We demonstrate an efficient, simple, and low-cost approach for enhanced nanoscopy in individual green emitting perovskite (CsPbBr3) nanocrystals via TiO2 dielectric nanoantenna. The observed three- to five-fold emission enhancement is attributed to near-field effects and emission steering promoted by the coupling between the perovskite nanocrystals and the dielectric sub-micrometric antennas. The dark-field scattering configuration is then exploited for surface-enhanced absorption measurements, showing a large increase in detection sensitivity, leading to the detection of individual nanocrystals. Due to the broadband spectral response of the Mie sub-micrometric antennas, the method can be easily extended to electronic transitions in other spectral regions, paving the way for absorption nanoscopy of many different quantum emitters from organic molecules to quantum dots.

We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.

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Lead halide perovskites (LHPs) have arisen as a new class of semiconductors with excellent perspectives to become an alternative to traditional III–V epitaxial nanostructures for applications in active photonics. From the earliest demonstration of amplified spontaneous emission (ASE) with CH3NH3PbX3 (X = Cl, Br, I) polycrystalline thin films in 2014, more than 200 papers have been published in this field with regards to the improvement of the ASE figures of merit or the understanding of the underlaying physical mechanisms in the generation of optical gain for different LHPs. This extraordinary progress has resulted in the synthesis of either CH3NH3PbX3 perovskites as polycrystalline thin films or layers made of fully inorganic CsPbX3 perovskite nanocrystals (PNCs) that can be integrated in different optical architectures or substrates using cheap and straightforward solution processing techniques. Consequently, ASE with thresholds smaller than a few nJ cm−2 or lasing under continuous wave operation, among other impressive results, have been recently achieved. The role of the radiative recombination time, nonradiative traps, Auger recombination, excitation fluency, and absorption coefficient are discussed in this chapter within the framework of available studies and results in the literature, as well as in the light of our own work. This chapter will also review the most important results obtained by the scientific community in the field of active photonic devices and integrated concepts based on LHPs, which contain the integration of bulk polycrystalline and PNC thin films on different substrates, even those which are flexible. Spontaneous emission and ASE will be discussed based on a rate equation model incorporated into a beam propagation algorithm, in the case of optical waveguides, to simulate the generation and propagation of emitted light and optical gain, as an important tool toward the design of active integrated photonics based on LHPs.

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