Diffusion-Dominated Luminescence Dynamics of CsPbBr3 Studied Using Cathodoluminescence and Microphotoluminescence Spectroscopy.

Time-resolved or time-correlation measurements using cathodoluminescence (CL) reveal the electronic and optical properties of semiconductors, such as their carrier lifetimes, at the nanoscale. However, halide perovskites, which are promising optoelectronic materials, exhibit significantly different decay dynamics in their CL and photoluminescence (PL). We conducted time-correlation CL measurements of CsPbBr3 using Hanbury Brown-Twiss interferometry and compared them with time-resolved PL. The measured CL decay time was on the order of subnanoseconds and was faster than PL decay at an excited carrier density of 2.1 × 1018 cm-3. Our experiment and analytical model revealed the CL dynamics induced by individual electron incidences, which are characterized by highly localized carrier generation followed by a rapid decrease in carrier density due to diffusion. This carrier diffusion can play a dominant role in the CL decay time for undoped semiconductors, in general, when the diffusion dynamics are faster than the carrier recombination.

Cathodoluminescence of green fluorescent protein exhibits the redshifted spectrum and the robustness.

Green fluorescent protein (GFP) and its variants are an essential tool for visualizing functional units in biomaterials. This is achieved by the fascinating optical properties of them. Here, we report novel optical properties of enhanced GFP (EGFP), which is one of widely used engineered variants of the wild-type GFP. We study the electron-beam-induced luminescence, which is known as cathodoluminescence (CL), using the hybrid light and transmission electron microscope. Surprisingly, even from the same specimen, we observe a completely different dependences of the fluorescence and CL on the electron beam irradiation. Since light emission is normally independent of whether an electron is excited to the upper level by light or by electron beam, this difference is quite peculiar. We conclude that the electron beam irradiation causes the local generation of a new redshifted form of EGFP and CL is preferentially emitted from it. In addition, we also find that the redshifted form is rather robust to electron bombardment. These remarkable properties can be utilized for three-dimensional reconstruction without electron staining in focused ion beam/scanning electron microscopy technology and provide significant potential for simultaneously observing the functional information specified by super-resolution CL imaging and the structural information at the molecular level obtained by electron microscope.

Storage and retrieval of a squeezed vacuum.

Storage and retrieval of a squeezed vacuum was successfully demonstrated using electromagnetically induced transparency. The squeezed vacuum pulse having a temporal width of 930 ns was incident on the laser cooled 87Rb atoms with an intense control light in a coherent state. When the squeezed vacuum pulse was slowed and spatially compressed in the cold atoms, the control light was switched off. After 3 mus of storage, the control light was switched on again, and the squeezed vacuum was retrieved, as was confirmed using the time-domain homodyne method.

Electromagnetically induced transparency with squeezed vacuum.

The squeezed vacuum resonant on the (87)Rb D1 line (probe light) was injected into an optically dense rubidium gas cell with a coherent light (control light). The output probe light maintained its quadrature squeezing within the transparency window caused by the electromagnetically induced transparency (EIT). The results reported here are the first realization of EIT in the full quantum regime.