The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
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.
We present THz quantum-cascade lasers in a superconducting double-metal waveguide. The active region is sandwiched between 300 nm thick Niobium layers. The current-voltage characteristic shows a pronounced photon kink at lasing threshold.
We demonstrate a terahertz quantum cascade laser based on the aluminum-free In0.53Ga0.47As/GaAs0.51Sb0.49 material system. Processed in a double metal waveguide configuration, disk devices reach operating temperatures up to 105 K and the spectral emission lies between 3.6 and 4.1 THz.
We present a new tuning scheme for THz quantum-cascade lasers based on active photonic crystal (PhC) resonators. An injected gas changes the resonance condition of the PhC and thereby the emission frequency of the device.
The coupling of broadband Terahertz pulses into metal-metal terahertz quantum cascade lasers is presented. A characterization of Terahertz transient generation on the subwavelength quantum cascade laser facet is investigated. The coupling inbetween two separate cavities is studied and modulation experiments were performed.
We present the design and realization of active photonic crystal (PhC) terahertz quantum-cascade lasers. The PhC consists of isolated pillars which are fabricated from the laser gain region. A stable single mode operation under all driving conditions is achieved.
Here, we present the design and realization of active PhC semiconductor lasers. The PhC used is based on a hexagonal lattice of free-standing pillars which are surrounded by air. Such structures have typically full bandgaps for TM-polarized light, which is the polarization of light emitted by QCLs. A calculated bandstructure of the PhC for a ration r/a of 0.3, where r is the radius of the pillars...
Nowadays quantum cascade lasers (QCLs) are the most promising candidates to enter the commercial market as semiconductor based sources for terahertz applications. However, the final breakthrough has not yet been achieved since operating temperatures of THz QCLs are still requiring cryogenic cooling. The record design reaches 178 K in pulsed mode, not accessible by thermoelectric coolers. In order...
We have combined few-cycle THz spectroscopy with quantum cascade technology. This combination allows to perform unique THz time-domain measurements of THz-QCLs. By coupling the few-cycle THz pulse into the waveguide of the QCL, the processes within the active zone can be probed. This gives direct information regarding the energy, dynamics and coherence of transitions in the QCL structure. In addition,...
The realization of terahertz (THz) quantum-cascade laser operating at photonic crystal modes is shown. The devices are showing stable single-mode operation under all driving conditions and a tuning range from 2.25 to 2.65 THz.
In this review, we report on the study of terahertz (THz) intersubband (ISB) transitions and on the optical devices based on them. We use time-resolved THz spectroscopy to examine ISB optical transitions in semiconductor quantum wells and quantum cascade lasers (QCLs). From these measurements, we obtain important information on the carrier relaxation, scattering mechanisms, and the gain. The waveguide...
The integration of photonic crystal (PC) resonators into the active region of terahertz quantum cascade lasers emitting around 2.7 THz is presented. The PC acts as frequency selective mirror and allows the tuning of the emission frequency throughout the entire gain region of the active zone. The PC and the gain region are embedded in a double-metal wave guide.
We present the observation of optical coupling in terahertz microdisk molecules based on quantum-cascade lasers and its tunability by the applied electric field. The spectral behaviour is in good accordance with performed finite-difference time-domaine simulations.
We present unique time-domain measurements of terahertz quantum cascade lasers. By coupling broadband terahertz pulses into the laser's waveguide the losses and gain in the frequency range 0.5 - 3.5 THz are determined. Furthermore internal processes and the laser dynamics can be tracked directly in the time- domain. The performance of THz-QCLs fabricated as double metal resonators is studied as a...
We present whispering-gallery mode terahertz quantum-cascade lasers with either "single-mode" or "double- mode" emission depending on the rotational symmetry of such resonators. Strong mode confinement in the growth and in-plane directions are provided by a double-plasmon waveguide and due to the strong impedance mismatch between the gain material and air. These ultra-compact devices...
The integration of photonic crystals (PC) and quantum-cascade lasers (QCL) can lead to a powerful set of new devices for various applications, such as multi-wavelength laser, detector arrays, on-chip integration and spectroscopy. The PCs are artificial crystals that have allowed and forbidden bands for the propagation of light. Typically PCs are built up by a regular pattern of air holes inside the...
Quantum-cascade lasers are sophisticated devices for a large number of applications such as imaging, spectroscopy and heterodyne detection. Significant steps forward in the temperature performance and available frequencies have been made over the last years. Nonetheless the influence of the doping concentration is not yet completely understood. The investigations which carried out by H.C. Liu et....
We present microdisk terahertz quantum-cascade lasers with dimensions comparable to the spatial mode distribution inside the microcavity and present 3D finite-difference time-domain simulations which are in good agreement with our experimental findings.
We present the influence of doping on terahertz quantum-cascade lasers. The active region is based on the longitudinal-optical phonon depopulation of the lower laser state. A linear dependency between the threshold current density and the doping is observed. We contribute that to the fact that quantum-cascade lasers require a sub-band alignment prior to lasing. Non-linear effects like electron-electron...
We present terahertz quantum-cascade lasers with small mode volumes based on whispering-gallery resonators. The strong mode confinement in the growth and in-plane directions are provided by a double-metal waveguide. This allows laser emission from devices with overall dimensions much smaller than the free-air emission wavelength. These ultra-small devices lase inherently single-mode and exhibit threshold...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.