Realization of ultra-compact and high contrast ratio all-optical 4-to-2 encoder based on 2D photonic crystals

Optical encoders are widely used circuits in digital systems. One of the most critical features of an optical encoder is the power values in two logic states; low and high. The difference between these two values is expressed with the contrast ratio (CR) parameter. This research has designed and simulated an optical encoder based on a two-dimensional (2D) photonic crystal with four inputs and two outputs. The results show that the proposed structure has low power in low mode and high intensity in high mode. This difference in two logical modes has caused the proposed encoder to have CR = 19.8 dB, which is improved compared to previous works. Also, the proposed structure is very compact and its footprint is as small as 96.88 µm². The data speed for the designed encoder is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>B</mml:mi> <mml:mi>R</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> <mml:mrow><mml:mspace></mml:mspace> <mml:mtext>Tb/s</mml:mtext></mml:mrow> </mml:mrow> </mml:math> . This encoder can be used in high-speed optical integrated circuits with low error according to the obtained values.