1,721,321 research outputs found
Quantum dots: Long life in zero dimensions
No full textElectron relaxation time in semiconductor quantum dots, for terahertz transition energies, can be slowed down to the nanosecond range - a very encouraging result for the development of quantum-dot-based quantum cascade lasers
Coherent absorption control in polaritonic systems
Full text linkCoherent Perfect Absorption is discussed in the context of strongly-coupled polariton systems. It occurs when the cavity loss rate matches the material one, as demonstrated for intersubband transitions in a photonic crystal resonator
Universal lineshapes at the crossover between weak and strong critical coupling in Fano-resonant coupled oscillators
Full text linkIn this article we discuss a model describing key features concerning the lineshapes and the coherent absorption conditions in Fano-resonant dissipative coupled oscillators. The model treats on the same footing the weak and strong coupling regimes, and includes the critical coupling concept, which is of great relevance in numerous applications; in addition, the role of asymmetry is thoroughly analyzed. Due to the wide generality of the model, which can be adapted to various frameworks like nanophotonics, plasmonics, and optomechanics, we envisage that the analytical formulas presented here will be crucial to effectively design devices and to interpret experimental results
BOUNDARY-PROBLEMS FOR POLARITON PROPAGATION IN THIN-LAYERS AND QUANTUM-WELLS
No full textWe show how to compute the optical functions (reflection and transmission) of a semiconductor thin slab, in the vicinity of nearly degenerate exciton states. Additional boundary conditions are not required in the coherent-wave-function approach and multiple-polariton effects are included since Maxwell equations are satisfied. When the slab thickness is comparable to the exciton Bohr radius, centre of mass quantization results. When the slab thickness is smaller than the Bohr radius, we obtain quantum well polaritons. Numerical examples appropriate to GaAs are given
Recent advances and future prospects of THz quantum cascade lasers
No full textThe development of quantum cascade lasers (QCLs) operating at terahertz frequencies is proceeding at a rapid pace. Improvements have been obtained both in output power and operating temperatures, thanks to a combination of quantum design and fabrication methods, while the range of lasing frequencies has been extended below 1 THz. Distributed feedback devices have been fabricated with a variety of techniques for the purpose of achieving predictable single-mode emission, and external cavity set-ups have been implemented for tunability. THz QCLs have also become an important test-bed for new device concepts like non-periodic resonators, low volume microcavity lasers, and phase-matched non-linear devices that generate a THz signal on a near-IR carrier. Future developments will likely include optical circuits with photonic crystals, random lasers, new electro-mechanical tuning mechanisms, and possibly quantum dot lasers, further expanding the range of possible applications in many research areas
Frequency tuning of THz quantum cascade lasers
No full textTunable single-mode THz quantum cascade lasers are crucial for spectroscopy applications. Current and temperature tuning are limited to a few GHz and other solutions have to be implemented. Tuning by gating of the waveguide will be discussed as well as the use of external cavity set-ups
HEAVY-HOLE AND LIGHT-HOLE EXCITONS IN ANISOTROPIC SEMICONDUCTORS
No full textWe show how to compute the eigenvalues of an anisotropic Schroedinger equation for light- and heavy-hole excitons using a simplified deltalike interaction potential. Performing the calculation with a potential appropriate to bulk GaAs crystal, we obtain the excitonic binding energies for the heavy- and light-hole excitons, with the heavy-hole binding energy greater than that for the light hole. Inversion of this order for the case of a quantum well is discussed and explained
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