fig5

Figure 5. (A) Incident optical power versus photocurrent; (B) A_InGaAs,x of grid UTC-PD at 1,550 nm x-polarized light illumination as a function of the number of units. The first and second elements in parentheses represent the number of grid units in the x- and y- directions, respectively, where n is an arbitrary value and N stands for infinity. Scattering boundary conditions are added in the dimension corresponding to n, whereas periodic boundary conditions are added in the dimension corresponding to N; (C) 3-dB-f_RC (black line), 3-dB-f_tr (blue line) and 3-dB-bandwidth (red line) of the grid UTC-PDs versus the number of units; (D) Schematic of a 2 × 2 PD array based on the grid structure. The period of the grid unit is 1.2 μm. When the number of grid units of one photodetector is 1,600, the area of the 2 × 2 array is 96 × 96 μm². UTC-PD: Uni-traveling-carrier photodiode; f_RC: frequency of resistor-capacitor bandwidth; f_tr: frequency of carrier transit time bandwidth.