High-speed All-optical Switching Research Articles

Photonic crystal all-optical switch based on a nonlinear cavity

We demonstrate high-speed all-optical switch structure using an ultra-small nonlinear cavity coupled to input and output waveguide. The whole structure is based on a square lattice photonic crystal formed by rods of refractive index nr=3.4 in an air background. Finite-difference time-domain method is used to analyze the device characteristics. By analyzing of behavior of structure, we show that switching from OFF to ON occurred because resonant wavelength shift is caused by Kerr effect. The simulation result shows that switch has a high-speed response of ∼26ps. Since the structure has an ultra-small length of 12μm, it has a potential to use in integrated optical-circuits.

Time-resolved chirp properties of semiconductor optical amplifiers in high-speed all-optical switches

The chirp properties of semiconductor optical amplifiers in all-optical switches are numerically investigated using a field propagation model. The chirp dynamics in the blue-shift and red-shift sideband are analyzed under the injection of random optical pump pulses. We also analyze the impact of the blue-detuned filtering scheme that is used to eliminate the pattern effect and enhance the operating speed of the optical switching. The reason for overshoots in eye diagrams in the blue-detuned filtering scheme is explained. We find that overshoots result from the ultrafast blue chirp induced by carrier heating and two-phonon absorption. These results are very useful for semiconductor optical amplifier-based ultrafast all-optical signal processing.

All Optical Switching With a Single Quantum Dot Strongly Coupled to a Photonic Crystal Cavity

We theoretically analyze the optical nonlinearity present at very low optical power in a system consisting of a quantum dot strongly coupled to a cavity, and show that this system can be used for ultralow power and high-speed all-optical switching. We also present numerical simulation results showing both the detailed temporal behavior of such switch and the time-integrated energy transmission through the cavity. We use two different approaches-a quantum optical one and a semiclassical one-to describe the system's behavior, and observe reasonable agreement between the outcomes of numerical simulations based on these two approaches.

Sub-femtojoule all-optical switching using a photonic-crystal nanocavity

Although high-speed all-optical switches are expected to replace their electrical counterparts in information processing, their relatively large size and power consumption have remained obstacles. We use a combination of an ultrasmall photonic-crystal nanocavity and strong carrier-induced nonlinearity in InGaAsP to successfully demonstrate low-energy switching within a few tens of picoseconds. Switching energies with a contrast of 3 and 10 dB of 0.42 and 0.66 fJ, respectively, have been obtained, which are over two orders of magnitude lower than those of previously reported all-optical switches. The ultrasmall cavity substantially enhances the nonlinearity as well as the recovery speed, and the switching efficiency is maximized by a combination of two-photon absorption and linear absorption in the InGaAsP nanocavities. These switches, with their chip-scale integratability, may lead to the possibility of low-power, high-density, all-optical processing in a chip. All-optical switching energies as small as 0.42 fJ — two orders of magnitude lower than previously reported — are demonstrated in small photonic crystal cavities incorporating InGaAsP. These devices can switch within a few tens of picoseconds, and may therefore have potential for low-power high-density all-optical processing on a chip.

Simultaneous generation of intersubband absorption and quantum well intermixing through silicon ion implantation in undoped InGaAs/AlAsSb coupled double quantum wells

We demonstrated the intersubband absorption in undoped InGaAs/AlAsSb coupled double quantum wells through silicon ion implantation and rapid thermal annealing. For an implantation dose of 1×1014 cm−2, the actual carrier density of a sample annealed at 600 °C for 1 min was ∼7.5×1013 cm−2 (∼75% activation efficiency); the activation energy was ∼1.41 eV. The simultaneously generated quantum well intermixing (QWI) was nonuniform due to the silicon ion distribution. The effects of QWI nonuniformity on both intersubband and interband transitions were explained by eight-band k⋅p calculation. This study will open a route for monolithic integration of intersubband-transition-based high-speed all-optical switches.

