Illustration of optical logic AND gate. We set α₀l = 3.75, R₁ = 0.8, and R₂ = 0.9, the linear fit curve in the saturated regime is plotted as a red dashed line. We can obtain the values of I_l, I_u, and a to be 4.74, 5.24, and 1.07 from the bistable curve, respectively. The two vertical green dotted lines characterize the bistable regime I_u − I_l and the horizontal green dotted line shows the value of a.