Analog-to-Digital Conversion Based on Single Ring 2-D Square-Lattice PCRR

In this paper, according to the benefits of all optical analog-to-digital converters (ADCs) and with the aid of a 2-D square-lattice all-circular photonic crystal ring resonator (PCRR), a 2-bit ADC is proposed. The rod of this structure is made of silicon with refractive index of n1?3.47 and the substrate area is air with refractive index n2=1.00 with the filling ratio r/a=0.22. The ADC with four different logical states i.e.00, 01, 10, and 11 that creates the condition of 2-bit conversion, in central wavelength 1.55?m is designed by creating two linear defect waveguides coupled to the resonator and selecting the appropriate coupling length. The general dimensions of the proposed structure are about 8.6?m×8.6?m. Dispersion diagram of linear defect waveguide and resonance modes of circular resonator are calculated using plain wave expansion method (PWE) and output power spectrum that create the logical states of the converter are calculated using finite difference time domain (FDTD) method.