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.

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

Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals “on the fly” in the optical domain.

https://science.sciencemag.org/content/sci/286/5444/1523.full.pdf

Nonlinear Optics for High-Speed Digital Information Processing.

Semiconductor optical amplifiers are useful building blocks for all-optical gates as wavelength converters and OTDM demultiplexers. The paper reviews the progress from simple gates using cross-gain modulation and four-wave mixing to the integrated interferometric gates using cross-phase modulation. These gates are very efficient for high-speed signal processing and open up interesting new areas, such as all-optical regeneration and high-speed all-optical logic functions.

/pdf/semiconductor-optical-amplifier-based-all-optical-gates-for-4wdu6yc0vj.pdf

Semiconductor optical amplifier-based all-optical gates for high-speed optical processing

A single wavelength channel, optical time division multiplexed and polarisation multiplexed 128 Tbit/s signal has been successfully transmitted over 70 km Third- and fourth-order simultaneous dispersion compensation was used with a 10 GHz synchronous phase modulator The input pulse width was 380 fs, and the transmitted pulsewidth was 400 fs All 128 channels demultiplexed to 10 Gbit/s had a bit error rate of less than 1/spl times/10/sup -9/

1.28 Tbit/s-70 km OTDM transmission using third- and fourth-order simultaneous dispersion compensation with a phase modulator

Recent progress toward multiterabit/s optical transmission systems employing all-optical ultrafast signal-processing technologies is described. Focus is placed on optical time-division multiplexing (OTDM), as well as optical time- and wavelength-division multiplexing (OTDM/WDM) technologies leading to multiterabit/s transmission capacity. The key technologies, including ultrafast pulse generation, all-optical multiplexing/demultiplexing, and optical timing extraction techniques, are also described, together with state-of-the-art performances and future prospects.

All-optical signal processing for terabit/second optical transmission

A 640 Gbit/s TDM signal has been successfully demultiplexed to 10 Gbit/s with a walk-off free, ultrafast, 450 m long nonlinear optical loop mirror (NOLM). The NOLM consists of nine 50 m long sections of dispersion flattened fibre (DFF) with different group delay characteristics. The walk-off between the signal and control pulses for each of the nine fibres was within /spl plusmn/400 fs. By properly connecting them, a total walk-off of <100 fs has been achieved.

T. Yamamoto

Papers

Ultrafast nonlinear optical loop mirror for demultiplexing 640 Gbit/s TDM signals