Abstract: The present invention relates to a hydrogel formulation in which the solid phase is composed of a continuous net work of siloxane bonds and one or more calcium phosphate phases doped with one or more metal dopants.

Abstract: The present invention relates to a photosensitive composition comprising synthetic nanocrystalline hydroxyapatite or a synthetic precursor thereof doped with a rare earth ion, the use of the composition in restorative or cosmetic dentistry, a process for preparing the composition and a method of generating an image of an exposed dentinal surface of a tooth.

Abstract: An ultrashort-pulse laser that has a resonator that includes a laser gain medium, dispersion compensation optics, and a deformable optical element adapted to change its shape and consequently one or more characteristics of pulses output from the cavity.

Abstract: The present invention relates to a photosensitive composition comprising synthetic nanocrystalline hydroxyapatite or a synthetic precursor thereof doped with a rare earth ion, the use of the composition in restorative or cosmetic dentistry, a process for preparing the composition and a method of generating an image of an exposed dentinal surface of a tooth.

Abstract: An ultrashort-pulse laser that has a resonator that includes a laser gain medium, dispersion compensation optics, and a deformable optical element adapted to change its shape and consequently one or more characteristics of pulses output from the cavity.

Abstract: There is provided an autocorrelator of ultrashort electromagnetic pulses, comprising an interferometer for receiving a parent electromagnetic pulse from an energy source and for deriving two daughter electromagnetic pulses from the parent pulse, an output means coupled to the interferometer to output the daughter pulses, and a photodiode in communication with the output means to detect the daughter pulses and to alter the frequency thereof so as to produce an electrical output signal that has a quadratic dependence on the power associated with the parent electromagnetic pulse. The temporal duration of the pulses ranges from TO picoseconds to 5 femtoseconds. A GaAsP photodiode is used with a broad band response of 700-1300 nm. The interferometer is either a Michelson interferometer or a Wollaston prism interferometer and a microscope objective is provided between the output means and the photodiode so that the pulses from the output means are focused onto a defined area of the photodiode.

Abstract: A Fourier-transform spectrometer contains a birefringent optical component, removing the need for a Michelson interferometer used in conventional instruments. A suitable birefringent element such as a Wollaston prism, is used to introduce a path difference between two light polarisations. Use of an extended light source so that all areas of the birefringent component are illuminated simultaneously ensures that different positions on the birefringent component correspond to different path differences between the two polarisations. A Fourier-transform of the resulting interferogram at the detector results in the spectral distribution of the input light being obtained. The use of an extended light source permits a Fourier-transform spectrometer with no moving parts to be achieved.

Abstract: A Fourier transform spectrometer for use, among others, for sensing gases or liquids includes two polarizers, a birefringent optical component interposed between the two polarizers and a detector. Light from an extended source is substantially polarized by a first of the two polarizers, split into divergent beams by the birefringent optical component, and again caused to converge by the birefringent optical component so that, after passing through a second of the two polarizers, the light forms an interferogram in a plane behind the birefringent optical component where the detector is situated. The Fourier transform spectrometer is thereby provided with a way of forming an interferogram of the light from the extended source without a lens or a second birefringent optical component. This improves the field of view of the spectrometer and is likely to reduce its cost.

Abstract: An all-solid-state laser comprising a slab (1) of gain medium, a diode laser pump system (3) configured in an end pumping geometry with the gain medium (1) and a heat sink thermally contacted to the gain medium (1) wherein the diode laser pump system (3) and the gain medium (1) are cooperably arranged so that in use a positive thermal lens is capable of being formed within the medium, the gain medium (1) having a thickness (d-d') made as small as possible while permitting the substantially unhindered passage through the slab of the laser mode established between the two mirrors (M1, M2).

Abstract: A laser 10 comprises a pump source 11, a resonator 13 including an etalon of gain material 15, and means 12 to focus the pump source 11 output onto one end 14 of the resonator 13 as a spot having a diameter in the range 50-150 .mu.m. The resonator 13 includes substantially parallel end faces 14,19 having a relative taper better than 0.25 milliradians, and the end faces 14,19 are substantially free of scratches greater than 10 .mu.m in size and pits greater than 5 .mu.m in size. A thermally induced microlens 22 is formed at the surface 14 of the gain material 15.

Abstract: An hybrid laser source has a ring structure including the optical path in a semiconductor amplifier chip (1) and optical fibres (2, 3 and 4). The fibre (2) is rare-earth doped and provides an additional gain medium in the ring, the chip providing its own gain medium. The two gain media are interactive and when the chip input current is modulated the source produces relatively high peak power ultrashort pulses (FIG. 1).

Abstract: Optical fibres comprised of a halide glass incorporating color centers, for example fluoride fibres, can behave as a laser or an amplifier when maintained at a low temperature, typically 77.degree. K., and optically pumped. A laser may be comprised by a length of such a fibre (1) wound on a spool (2) and disposed in liquid nitrogen (4), the ends of the fibre are outside of the coolant and associated with input and output mirrors (5,6) which define the extremities of a lasing cavity. An optical pumping signal (7) is provided by a laser (8), for example a Krypton ion laser operating in the visible range. The output of the fibre laser is in the infra-red. Higher gain than with conventional color center lasers is achieved due to the longer interaction length and cooling problems are overcome.

Abstract: The spatial or temporal characteristic of a beam of light or other electromagnetic radiation or a beam of sub-atomic particles is measured by an array of detectors. The array comprises the layer 1 of photosensitive material on which there are positioned pairs of electrodes 1a, 2a and 1b, 2b etc., with gaps between the electrodes of a pair. The gaps are spaced apart linearly and the material is chosen so that incident light affects current flow between the electrodes defining a gap. Changes in current flow between the individual pairs of electrodes are measured. For measurement of spatial profile layer 1 has a resistivity which varies linearly with the amplitude of incident light. For measurement of temporal profile the beam is split with the split beams being directed on to the array with different angles of incidence and the material is chosen to have a two-photon conductivity.

Abstract: An electron-optical image tube including a photocathode, an extraction electrode consisting of a mesh on the emission side of the photocathode, and a focussing electrode on the side of the mesh remote from the photocathode, achieves increased time resolution, improved spatial resolution, and reduced magnification at a phosphor screen by making the photocathode to mesh spacing small compared with the mesh to focussing electrode spacing. An improved photocathode plate avoids large electric fields at sharp points on the photocathode surface. Additional annular electrodes and flared deflector electrodes in the drift section of the tube prevent scattering of electrons from the tube walls on to the screen.