Spectral logic gates for byte-wide WDM signal processing

We propose a new class of all-optical logic gates based on four-wave mixing, designed to operate on multiwavelength input signals. We demonstrate the XOR function with two 2.5-Gbit/s modulated input signals

Quantum-well capture and interwell transport in semiconductor active layers

The dynamics of electrons and holes in multiquantum-well semiconductor gain media involves several different transport processes, such as diffusion and drift across the barrier region, as well as capture and escape transitions between the bound and the unbound states of the quantum wells. In addition to their fundamental interest, these processes are important because of their implications for the dynamic properties of multiquantum-well lasers and optical amplifiers. Experimentally, they have been studied with several time-domain optical techniques having (sub)picosecond resolution and, more recently, with frequency-domain techniques based on laser modulation measurements. This article gives a brief review of the work done in this area and then presents in detail a frequency-domain approach, four-wave mixing spectroscopy in semiconductor optical amplifiers, to investigate intrinsic capture and interwell equilibration. This technique allows one to extend the device modulation frequency to several hundreds of gigahertz, thus providing the required time resolution, and can be configured to isolate and directly study the transport process of interest

Measurement of the stimulated carrier lifetime in semiconductor optical amplifiers by four-wave mixing of polarized ASE noise

We present a simple experiment aimed at measuring the stimulated carrier lifetime in semiconductor optical amplifiers (SOA's). The technique relies on polarization-resolved nearly degenerate four-wave mixing (FWM) of a laser source with an amplified spontaneous emission (ASE) noise source. The method can quickly characterize the bandwidth performance of active layers for application in a cross-gain or cross-phase wavelength converter

Four-wave mixing mediated by the capture of carriers in semiconductor quantum-well amplifiers

We demonstrate a technique to measure the intrinsic capture lifetime, using frequency-resolved four wave mixing (FWM). The work is based on a frequency-domain measurement of the response function associated with the transfer of a modulation from three-dimensional states above the QW to the quantum-confined two dimensional states. The principle of the experiment is shown using two DFB semiconductor quantum well lasers

Four-wave mixing mediated by the capture of electrons and holes in semiconductor quantum-well laser amplifiers

An experimental technique based on frequency-resolved four-wave mixing is proposed for the investigation of phonon-assisted capture of electrons and holes in electrically pumped semiconductor quantum wells. We show how this technique can be used to directly measure the intrinsic capture lifetime, with no need for involved numerical fits. We also present experimental results from an application of the technique to a multiquantum-well semiconductor optical amplifier. The possible impact of phase matching on the results is discussed

Polarization-dependent optical nonlinearities of multiquantum-well laser amplifiers studied by four-wave mixing

We present a detailed study of the polarization properties of four-wave mixing in multiquantum-well (MQW) semiconductor optical amplifiers (SOA's). In particular, the polarization selection rules relevant to all processes contributing to the generation of the four-wave mixing signal are rigorously derived and discussed. We then show the importance of these results in applications where four-wave mixing is used as a spectroscopic tool to study the optical nonlinearities of semiconductor gain media. For illustration, we demonstrate two novel applications of polarization-resolved four-wave mixing. The first is a new technique for measuring the recombination lifetime in SOA's, based on mixing of a pump wave with polarized amplified spontaneous emission noise. In the second, we use the same polarization selection rules to measure the interwell transport lifetime in alternating-strain MQW amplifiers. Finally, we also discuss the possibility of studying the dynamics of the optically induced phase coherence between spin-degenerate states

Wavelength conversion by cavity-enhanced injection-locked four-wavemixing in a fiber-Bragg-grating coupled diode laser

Four-wave mixing (FWM) in a fiber-Bragg-grating (FBG) coupled semiconductor laser is investigated. We show that a large resonance enhancement of the FWM conversion efficiency can be obtained when the laser cavity is injection-locked by the converted signal, and apply this technique to the wavelength conversion of 1-Gb/s modulated signals. Furthermore, we discuss how the spectral width of these resonances can be increased to make this approach suitable to higher bit rates

Folded-path self-pumped wavelength converter based on four-wave mixing in a semiconductor optical amplifier

A four-wave mixing wavelength converter with no external pump laser and very low input signal power requirements is characterized. The wavelength conversion occurs inside a high-reflection/antireflection coated semiconductor optical amplifier pigtailed with a fiber Bragg grating. The pump signal is provided by the lasing mode at the Bragg wavelength. A 1-mW optical signal modulated at 2.5 Gb/s is converted over 9 mm with error rates below 10^-9

Polarization-independent wavelength conversion at 2.5 Gb/s by dual-pump four-wave mixing in a strained semiconductor optical amplifier

We give a general expression for the polarization dependence of the four-wave mixing (FWM) efficiency in the dual-pump configuration. This expression, along with some general properties of the FWM susceptibility tensor, is used to propose a simple scheme to generate a nearly (1.5-dB variation) polarization independent FWM converted signal. The viability of this scheme is verified in a wavelength conversion experiment at 2.5 Gb/s