Abstract: A method is for making a semiconductor device by forming a superlattice that, in turn, includes a plurality of stacked groups of layers. The method may also include forming regions for causing transport of charge carriers through the superlattice in a parallel direction relative to the stacked groups of layers. Each group of the superlattice may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion and an energy band-modifying layer thereon. The energy-band modifying layer may include at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions so that the superlattice may have a higher charge carrier mobility in the parallel direction than would otherwise occur. The superlattice may also have a common energy band structure therein.

Abstract: A method is for making a semiconductor device by forming a superlattice that, in turn, includes a plurality of stacked groups of layers. The method may also include forming regions for causing transport of charge carriers through the superlattice in a parallel direction relative to the stacked groups of layers. Each group of the superlattice may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion and an energy band-modifying layer thereon. The energy-band modifying layer may include at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions so that the superlattice may have a higher charge carrier mobility in the parallel direction than would otherwise occur. The superlattice may also have a common energy band structure therein.

Abstract: A method for producing aperiodic gratings and waveguides with aperiodic gratings uses a simulated annealing process that starts with a random configuration of grating elements and iteratively computes a spectral response from a Fourier transform of the configuration of grating elements obtained in successive iterations. A cost function is computed as a convergence criterion. The aperiodic grating can be used, for example, as a filter in WDM applications.

Abstract: A laser device, in particular a semiconductor laser, emitting optical radiation with a defined mode pattern can be produced from a standard Fabry-Perot (FP) laser by post-processing at the wafer level, i.e. before the wafer is separated into individual dies by cleaving/dicing. A sub-cavity is formed within the FP laser cavity. The sub-cavity has a predetermined length and is located between the FP facets. An aperiodic grating composed of a small number of contrast elements, typically less than 10, with predetermined inter-element separations and predetermined spacings relative to the sub-cavity is formed on or in the optical waveguide. The inter-element separations and the spacings relative to the sub-cavity produce a filtering function of the aperiodic grating for optical radiation propagating in the waveguide. The laser device is suitable for telecommunications applications due to its high side-mode-suppression ratio and narrow-linewidth.

Abstract: A laser device, in particular a semiconductor laser, emitting optical radiation with a defined mode pattern can be produced from a standard Fabry-Perot (FP) laser by post-processing at the wafer level, i.e. before the wafer is separated into individual dies by cleaving/dicing. A sub-cavity is formed within the FP laser cavity. The sub-cavity has a predetermined length and is located between the FP facets. An aperiodic grating composed of a small number of contrast elements, typically less than 10, with predetermined inter-element separations and predetermined spacings relative to the sub-cavity is formed on or in the optical waveguide. The inter-element separations and the spacings relative to the sub-cavity produce a filtering function of the aperiodic grating for optical radiation propagating in the waveguide. The laser device is suitable for telecommunications applications due to its high side-mode-suppression ratio and narrow-linewidth.

Abstract: An active device (FIG. 1) comprising a length of doped fiber (1) and an end-coupled pump source (11). The fiber (1) is of single-mode geometry and incorporates rare-earth or transition metal dopant ions. These latter are incorporated at a low-level uniform concentration (.ltorsim.900 ppm). The fiber host (1) selected exhibits an inherently ultra low attentuation loss (.ltorsim.40 dB/km) at the emission wavelength. The fibers (1) are generally of long length (e.g. 5 m to 300 m) and may be coiled for compact packaging. The fiber (1) may be formed as part of a Fabry-Perot cavity (1, 7, 9); or, as a ring cavity (FIG. 8) using a doped fiber coupler (29) spliced to form a ring (27). Q-switch and mode-locking devices (19) and gratings (25) may be included as part of the Fabry-Perot cavity to allow pulse-mode operation and/or wavelength tuning, respectively. The fiber (1) may also be utilised as an amplifier.

Abstract: A fibre laser (1) of the type comprising a doped single-mode optical fibre (3) arranged between reflectors (5,7), and which is coupled (11) to an optical pumping source (9). For the given reflection efficiency of the reflectors (5,7), the length of the optical fibre (3) is chosen such that it exceeds that affording saturation and provides at its end a region for absorption (FIG. 1). The resultant hysteretic behavior of this bistable device may be utilized for logic memory (bistable), and regenerative amplification applications. To this end a second source (9') can be coupled (11',19) to the laser fibre (3).

Abstract: A method of making a preform for drawing optical fibers includes the steps of depositing a dopant material 3 in a dopant carrier chamber 1, heating the dopant material to cause it to vaporise at a predetermined rate, depositing from a mixture of a source material (GeCl.sub.4, SiO.sub.4, O.sub.2) and said vaporised dopant a mixture of solid components 8 and fusing said solid components to form a doped glass.