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This work provides a comprehensive study of the incorporation behavior of B in growing GaAs under molecular beam epitaxy conditions. Structural characterization of superlattices revealed a strong dependence of the BAs growth rate on the GaAs growth rate used. In general, higher GaAs growth rates lead to a higher apparent BAs growth rate, although lower B cell temperatures showed saturation behavior...
Quantum cascade lasers (QCLs) are compact and powerful sources that cover a wide spectral range from infrared to terahertz (THz) radiation. The emission characteristics of QCLs depend on design parameters such as layer thickness, material composition and doping. Therefore, the material system has to be chosen accurately. Most commonly used material systems for THz QCLs are GaAs/AlGaAs and InGaAs/InAlAs...
We present gas sensors based on two concentric vertically emitting and detecting quantum cascade ring structures on the same chip. Both rings can be used as laser and detector at the same wavelength.
We present a compact laser source emitting orbital angular momentum beams created by an on-chip gradient-index metamaterial. In combination with the tailorable wavelength of our emitter this enables on-demand applications in a variety of fields.
High power terahertz quantum cascade lasers with symmetric, wafer bonded active regions are presented, which are ideally suited for object illumination for real-time terahertz imaging using a microbolometer camera.
We present high performance quantum cascade lasers with a peak output power of 0.94 W. This development is based on new materials and new symmetric designs for the active region. The devices are fabricated by a wafer-bonding technique of two symmetric active regions.
We demonstrate terahertz quantum cascade lasers based on arrays of subwavelength micropillar structures, corresponding to scaled-down photonic crystals. Stimulated emission is measured at 4 THz for devices operating in the effective medium regime of the photonic bands.
Terahertz quantum cascade lasers have not reached watt-level output powers yet. We present surface-plasmon devices with a peak power of 0.94 W. The device consists of two symmetric active regions combined by a wafer-bonding step.
Quantum cascade lasers (QCLs) are reliable and versatile semiconductor light sources that emit in the mid-infrared (MIR) and terahertz (THz) spectral region. They feature precisely designable single-mode emission along with cw power levels of several watts at room temperature [1]. Besides their usage for military purposes, they are more and more applied in the field of chemical sensing, detection...
We are presenting results from the fabrication and characterization of GaAs/Al0.15Ga0.85As micropillar arrays formed by structuring a terahertz quantum cascade laser heterostructure. The micropillar arrays are arranged in a double metal waveguide for providing electrical contacts and collection of terahertz radiation. The diameters of the micropillars are about one order of magnitude smaller then...
The miniaturization of spectroscopic setups is a fascinating research topic, gaining momentum during the last couple of years. Quantum cascade lasers are known as one of the most important and influential sources in the mid-infrared region. In the so called “fingerprint” region (3–20μm) most molecules have their resonances, that can be observed by optical absorption or a change of the refractive index...
We present experimental results on coupled pairs of microdisk quantum cascade lasers (QCLs) emitting in the terahertz (THz) spectral region. This resonator type allows to control and to strongly confine the optical mode within the cavity. The coupling is based on the evanescent field of whispering gallery modes (WGMs) formed in each disk [1].
We report studies on bidirectional emission of ring cavity surface emitting quantum cascade lasers. Special attention is put on substrate emission and methods for favoring one single emission direction.
We present terahertz quantum cascade lasers based on symmetric active regions. Polarity dependent performance differences are observed in the GaAs/AlGaAs and the InGaAs/GaAsSb system. The growth-induced asymmetries and their influence are discussed.
Detectivity enhancement up to 20 times is achieved by fabricating a quantum well infrared photodetector as a photonic crystal slab. This enhancement is the combined effect of increased responsivity and noise current reduction. We report a peak detectivity of 2.6E10 cmHz1/2/W at 80 K and were able to operate the device up to 200 K.
We have investigated several new concepts and geometries for graphene-based photodetectors. In particular these are: a metal-graphene-metal photodetector, a photodetector with shadow masks, and a microcavity-enhanced graphene photodetector.
In this work a detailed study of Si-doped GaAs 0.51 Sb 0.49 grown lattice-matched to InP substrates by molecular beam epitaxy is presented. Electronic characterization using Hall measurements revealed n-type behavior, although with reduced carrier concentrations and mobilities compared to GaAs, ranging from 8.5×10 15 to 1.8×10 18 cm −3 . Electron mobilities...
The terahertz (THz) spectral region, covering frequencies from 1 to 10 THz, is highly interesting for a large variety of applications. The typical ones are: real-time imaging, heterodyne detection or spectroscopy. A strong need for a reliable semiconductor source with a high design potential exists. The THz quantum-cascade laser (QCL) has become the preferred solution due to the flexibility of the...
Quantum cascade lasers (QCLs) are the only compact sources of coherent terahertz (THz) radiation. This spectral region is very interesting for various applications like spectroscopy or imaging. Up to now THz QCLs are operating in the regime between 1 and 5 THz. One of the advantages of QCLs is that the wavelength of the device can be tailored by the design of the active region. In addition the waveguide...
The study of quantum cascade lasers (QCL) in the terahertz frequency region by the use of THz time-domain spectroscopy has gained a lot of interest within the last few years [1]. Good physical insight was obtained for THz QCLs employing a single plasmon waveguide (surface plasmon waveguide) [2,3]. In comparison to that the double plasmon or metal-metal waveguide QCL uses a metal/semiconductor/metal...
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