ABSTRACT. Quantum Cascade Laser (QCL) based products are finding widespread adoption in several commercial markets. Diverse applications that range from cancer detection to nanoscale imaging to applied spectrometry are now benefiting from such technologies. Daylight discusses state-of-the-art performance of QCL devices and their applications in commercial markets.

ABSTRACT. We present the latest results obtained with a dual-comb spectrometer based on QCLs emitting at wavelengths close to 8micron coupled to a shock tube experiment. A 1ms reaction between propyne and oxygen at high-temperature is used to validate this technology and its accuracy is confirmed by use of other well-established laser diagnostics. In a second part, the remaining challenges to obtain suitable QCL frequency comb for dual-comb spectroscopy will be highlighted.

ABSTRACT. Quantum cascade technology provides innovative devices for experiments in the mid-infrared spectral region where molecules show their unique fundamental absorption features. In this work, we present a room-temperature monolithically-integrated quantum cascade laser detector device for liquid-sensing of µl-samples so compact it can easily fit inside a golf ball. In the first experiments, concentration-dependent absorption, rapid-response and long-term-stability measurements are shown.

ABSTRACT. By using a saddle-shape gain spectrum composed of tri-stack active regions, we achieve a single-chip tuning range of 400 cm-1 (from 1030 cm-1 to 1430 cm-1, namely 7.0 µm to 9.7 µm in wavelength). The lasers were adapted with external cavity configuration for narrow-band emission, incorporating Micro-Opto-Electro-Mechanical-Systems (MOEMS) scanners with integrated diffraction gratings, and were used for the realtime identification of substances e.g. pharmaceuticals.

ABSTRACT. We have implemented a sensor based on quantum cascade laser spectroscopy and multivariate data analysis to predict blood glucose concentrations from light backscattered off the dermis layer of the skin. In our most recent usability study with a single human subject, our system predicted 91.2% of the glucose concentrations with clinical accuracy and had an average empirical error of only 7.29%.

ABSTRACT. Frequency combs are ideal candidates to realize miniaturized spectrometers without moving parts. We present an overview of our current work on ICLs and QCLs ranging from fundamental aspect of their laser dynamics to the realization of monolithic devices. We highlight the similarities and differences between QCLs and ICLs, show how both FM and AM type frequency combs can be realized and discuss why the ICL comb platform is perfect for the realization of miniaturized spectrometers.

ABSTRACT. We report injection locking of the roundtrip frequency of an interband cascade laser (ICL) frequency comb emitting at a center wavelength of 3.25 µm. An external microwave source with milliwatt power level modulates the absorber section of the device in a split-contact geometry, which enables locking over a MHz frequency range. To optically characterize the locking properties, we exploit the ICL’s bifunctional operation as a fast photodetector with microwave electrical bandwidth.

ABSTRACT. In the work, mid-infrared frequency comb based on a ring cavity quantum cascade laser (QCL) is demonstrated using the plasmon-enhanced and buried-heterostructure waveguide. The device shows narrow beatnote spectra across almost all the dynamic range, demonstrating high stability of the comb operation with respect to the driving condition. The multiheterodyne beating experiment was carried out to further verify the comb nature of the device.

ABSTRACT. Mode-locking of mid-infrared quantum cascade lasers (QCL) remains challenging to date due to their ultrafast gain dynamics. We report on active mode-locking of mid-infrared QCLs resulting in the emission of intense picosecond pulses. We investigate the temporal dynamics of the QCL using both linear and quadratic autocorrelation techniques. Both methods confirm independently that the QCL emits a train of isolated pulses.

ABSTRACT. We present a broadband, homogeneous THz QCL spanning 1.65 THz around 3.4 THz in a bistable operation in the NDR. In the stable regime, the structure shows a single narrow beatnote with spectral emission of nearly 1 THz indicating comb operation. Further, low power injection locking is demonstrated. This injection locking capability and its broadband nature are advantage to the normally heterogeneous based broadband THz QCLs and could lead to the octavespanning, on-chip frequency comb.

