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We demonstrate single-mode, surface-emitting terahertz lasers at lambdaap110 mum employing photonic-crystal resonators. The devices employ metal-metal waveguides, and the photonic-crystal lattice is implemented by the sole patterning of the top metal contact, without deep-etching the semiconductor in the photonic crystal holes. The device emission wavelength correctly tunes with the photonic crystal...
We demonstrate full control of the spectral and spatial emission properties of terahertz quantum cascade lasers using metallic photonic-crystals for lateral confinement. Single-mode, surface-emission is obtained at a frequency of 2.8-2.9 THz using a photonic-crystal design with a square lattice geometry. The resonator quality factor is then optimised, using a graded photonic-crystal architecture,...
Recent results are presented on the non-linear intra-cavity up-conversion in the telecom range and the microwave modulation of THz quantum cascade lasers.
Terahertz time-domain spectroscopy is used to determine gain related parameters of terahertz quantum-cascade lasers. Due to the techniquespsila insensitivity to the QCL emission, spectral gain narrowing is observed above laser threshold. By correlating these measurements with bandstructure simulations, insight into the subband alignment as a function of the applied field is acquired.
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,...
Distributed feedback quantum-cascade lasers based on loss-coupled two-metal gratings are presented. Devices lasing on single longitudinal modes between 2.62 and 2.69 THz are demonstrated, with sidemode suppression of 30 dB. In addition, controllable grating coupling strength is demonstrated.
Study of gain medium of terahertz quantum cascade lasers based on the interaction with broadband coherent radiation is presented. The phase resolved emitted field provides information on gain bandwidth, saturation recovery dynamics and coherent processes.
We demonstrate single-mode, surface-emitting terahertz lasers at lambdaap110 mum employing photonic-crystal resonators. The devices employ metal-metal waveguides, and the photonic-crystal lattice is implemented by the sole patterning of the top metal contact, without deep-etching the semiconductor into the photonic crystal holes. The device emission wavelength correctly tunes with the photonic crystal...
THz quantum cascade (QC) lasers with an active-region thickness of 5.86 mum was demonstrated. The current threshold was then reduced by reducing the device surface. The laser resonator is based on a micro-cylindrical geometry. In general micro-cylindrical resonators rely on total-internal reflection on the cavity sidewalls in order to confine the light. The small (r=25 mum) and medium (r=37.5 mum)...
Intra-cavity THz-sideband generation over the entire telecom range is demonstrated by injecting a near-infrared beam into a quantum cascade laser (f=2.8 THz). This process is phase- matched due to the phonon-induced anomalous dispersion typical of semiconductor compounds.
We demonstrate terahertz microcavity lasers at lambda=112 mum with ultra-low current thresholds of 4 mA and with mode volumes of less than one-cubic-wavelength. Confinement in the longitudinal direction is obtained using almost-circular micro-disk resonators. The guiding properties of surface-plasmons are exploited to guide the mode with the metal contact. The devices laser up to 70 K in pulsed mode,...
Quantum Cascade Lasers are one the most promising approach for the generation of THz waves and particularly in a double plasmon waveguide topology. Stripline resonators with a quasi-TEM mode are indeed interesting for THz-QCLs thanks to a high confinement factor combined with low losses. However they present two major drawbacks: the first is a poor outcoupling of the radiation, and the second is a...
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