Compact and low-power optical logic NOT gate based on photonic crystal waveguides without optical amplifiers and nonlinear materials

Abstract

An optical logic NOT gate (OLNG) is presented based on photonic crystal (PhC) waveguides without nonlinear materials and optical amplifiers. Also, a way of determining the operating parameters is presented. It is demonstrated through finite-difference time-domain simulations that the structure presented can operate as an OLNG. The optimized contrast ratio, defined as the logic-"1" output power divided by the logic-"0" output power, is found to be 297.07 or 24.73 dB. The size of the OLNG can be as small as 7a×7a, where a is the lattice constant of the PhC. Further, the OLNG presented in this paper can operate at a bit rate as high as 2.155 Tbit/s, which is much higher than that of electronic or optical logic gates developed until now. Moreover, as it is not based on the nonlinear effect, the OLNG can operate at very low powers and a relatively large operating bandwidth. This is favorable for large-scale optical integration and for developing multiwavelength parallel-processing optical logic systems.

All‐optical NOT and XOR logic gates using photonic crystal nano‐resonator and based on an interference effect

“…The main mechanisms employed in PhC-based logic gates are generally based on one of the following methods [10][11][12][13][14][15][16][17][18]: (i) the use of non-linear materials; (ii) the self-collimation effect; and (iii) the interference effect.…”

Investigation on photonic crystal based all‐optical clocked D‐flip flop

“…Space grids are chosen such that Δ x < λ /10 and Δ z < λ /10, to guarantee convergence in the simulation, where x and z axes are the horizontal and vertical direction coordinates, respectively. To obtain stable simulations, the space grid and the time grid are chosen in order to satisfy the following Courant condition [10] where c is the speed of light in free space.…”

“…The delay offered by the proposed flip flop is its response time. The response time of the proposed flip flop is calculated from the time evolving curves extracted from the outputs Q and same as in [10], as it depends solely on the linear materials. From Fig.…”

“…This time t consists of two components, one is the time due to transmission delay t 1 which is 0.049 ps and the another one is the time t 2 required to move from 0.1 to 90% of the P avg which is 0.056 ps. As the proposed structure operates on the linear materials, the falling time is from P avg to 10% of P avg which is nearly equal to t 2 [10]. With this, the pulse width can be 2 t 2 = 0.112 ps and hence the response time of the signal is 0.224 ps.…”

“…They can control, guide and limit the light in nanometre scale [9]. Many concepts such as interference [10], resonance [11–14] and self‐collimation [15] have been introduced in the design of logic devices. Among them, the multi‐mode interference (MMI) based design has occupied its own and significant place due to high contrast ratio (CR) and compactness [16–18].…”