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C Ell,
P Brick,
M Hübner,
E S Lee,
O Lyngnes,
J P Prineas,
G Khitrova,
H M Gibbs,
M Kira,
F Jahnke,
S W Koch,
D G Deppe, D L Huffaker
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ABSTRACT: The nonlinear optical response of semiconductor microcavities in the nonpertubative regime is studied in resonant single-beam-transmission and pump-probe experiments. In both cases a pronounced third transmission peak lying spectrally between the two normal modes is observed. A fully quantized theory is essential for the agreement with the experimental observations, demonstrating that quantum fluctuations leading to intraband polarizations are responsible for this effect.
Physical Review Letters 01/2001; 85(25):5392-5. · 7.37 Impact Factor
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ABSTRACT: The photon density required for the saturation of normal-mode coupling in oxide-apertured nanocavities is measured to be 90 photons/μm2 by pump-probe experiments. The photon number is only 300 for a semiconductor nanocavity with a 2 μm diameter aluminum-oxide aperture, drastically reduced from 200 000 for a 50 μm waist on a planar microcavity. © 2001 American Institute of Physics.
Journal of Applied Physics. 12/2000; 89(1):807-809.
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ABSTRACT: Rate equations are used to show that the modulation response of quantum dot lasers can be limited by entropy change due to carrier relaxation from a wetting layer. The entropy change is due to the difference in the spectral density of quantum states between the two-dimensional wetting layer and the zero-dimensional quantum dot. When limited by this effect, the laser’s 3 dB modulation response becomes strongly temperature dependent. © 2000 American Institute of Physics.
Applied Physics Letters 11/2000; 77(21):3325-3327. · 3.84 Impact Factor
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ABSTRACT: Data are presented on continuous wave operation of two-stack quantum dot lasers designed with reduced temperature sensitivity in their threshold. The InAs quantum dots are designed to have a wide energy spacing (/spl sim/102 meV) between the ground and first excited radiative transitions. Selectively oxidized stripe lasers have continuous wave threshold currents as low as 1.2 mA for 2 /spl mu/m wide stripes and minimum threshold current densities of 26 A/cm/sup 2/ for 13-/spl mu/-m wide stripes. Broad area lasers have continuous wave threshold current densities as low as 40 A/cm/sup 2/, even for p-up mounting. Ground state lasing is obtained up to the highest temperature measured of 326 K.
IEEE Photonics Technology Letters 10/2000; · 2.19 Impact Factor
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ABSTRACT: Continuous-wave operation of InGaAs quantum dot lasers is studied.
A very low threshold current of 460 μA is achieved at 200 K for a 5
μm×1170 μm oxide-confined stripe laser. For a larger stripe
width of 11 μm, a threshold current density of 5.2A/cm<sup>2</sup> is
demonstrated. The characteristic threshold temperature is -700 K in the
temperature range of 14-200 K, and drops rapidly around room temperature
Electronics Letters 08/2000; · 0.96 Impact Factor
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ABSTRACT: Summary form only given. Recent progress in microfabrication involving, etching processes makes it possible to engineer three-dimensional (3D) nanostructures from MBE-grown planar Fabry-Perot micro-cavities. The optical mode is confined laterally by implementing a thin dielectric (native oxide) aperture layer on top of the cavity spacer. The sample under investigation consists of a 16 period GaAs/AlAs bottom mirror, a λ GaAs spacer, and a 4 period ZnSe/MgF<sub>2</sub> dielectric mirror on top of the oxide aperture. The aperture diameters range from 1 to 7 μm. A high-quality 85 Å InGaAs single quantum well is located in the anti-node of the spacer.
Quantum Electronics and Laser Science Conference, 2000. (QELS 2000). Technical Digest; 06/2000
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ABSTRACT: The understanding of material quality and luminescence
characteristics of InGaAs-GaAs quantum dots (QD's) is advancing rapidly.
Intense work in this area has been stimulated by the recent
demonstration of lasing from a QD active region at the technologically
important 1.3-μm wavelength from a GaAs-based heterostructure laser.
