Abstract: External Cavity Laser An external cavity laser comprising first and second feedback means with an optical gain medium (2) therebetween, one of the feedback means is provided by a grating (4) formed in a silicon waveguide and the other feedback means is provided by a reflective back facet (2B) of the optical gain medium (2). The output wavelength of the laser, at a given temperature, can thus be determined during its manufacture and the laser can be made by mass production techniques. The grating (4) may be thermally isolated to obviate the need for temperature control means (6) to control the temperature of the grating (4). An array of lasers may be provided on a single chip.

Abstract: A method of forming a smooth, continuous compound semiconductor film, e.g., a GaN film, is provided. When a GaN film is formed in accordance with this method, Ga is caused to arrive at a sapphire substrate in accordance with a first arrival rate profile over a growth period during which the film is formed, and nitrogen is caused to arrive at the substrate in accordance with a second arrival rate profile over the growth period. The first and second arrival rate profiles are such that the Ga and N are caused to arrive simultaneoulsly at the substrate over the growth period and so that (i) during an initial part of the growth period, growth of the film takes place under a stoichiometric exccess of Ga and (ii) during a subsequent part of the growth period, growth of the film takes place under a stoichiometric excess of N.

Abstract: A single cavity mode optoelectronic device, such as a VCSEL, an RCLED or a DFB laser diode, comprises an etched-pillar or mesa structure including an optically active region and strain-applying means in the form of a layer of polymer material having a coefficient of thermal expansion which is greater than that of the optically active region. The layer surrounds the optically active region so as to apply a compressive strain to the latter so as to compensate at least partially for temperature-induced changes in the gain spectrum peak of the optically active region caused by ohmic heating of the device.

Abstract: An (Al,Ga)As/(Al,Ga,In)P semiconductor layer structure is etched using an SiCl.sub.4 or an SiCl.sub.4 /(He,Ne) plasma. The etching is carried out at 0.degree. to 80.degree. C. and at a plasma pressure below 1.33.times.10.sup.-1 Pa (1 mTorr). The etched surfaces are sufficiently smooth for the etching process to be used in the production of (Al,Ga)As/(Al,Ga,In)P semiconductor lasers.

Abstract: A surface-emitting laser contains an optical cavity including a multiple quantum well (MQW) active region providing a source of optical emission in use. Top and bottom mirrors are disposed respectively above and below the MQW active region. The MQW active region is profiled so that it has a greater number of quantum wells in a central portion thereof than in a peripheral portion thereof. In alternative embodiments, a current-guiding region is profiled so that it has a first current-guiding portion with a relatively smaller aperture therethrough extending over a central portion of the MQW active region, and a second current-guiding portion with a relatively larger aperture therethrough; and one of the mirrors has a layer structure which, in a central portion of the cross-sectional area of such mirror, is different to that in a peripheral portion of said cross-sectional area.

Abstract: A resonant-cavity optical device, eg a vertical cavity surface emitting laser, has a substrate upon which are provided a Bragg reflector multilayer bottom mirror, a semiconductor lower spacer region, an active region, and a dielectric region which surrounds the bottom mirror, the active region and the lower spacer region. An upper spacer region and a top mirror are provided on top of the active region. The top mirror has a window in which a metal terminal is provided. The terminal is in direct contact with the upper spacer region which is formed of a transparent electrically conducting oxide, eg indium tin oxide.