We establish an extensive experimental registration technique to study the dependence of the pulsation in a three-section DFB-laser. The common feature of continuous pulsation domains is highlighted and the impact of geometrical parameters is investigated. (C) 1999 Optical Society of America.

A theoretical model of a self-pulsating three-section DFB laser with an integrated phase tuning section is established. It is based on traveling wave equations and the standard carrier rate equations. Parameters of an existing device are used for applying the model. Key conditions and characteristics of self-pulsations (SPs) are modeled and compared with experimental results. The important role of phase tuning for turning on the SP is pointed out. The dependence of the SP regime on the detuning between the Bragg wavelengths in the laser and reflector is determined and the essential role of phase-readjustement is identified. Frequency tuning via the laser currents, as well as the pulse shape at various frequencies, is investigated. This allows us to identify the mechanism for frequency tuning. The model turns out to be a good tool to improve our knowledge of the self-pulsation effect and to design optimized devices.

The locking time of an all-optical clock is investigated. Self-pulsating, DFB lasers with detuned gratings are applied the clock locks within 10 "one" bits (1 ns) to injected data packets and keeps synchronized for some hundred "zero" bits.

Multisection DFB lasers showing high-speed self-pulsations (SP) have opened a new field for the optical clock recovery at high bit rates. The basic effect was discovered in 1992 with 2-section devices [1]. Since then, optimization of the devices led to much improvement and the system capability has been demonstrated [2]. The present generation of devices is AR-coated and consists of two DFB sections and one phase section integrated in between (Fig. 1). The two DFB sections are basically identical, only lengths and pump levels are different.

The system performance of an all-optical clock recovery module based on a self-pulsating DFB laser is characterized at 10 Gb/s. Penalty free operation is verified relative to a synthesizer in back to back experiments and relative to an electronic PLL in a transmission experiment over 105 km fibre.

In this work high bandwidth and polarization independence were tackled by employing a travelling wave electrode and a tunnelling barrier QW (TBQW) structure, respectively, as the basic guidelines in the design of the switching element, a Mach-Zehnder interferometer (MZI). With a small variation of the waveguide network connecting the MZI either a time division demultiplexer (DEMUX) or a modulator were fabricated. The development of the DEMUX is part of the European ACTS HIGHWAY project.

Large electro-optic modulation is available in InP based photonic devices for communication systems working in the 1.55 mu m window. This is because the quantum confined Stark effect (QCSE) can be exploited to switch and modulate the light wave. But signal processing in the receiver front end often has to be polarisation independent. However, the QCSE proves to be inherently polarisation dependent. In the present work this problem was tackled by applying a tunnelling barrier QW (TBQW) structure. This concept was reported recently for the GaAs material system [1] and is transferred here to InP based devices for the first time. Its realisation necessitates to optimise the electrical, optical and structural material quality in order to make it suitable for device applications. First the investigations concerning the epitaxial growth conditions are described. Then the experimental results for TBQW structures are reported, including the polarisation independent electro-absorption characteristics of Mach-Zehnder interferometers (MZI) incorporating strained TBQWs. Such a MZI switch is the basic building block of a high speed time division demultiplexer (DEMUX). The development of the DEMUX is a part of the European ACTS HIGHWAY project.

Recently, a novel optical modulator heterostructure has been introduced based on voltage controlled electron transfer from a reservoir to a closely spaced quantum well. It has proven to exhibit large absorptive and refractive modulation at high speed and low power dissipation. In order to achieve monolithic integration with the existing high quality InGaAsP/InP lasers for high bit-rate systems, it is crucial to implement such devices within the same material system. In this letter, we demonstrate for the first time, InGaAsP/InP electron-transfer modulators grown using metalorganic vapor phase epitaxy.

Electro-absorptive long wavelength (λ=1550 nm) semiconductor modulators with low drive voltage are indispensable components for future high bit-rate communication networks. Recently, Wannier-Stark Localization (WSL) in an InGaAs/InAlAs superlattice was employed to achieve sub-volt operation combined with high extinction [1]. However, such devices are not readily integrable with the existing high quality InGaAsP/InP lasers. In this work we demonstrate for the first time electro-absorptive optical modulation by WSL in an InGaAs/InGaAsP superlattice. The WSL sample is grown as a p-i-n heterostructure (cf. Fig. 1) on an n+-InP substrate by low pressure (2×103 Pa) metalorganic vapor phase epitaxy. The intrinsic region consists of five Wannier superlattices each of them with five periods of quantum well and barrier layers. Moreover, quaternary spacer layers were employed to improve the quality of epitaxial growth. Superlattice formation was verified by the observation of satellite peaks in the double crystal x-ray diffraction rocking curves. Photoluminescence peak (300 K) for the Wannier superlattice was seen at 1450 nm without any traces of ternary signal.