ABSTRACT. The combination of the unipolar barrier device architecture and the type-II superlattice infrared absorbers have led to a new generation of versatile, cost-effective, high-performance infrared detectors and focal plane arrays (FPAs) based on robust III-V semiconductors. In particular, mid-wavelength infrared (MWIR) InAs/InAsSb strained-layer superlattice (SLS) barrier infrared detector FPA has demonstrated significantly higher operating temperature than the market-leading InSb.

ABSTRACT. We report progresses on MIR heterodyne detection using room temperature patch-antenna QWIP receivers. By using an optimized active region and passively stabilized DFB QCLs, we have reached NEP in the pW range at 1.7GHz at 300K, an improvement of 5 orders of magnitude with respect to our previous results. Remarkably, we have shown that QWIP receivers, with an applied microwave bias, can also act as frequency mixer. This enables to shift the heterodyne signal over the all band pass of the system.

ABSTRACT. We have developed an electrically tunable THz mixer based on the intersubband transition of a high-mobility 2-dimensional electron gas (2DEG) confined in a single 40 nm GaAs/AlGaAs quantum well. The fabricated device shows tunability of the detection frequency between 2.52 THz and 3.11 THz and mixing at 2.5 THz has been observed at 60 K with an intermediate frequency (IF) bandwidth of 6 GHz.

ABSTRACT. The performance of state-of-the-art THz optoelectronic devices is limited by parasitic LO phonon transitions, e.g. preventing the operation of GaAs-based THz-QCLs above ~200 K. This can be overcome by using alternative, novel material systems with higher LO-phonon energies like ZnO [1]. Here we present the first mid-IR ZnO/ZnMgO-based QCD with a peak responsivity of 0.15 mA/W at 77 K.

ABSTRACT. Quantum cascade detectors (QCD) are a promising candidate for both sensitive and high-speed detection at room temperature due to their fast carrier dynamics and because they operate at zero bias. We report on high-speed QCDs connected to a coplanar microwave transmission line, which allows a 3 dB bandwidth larger than 10 GHz. A single period QCD exhibits a particularly high responsivity of more than 0.8 A/W at room temperature. It is used to investigate an interband cascade laser frequency comb.

ABSTRACT. The ground state of electromagnetic radiation contains zero photons but is characterised by a fluctuating electromagnetic field. We measure the correlation function on the electric field of the ground state as a function of time and space using fast electro-optic correlations at terahertz frequencies. In this fashion, we determine, among other characteristics, the spectral content and the electric field amplitude of this state and find excellent agreement with the second quatisation theory.

ABSTRACT. We have investigated the intersublevel transitions in individual, metallic carbon nanotube quantum dots (CNT-QDs) by terahertz-induced photocurrent spectroscopy. An ultranarrow photocurrent peak with a linewidth of 0.3 meV is observed at the photon energy expected from the linear band dispersion. The linewidth is well explained by the tunneling rates between the CNT-QD and the electrodes, indicating that the scattering time of electrons in the present CNT is comparable to or longer than 10 ps.

ABSTRACT. When Rabi energy exceeds the exciton binding energy a Wannier Exciton-Plasmon Polariton (WEPP) bound to the metal nanoparticle is formed. It is characterized by small excitonic radius and higher ionization energy that can exceed 100meV

ABSTRACT. We have introduced two metallic quantum wells (MQWs) material platforms, i.e., Au/Al2O3 and TiN/Al2O3 multilayers, and have demonstrated extremely high third-order and second-order susceptibilities at visible/near-infrared (NIR) frequencies—a few orders of magnitude higher than those of classic plasmonic materials. Our quantum plasmonic heterostructures will lead important applications in efficient wave mixing at visible/NIR frequencies and ultracompact nonlinear optical devices.

ABSTRACT. We demonstrate a new method for high-speed modulation of the electron transport and photon generation within a terahertz-frequency quantum-cascade laser (THz QCL). An amplified femtosecond laser is used to generate coherent acoustic-phonon pulses, which are injected into the device, resulting in an electronic bandstructure perturbation, with ~1-ns rise-time. The corresponding change in optical gain allows up to ~6% amplitude modulation, with results explained accurately using a model.