Already, several groups have achieved low-threshold currents and current
densities at room temperature from In(Ga)As QD active regions that emit
at or close to 1.3 μm. In this paper, we discuss crystal growth, QD
emission efficiency, and low-threshold lasing characteristics for
1.3-μm InGaAs-GaAs QD active regions grown using submonolayer
depositions of In, Ga, and As. Oxide-confinement is effective in
obtaining a low-threshold current of 1.2 mA and threshold-current
density of 19 A/cm<sup>2</sup> under continuous-wave (CW) room
temperature (RT) operation. At 4 K, a remarkably low threshold-current
density of 6 A/cm<sup>2</sup> is obtained
IEEE Journal of Selected Topics in Quantum Electronics 06/2000; · 3.78 Impact Factor
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ABSTRACT: Data are presented on low threshold, 1.3-/spl mu/m oxide-confined InGaAs-GaAs quantum dot lasers. A very low continuous-wave threshold current of 1.2 mA with a threshold current density of 28 A/cm/sup 2/ is achieved with p-up mounting at room temperature. For slightly larger devices the continuous-wave threshold current density is as low as 19 A/cm/sup 2/.
IEEE Photonics Technology Letters 04/2000; · 2.19 Impact Factor
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ABSTRACT: Data are presented characterizing a low-threshold vertical-cavity surface-emitting laser designed for cryogenic operation. A threshold current of 12 /spl mu/A and current density of 25 A/cm/sup 2/ are obtained at 77 K with the low-loss cavity design. From 77 K to 160 K, the threshold increases linearly with temperature, but only approximately tracks the detuning of the cavity resonance from the minimum energy transition of the quantum well. At 77 K, we estimate that the 25-A/cm/sup 2/ threshold current density is about twice that required for transparency.
IEEE Photonics Technology Letters 02/2000; · 2.19 Impact Factor
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ABSTRACT: Summary form only given. Research on GaAs-based quantum dot (QD)
lasers operating at 1.3 μm wavelength has been rapidly advancing
since the demonstrations of room-temperature operation in pulsed-mode
and continuous wave (CW) operation. Native oxide confinement is of
interest for this type of laser, similar to that used for quantum well
edge-emitting lasers and quantum dot vertical cavity surface emitting
lasers. The native oxide confinement is especially interesting due to
the lateral “built-in” electronic confinement potentials
that confine the current in lateral direction. We report on the
room-temperature CW operation of oxide-confined single-layer InGaAs QD
lasers with very low threshold current of 1.2 mA. The low threshold
operation is achieved due to low optical waveguide loss of the native
oxide
Lasers and Electro-Optics, 2000. (CLEO 2000). Conference on; 02/2000
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ABSTRACT: Spontaneous emission characteristics from apertured microcavities
are studied using quantum-dot light emitters. Spatial averaging over the
emitter positions within the apertures significantly impacts the
measured lifetime changes, but lifetime changes due to the aperture
modes are still readily observed. A maximum increase of a factor of ~2.5
over the cavity-free emission rate is measured. We argue that, for a
narrow bandwidth emitter, the microcavity enhancement can lead to
nearly-single-mode and high-speed operation even in the spontaneous
regime
IEEE Journal of Quantum Electronics 11/1999; · 1.88 Impact Factor
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ABSTRACT: The spontaneous emission spectra and lasing characteristics of
long-wavelength (1.3-μm) quantum-dot lasers are studied. It is found
experimentally that nonradiative recombination can dominate the
room-temperature efficiency and limit threshold, By describing the
quantum-dot spectral emission as due to energy levels of a
two-dimensional harmonic oscillator, rate equations are developed to
account for the temperature-dependent spontaneous and lasing
characteristics
IEEE Journal of Quantum Electronics 09/1999; · 1.88 Impact Factor
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ABSTRACT: Very low threshold vertical-cavity surface-emitting lasers are demonstrated using intracavity contacts, an upper dielectric Bragg reflector, and an undoped lower AlAs-GaAs Bragg reflector. The undoped lower mirror allows the demonstration of the highest differential efficiency yet achieved for sub-100-/spl mu/A threshold, which is 60% for a 67-/spl mu/A threshold. Devices with smaller output coupling show threshold current densities as low 98 A/cm/sup 2/, and a minimum threshold current of 23 /spl mu/A for a small aperture.
IEEE Photonics Technology Letters 09/1999; · 2.19 Impact Factor
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ABSTRACT: Data are presented on the room-temperature, continuous-wave ground state lasing characteristics from a quantum dot vertical-cavity surface-emitting laser. A threshold current of 703 μA is obtained for a 10-μm-diameter oxide aperture using a three-stack active region, with the lasing wavelength of ∼1.06 μm. Lasing is obtained for apertures as small as 2 μm square with threshold current of 268 μA. The threshold conditions are discussed with an emphasis on the spontaneous and stimulated decay rates due to resonant excitation. © 1999 American Institute of Physics.