ABSTRACT. Recent years have witnessed an inflow of ideas from quantum field theory and condensed matter physics into the field of optics. In this talk, we describe how notions from topological physics and supersymmetry can be used in designing novel laser arrays with properties that are of interest in some applications. Likewise, such lasing arrangements can be used to emulate a variety of topological and supersymmetric phenomena, beyond what is possible in their respective original platforms.

ABSTRACT. We demonstrate a ~5x enhancement in luminescence from a long wavelength infrared (LWIR) emitter grown on a highly doped semiconductor ‘designer metal’ virtual substrate. Our structures’ reflectance and photoluminescence are characterized experimentally by Fourier transform infrared spectroscopy and modeled analytically using a Dyadic Green’s function formalism. The results presented offer a potential path towards efficient LWIR emitter devices.

ABSTRACT. We present the first direct spectral measurements using reflection-mode THz time-domain spectroscopy (TDS) of an amplifying quantum-cascade (QC) metasurface resonant at 2.6 THz. Such metasurfaces are the critical component of terahertz (THz) QC vertical-external-cavity surface-emitting-laser (QC-VECSEL).

ABSTRACT. We realize highly efficient (>80%) broadband hybrid metasurfaces based on integrated dielectric and plasmonic metasurfaces for full-stokes polarimetric detection and imaging in NIR wavelengths. Moreover, we introduce a novel approach for realizing highly efficient plasmonic metasurfaces for phase and polarization control of light in MIR range with transmission efficiency >90% and CP extinction ratio >93 at 4 µm, which enables ultra-compact polarimetric detection and imaging in MIR wavelengths.

ABSTRACT. We report optical power limiting metasurfaces based on the saturable absorption of intersubband transitions in n-doped multiple quantum wells coupled to resonances in plasmonic nanocavities. Saturating the intersubband transition leads to a strong reduction in reflectivity as the nanocavities become critically coupled to incident light. Experimentally, we observe over 50% reduction in reflectivity for pump intensities less than 90 kW/cm2.

ABSTRACT. Photo-induced intersubband (ISB) transitions at room temperature (RT) usually imply free carriers. We show the first evidence of hh1-e1 to hh1-e2 excitonic transitions at room temperature induced by intersubband absorption in nonpolar ZnO/Zn0.6Mg0.4O undoped quantum wells. This ISB induced excitonic effect is a consequence of the huge binding energy of excitons in the ZnO material system, which is further enhanced in QWs due to the quantum confinement.

ABSTRACT. Using non-equilibrium Green’s functions calculations, we compare the temperature dependence of the terahertz gain properties of an existing GaAs/AlGaAs THz QCL design with an equivalent design based on n-type Ge/SiGe. In the latter case, the gain is found to be much more robust to temperature increase, enabling operation up to room temperature. The better temperature robustness with respect to III–V is attributed to the much weaker interaction with optical phonons.

ABSTRACT. Near-infrared intersubband absorption in non-polar strain-balanced AlGaN/InGaN superlattices is reported for the first time. M-plane Al0.22Ga0.78N/In0.11Ga0.89N heterostructures were grown by plasma-assisted MBE as an alternative to high Al-composition non-polar AlGaN/GaN. AFM, XRD, and TEM analysis reveal low surface roughness and excellent structural properties of all samples. The optical measurements indicate an intersubband transition energy around 4 μm for 3 nm quantum wells.

ABSTRACT. We study intersubband optical transitions and structural properties of n-type Ge/SiGe coupled quantum well systems grown by ultra-high vacuum chemical vapor deposition. The samples have been structurally investigated at the atomic level in order to assess the growth capability against quantum cascade laser design requirements carefully identified by means of a state of the art modelling based on the non-equilibrium Green function formalism.

ABSTRACT. Along the path of realizing a room-temperature n-type Ge/SiGe terahertz quantum cascade laser, we present electroluminescence measurements of quantum cascade structures with top diffraction gratings. The devices for surface emission have been fabricated out of a 4-well quantum cascade laser design with 30 periods. An optical signal was observed with a maximum between 8-9 meV and full width at half maximum of roughly 4 meV.