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- Logic functions based on optical bias controlled SIC Tandem devicesPublication . Vaz da Silva, V; Vieira, Manuel; Vieira, Manuela; Louro, Paula; Fantoni, Alessandro; Barata, ManuelThe purpose of this paper is the design of an optoelectronic circuit based on a-SiC technology, able to act simultaneously as a 4-bit binary encoder or a binary decoder in a 4-to-16 line configurations and show multiplexer-based logical functions. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n multilayered structure produced by PECVD. To analyze it under information-modulated wave (color channels) and uniform irradiation (background) four monochromatic pulsed lights (input channels): red, green, blue and violet shine on the device. Steady state optical bias was superimposed separately from the front and the back sides, and the generated photocurrent was measured. Results show that the devices, under appropriate optical bias, act as reconfigurable active filters that allow optical switching and optoelectronic logic functions development providing the possibility for selective removal of useless wavelengths. The logic functions needed to construct any other complex logic functions are the NOT, and both or either an AND or an OR. Any other complex logic function that might be found can also be used as building blocks to achieve the functions needed for the retrieval of channels within the WDM communication link. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- Majority logical function using a pi'npin a-SiC:H structurePublication . Silva, V.; Barata, Manuel; Louro, Paula; Vieira, Manuel; Vieira, ManuelaThe majority logic function has a true output value whenever more than half of the inputs have a true value. Majority logic, also known as majority voting, is used in many systems, for fault-tolerant design, in bioelectronics, and quantum dot cellular automata. The pi'npin heterostructure p-i'(a-SiC:H)-n/p-i(a-Si:H)-n can be illuminated from both back and front surfaces. Steady state illumination, optical bias, controls the light-to-dark sensitivity in the visible range. Several input data channels, each with a different wavelength, illuminate the front surface. Results show that a majority function of 3 and 5 inputs (MAJ-3, MAJ-5) is built with the pi'npin device projecting the way for a MAJ-n function.
- Logical functions in a tandem SiC devicePublication . Vaz da Silva, V; Vieira, Manuel; Louro, Paula; Barata, Manuel; Vieira, ManuelaThis study demonstrates logical functions based on SiC technology. The device consists of a p-i’(a-SiC:H)-n/p-i(a-Si:H)-n heterostructure with low conductivity doped layers. Experimental optoelectronic characterization of the fabricated device is presented and shows the feasibility of tailoring channel bandwidth and wavelength by optical bias through illumination in the back and front sides with violet light. Two digital light signals are applied to the front side of the device while violet light steadily shines either at the back or front sides. Each digital light signal is composed by two wavelengths, one from the long and the other from the short visible wavelength range. One digital signal is the Red–Blue pair and the other the Green–Violet. The NOT logical function is shown with the Red–Blue pair likewise with the Green–Violet pair. The background biasing either at front or at the back side allows for an inverted signal or non inverted signal. Experimental results show and explain the interaction of two digital signal pairs and the identification of the logical AND, OR and XOR operations by the selection of the violet biasing illumination side.
- Reconfigurable photonic logic architecture: an overviewPublication . Vaz da Silva, V; Barata, Manuel; Vieira, ManuelaThe photosensor studied in this document, is an amorphous silicon structure deposited on transparent glass allowing illumination on both sides. It responds to wavelengths from near infrared range to the ultra-violet. The front illumination surface is used for inputting light signal. The dynamic characteristics of the photosensor are altered by using optical bias on either surface of the sensor, thus the same input results in different outputs. Experimental studies made with the photosensor evaluate its applicability as a multiplexer, demultiplexer and logical operations device. A memory effect was observed. A programmable pattern emission system, and a validation and recovery system were built to illuminate the sensor with input light signals and to analyze the resulting output.