical quality and single photon emission behavior. Furthermore, time resolved measurements reveal excitonic decay times typically in the range between 800 and 2300 ps and biexcitonic decay times around 300 ps.
Publication:
Low density MOVPE grown InGaAs QDs exhibiting ultra-narrow single exciton linewidths
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Low Threshold InP/AlGaInP Quantum Dot In-Plane Laser Emitting at 638 nm
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Within this contribution, results for a laser structure consisting of InP quantum dots embedded in an (AlxGa1-x)0.51In0.49P matrix lattice matched to GaAs are presented. The structure was fabricated using metal–organic vapor-phase epitaxy, showing electrically pulsed laser operation at room temperature with a low threshold current density of 870 A/cm2 and a lasing wavelength of 638 nm for a 2000 µm long device with uncoated facets. Optical output powers of more than 55 mW per facet and lasing up to 313 K is demonstrated.
Publication:
Low Threshold InP/AlGaInP Quantum Dot In-Plane Laser Emitting at 638 nm
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Room-temperature lasing of electrically pumped red-emitting InP/(Al0.20Ga0.80)0.51In0.49P quantum dots embedded in a vertical microcavity
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We demonstrate electrically pumped laser light emission in the visible red spectral range using self-assembled InP quantum dots embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. We used common semiconductor laser processing steps to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical wave-guiding and electrical current constriction. Ultra-low threshold of around 10 A/cm2 and room temperature lasing were demonstrated. Additionally, the temperature independence of the threshold current, which was predicted in theory for quantum dot lasers, is displayed.
Publication:
Room-temperature lasing of electrically pumped red-emitting InP/(Al
0.20Ga
0.80)
0.51In
0.49P quantum dots embedded in a vertical microcavity
Contact person: Susanne Weidenfeld |
Optical and structural properties of InP quantum dots embedded in (AlxGa1-x)0.51In0.49P
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Within this work we present optical and structural properties of InP quantum dots embedded in (Al xGa 1-x) 0.51In 0.49P barriers. Atomic force microscopy measurements show a mainly bimodal height distribution with aspect ratios (ratio of width to height) of about 10:1 and quantum dot heights of around 2 nm for the smaller quantum dot class (type A) and around 4 nm for the larger quantum dot class (type B). From ensemble photoluminescence measurements we estimated thermal activation energies of up to 270 meV for the type-A quantum dots, resulting in a 300 times higher luminescence intensity at 200 K in comparison to our InP quantum dots in Ga 0.51In 0.49P at the same emission wavelength. Photon statistic measurements clearly display that InP quantum dots in (Al 0.20Ga 0.80) 0.51In 0.49P emit single photons up to 80 K, making them promising candidates for high-temperature single-photon emitters.
Publication:
Optical and structural properties of InP quantum dots embedded in (Al
xGa
1-x)
0.51In
0.49P
Contact person: Elisabeth Koroknay |
Electrically pumped single-photon emission
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An electrically pumped single-photon emitter in the visible spectral range, working up to 80 K
has been realized using a self-assembled single InP quantum dot embedded in AlGaInP. Aluminum was
added to the barrier material in order to provide a higher QD confinement potential.
Publication:
Electrically pumped single-photon emission in the visible spectral range up to 80 K
Contact person: Elisabeth Koroknay |
Red single-photon emission from an InP/GaInP quantum dot embedded in a planar monolithic microcavity Red single-photon emission from an InP/GaInP quantum dot in a planar microcavity
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Using micro-photoluminescence we demonstrate single-photon emission in the visible (red) spectral range using self-assembled InP quantum dots embedded in a planar microcavity realized by monolithically grown high reflectivity AlGaAs distributed Bragg reflectors. A full width at half maximum of 130 µeV at 5 K was observed from a single quantum dot coupled to the fundamental cavity resonance. Photon correlation measurements performed under continuous wave excitation show a clear antibunching behavior (g²(0)=0.13) as expected for a single-photon emitter. Saturation count rates up to 1.5 MHz (8.1 MHz into the first lens, with an extraction efficiency of 4.1%) were observed.