Applied Physics Letters 07/1999; 75(1):22-24. · 3.84 Impact Factor
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ABSTRACT: Recently ground-state 1.3 μm wavelength lasing has been
demonstrated at room temperature from GaAs-based uncoated
heterostructure lasers using an InGaAs quantum dot (QD) active region.
Despite low threshold current density at 77 K, lasing at the higher
temperatures shows a rapid increase in threshold occurring above 200 K.
In this talk we present data characterizing the QD laser's threshold
temperature dependence, and show that it comes mainly from nonradiative
recombination from the QD higher energy levels and wetting layer. The
results suggest that very low threshold current density can be obtained
at room temperature once nonradiative recombination is eliminated
Quantum Electronics and Laser Science Conference, 1999. QELS '99. Technical Digest. Summaries of Papers Presented at the; 06/1999
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ABSTRACT: Spontaneous lifetime control is demonstrated using very small apertured microcavities, with quantum-dot light emitters used to obtain electronic confinement within the aperture. A factor of 2.3 increase in the averaged spontaneous emission rate is achieved due to the optical confinement. The enhancement/inhibition ratio of the spontaneous emission rate tracks the optical mode size and spectral response of the apertured microcavity. © 1999 American Institute of Physics.
Applied Physics Letters 04/1999; 74(17):2408-2410. · 3.84 Impact Factor
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ABSTRACT: Data are presented on the temperature dependence of 1.3-/spl mu/m wavelength quantum-dot (QD) lasers. A low-threshold current density of 90 A/cm/sup 2/ is achieved at room temperature using high reflectivity coatings. Despite the low-threshold current density, lasing at the higher temperatures is limited by nonradiative recombination with a rapid increase in threshold current occurring above /spl sim/225 K. Our results suggest that very low threshold current density (/spl les/20 A/cm/sup 2/) can be achieved at room temperature from 1.3-/spl mu/m QD lasers, once nonradiative recombination is eliminated.
IEEE Photonics Technology Letters 04/1999; · 2.19 Impact Factor
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ABSTRACT: Data are presented on modified spontaneous emission rates in quantum dot microcavity arrays. Three-dimensional optical confinement is achieved using apertured microcavities with square aperture sizes varied from 5 to 1 μm on a side. A maximum measured increase in the on-resonance spontaneous emission rate over that off resonance is ∼50%, and we identify this enhancement with apertured modes of the microcavity. Oscillations in the spontaneous emission rate versus wavelength correspond to spectral resonances in the higher order aperture modes. © 1999 American Institute of Physics.
Journal of Applied Physics. 03/1999; 85(6):3383-3385.
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ABSTRACT: Presents data characterizing room-temperature, continuous-wave (CW) ground state lasing from a 1.07 μm quantum dot (QD) VCSEL, and the luminescence characteristics from QDs confined in small oxide apertures. For the QD VCSEL, the threshold current of 703 μA is obtained for a 10 μm diameter oxide aperture using a three-stack active region, with the lasing wavelength of ~1.06 μm. Threshold currents as low as 268 μA are achieved from a 2 μm square aperture VCSEL. The threshold conditions are discussed with an emphasis on the spontaneous and stimulated decay rates due to resonant excitation. For very small apertures that provide strong optical confinement, the spontaneous lifetime is altered due to the Purcell effect
Nanostructures and Quantum Dots/WDM Components/VCSELs and Microcavaties/RF Photonics for CATV and HFC Systems, 1999 Digest of the LEOS Summer Topical Meetings; 02/1999
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ABSTRACT: Currently, there is high interest in extended wavelength emission from GaAs-based devices for compatibility with AlAs/GaAs distributed Bragg reflectors (DBRs) and selective oxidation for 1.3 μm VCSELs. Our approach is using InGaAs quantum dots (QDs) which emit from 1.0 to 1.3 μm depending on the growth technique. However, the optical gain from a single layer of QDs is relatively small making a 1.3 μm QD VCSEL difficult to achieve. We present results on 1.3 μm edge emitters based on InGaAs QDs as well as 1.07 μm ground state VCSELs to demonstrate the great potential of the QDs for 1.3 μm VCSELs
Nanostructures and Quantum Dots/WDM Components/VCSELs and Microcavaties/RF Photonics for CATV and HFC Systems, 1999 Digest of the LEOS Summer Topical Meetings; 02/1999
