A condensed-matter platform for analog simulation of complex two-dimensional molecular bonding configurations, based on optically trapped exciton-polariton condensates is proposed. The stable occupation of polariton condensates in the excited states of their optically configurable potential traps permits emulation of excited atomic orbitals. A classical mean-field model describing the dissipative coupling mechanism between $p$-orbital condensates is derived, identifying lowest-threshold condensation solutions as a function of trap parameters corresponding to bound and antibound $\pi$ and $\sigma$ bonding configurations, similar to those in quantum chemistry.

In this work, we demonstrate the features of a two-stage epitaxial growth technique and show the results of power and efficiency measurements for three different designs of quantum cascade lasers with a record-high peak power in the 8 $\mathsf{\mu }$m spectral region. The time-resolved QCL spectral study proves that InP-based upper cladding paired with an InP contact layer provides better heat dissipation and allows one to reach better power characteristics in comparison with InGaAs-based contact, even with short pulse pumping.

Simulations of propagation of light beams in specially designed multilayer semiconductor structures (one-dimensional photonic crystals) with embedded quantum wells reveal characteristic optical properties of resonant hyperbolic metamaterials. A strong dependence of the refraction angle and the optical beam spread on the exciton radiative lifetime is revealed. We demonstrate the strong negative refraction of light and the control of the group velocity of light by an external bias through its effect upon the exciton radiative properties.

Mid IR Quantum cascade lasers are of high interest for the scientific community due to their unique applications. However, the QCL designs require careful engineering to overcome some crucial disadvantages. One of them is active region (ARn) overheating, which significantly affects laser characteristics, even in the pulsed mode. In this work, we consider the effects related to the nonequilibrium temperature distribution when thermal resistance formalism is irrelevant. We employ the heat equation and discuss the possible limitations and structural features stemming from the chemical composition of the ARn. We show that the presence of solid solutions in the ARn structure fundamentally limits the heat dissipation in pulsed and CW regimes due to their low thermal conductivity compared with binary compounds. Also, the QCL postgrowths affect the thermal properties of a device closer to CW mode, while it is by far less important in the short-pulsed mode.

We present an experimental study of the turn-on delay in pulsed mid-infrared quantum cascade lasers. We report the unexpectedly long delay time depending on the pumping current, which does not agree with conventional theoretical predictions for step-like excitation. Similar behavior has been observed in InP- and InAs-based QCLs emitting near 8 $\mu$ m. Numerical simulations performed using a model based on rate equations for excitation by current pulses with non-zero rise time provide fair agreement with our observations.

In analogy with superfluidity, nonequilibrium polariton condensation can be phenomenologically described in terms of separated condensed and normal fractions. Under the assumption of a significantly shorter characteristic timescale, the incoherent part is frequently traced out adiabatically. In this work, we stress the importance of accounting for the time-resolved coupling between the condensed and normal fractions. Even in the case of a significant mismatch in the evolution rates, the coupling with the normal fraction drastically alters the condensate dynamics and leads to a variety of previously overlooked phases in a confined configuration. Focusing on the case of annular optically induced traps for polaritons, we elaborate on the nonadiabatic model of polariton condensation. Using the two-mode approximation, accounting for a couple of quantized polariton vortices with opposite angular momenta, we identify the range of validity for the adiabatic elimination of the incoherent reservoir. Beyond this range, the nonadiabatic interaction with a circularly symmetric trapping reservoir supports multistability, limit cycle dynamics, and the formation of a neutral equilibrium standing-wave phase featuring spontaneous breaking of the continuous radial symmetry. In the presence of a weak trap asymmetry, the nonadiabaticity prevents the formation of giant polariton vortices. We argue that our detailed description provides an interpretation of the dominance of the standing-wave phase over the persistent vortex phase in experimental observations.