R.J. Manning

Three-wavelength device for all-optical signal processing.

We describe the operation of a semiconductor laser amplifier as a nonlinear element, using a novel three-wavelength configuration, which enhances the recovery rate of the nonlinear refractive index and permits choice of its sign and magnitude. Simple rate-equation analysis suggests that 100-GHz operation should be possible with powers of ~1 W.

Semiconductor laser amplifiers for ultrafast all-optical signal processing

Recent progress in the use of semiconductor laser amplifiers (SLAs) for high-speed all-optical switching is reviewed. We show that, despite SLAs 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.

All-optical full adder with bit-differential delay

We experimentally demonstrate an all-optical digital processing circuit that can perform the full addition of binary optical words. The circuit comprises two coupled all-optical regenerative memories. One memory performs the modulo-2 addition and the other memory generates the carry bits from the addition. The two memories are configured to differ in capacity by a single bit so that the full adder operates in bit-differential mode.

All-optical pseudorandom number generator

We demonstrate an all-optical pseudorandom binary number generator comprised of two coupled regenerative optical memories and an XOR gate. Both sub-maximal binary sequences and maximal length pseudorandom sequences were successfully demonstrated.

All-optical binary half-adder

We demonstrate an all-optical binary half-adder which simultaneously generates the bit-serial SUM and CARRY bits from two binary modulated input pulse trains. Additionally, the circuit can implement the XOR function of the two input data streams.

Ultra-high-speed OTDM networks using semiconductor amplifier-based processing nodes

The use of semiconductor amplifiers in high speed communications systems is reviewed. Processing of signals at 10 Gb/s in a 40-Gb/s OTDM network is demonstrated using nonlinear loop mirror configurations, and mode locked ring lasers. Particular attention is paid to the role of carrier density modulation, long believed to be a detrimental effect, and its useful exploitation. >

All-optical parity checker with bit-differential delay

We demonstrate an all-optical digital processing circuit that can check the parity of a binary optical word. The circuit operates by repetitively inputting the binary word to be checked into an optical memory whose capacity differs from the repeat time of the input word by one bit. The accumulated parity of the input word is generated by applying the XOR logical function to the repeated input word and the time-shifted stored word in the memory.

Electron and hole dynamics of InAs∕GaAs quantum dot semiconductor optical amplifiers

Single-color and two-color pump-probe measurements are used to analyze carrier dynamics in InAs∕GaAs quantum dot amplifiers. The study reveals that hole recovery and intradot electron relaxation occur on a picosecond time scale, while the electron capture time is on the order of 10ps. A longer time scale of hundreds of picoseconds is associated with carrier recovery in the wetting layer, similar to that observed in quantum well semiconductor amplifiers.

On ultrafast optical switching based on quantum-dot semiconductor optical amplifiers in nonlinear interferometers

It is shown that interferometers containing quantum-dot semiconductor optical amplifiers can be effective for ultrafast cross-phase modulation and digital signal processing with low dependence on the specific random data pattern.

Non-linear optical studies of nickel dithiolene complexes

The third-order optical non-linearity, χ(3), linear absorption coefficient, α, and the ratio of the real to imaginary parts of χ(3)have been measured at 1.06µm for a range of nickel dithiolene complexes with absorption bands between 0.77 and 1.06µm. From these data the non-linear retractive index, n2, and the device-based figure of merit, W(=Δnsat/αλ), were calculated. W was found to exceed 2 for materials with absorption maxima below 0.8–0.85µm. The non-linear refractive index of a poly(methyl methacrylate) host doped with 8 × 1019 molecules cm–3 of a nickel dithiolene was also measured and found to be nearly 2 × 10–9cm2 kW–1.