Active multi-mode interferometer (MMI) laser diodes were realized in InGaAsP/InP for high-power applications. They achieved increases in output powers of 90 mW, which correspond to 30% increases, as compared to the powers of regular single-lobe laser diodes fabricated simultaneously with the active MMI-LDs. The resulting maximum powers of the active MMI-LDs were 380 mW at a wavelength of 1.45 μm. The implemented active MMI-LDs showed stable regular single-transverse-mode outputs up to the maximum power.

A new type of semiconductor optical amplifier (SOA), consisting of a singlemode waveguide with a 1/spl times/1 multimode-interferometer (MMI) section, is proposed and experimental results presented. Maintaining single lobed outputs these new MMI amplifiers show improvements of 2 dB in gain and 5 dB in saturation output compared to regular single-stripe SOAs.

An active multimode interferometer (MMI) laser diode (LD) concept is presented, which has been verified via a 1.48 mu m high power application. The active MMI-LDs, having a larger pumping area compared to that of regular single-stripe LDs with the same length showed no significant degradation in slope efficiency and up to 50mW power improvement resulting in 170 mW saturated output power.

A novel laser diode, in which the pumping area is increased by a multi-mode interference (MMI) coupler, is proposed to maintain single-lobe outputs up to high powers. Utilising active 1x1 MMI couplers between singlemode waveguides, up to 90% higher single-lobe and fibre-coupled output powers were obtained at 1.3 mu m.

Semiconductor optical amplifiers for 1.3 mu m are realized combining single-step grown bulk active region with ridge-waveguides. Achieved fiber-to-fiber gains are in excess of 27 dB with spectral ripples below 0.2 dB, Gain is polarization insensitive to within 1 dB over the entire range of driving current, 1.28 mu m to 1.34 mu m wavelength and 10 degrees C to 50 degrees C heat sink temperature. Intrinsic noise figure is 6.3 dB, Gain saturates at +10 dBm.

Improved extinction ratios reaching 20 dB are experimentally demonstrated for optically controlled Mach-Zehnder interferometer type InP waveguide switches with semiconductor optical amplifiers and phase control sections in their arms. The improvements are due to optimisation of both the bias currents of the optical amplifiers and the relative phases in both arms of the interferometer.

A novel, monolithically integrated gain-clamped semiconductor optical amplifier exploiting a Mach-Zehnder interferometer configuration for spatial separation of travelling-wave signal and clamping laser light is demonstrated. The allowed total signal input power for undistorted multichannel amplification is improved by 16 dB to +1 dBm.

We report on the fabrication and characteristics of multifunctional two-section polarization independent bulk ridge-waveguide semiconductor optical amplifiers operating in the 1.3 mu m wavelength region. These devices can be used as optically preamplified photodetectors and as high-gain in-line transparent detectors/travelling wave amplifiers. The polarization-independent optically preamplified photodetectors reach overall responsivities of 230 A W-1 or 11500 V W-1 in a 50 Omega system and sensitivities of -28.3 dBm at 1.2 Gbit/s and -24.4 dBm at 3 Gbit/s respectively. As in-line transparent detector/travelling wave amplifier the same devices reach polarization independent fibre-to-fibre gains of 11 dB and detection sensitivities of -27.5 dBm at 1.2 Gbit/s.

A passively mode-locked 1.3 mu m InGaAsP/InP semiconductor laser amplifier in a fibre loop mirror configuration, is demonstrated for the first time, to the authors' knowledge. Pulse durations of <20 ps at repetition rates of 0.5 - 2GHz, an average output power level in the order of 1 mW and a tuning range of 1300 - 1320nm were achieved. The laser has the potential for integration on a single chip, which would result in a compact and high repetition rate source of picosecond pulses in the second communication window.

Semiconductor optical amplifiers in novel monolithic InP-waveguide Mach-Zehnder Interferometer with multi-mode interference couplers exploit gain and refractive index dynamics to amplify and switch Gb/s signals from port-to-port with on-off ratios exceeding 15 dB and optical control powers at the milliwatt level.

The authors report here the realization of InGaAsP/InP traveling wave optical amplifiers operating at λ = 1.3 μm integrated with passive waveguides. The fabrication is based on two stage low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) using thin etch-stop layers for easy fabrication and high reproducibility. The optical amplifiers are butt-jointed to the passive waveguides leading to high amplifier interface coupling efficiencies of over 90% and interface reflectivities below 5 × 10-6. Single pass fiber-fiber gains of +17 dB (TE) and +6 dB (TM) with high saturation output power of -3.8 dBm were achieved