Coupling photoluminescent emitters to photonic nanostructures depends critically on the emitter orientation. Researchers show that emission polarization analysis can be used to measure the three-dimensional orientation of single nanoemitters, making it possible to isolate nanoemitters whose orientations are favorable for specific nanostructure cavities.

Coupling nano-emitters to plasmonic antennas is a key milestone for the development of nanoscale quantum light sources. One challenge, however, is the precise nanoscale positioning of the emitter in the structure. Here, we present a laser etching protocol that deterministically positions a single colloidal CdSe/CdS core/shell quantum dot emitter inside a subwavelength plasmonic patch antenna with three-dimensional nanoscale control. By exploiting the properties of metal–insulator–metal structures at the nanoscale, the fabricated single-emitter antenna exhibits a very high-Purcell factor (>72) and a brightness enhancement of a factor of 70. Due to the unprecedented quenching of Auger processes and the strong acceleration of the multiexciton emission, more than 4 photons per pulse can be emitted by a single quantum dot, thus increasing the device yield. Our technology can be applied to a wide range of photonic nanostructures and emitters, paving the way for scalable and reliable fabrication of ultra-compact light sources.

In this paper, we demonstrate that for colloidal CdSe/CdS nanoplatelets, a rectangular shape induces emission asymmetry, in terms of both polarization and emission patterns. Polarimetry and emission pattern analyses are combined to provide information on the orientation of the transition dipoles involved in the nanoplatelet emission. It is shown that for rectangular nanoplatelets, the emission is polarized and the emission patterns are anisotropic, whereas they remain nonpolarized and isotropic for square nanoplatelets. This can be appropriately described by the dielectric antenna effect induced by the elongated shape of the rectangular platelet. Open image in new window

Heat measurement induced by photoexcitation of a plasmonic metal nanoparticle assembly under environmental conditions is of primary importance for the further development of applications in the fields of (photo)catalysis, nanoelectronics and nanomedicine. Nevertheless, the fine control of the rise in temperature remains difficult and limits the use of this technology due to the lack of local temperature measurement tools working under environmental conditions. Luminescence nanothermometers are an alternative solution to the limitations of conventional contact thermometers since they are able to give an absolute temperature value with high spatial resolution using common optical equipment. As a proof of concept of this nanothermometry approach, a high local temperature exceeding one hundred degrees is measured on the thermalized photoexcited aggregate of gold nanorods using ZnGa₂O₄:Cr³⁺,Bi³⁺ nanothermometers that have a strong temperature dependence on the luminescence lifetime of chromium(III) and high sensitivity over an extensive range of temperatures. A study on the influence of the average distance between nanosensors and nanoheaters on the measured temperature is carried out by coating the nanosensors with a silica layer of tunable thickness, highlighting the temperature gradient at the vicinity of the nanoheater as the theory predicts. The variation of the optical nanosensor response is relevant and promising, and it could be further envisioned as a potential candidate for local temperature measurement at the nanoscale since no plasmonic effect on Cr³⁺ lifetime is observed. The results reported here open up an even wider field of application for high temperature nanothermometry on real samples such as aggregate particles for many applications including catalysis and nanoelectronics. Thermometry using luminescent nanoprobes, which is complementary to thermal microscopy techniques, will allow in situ and in operando temperature monitoring at very small scales.

Single‐emitter plasmonic patch antennas are room‐temperature deterministic single‐photon sources, which exhibit highly accelerated and directed single‐photon emission. However, for efficient operation these structures require 3D nanoscale deterministic control of emitter positioning within the device, which is a demanding task, especially when emitter damage during fabrication is a major concern. To overcome this limitation, the deterministic room‐temperature in situ optical lithography protocol uses spatially modulated light to position a plasmonic structure nondestructively on any selected single‐emitter with 3D nanoscale control. Herein, the emission statistics of such plasmonic antennas that embed a deterministically positioned single colloidal CdSe/CdS quantum dot, which highlight acceleration and brightness of emission, are analyzed. It is demonstrated that the presented antenna induces a 1000‐fold effective increase in the absorption cross‐section, and, under high pumping, these antennas show nonlinearly enhanced emission.

Up to now, transverse quantum effects (usually labeled as “quantum imaging” effects) which are generated by nonlinear devices inserted in resonant optical cavities have been calculated using the “thin-crystal approximation,” i.e., taking into account the effect of diffraction only inside the empty part of the cavity, and neglecting its effect in the nonlinear propagation inside the nonlinear crystal. We introduce in the present paper a theoretical method which is not restricted by this approximation. It allows us in particular to treat configurations closer to the actual experimental ones, where the crystal length is comparable to the Rayleigh length of the cavity mode. We use this method in the case of the confocal optical parametric oscillator, where the thin-crystal approximation predicts perfect squeezing on any area of the transverse plane, whatever its size and shape. We find that there exists in this case a “coherence length” which gives the minimum size of a detector on which perfect squeezing can be observed, and which gives therefore a limit to the improvement of optical resolution that can be obtained using such devices.