We investigate the emission directionality of electronic intraband (intersubband) transitions in stacked coupled quantum dots. Using a well-established eight-band $k \cdot p$ method, we demonstrate that minor contributions from valence band mixing into conduction govern polarization and $p$-to-$s$-type transitions. Despite contribution central-cell part to momentum matrix element is dominant, f...

The possibility to achieve laser action at different THz frequencies employing the so-called vertical transition will be discussed. The intra-well or vertical optical transition presents a number of features that makes it an ideal candidate for a systematic study of resonant tunnelling and dephasing in quantum cascade lasers. Laser action at 3.5 THz with very low threshold employing a single qu...

We realize and investigate a nonlinear metasurface taking advantage of intersubband transitions in ultranarrow GaN/AlN multi-quantum well heterostructures. Owing to huge band offsets, the structures offer resonant telecom window around 1.55 µm. These heterostructures are functionalized with an array plasmonic antennas featuring cross-polarized resonances at these near-infrared wavelengths their...

The mid-infrared spectral region can be covered by quantum cascade (QC) semiconductor lasers, where the emission wavelength is tailored by bandstructure engineering. For a detailed review on QC lasers see Ref. [1]. Their emission energy is well below the band gaps of the hosting material system. Typical GaAs QC lasers operate in the mid-infrared regime with corresponding energies of ~100 meV, w...

Grating-coupler-induced collective intersubband transitions in a quasi-twodimensional electron system are investigated both experimentally and theoretically. Far-infrared transmission experiments are performed on samples containing a quasi-two-dimensional electron gas quantum-confined in a parabolic quantum well. For rectangular shaped grating couplers of different periods we observe a strong d...

Abstract Many applications of photonics require efficient nonlinear optical interactions with low power and small footprints. However, the current needs for long interaction lengths strong laser sources devices make them unsuitable nanophotonic integrated optics. New materials stronger properties have been developed using various approaches in past few years. One largest responses reported to d...