A first demonstration of a 40 Gbit/s all optical clock recovery module based on a design for a novel self-pulsating DFB laser is presented. The role of detuned gratings in the new device concept is evaluated and experimental results of self-pulsation at 40 GHz are reported. The successful locking to 40 Gbit/s optical data signals emphasises the future application in an all-optical 3R-regenerator

The energy of picosecond pulses emitted by single-mode stripe Q-switched and gain-switched laser diodes typically does not exceeed 10 pJ. To obtain high-brightness picosecond pulses with energies as high as 50 pJ, more complex specialist constructions such as bow-tie lasers [ 11 or master laser -power amplifier systems [2] are required. Here, we propose to increase the energy of a picosecond pulse in a non-tapered, single-lobe laser by using an ion-implantation induced saturable absorber in the form of separate sections 3-5 pm long, positioned at regular intervals within the laser cavity. Such geometry allows the volume fraction of the absorber to be increased compared with the tandem construction with a lumped absorber whilst preserving the Qswitching efficiency, makes for higher injected carrier density, and enables the use of longer lasers, all of which result in a higher pulse energy.To create the 1.5-pm single-lobed Q-switched picosecond lasers with pulse energies over 50 pJ, we used a simple InGaAsP/InP double heterostructure with a 0.25 pm thick active layer. This choice of active layer thickness was a compromise between the capacity for storing large carrier densities in the active layer and preserving single transverse mode operation. The ultrafast saturable absorber was created by high-energy heavy ion implantation; this method has been established as highly suitable for structures with thick active layers [3]. To fabricate the multisection absorber, we used the surface (as opposed to facet) implantation method developed in our earlier work for quantum-well structures [4]. The implantation by Ar ions of an energy of 3.1 MeV using a 7 pm thick photoresist layer as the protective mask enabled us to fabricate absorbers of a virtually arbitrary geometry.In the experiments, we studied gain-guided lasers with a stripe width of 10 pm. Saturable absorber sections were located symmetrically in the laser cavity, and their number was varied from one to 20 (Fig. 1). The laser was pumped by current pulses of 3 ns FWHM. Fig. 2 shows the light-current characteristics of the 500pm long implanted lasers, with the total volume fraction of the absorber fixed at 20% and different absorber geometry. The curves for lasers with several absorber sections clearly display a characteristic kink which is the signature of the saturable absorber action and corresponds to a single pulse generation. For lasers with a single, lumped absorber, no pronounced Q-switching was observed in the entire range of currents studied. The variation in the (first) pulse energy with the number of absorber sections is shown in Fig.3, demonstrating pulse energies in excess of 100 pJ for some samples with multiple absorber sections. Auto-correlation measurements give the pulse width of 30-35 ps for a 500 pm long laser with 20 absorber sections. The lateral far field of such lasers has a half width of -9-10.5 O, which implies a pulse power of 3-5 W in a single lobe.We used the earlier developed [5] distributed time-domain model to simulate the variation...

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

No abstract

No abstract