Publication:
Contact person: Dr. M. Jetter |
Site-controlled pyramidal nanostructures
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We have fabricated site-controlled nitride nanostructures by deposition of GaInN on GaN micro pyramids by selective metal-organic vapor-phase epitaxy on sapphire. The nature of the growth process implies the formation of quantum wells on the sidewalls of the pyramid, quantum wires at its edges and a quantum dot on the tip of the pyramid. The luminescence properties of these structures confirm the existence of regions with different dimensionality.
Publication:
2.
Selective Growth of GaInN Quantum Dot Structures
Related work:
Contact person: Dr. M. Jetter |
Structural and optical characterization of (AlIn)GaN quantum dots
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AlyInxGa1-x-yN quantum dots have been grown by MOVPE on (0001) sapphire substrates and the dependence of the self-assembled QDs density and height on the growth conditions was investigated. A maximum dot density of 4·1010cm-2 was achieved. The optical properties were studied after overgrowing the QDs with a GaN cap layer, where very intense luminescence in the region between 2.4 and 2.8 eV could be found.
Publication:
Structural- and optical characterization of AlyInxGa1-x-yN quantum dots
Contact person: Dr. M. Jetter |
Pulsed layer growth of AlInGaN nanostructures Pulsed layer growth of AlInGaN nanostructures
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A pulsed layer growth mode in the MOVPE was used to fabricate excellent quality AlInGaN nanostructures. The amount of material was varied, resulting in AlInGaN layer thicknesses between nominally 1.5 nm and 6 nm, respectively. Analyzing the material properties by x-ray diffraction (XRD) as well as photoluminescence (PL) spectroscopy the high quality of the deposited material could be confirmed. An energetic shift of the resonance lines from 2.65 eV to 3.33 eV with decreasing well thickness was found which was attributed mainly to the presence of internal electric fields at the AlInGaN/GaN interface. Comparing the luminescence at elevated temperatures, the pulsed layer epitaxy structures reveal a much higher intensity as the conventional grown samples.
Publication:
Pulsed layer growth of AlInGaN nanostructures
Contact person: Dr. M. Jetter |
Epitaxy and processing of red VCSEL Epitaxy and processing of red VCSEL
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Red VCSEL emitting around 660 nm are grown by MOVPE to provide a fast and powerful emitter device for data transmission via polymer optical fibers (POF). The 8-9 µm thick structure consists out of around 180 layers which we control during growth with an in-situ measurement setup to achieve a very high accuracy. By using a heat dissipation model the diameters of the oxide aperture and the mesa could be optimized resulting in continuous-wave lasing operation up to 70°C at 660 nm. In pulsed mode the AlGaInP-based active zone showed lasing up to 170°C. For data transmission the VCSEL were modulated in small-signal modulation up to a bandwidth of 5 GHz. For large-signal modulation we obtained at 1.25 Gbit/s wide open eyes and even at 2.1 Gbit/s a bit error free data transmission was possible.
Publication:
2.
Analog Modulation of 650 nm VCSEL
3.
Rote VCSEL für Hochgeschwindigkeits-Datenübertragung über POF
Contact person: Dr. M. Jetter and Susanne Weidenfeld |
InP quantum dots in the visible spectral range
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InP quantum dots have been grown in the Stranski-Krastanow growth mode by MOVPE. As the surrounding barrier material we used AlxGaInP barriers with different Al-content. With this method we could achieve photoluminescence from red to the green spectral range. By using a novel AlGaInP/AlInP distributed Bragg reflector in the green spectral range we could increase the luminescence intensity by nearly a factor of two.
Publication:
2.
Green Photoluminescence of Single InP-Quantum Dots grown on Al0.66Ga0.33InP/AlInP Distributed
Bragg Reflectors
Contact person: Elisabeth Koroknay |
InP quantum dot molecules
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Larger and smaller InP quantum dots were grown on top of each other on GaInP separated by a GaInP spacer layer. TEM measurements showed that the smaller quantum dot is positioned on top of the underlying larger quantum dot. We observed in power dependent ensemble measurements that for thick spacer layers both ensembles increase independently. For thin spacer layers photoluminescence of the smaller QD layer at 1.89 eV is detected only at high excitation powers indicating a tunnelling process in between the two different QD layers. Time-resolved ensemble measurements confirmed our assumptions.
Publication:
Vertical asymmetric double Quantum Dots
Contact person: Elisabeth Koroknay |