Anisotropic Radiation in Heterostructured “Emitter in a Cavity” Nanowire

Tailorable synthesis of axially heterostructured epitaxial nanowires (NWs) with a proper choice of materials allows for the fabrication of novel photonic devices, such as a nanoemitter in the resonant cavity. An example of the structure is a GaP nanowire with ternary GaPAs insertions in the form of nano-sized discs studied in this work. With the use of the micro-photoluminescence technique and numerical calculations, we experimentally and theoretically study photoluminescence emission in individual heterostructured NWs. Due to the high refractive index and near-zero absorption through the emission band, the photoluminescence signal tends to couple into the nanowire cavity acting as a Fabry–Perot resonator, while weak radiation propagating perpendicular to the nanowire axis is registered in the vicinity of each nano-sized disc. Thus, within the heterostructured nanowire, both amplitude and spectrally anisotropic photoluminescent signals can be achieved. Numerical modeling of the nanowire with insertions emitting in infrared demonstrates a decay in the emission directivity and simultaneous rise of the emitters coupling with an increase in the wavelength. The emergence of modulated and non-modulated radiation is discussed, and possible nanophotonic applications are considered.

Effects of synthesizing time and Eu2+ concentration on photoluminescence properties of Ca2−xEuxMgSi2O7 phosphors

Phosphors with the compositions of [Formula: see text] ([Formula: see text], 0.015, 0.025, 0.035, and 0.045) are synthesized in a reduction atmosphere (5% H2 + 95% N2) using a solid-state reaction method. At first, the [Formula: see text] powder is synthesized at 1350[Formula: see text]C with a duration of [Formula: see text] h to find the optimum synthesizing time. SEM images show that the particle sizes increase with synthesizing time and as the synthesizing time is more than 4 h, the abnormal particles appear and the intensities at the emission peaks of photoluminescence excitation (PLE) and photoluminescence emission (PL) spectra decrease. Next, 1350[Formula: see text]C and 4 h are used as synthesized parameters, which are used to find the concentration quench effect of [Formula: see text] phosphors. As the concentration of [Formula: see text] ions of [Formula: see text] phosphors increases, the intensities at the emission peaks of PLE and PL spectra first increase and reach the maximum values at [Formula: see text], and then they decrease as the concentration of [Formula: see text] ions further increases. These results prove that the synthesizing time and concentration of [Formula: see text] ions are two important factors to affect the photoluminescence properties of [Formula: see text] phosphors.