High-speed all-optical switching in ion-implanted silicon-on-insulator microring resonators

We demonstrate high-speed all-optical switching via vertical excitation of an electron-hole plasma in an oxygen-ion implanted silicon-on-insulator microring resonator. Based on the plasma dispersion effect the spectral response of the device is rapidly modulated by photoinjection and subsequent recombination of charge carriers at artificially introduced fast recombination centers. At an implantation dose of 1 x 10(12) cm(-2) the carrier lifetime is reduced to 55 ps, which facilitates optical switching of signal light in the 1.55 mum wavelength range at modulation speeds larger than 5 Gbits/s.

All-optical switching with fast-response variable-index materials

A high-speed all-optical switch using a fiber optic coupler and a light-sensitive variable-index material is described. The mechanism of index variation with light is discussed, as well as the results of switching with polydialkylsilane and polythiophene for index modulation.

Design of packet-switched network using optical signal processing techniques

In this paper, we design an optical packet-switched network with an optical ring resonator (ORR), a delay line decoder (DLD), and an optical address translator (OATR). The ORR can discriminate the header/payload directly in the optical domain. The DLD, together with the optical threshold device, can be used as an optical correlator for the routing control signal. The OATR uses time-slot-interchange (TSI) technology to translate the optical address for the next optical switching stages. These optical signal processing techniques can be applied to future high-speed all-optical switching networks. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 104–109, 1999.

Semiconductor laser amplifiers for ultrafast all-optical signal processing

Recent progress in the use of semiconductor laser amplifiers (SLA's) for high-speed all-optical switching is reviewed. We show that, despite SLA's having lifetimes of ⩾100 ps, they are, to date, the most promising material system for all-optical ultrafast signal processing. We highlight the role of SLA carrier dynamics, which permits switching rates faster than the recovery time. Experimental results are presented that imply that switching rates of as much as ∼100 GHz should be possible. Recent experiments are described in which SLA-based switches were incorporated into novel all-optical architectures.

Constraints on coherent control of quantum-well excitons for high-speed all-optical switching

Coherent control of excitons in quantum wells at high repetition rates is investigated theoretically to determine the practical constraints for application in high-bit-rate optical switching. A tradeoff between optical pathlength (number of quantum wells) and excitation density is found that severely limits the applicability of this mechanism for implementation in 100-Gb/s optical systems.

Coherent control of quantum-well excitons in a resonant semiconductor microcavity for high-speed all-optical switching

Coherent control of excitons in quantum wells embedded in a resonant planar semiconductor microcavity versus in quantum wells without the cavity at high repetition rates is investigated theoretically to determine the practical constraints for application in high bit-rate optical switching. It is shown that /spl pi/-shifted pulse pairs are optimal to coherently populate and depopulate the QW on the 100-fs timescale. For the cavity-free case, the small optical nonlinearity will require devices incorporating /spl sim/100 quantum wells; the resonant enhancement of the confined mode for the case of the cavity leads to an effective increase in the optical nonlinearity and thus a reduction of the required number of quantum wells to /spl sim/10. In addition, switch architectures that avoid interferometers, and thus will have superior temperature and mechanical stability, based on the microcavity are proposed. We believe that although room-temperature operation of a 100-Gb/s switch based on this principle may be difficult, operation at liquid-nitrogen temperature should be feasible.

High-speed all-optical switching experiment in Mach–Zehnder configuration using GaAs waveguide

We report the results of a high-speed all-optical switching experiment in Mach–Zehnder configuration using a GaAs waveguide. The all-optical switching is based on the nonlinear refractive index change induced by the band-filling effect in the GaAs waveguide. To achieve high-speed operation without being limited by the slow carrier relaxation time, a dc electric field is externally applied to the nonlinear waveguide to sweep carriers away from the light guiding region. The FWHM (full width at half maximum) of the switching waveform without the externally applied electric field is about 800–900 ps. As the electric field is increased, the FWHM is reduced to about 80–90 ps.