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Recent progress in the field of quantum dot/dash based semiconductor optical amplifiers (SOAs) for slow and fast light is discussed. Room temperature fast light has been obtained in InAs/InP QDash based SOAs by means of coherent population oscillation and four wave mixing (FWM) effects. Typical optical delays amount to 55 ps at 2 GHz. Growth optimization of the QDashes allowed us to achieve high modal gain, leading to very similar performances, e.g. gain and FWM efficiency, to those of a bulk SOA. A novel approach based on linear spectrograms is also introduced to measure the phase shift induced by wave mixing in an SOA.

The ability of the InGaAs/InGaAlAs multi-quantum-well (MQW) system to achieve ultra-low-chirp operation under 10-Gb/s operation is experimentally demonstrated. The MQW active layer has been grown by a solid-source molecular beam epitaxy (MBE) method. Two metalorganic chemical vapor deposition (MOCVD) regrowths were used to fabricate the distributed-feedback (DFB) buried ridge structure (BRS) lasers. DFB BRS lasers with good static and spectral performance have been obtained. Under 10-Gb/s modulation those lasers exhibited a chirp value as low as 0.11 nm at -20 dB, which is attributed to an extremely small phase-amplitude coupling coefficient of 1.8. An analysis of the AM and FM modulated laser field under digital pseudorandom signal confirms the observed spectra and shows the possibility of an optimum spectrum width for lasers with small chirping. >

The linewidth enhancement factor of an InGaAs/InGaAsP strained multiquantum well optical amplifier was measured interferometrically. It varied from 3 to 18 over the wavelength range from 1500 to 1600 nm with injection currents varying from one to four times the lasing threshold of the uncoated device. A rate equation model gave differential gain and refractive index change per carrier, respectively, in the range 0.3 to 2.5*10/sup -15/ cm/sup 2/ and -5 to -8*10/sup -20/ cm/sup 3/. >

A new architecture for low-cost WDM-PON is proposed, which combines a multi-wavelength CW source with a Reflective SOA at 2.5 Gbps, with an optical budget up to 20 dB.

Conditions for the optimization of short pulse amplification and gating times in vertical cavity laser amplifiers are elucidated using femtosecond photoexcitation. The experimental results pertaining to the temporal response are analyzed by a theoretical model taking into account the carrier heating and the Fabry–Perot nature of the cavity. A 20 dB amplification gain is obtained in a vertical cavity structure at 1.53 μm with a capacity to function at a rate >25 Gb/s.

This invited paper gives an overview of the recent advances on two-dimensional photonic crystals on InP based materials. In particular, the fabrication approach developed at Alcatel-Thales III-V Lab is described in detail. Optical characterisation of photonic crystal building blocks is presented. Results on functional optoelectronic devices, such as high power lasers, tunable lasers and wavelength monitor, integrating these building blocks, are summarized.

A new tunable laser structure using a single electroabsorption (EA) tuning super structure grating section for fast wavelength switching operation, has been realized. The tuning mechanism of this absorption change distributed Bragg reflector (DBR) laser is based on a localized absorption variation induced in a multielectrode EA-SSG section. These devices exhibit a 2.5-nm tuning range with three modes and a switching time, between two successive wavelength channels, shorter than 250 ps. The output power variation under tuning is lower than 1.2 dB.

Summary for only given. We describe a very fast wavelength tuning capability (13 ps) DFB laser with an intracavity Franz-Keldysh (F-K) electroabsorptive section. The DFB laser comprises two gain sections and an intracavity F-K section providing wavelength control by an applied voltage.

By enhancing excitonic absorption in a new design of a polarization independent EA modulator, a 50 nm flat absorption spectrum, 42 GHz bandwidth devices together with 14-30 dB/V modulation sensitivity are obtained for 75 /spl mu/m long devices.

The continuous tuning range of a three-section DFB amplifier-filter with a passive centre section can be strongly enhanced by combining the carrier-induced Bragg wavelength shift with the conventional wavelength shift due to the phase shift between the two lateral gain sections. This principle is demonstrated by the fabrication of filters exhibiting a nearly constant gain of 15 dB as well as a 4 GHz filtering bandwidth over a 2.2 nm continuous tuning range.

A highly nondegenerate (up to 1 THz) four‐wave mixing experiment is performed in a bulk semiconductor amplifier. The simultaneous presence of carrier heating and spectral hole burning shows up in a four‐wave mixing experiment. A simple physical picture is given that explains the relative weight of the two saturation mechanisms in active semiconductor devices.

A laser structure having an active layer composed of several thin bulk layers is described. Buried ridge structure type Fabry-Perot lasers fabricated by using this structure exhibit a low internal loss of 15.6 cm/sup -1/ and a RC-limited modulation bandwidth as wide as 10 GHz. A reduced polarization sensitivity was demonstrated by a test optical amplifier. >

An application of nonplanar metalorganic chemical vapor deposition (MOCVD) growth to the monolithic integration of a buried ridge stripe (BRS) type distributed feedback (DFB) laser and a passive waveguide is described. The vapor phase properties have been used to butt-join a passive guide layer and an active laser layer grown successively, without growth pause. CW threshold currents as low as 17 mA have been achieved for a 1.3 mm long monolithic device. The coupling coefficient is in excess of 60%. >

Photo-written external cavity laser are a solution for DWDM sources. However, instability of the output optical power has been reported. We present our modelling results and the parameters we obtained to optimise the device. An experimental laser has been realised which shows good performances for access network applications.

