Inhibition and enhancement of the spontaneous emission of quantum dots in micropillar cavities with radial-distributed Bragg reflectors

Spatial photoluminescence and lifetime mappings of quasi-2D perovskites coupled with a dielectric metasurface

Light-matter interaction between quantum emitters and optical cavities plays a vital role in fundamental quantum photonics and the development of optoelectronics. Resonant metasurfaces are proven to be an efficient platform for tailoring the spontaneous emission (SE) of the emitters. In this work, we study the interplay between quasi-2D perovskites and dielectric TiO2 metasurfaces. The metasurface, functioning as an open cavity, enhances electric fields near its plane, thereby influencing the emissions of the perovskite. This is verified through angle-resolved photoluminescence (PL) studies. We also conducted reflectivity measurements and numerical simulations to validate the coupling between the quasi-2D perovskites and photonic modes. Notably, our work introduces a spatial mapping approach to study Purcell enhancement. Using fluorescence lifetime imaging microscopy (FLIM), we directly link the PL and lifetimes of the quasi-2D perovskites in spatial distribution when positioned on the metasurface. This correlation provides unprecedented insights into emitter distribution and emitter-resonator interactions. The methodology opens a new (to the best of our knowledge) approach for studies in quantum optics, optoelectronics, and medical imaging by enabling spatial mapping of both PL intensity and lifetime, differentiating between uncoupled quantum emitters and those coupled with different types of resonators.

Spherical Bragg resonators for lasing applications: a theoretical approach

This work considers a perfect 3D omnidirectional photonic crystal; Spherical Bragg Resonators (SBR), for lasing applications. We use the recursive transfer matrix method to study scattering in an Er³⁺ doped SBR. We find the threshold gain factor for lasing by scanning poles and zeros of the S-matrix in the complex frequency plane. For a six Si/SiO₂ bilayer SBR, the threshold gain factor corresponds to a dopant density of Er³⁺ of 5.63 × 10²⁰ions/cm³. We believe, our work is the first theoretical demonstration of the ability to engineer optical amplification and threshold gain for lasing in SBRs.

Cold and Hot Spots: From Inhibition to Enhancement by Nanoscale Phase Tuning of Optical Nanoantennas

Optical nanoantennas are well-known for the confinement of light into nanoscale hot spots, suitable for emission enhancement and sensing applications. Here, we show how control of the antenna dimensions allows tuning the local optical phase, hence turning a hot spot into a cold spot. We manipulate the local intensity exploiting the interference between driving and scattered field. Using single molecules as local detectors, we experimentally show the creation of subwavelength pockets with full suppression of the driving field. Remarkably, together with the cold excitation spots, we observe inhibition of emission by the phase-tuned nanoantenna. The fluorescence lifetime of a molecule scanned in such volumes becomes longer, showing slow down of spontaneous decay. In conclusion, the spatial phase of a nanoantenna is a powerful knob to tune between enhancement and inhibition in a 3-dimensional subwavelength volume.

Design and fabrication of bi-functional TiO2/Al2O3 nanolaminates with selected light extraction and reliable moisture vapor barrier performance

Bi-functional thin film with both selected light extraction and reliable moisture vapor barrier was proposed for simultaneous light management and encapsulation in the fields of lighting and display. Atomic layer deposition (ALD) was employed to obtain TiO₂ and Al₂O₃ films with high uniformity, forming distributed Bragg reflector (DBR) structure. The DBRs exhibited excellent and tunable optical properties, as well as reliable moisture barrier performance. With increasing the DBR layers, the transmittances decreased obviously. The transmittance in the blue light region was as low as 0.66% for DBR with 6.5 pairs and the water vapor transmission rates value was 3.06 × 10^-5 g m^-2 d^-1 for DBR with 4.5 pairs. These DBRs were integrated in the red quantum dot (QD) based color converters excited by blue LED, enabling an obvious increase in red emission and a strong decrease in blue light transmittance. Furthermore, these DBRs can prolong the lifetime of QDs evidently by isolating the QDs from the moisture (oxygen) vapor. These results highlight the potentials for the exploitation of DBRs fabricated using ALD in the application of lighting and display devices based on QD photoluminescence and electroluminescence.

Highly indistinguishable on-demand resonance fluorescence photons from a deterministic quantum dot micropillar device with 74% extraction efficiency

The implementation and engineering of bright and coherent solid state quantum light sources is key for the realization of both on chip and remote quantum networks. Despite tremendous efforts for more than 15 years, the combination of these two key prerequisites in a single, potentially scalable device is a major challenge. Here, we report on the observation of bright single photon emission generated via pulsed, resonance fluorescence conditions from a single quantum dot (QD) deterministically centered in a micropillar cavity device via cryogenic optical lithography. The brightness of the QD fluorescence is greatly enhanced on resonance with the fundamental mode of the pillar, leading to an overall device efficiency of η = (74 ± 4) % for a single photon emission as pure as g⁽²⁾(0) = 0.0092 ± 0.0004. The combination of large Purcell enhancement and resonant pumping conditions allows us to observe a two-photon wave packet overlap up to ν = (88 ± 3) %.