All-optical Processing Systems Research Articles

Tunable delay line based on balanced coupled resonators cladded with VO2 films.

A delay line consisting of a balanced side-coupled integrated spaced sequence of resonators and phase change material VO2 films is employed to realize continuously tunable delays with ultrafast response and low distortion. Simulation results show that a tunable delay of up to 80 ps with a 10% broadening, 150 GHz bandwidth, and 0.087 dB/ps delay loss is achieved from this structure. Taking advantage of photoinduced phase transition of VO2 films, this device obtains a switching time of less than 0.6 ps and effective compensation for group delay dispersion. This delay line shows advantages in the high-bit-rate all-optical processing systems.

Design Plasmonic Optical 4 × 2 Encoder Based on 2D Photonic Crystal Ring Resonator

Digital encoders are one of the key devices required in optical communication and digital signal processing systems. In this paper, a new photonic crystal structure is used to design all-optical 4 × 2 encoder constructed from GaAs rods with square lattice in the pentane background based on plasmonic effect. Gold rods have also been used at the interface of dielectric rods and lines defect, which create plasmonic properties into the photonic crystal structure. The designed optical device is composed of four input waveguides and two output waveguides with two ring resonators at the resonant wavelength of 1.14 μm with TM polarization. The presented encoder platform has the small size of 19 μm × 33 μm that makes it to integration into compact all-optical processing systems. The encoder operation is simulated and analyzed with numerical finite-difference time-domain (FDTD) method and plane wave expansion (PWE) method. In the proposed structure, we have shown that by selecting the appropriate radius size for the resonant cavities, the desirable wavelength can be obtained. The maximum values of transmission efficiency for the first and second outputs are 82% and 96%, respectively. Resonant cavities are also located in the crystal lattice in such a way that by activating third input, 50% and 48% of the input signal will be obtained in each output ports indicating (1,1) logic state. So the new plasmonic photonic crystal encoder could be future applicable in the field of optical computing.

Design of an Ultrafast Frequency Doubling Photonic Device**Supported by the Natural Science Foundation of Heilongjiang Province under Grant Nos F201312, F2016023 and QC2015086, and the National Natural Science Foundation of China under Grant No 61405049.

Ultrashort pulses complicate the frequency conversion in a nonlinear crystal, where group velocity mismatch becomes the main obstacle due to dispersion. We present a design for group velocity compensated second harmonic generation in a modulated nonlinear structure, embedded in a liquid crystal box. In this structure, nonlinear crystals act as sources of signal and liquid crystals compensate for group velocity mismatch originating from nonlinear crystals. There are the advantages of the flexible, controllable birefringence of liquid crystals. Meanwhile, a method calculating the parameters of this type of structure is presented. To make it clear, an example is provided. Furthermore, the structure can also be shaped as a waveguide to support integration into other optical devices, applicable to all-optical processing systems.

One-way light transmission in compact SOI structures

Nonreciprocal transmission of the light is fundamental in all-optical processing systems and, it is in a great demand in advanced optical communication networks. Optical devices based on one-way light transport are essential to prevent interference between various integrated components of the optical networks. The integration of these devices in a single platform is a challenging task due to material incompatibilities between the integrated devices. We report all-silicon-on-insulator waveguides where the asymmetric light propagation is obtained. These waveguides are coupled using micro rings with modified gaps. We show that unidirectional optical transmission of the light can be accomplished by non-symmetric distribution of micro rings and gaps between the waveguides. We also show the time domain snapshot of the light propagation from left to right and from right to left behaves differently. The advantageous properties of the proposed structure are the compatibility with the integrated photonics and can serve as a main building block for designing integrated silicon nanophotonic devices.

Realization of All Optical Half Adder by Utilizing DM Soliton Pulses

optical processing deals with realizing digital circuits using optical elements only. To achieve higher bit rates and reduced cost efficiency all- optical processing became the need of the hour. All- optical logic gates are the key components in the all-optical processing systems. In this paper an all-optical Half Adder using dispersion managed solitons as input pulses and employing cross gain modulation of Semiconductor amplifier is simulated at 100 Gb/s. The circuit employs two all-optical XOR and AND gate.

Ultrahigh-Speed Optical Processing Using Space-Time Duality

Temporal all-optical processing systems—which are based on the space-time duality of light—provide a practical approach for meeting the bandwidth demands of next-generation ultrahigh-speed technologies.