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Semiconductor nanostructures of various material systems are heavily researched for information processing applications as single-photon sources for communication and as a spin memory for storage. Here, exciton, electron, and hole properties in single InAs/InP asymmetric quantum dots (quantum dashes) emitting in a broad spectral range from 0.8 to above 1 eV are studied experimentally and theoretically. Experiments using magneto-microphotoluminescence allowed us to determine g-factor tensor components and diamagnetic coefficients. The growth-axis exciton g-factor is in a 0.0–2.9 range with a constant hole g-factor of 4.5 and variation governed by electron contribution. The in-plane g-factor is more stable with the size of the nanostructure exhibiting values of around −0.7 and −1.6 for holes and electrons, respectively. The diamagnetic coefficients are [Formula: see text] and [Formula: see text] in the growth and in-plane directions, respectively. Simulations based on the eight-band k⋅p model qualitatively reproduce the key experimental features, including the vanishing of the inverse fine-structure splitting of bright exciton at around 3 T, making these structures prospective for the generation of entangled photons.

Quantum-dot-based semiconductor saturable absorber mirrors (SESAMs) with fast response times were developed by molecular beam epitaxy (MBE). Using quantum dots (QDs) in the absorber region of the SESAMs instead of quantum wells, enables additional degrees of freedom in the design, the control of saturation parameters and the recovery dynamics. However, if one wants to integrate such a SESAM element into semiconductor surface emitting lasers such as a mode-locked integrated external-cavity surface-emitting laser (MIXSEL), the saturable absorber layers have to withstand a longer high-temperature growth procedure for the epitaxial formation of distributed Bragg reflectors (DBR). Typically defect related SESAMs will be annealed at those growth temperatures and lose their high-speed performance. Here we present a systematic study on the growth parameters and post-growth annealing of SESAMs based on high-quality In

Static and dynamic properties of InP-based 1.55 µm quantum dot (QD) lasers were investigated. Due to the reduced size inhomogeneity and a high dot density of the newest generation of 1.55 µm QD gain materials, ridge waveguide lasers (RWG) exhibit improved temperature stability and record-high modulation characteristics. Detailed results are shown for the temperature dependence of static properties including threshold current, voltage-current characteristics, external differential efficiency and emission wavelength. Similarly, small and large signal modulations were found to have only minor dependences on temperature. Moreover, we show the impact of the active region design and the cavity length on the temperature stability. Measurements were performed in pulsed and continuous wave operation. High characteristic temperatures for the threshold current were obtained with T

We have observed gain-coupled distributed feedback (DFB) laser emission from CdZnSe/(Zn,Mg)(S,Se) structures at room temperature. First order DFB gratings with periods in the 90 nm range were defined by maskless Ga + -implantation using a focused ion beam technique. For optical pumping a lasing threshold of about 100 kW/cm 2 was found. The DFB emission is characterized by single mode emission and a temperature dependence of ΔE/ΔT = -0.11 meV/K, reduced by a factor of four compared to the spontaneous emission. From the Bragg condition a wavelength dispersion of the effective refractive index of Δn eff /Δλ = -0.23 x 10 -2 nm -1 and a temperature variation of the refractive index of Δn eff /ΔT = 1.7 x 10 -4 K -1 can be deduced.

The time‐resolved photoluminescence experiment has been used to examine temperature dependent dynamics in the quantum well‐quantum dots tunnel injection structures. The obtained pictures of the photoluminescence kinetics for the reference quantum dots and tunnel injection structures indicate a very different relaxation scenario influenced strongly by the temperature dependent phenomena. We point out the role of the phonon bath which affects the back tunneling and carriers escape processes from the quantum dots in the tunnel injection structures.

We present the first experimental evidence for the existence of strongly localized photonic modes due to random fluctuations in the dielectric constant in a two dimensional planar microcavity.

Electrically pumped gain‐coupled distributed feedback lasers with first order gratings have been fabricated on a (Ga,In)As/(Al,Ga)As separate confinement heterostructure by focused ion beam implantation and epitaxial overgrowth. The lasers are operating at room temperature at wavelengths around 950 nm. All investigated devices show single longitudinal mode emission at all operating conditions.