A low cost integration technology has been developed to assemble 2.5 and 10 Gb/s photodiodes. It relies on flip-chipped devices with lensed fibres positioned in V-grooves. For 2.5 Gb/s the photodiode, the fibre and the transimpedance amplifier are integrated on a single Si motherboard compatible with mounting in a mini-dil module. The sensitivity is -23.5 dBm at 10/sup -10/ BER with no error floor.

A new compact photonic-integrated modulator utilising a four-element reflective electro-absorption modulator-semiconductor optical amplifier (EAM-SOA) array and silica interferometric guide arrangement is presented. The EAM-SOA active layer consists of AlGaInAs quantum wells designed in selective area growth technology, which enables an insertion gain, and the mature silica platform provides reduced optical losses. As a result, error-free 50 Gbit/s RZ-QPSK signal generation is shown.

Passive modelocking in one-section monolithic semiconductor laser diodes based on a quantum dash active layer at very high repetition rate (>40 GHz), in the 1.5 µm window, is demonstrated. 800 fs pulse generation, without any pulse compression scheme, at 134 GHz, is reported. A 50 kHz linewidth of the radiofrequency (RF) spectrum at 42 GHz is also demonstrated, the lowest value reported for any semiconductor passively modelocked laser.

A novel and very simple approach is demonstrated for distributed feedback laser-electroabsorption modulator monolithic integration. This uses the same strained multiquantum well active layer for both optical functions. Very high performance (13.6 dB extinction ratio at 1.5 V operating voltage for a 70 mu m long modulator) is reported at 1.5 mu m.

An optimised sampled-grating DBR laser, with two tuning currents, exhibits a record number of 80 accessible wavelength channels over 33 nm, with a SMSR>30 dB. A small signal AM bandwidth >3 GHz has been measured on all channels, compatible with 2.5 Gbit/s modulation. Handling of this device requires low tuning currents, leading to low power consumption.

Simultaneous emission and reception have been demonstrated with an in-line-type transceiver emitting at 1.3 µm and receiving at 1.55 µm. A receiver sensitivity of –14.6 dBm is reported at 68 Mbit/s by modulating the 1.3 µm laser simultaneously at 50 Mbit/s. The power penalty caused by the modulation was 7.4 dB.

Four-wavelength DBR laser arrays have been fabricated using a very simple approach that yields very high performance devices (10-15 mA threshold currents, 15 mW output powers at 100 mA active current, 12 nm tuning ranges and 7 GHz IM bandwidths). The array tuning range is 28 nm with 50 accessible channels.

A pigtailed transceiver module which exhibits a record responsivity of 0.5 A/W is described. A single laser chip of Fabry-Perot type V-on-U-groove (VUG) laser is packed in a butterfly type package. By improving the fibre-chip coupling, a responsivity as high as 0.5 A/W is demonstrated together with a bandwidth of 1.5 GHz. The power penalty, compared with that of a p-i-n photodiode within the same experimental configuration, is only 1.2 dB at 800 Mbit/s. >

Low‐current cw stripe double‐heterostructure (DH) lasers have been realized using a shallow proton‐bombardment technique; unlike usual proton DH lasers they involve a resistive p (GaAl)As confinement layer and a rather highly doped GaAs active region both to reduce spreading current and stripe injected carrier outdiffusion. Threshold currents are on the order of 50 mA for a 12‐μm‐wide by 200‐μm‐long cavity.

A new (GaAl)As stripe laser in which a refractive index step is created by a zinc diffusion on both sides of a conventional proton stripe structure, called a diffused bombarded stripe (DBS) laser, is presented. This diffusion provides passive transverse guiding with a relatively simple technology. The index step can be adjusted by controlling the diffused zinc concentration in relation to the active region doping level. A self-alignment technique for the diffused and bombarded stripes reduces the current leakage through the diffused regions. Lasing threshold currents as low as those of conventional proton stripe lasers are obtained. A significant improvement of light-current linearity, transverse mode stability and longitudinal mode structure are observed with the DBS lasers.

From subthreshold spectra, the gain coefficients of the distributed feedback laser modes have been deduced. Using low temperature ion beam etching, the position of one of the facets was changed and the resulting effect on the mode threshold gain difference has been investigated.

We describe in this paper the design and characteristics of buried heterostructure (BH) distributed feedback (DFB) lasers grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Typically, threshold current is 30mA for 240µm-long lasers with two cleaved facets and 40mA for lasers with one facet anti-reflection coated. Experimental values are in good agreement with theoretical predictions, based on the laser structure and the coupling coefficient of the diffraction grating. Single longitudinal mode operation is observed for temperatures up to 70°C and output powers up to 6mW. The mode rejection ratio between the DFB mode and the strongest side mode is greater than 30dB.