Abstract: A device for the in vivo measurement of the concentration of an analyte in an aqueous solution comprises a transmitter for illuminating a body part with light at a plurality of predetermined wavelengths. A detector receives light from such body part and generates input signals representative of the intensity of received light at each of the predetermined wavelengths, and a computer coupled to the detector generates an output signal representative of the analyte concentration in the body part by analysis of the input signals received from the detector. The detector is adapted to generate input signals representative of the intensity of light received at three discrete wavelengths, and a formula is provided for calculating the output signal on the basis thereof.

Abstract: A light emitting device (10) incorporates a layer (12) of porous silicon of low dimensionality surmounted by a discontinuous layer of silver in the form of discrete islands (20). A digitated electrode (13) is connected to the islands (20). The islands (20) have diameters in the range 5 nm to 20 nm and spacings in the range 10 nm to 50 nm, and they form a Schottky diode structure on the silicon (12). Under electrical bias, the diode structure conducts and light is generated. The device (10) is produced by vacuum deposition of silver onto a silicon wafer at a temperature which provides for the silver to separate into individual balls (20). The wafer is then anodized to produce a porous layer incorporating columns of silicon and silicon dioxide surmounted by respective silver islands (20). Each silver island (20) protects the underlying silicon (21) from the anodizing medium, and subsequently provides an electrical contact to the silicon.

Abstract: A method of modulating an optical beam (1) and apparatus for use in such a method are described. An etalon structure (2) is provided which has an absorption edge in the vicinity of the wavelength of the optical beam (1) and which comprises material of a smaller band gap, for example gallium arsenide, sandwiched between layers of material of a larger band gap, for example aluminium gallium arsenide, so that the smaller band gap material forms a quantum size effect confinement region for electrons and holes. The smaller band gap material may consist of layers (4) separated by barrier layers (3) of the larger band gap material so that the layers (4) form quantum wells.

Abstract: A method of modifying a surface of a body such as a semiconductor body is described in which a beam of electromagnetic radiation is directed towards the surface so that the electromagnetic radiation is incident on the surface at or near the Brewster angle, the electromagnetic radiation incident on the surface preferably being so polarised that the electric vector of the electromagnetic radiation lies in the plane of incidence of the electromagnetic radiation at the surface.

Abstract: A device and method for doubling the frequency of electromagnetic radiation of a given frequency are described. The device comprises a substrate (1) on which is provided a first layer (2) and a second layer (3). One of the first and second layers (2) has a plasma oscillation frequency equal to the given frequency for causing an electric field at twice the given frequency to be produced across the device in response to electromagentic radiation at the given frequency being incident on the device normally of the first and second layers (2and 3). A thus-produced electric field is converted to electromagnetic radiation at twice the given frequency by the said other of the first and second layers (3) which forms a waveguide for electromagnetic radiation at twice the given frequency. A further layer (2') similar to the said one layer (2) may be provided so that the said other layer (3) is sandwiched between the said one and further layers (2 and 2').

Abstract: A method of etching a semiconductor body having first (6) and second opposed surfaces and having a first semiconductor region (1) adjacent the first surface (6) and a second semiconductor region (2) disposed between the first semiconductor region and the second surface, the first (1) and second (2) semiconductor regions being formed such that the second semiconductor region (2) first absorbs radiation at a wavelength less than the wavelength at which the first semiconductor region first absorbs radiation. The second surface provides an optically distinguishable feature, for example an optically opaque conductive layer (3) formed with an aperture (4).

Abstract: A method of growing an alloy film by a layer-by-layer process on a substrate is described, together with a method of making an semiconductor device in which an alloy film is grown on a substrate by a layer-by-layer process. The atomic ratio of constituents present in the alloy film is determined during growth of the film from the growth rates of the alloy film and of at least one intermediate film consisting of at least one constituent of the alloy. The intermediate film or films are grown between the alloy film and the substrate. During growth of each film, the growth surface is irradiated with a beam of electrons and measurement is carried out of the period of oscillations in the intensity of the stream of electrons diffracted at the growth surface, or specularly reflected by the growth surface, or emitted from the growth surface, or of the current flowing to ground through the substrate. These periods are equal to the respective times taken to grow on a monolayer of the respective film.