First order gain and index coupled distributed feedback (DFB) gratings were realized in ZnSe‐based laser structures using direct implantation with a focused ion beam for gain‐modulated structures and conventional electron beam lithography for index modulation. With both technologies, gratings with periods below 90 nm could be achieved, permitting DFB emission in the blue spectral range. Fine tuning of the emission wavelength in steps of 0.14 nm is demonstrated by sampled DFB gratings based on a periodic modulation of the resonator period.

Argon ions at an energy of 50 keV were implanted in patterned GaInAs/GaAs quantum well structures to investigate the lateral broadening of the implantation induced defect profile. In order to study the influence of ion channeling on the lateral spread of the damage distribution, implantations were carried out along channeling axes and along random directions. The degradation of the photoluminescence emission intensity of the laterally damaged quantum well layers was measured as a function of the implantation mask width. The experimental results were modeled by using a simple diffusion calculation, which considers the diffusivity of the electron‐hole pairs beneath the implantation mask. This model allows the evaluation of an effective lateral straggling length for channeling as well as for random implantations. In comparison to randomly implanted samples, a clearly reduced lateral spread of the damage profile could be determined for implantations along the [100]‐ or the [110]‐axis of the crystal.

A lot of knowledge about the formation of InAs or InGaAs quantum dots on GaAs based materials was obtained within the last decade and high quality quantum dot lasers could be realized with emission wavelengths between I and 1.3 /spl mu/m. But the realization of quantum dot lasers well beyond 1.3 /spl mu/m is still difficult. Very recently first device results of self-assembled InAs nanostructures on InP based materials with emission wavelengths between 1.4 and 1.8 /spl mu/m were reported. This new type of quantum dot gain material offers the opportunity to take advantage of dot specific properties like broad band amplification, low threshold current and reduced chirp factor within the long communication wavelength range of 1.45-1.65 /spl mu/m. In this paper the influence of the surface composition and of growth parameters on the formation of InAs quantum dashes and their optical properties is studied. Device data of corresponding quantum dash lasers is presented.

High‐resolution proximity free lithography was developed using InP as anorganic resist for ion beam exposure. InP is very sensitive on ion beam irradiation and show a highly nonlinear dose dependence with a contrast function comparable to organic electron beam resists. In combination with implantation induced quantum well intermixing this new lithographic technique based on focused ion beams is used to realize high performance nano patterned optoelectronic devices like complex coupled distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers.

Gain-coupled distributed feedback (DFB) quantum well laser diodes have been made by focused ion beam implantation and subsequent thermal annealing. The uncoated laser devices show single longitudinal mode emission with very high yield.

High resolution focused ion beam implantation was used for the definition of key elements for the monolithic integration of optoelectronic devices like waveguide sections and distributed feedback gratings. By implantation induced thermal intermixing the band gap in semiconductor heterostructures can be shifted with high spatial resolution. In InP-based material, e.g., a maximum band gap shift of 65 meV was achieved, which can be controlled by the implantation dose. Due to the small beam diameter first order gain coupled gratings were realized in InP, GaAs and ZnSe based material systems, which allows single mode laser operation from the long wavelength (1.5 μm) down to the blue emitting regime (

We have studied strained InGaAs quantum wells with GaAlAs barriers, grown by molecular beam epitaxy, varying In content and well thickness. Photoluminescence measurements were made at 12 K. The appearance of a characteristic additional exciton‐like photoluminescence peak indicates the transition between elastically strained and relaxed layers. This transition was also observed by the occurrence of misfit dislocations in the corresponding transmission electron microsope (TEM) images. Layer thicknesses and In content were also determined by TEM. The results give a critical layer thickness of 29±0.5 nm at an In content of 32±2%. This value lies about a factor of 3–4 above the critical layer thickness calculated by Matthews and Blakeslee [J. Cryst. Growth 27, 118 (1974)].