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Typical directional couplers in semiconductor waveguides require long (several millimetre) interaction lengths, potentially limiting their use in future optoelectronic integrated circuits (OEICs). We report the fabrication and operation of a newly designed integratable waveguide beam-splitter device only micrometres in size, consisting of a groove at the intersection of two perpendicular AlGaAs/GaAs ridge waveguides which was milled with a microfocused gallium ion beam. Single-mode propagation of both transmitted and reflected beams was observed, and the power ratio between both beams was adjustable by varying the groove depth.

A broadband 1.5μm GaInAsP travelling-wave laser ampli-fier has been realised with angled facets instead of anti-reflection coatings. The measured signal gain for the TE mode is 19dB at the wavelength around 1.49μm with a 2dB gain ripple over one free spectral range and a 3dB band-width of 55 nm. The estimated residual modal reflectivity is 0.2%.

The results of a laser design that uses dual Si impurity-induced disordering stripes to both bury the active region and provide lateral electron injection are reported. Without heatsinking, lasers have room temperature CW threshold current as low as 2.77 mA and a single facet external quantum efficiency as high as 30%.

The first singlemode room temperature AlGaInP monolithically frequency-stabilised lasers are reported. Single frequency and single spatial mode operation is obtained using a second order diffraction grating to stabilise the operating wavelength. The device produced > 20 mW CW with a differential efficiency of 0.18 W/A and a sidemode suppression ratio of > 30 dB.

A tunable pulsed UV laser holographic system is described which has the capability for ease of fabrication of multiplexed laser arrays, chirped gratings and millimetre-long distributed feedback lasers. First-order optoelectronic gratings (periods of approximately 2500 A˚) have been produced over the entire surface of 2 in (50.8 mm) InP substrate wafers. Diffraction efficiencies above 90% and grating depths of 1400 A˚ are reported.

Pumping of a green (λ ≃ 549 nm) Ho-doped fluorozirconate glass fibre laser with a high power (~30 mW) singlemode red diode laser is demonstrated. CW output powers exceeding 1.2 mW have been generated from a 22 cm long Ho:ZBLAN fibre for ~24 mW of incident pump power (10.5 mW launched) at 643 nm and a cavity output coupling of 24%. The threshold pump power, 3.5 mW launched (2.1 mW absorbed), is the lowest reported for any upconversion fibre laser. The maximum slope and optical conversion efficiencies measured to date are 18.5 and 12%, respectively, with respect to launched pump power. These results represent the first demonstration of a fibre laser driven by a red semiconductor diode laser.

Threshold current behaviour of InGaAs/InP quantum well laser diodes grown by atmospheric pressure MOCVD is measured and used as a means for determining characteristic modal gain constants. Structures incorporating 1.1&percent; strain in the multiquantum well active region exhibit a threshold current density of 506 A/cm2 at a cavity length of 1498 μm, and are described by a characteristic modal gain constant that is 70&percent; higher than in a similar device with 0.2&percent; strain.

High power 635 nm singlemode lasers have been demonstrated by a ridge waveguide design, showing a catastrophic optical damage (COD) power of 150 mW with a single transverse mode power up to 120 mW, an aspect ratio of 3:1, and a characteristic temperature T0 of 82 K.

A high continuous-wave (CW) power of 6 W at 626 nm and 15 W at 637 nm with 15 and 30% power conversion efficiencies, respectively, has been demonstrated from AlGaInP/GaInP laser diode arrays. Fibre-coupled 630 nm CW bars demonstrate good reliability at 3 W. Such devices are useful for photo-dynamic therapy (PDT) or display applications.

400 mw of continuous-wave (CW) diffraction-limited power is demonstrated for the first time from a flared unstable resonator semiconductor laser at a wavelength of 635 nm. More than 75% of the total power is contained in the central lobe of the far field.

The first monolithically integrated master oscillator power amplifier is reported in the GAInP/AlInP material system. A distributed Bragg reflector forms the master oscillator, and a flared amplifier provides gain. The device provides 250 mW of single frequency and single spatial mode power at 664 nm.

Low-parasitic ridge waveguide 635 nm low-divergence singlemode lasers have been fabricated with isolation etching though a quantum well region and p-contact lift-off process to reduce the junction capacitance. An electrical modulation speed of up to 2.7 GHz has been achieved at 20°C and of 1.4 GHz at 50°C.

The fabrication and performance of 1.3 μm InGaAsP buried crescent lasers with semi-insulating Fe-doped InP current blocking layers grown by MOVPE are reported. A modulation bandwidth above 8.3GHz has been achieved at room temperature without using a mesa-stripe geometry. CW output power up to 30 mW per facet at 20°C and CW operation up to 95°C have been obtained. The semi-insulating InP layer alone is proved to be an effective current blocking layer.

Data are presented on strained-layer InGaAs/InGaAsP double quantum well laser diodes operating at 2.0 μm. A 200 μm broad area laser diode produces 1.1 W continuous wave (CW). The spectral full width at half maximum is 10 nm at 0.63 W CW and broadens to 17 nm at an output power of 1.03 W CW. A 1000 h lifetest is presented. A power of 8.5 W CW is achieved from a monolithic array of broad array laser diodes.