Michael Wiesner

Room-temperature lasing of electrically pumped red-emitting InP/(Al0.20Ga0.80)0.51In0.49P quantum dots embedded in a vertical microcavity

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.

Optical properties of red emitting self-assembled InP/(Al0.20Ga0.80)0.51In0.49P quantum dot based micropillars

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(0.20)Ga(0.80))(0.51)In(0.49)P 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 mum diameter, single-photon emission is demonstrated by performing photon correlation measurements under pulsed excitation.

Influence of the oxide aperture radius on the mode spectra of (Al,Ga)As vertical microcavities with electrically excited InP quantum dots

In this letter, we report about mode characteristics of microcavity lasers with red-emitting InP quantum dots. The mode spectra and the quality factor of devices with different oxide aperture sizes are analyzed. The lateral mode confinement in the electrical devices is defined via oxide apertures. We found a good agreement between a simple analytical modeling of the mode structure and measurements, which allows to adjust the design of future devices. The quality factors show an analogous behavior as etched micropillars. The enhanced intensity of the higher order modes compared to the fundamental mode can be explained with the current density distribution within the device favoring higher order modes.

Transverse-Mode Analysis of Red-Emitting Highly Polarized Vertical-Cavity Surface-Emitting Lasers

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.

Epitaxially Grown Indium Phosphide Quantum Dots on a Virtual Ge Substrate Realized on Si(001)

An ultrathin virtual Ge substrate (GeVS) with low defect density was realized on CMOS-compatible Si(001) by molecular beam epitaxy. On top, III–V layers were deposited by metal–organic vapor-phase epitaxy, at which diffusion of Ge was successfully suppressed. Nonclassical light emitters, based on InP quantum dots (QDs), were realized on a thin GaAs buffer (thickness ≈ 1 µm). The quantum dots show emission in the red spectral region, meeting the range of the highest detection efficiency of silicon avalanche photodiodes. The decay dynamics and emission characteristics of single QDs were investigated. Autocorrelation measurements prove single-photon emission with a value of g(2)(0)=0.32.

AlGaInP‐based Vertical‐Cavity Surface‐Emitting Lasers for Sensoring and Polarization Switching

We present a detailed analysis of the transverse beam profile and the polarization characteristics of red‐emitting oxide‐confined vertical‐cavity surface‐emitting lasers (VCSELs). We demonstrate that oxide aperture sizes smaller than 6 μm are required for emission in fundamental mode. We further show first steps towards integrating beam shaping optics directly into the top mirror of the VCSEL.

Approaches for III/V Photonics on Si

We investigated different approaches to overcome difficulties in III/V‐on‐Si heteroepitaxy, namely growth on compliant substrates and virtual Ge substrates, both realized on top of Si substrates, and in addition, directly on Si. The prospect of this work was the realization of a light emitter on standard Si(100) substrate, capable of being integrated in established industrial processes.

Low threshold and room-temperature lasing of electrically pumped red-emitting InP/(Al0.20Ga0.80)0.51In0.49P quantum dots

In this letter, we report on laser light emission in the red spectral range. Self-assembled InP quantum dots being electrically pumped were embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. Common semiconductor laser processing steps were used to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical transverse mode confinement and electrical current constriction. Ultra-low threshold current densities of around 10A/cm2 and room temperature lasing were achieved.

Low threshold electrically pumped red emitting InP/Al 0.20 GaInP quantum dot vertical microcavity laser

Using quantum dots (QDs) as gain medium for semiconductor laser, theory has predicted excellent properties such as low laser thresholds or broad gain spectra [1]. Especially microdisk structures and microcavities, for example vertical-cavity surface-emitting laser (VCSEL), provide very low threshold operation in the submilliampere regime [2] and smallest sensitivity of wavelength and threshold current changes with temperature if QDs were used [3]. For various applications, as for emitters for on-board interconnects or polymer optical fiber communication, it is preferable to operate at short wavelength, especially in the red spectral range.