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The coupling effect between two gold nanospheres (GNSs) is investigated for second-harmonic generation (SHG) in this paper. When the two GNSs approach each other, the coupling effect becomes stronger, and it consequently leads to stronger enhancement of SHG. A strong coupling area between two GNSs is also found. We propose a physical quantity, the coupling strength to describe the coupling effect on SHG enhancement and show that it can fully illustrate the relationship between the SHG enhancement and the gap of two GNSs. Moreover, further calculations reveal the existence of hot spots of both fundamental wave (FW) and excited second harmonic wave in the intermediate region of two GNSs. Our study can not only help to understand the coupling effect on SHG precisely but also offer some possibility to design a nonlinear plasmonic nano-ruler. [ABSTRACT FROM AUTHOR]

Computing-in-memory (CIM) based on embedded nonvolatile memory is a promising candidate for energy-efficient multiply-and-accumulate (MAC) operations in artificial intelligence (AI) edge devices. However, circuit design for NVM-based CIM (nvCIM) imposes a number of challenges, including an area-latency-energy tradeoff for multibit MAC operations, pattern-dependent degradation in signal margin, and small read margin. To overcome these challenges, this article proposes the following: 1) a serial-input non-weighted product (SINWP) structure; 2) a down-scaling weighted current translator (DSWCT) and positive–negative current-subtractor (PN-ISUB); 3) a current-aware bitline clamper (CABLC) scheme; and 4) a triple-margin small-offset current-mode sense amplifier (TMCSA). A 55-nm 1-Mb ReRAM-CIM macro was fabricated to demonstrate the MAC operation of 2-b-input, 3-b-weight with 4-b-out. This nvCIM macro achieved $T_{\text {MAC}}= 14.6$ ns at 4-b-out with peak energy efficiency of 53.17 TOPS/W. [ABSTRACT FROM AUTHOR]

Polarization, an intrinsic ingredient of photon, plays a critical role in its interaction with matter. A general polarization state can be an appropriate superposition of two basic polarization states, say, the vertical and horizontal linear polarized state. Here we study spontaneous emission of a V-type three-level atom (with two upper states close in energy level) strongly coupled with a single-mode damped optical cavity. By defining a general polarization state of atom as a specific superposition of the two upper quantum states, we can prepare atoms with linear polarization at arbitrary direction, left and right circular polarization, and left and right elliptical polarization, similar to photons. We find that the spontaneous emission of light from these “polarized” three-level atoms shows very different profiles of side and axis spectra. This means that the polarization state of three-level atoms can become an active ingredient to manipulate its interaction with light and control the quantum interference effect. Exploitation of the coherent superposition and interference of quantum states in “polarized” atoms would allow one to deeply explore new frontiers of light–matter interaction. [ABSTRACT FROM AUTHOR]

Gold nanorods are too tiny to be manipulated using conventional mechanical methods. In this paper, we demonstrate the trapping, transferring, positioning and patterning of gold nanorods with dual-optical tweezers. The convenient manipulations are achieved by taking advantage of the longitudinal surface plasmon resonance of gold nanorods and the anisotropic optical trapping forces formed by two linearly polarized Gaussian beams. The trapped gold nanoparticles are positioned extremely firmly and quickly on a substrate compared with randomly dispersed ones. It is observed that gold nanorods show advantages over gold nanospheres with regard to positioning speed and stability. More importantly, versatile plasmon coupling effects have been achieved in some patterned nanorods. [ABSTRACT FROM AUTHOR]