Optical Computing Research: One Device, Five Logic Gate Operations

May 26, 2022 by Ikimi .O

Researchers recently developed a multifunctional logic gate device that promises speed and performance at low energy for data processing.

Universities are surging ahead with logic gate research to accommodate high-speed and high-performance applications, such as artificial intelligence, autonomous vehicles, machine learning, and metaverse technology.

A recent study by researchers from the Korea Institute of Science and Technology (KIST) and the Gwangju Institute of Science and Technology (GIST) introduced an optical logic gate said to conduct all five logic operations (AND, OR, NAND, NOR, and NOT) on one device.


Conceptual representation of the perovskite OELG device

Conceptual representation of the perovskite OELG device. Image used courtesy of Kim et al.


How might this research benefit future applications in data processing?


A Brief Review of All-optical Logic Gates

Many designers are currently switching to all-optical logic gates to maximize computation speeds and minimize power consumption. All-optical gates leverage optical signal processing to achieve faster computations for data processing.

The use of light inputs and outputs allows these gates to replace components such as binary counters, optical processors, electronic binary adders, decision circuits, bit-pattern recognition circuits, and data encoders. All-optical logic gates involve a number of optical components, including nonlinear interferometers, terahertz asymmetric demultiplexers, and semiconductor amplifiers.

Some key applications of these logic gates include computation, data transfer, electronic circuit control, and data processing. Designers can also leverage all-optical logic gates for pseudo-random bit sequence generation, all-optical encryption, and all-optical latches. 


All-optical Logic Gates Optimize Data Processing 

The two major categories of all-optical logic gates are logical gates with a semiconductor optical amplifier (SOA) and ones without. The SOA-based gates offer several benefits to optical computing and optical networking, including small footprints, low power consumption, high operating speeds, and high optical integration.


Classifications of all-optical logic gates

Classifications of all-optical logic gates. Image used courtesy of Singh et al.


All-optical gates exhibit exceptionally high operating speeds—up to 100 Gb/s for the Sagnac interferometer and 300 Gb/s for the acousto optical tunable filter (AOTF)—which are useful for data processing applications. All-optical processors with SOAs exhibit low power consumption and offer small footprints—desirable features for battery-powered devices. 


KIST and GIST Combine All Five Gate Operations 

Researchers from the Korea Institute of Science and Technology (KIST) and the Gwangju Institute of Science and Technology (GIST) recently developed a multifunctional logic gate device that promises unprecedented speed and performance at low energy consumption for a wide range of data processing applications.

The researchers opted for optoelectronic logical gates (OELGs) due to their rapid data transmission, broad bandwidth, and low costs. The high efficiency and high-speed capabilities of these gate types result from their ability to operate light energy in the absence of electricity.


3D chart for all logical operation outputs

3D chart for all logical operation outputs. Image (modified) used courtesy of Kim et al.


The team achieved the desired binary logic operation by vertically stacking perovskite OELGs and inputting two light signals with varying intensities and wavelengths. Consequently, they executed several logic gate operations with similar input values.

Unlike conventional logic gates that are limited to one logical operation per device, the newly developed perovskite OELG device can implement up to five basic logic operations, including AND, OR, NAND, NOR, and NOT. With this device, designers may now develop optical processors with high integration and spatial efficiency.


Caveats to Operating the Multifunctional Logic Gate Device 

In this study, the researchers concede that this multifunctional logic gate device can only operate under a number of tight parameters. 

The device depends on the bipolar spectral photoresponse characteristics of a self-powered perovskite photodetector (SPPD). The researchers also found that they needed polarity control to achieve all five logic operations. The device also requires nearly perfect accuracy in the logic gate operations—independent of current variation between pixels.

The researchers believe these findings may make it possible for designers to use optical input for ultra-small and low-power optical sensor platforms. This study may also open doors to more efficient next-gen optical networks, optical communication, and healthcare research and development.