We study the directional amplification of an optical probe field in a three-mode optomechanical system, where the mechanical resonator interacts with two linearly-coupled optical cavities and the cavities are driven by strong optical pump fields. The optical probe field is injected into one of the cavity modes, and at the same time, the mechanical resonator is subject to a mechanical drive with the driving frequency equal to the frequency difference between the optical probe and pump fields. We show that the transmission of the probe field can be amplified in one direction and deamplified in the opposite direction. This directional amplification or de-amplification results from the constructive or destruction interference between different transmission paths in this three-mode optomechanical system.

Beams carried orbital angular momentum (OAM) are proposed for wireless optical interconnects on chip and a full scheme of encoding and decoding of OAM at single frequency is demonstrated with numerical simulation. With proposed structure, beams with OAM order of -3 to 4 are generated and four orders of them (0 to 3) are used to encode and decode data so that the increased data density of two folds is achieved. According to such results, we believe that if OAM is utilized as an additional dimension in wireless optical interconnects, the data density can be significantly increased since the adopted orders of OAM could be infinite in principle. Moreover, such improvement could be easily applied to the existing architecture without any more complex technology.

A comparative study of the optical absorption and luminescence of crystals of NdAl3(BO3)4 (NAB), Nd:GdAl3(BO3)4 (NGAB) and Nd:Gd0.2Y0.8Al3(BO3)4 (NGYAB) is presented. The Judd-Ofelt theory is applied to the fitting of experimental absorption line strengths to obtain the intensity parameters Ωt (t = 2,4,6) with root mean square errors of 11.8%, 3.8% and 8.6% for NAB, NGAB and NGYAB respectively. The intensity parameters are used to calculate the radiative transition rates, branching ratios and radiative lifetimes of Nd3+ ions undergoing transitions from 4F3/2 to 4IJ manifolds. The relevant spectroscopic parameters for laser applications (quantum efficiency and emission cross section) are also estimated. The results are compared among the three samples and other borate crystals. It is concluded that NAB is a laser crystal with high gain and thus a promising candidate for microchip laser application, while NGAB (or NGYAB) can be used as an alternative to the celebrated nonlinear laser crystal NYAB.

We present an investigation on utilizing plasmonic aluminium (Al) nanoparticles (NPs) to enhance the optical absorption of dye-sensitized solar cells (DSCs). The Al NPs exhibit not only the light absorption enhancement in solar cells with localized surface plasmon (LSP) effect but also the chemical stability to iodide/triiodide electrolyte. Besides, the lower work function (~4.06 eV), compared with that of TiO(2) (~4.6 eV), may suppress the quenching processes, such as charge transfer to metal NPs, to reduce the loss. Thus, high concentration of Al NPs could be incorporated into the TiO(2) anodes, and the power conversion efficiency (PCE) of DSCs is improved by nearly 13%. Moreover, electrochemical impedance spectroscopy (EIS) characterization also indicates that the plasmonic DSCs with Al NPs present better electrochemical performance than regular ones, which contributes to the improvement of PCE of the device.