We demonstrate continuous voltage control of the nonradiative transition lifetime in semiconductor heterostructures. The results were obtained by picosecond time-resolved experiments on biased SiGe valence band quantum well structures using a free electron laser. By varying the applied voltage, the intersubband hole relaxation times for quantum well structures were varied by a factor of 2 as th...

A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material. The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular near-diffraction limited Gaussian beam with M2</sup...

We perform ray and wave simulations of passive and active spiral-shaped optical microcavities, comparing our results to experimental data obtained with mid-infrared quantum cascade spiral microlasers. Focusing on the angular emission characteristics, we find that both ray and wave simulations are consistent with the experimental data, showing richly-featured, multidirectional far-field emission...

A comprehensive investigation of the frequency-noise spectral density of a free-running midinfrared quantum-cascade laser is presented for the first time. It provides direct evidence of the leveling of this noise down to a white-noise plateau, corresponding to an intrinsic linewidth of a few hundred hertz. The experiment is in agreement with the most recent theory on the fundamental mechanism o...

The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges ...

A quantum theory of a two and three-level laser with injected atomic coherence is developed by using a density operator method, to the best of our knowledge, for the first time. The initial atomic coherence plays an essential role. At steady state, the equation of motion for the density operator yields to exhibit laser without inversion and a phase locking but no threshold for the laser fie...

A mid-IR photothermal imaging system is presented that features an integrated ultrafast erbium-doped fiber probe laser for the first time. With a mid-IR tunable quantum cascade laser (QCL) as the pump laser, vibrational molecular modes are excited and the thermally-induced changes in the refractive index are measured with a probe laser. The custom-built, all-fiber ultrafast probe laser at telec...

Low dimensional structures have come a long way from being mere examples of applied quantum mechanics tv widespread applications in many modem devices and instruments. Quantum well, quantum cascade and quantum dot lasers make use of the very fundamental idea of carrier confinement within dimenswns that match their de Broglie wavelength. Quantum well lasers are used in many modern optoelectronic...

There is an increasing need in many chemical sensing applications ranging from environmental science to industrial process control as well as medical diagnostics for fast, sensitive, and selective trace gas detection based on laser spectroscopy. The recent availability of novel pulsed and continuous wave (cw) quantum and interband cascade distributed feedback (QC and IC DFB) lasers as mid-infra...

We demonstrate microfluidic laser intra-cavity absorption spectroscopy with mid-infrared lambda approximately 9mum quantum cascade lasers. A deepetched narrow ridge waveguide laser is placed in a microfluidic chamber. The evanescent tails of the laser mode penetrate into a liquid on both sides of the ridge. The absorption lines of the liquid modify the laser waveguide loss, resulting in signifi...