Broadband Multifunctional Plasmonic Logic Gates

Abstract

beyond the diffraction limit, provide a promising platform for the development of all-optical logic circuits. [12][13][14][15][16][17][18] Recently, several groups have reported that plasmonic microstructures, either nanowires or nanogrooves, could be used to build microscale all-optical logic gates. [19][20][21][22][23] Using different microfabrication techniques, devices with varying scales and output intensity contrast ratios have been demonstrated. In spite of the progress so far, these devices either have a small contrast ratio which affects the signal extraction, or have a big loss which is hard for integration. More importantly, broadband response and multifunctionality have not been demonstrated, which are crucial for high-density data transmission and processing.In this work, we propose and demonstrate broadband (over 100 nm in free-space wavelength) Boolean logic devices, including seven fundamental logic gates, while maintaining their high-contrast-ratio properties. Each device contains a curved grating with a rectangular groove profile for the input port(s) and a subwavelength hole as the output port. Because of its unique geometric property, the curved grating can transduce the input optical signals to propagating surface plasmon polaritons (SPPs), and focus them to the focal point without using any additional guiding structure. Consequently, the SPPs from different input ports can interfere at the focal point, and are coupled out to the far-field by using the hole as the output signal port. Essentially, this configuration is a zero-order interferometer, which naturally has a wide operating bandwidth. Besides, when propagating freely, the SPPs experience minimal losses in comparison with the case propagating in waveguides. [24] The loss is further decreased by using single-crystalline silver, instead of the polycrystalline silver films usually prepared by thermal evaporation. Meanwhile, these logic gates can maintain the high intensity contrast ratio even using front illumination. Here, we obtain a maximum contrast ratio of 29 dB. In addition, we used only one geometric configuration to realize all the fundamental logic gates, making this method easy for device fabrication and system integration.The designed device configuration is illustrated in Figure 1a. The input optical signal is incident on the curved grating and transduced into SPPs, which are focused to the grating focal point. To build a broadband device, two conditions need to be met: the first one is that the grating has a broadband spectral response to the incident signals, and the second one is that the focus of the input signals from different input ports is achromatic, i.e., independent of the operating wavelength.Plasmonic logic gates provide a promising platform to realize diffractionunlimited all-optical logic circuits. However, previous plasmonic logic gates suffer from narrow bandwidth and high loss. Here, broadband plasmonic logic gates are proposed and demonstrated using a unique design based on curved silver gratings. These log...

Reconfigurable MEMS Fano metasurfaces with multiple-input–output states for logic operations at terahertz frequencies

“…5f . Experimental extraction of the near-field information in the THz part of the spectrum is challenging, however, recent demonstrations using tip based THz near-field microscopy 41 – 43 can be used as one of the ways to retrieve the near-field information in terms of output field intensity states that in turn can be used to sequentially trigger the input voltage of the cascaded NAND device. This could enable the near-field cascading of the logic gates in the complementary metal-oxide-semiconductor (CMOS) configuration.…”

Performing optical logic operations by a diffractive neural network

“…Note that this judgement criterion remains valid and consistent for all logic operations being considered, distinct from the case in refs. 11,16 . Before implementing the diffractive neural network, the transmission coefficients tr l…”

“…The logic operation lies at the heart of all computers 7 . Correspondingly, optical logic gates [8][9][10][11][12][13] , including plasmonic logic gates, are essential for the further exploration and development of optical analogy computing, nanophotonic processing 14,15 , and the field of cryptographically secured wireless communication 16 . As such, there are growing and strong interests to provide optical logic gates with complete logic functionality in photonic systems with compact dimensions.…”

“…Previous methodologies towards optical logic gates considered mainly constructive/destructive interference effects, including linear [8][9][10][11] and nonlinear interference 12,13 , between the input light signals. We note that the reported works are heavily dependent on the precise control of the basic properties of two input light signals, the control light and/or the pump light, including their phase difference, polarization, and intensity 7 (Supplementary Note 6); if the two nanowires are close to each other, such as for the plasmonic logic gate, there is also a stringent requirement on the size of input light beams to avoid a potential false input.…”

Frequency-domain ultrafast passive logic: NOT and XNOR gates

“…The primary obstacle is the impractical amount of energy consumed while switching transistors from one logic state to another at high speeds 2,3 . Alternatives to electronic gates have been proposed using optics [6][7][8] , plasmonics [9][10][11][12] , magnetism 13,14 , phononics 15,16 , and electromechanics 17 . Such gates operate by nonlinearity, similarly to an electronic transistor, or by splitting/combining the signal in linear interferometric devices.…”