Abstract: A battery operated device such as a road stud comprises a micro-controller, a battery, and a light source. The micro-controller is configured to operate the battery to provide a train of power pulses to the light source, and each power pulse has a characteristic pulse period and a characteristic duty cycle comprising an on-cycle and an off-cycle. The micro-controller is turned on during the on-cycle and turned into a power saving or sleep mode during the off cycle. Setting the micro-controller into the power saving or sleep mode during the off cycle of the power pulse means substantial battery power saved to extend the operation time per charging of the battery.

Abstract: A method for embedding an entire image, audio or video watermark sequence within another image, audio or video data sequence with minimum loss of data quality is presented. The method exploits the de-correlation property of data coefficients in the orthogonal transform domain, similar to the application in data compression through transform coding. The present invention describes the usage of a Discrete Cosine Transform as the embedding domain. However, other orthogonal transforms such as Fourier, Walsh-Hadamard, Haar, Sine and Wavelet can also be used for this operation. A unique key derived adaptively from spatial locations registering the thresholds of the ac transform energies is used to unlock or de-watermark the embedded image or audio sequence. Moreover, an exponential filter has been developed to compress and expand the watermark coefficients prior to the embedding and retrieval process.

Abstract: A semiconductor wafer with variable transmittance, serves as a saturable absorber for performing passive Q-switching in a laser system to produce laser pulses having defined output characteristics. By translating or rotating the semiconductor saturable absorber, loss properties of a laser cavity may be altered. In this manner, the output characteristics of the laser pulses can be varied without changing other parameters of laser operation. The output characteristics may include pulse duration, pulse repetition rate, peak power and average output power of the laser pulses. The semiconductor wafer can be made of doped or undoped GaAs, AlGaAs, InP, etc. Furthermore, the tunable Q-switch may simultaneously serve as an output coupler for the laser cavity.

Abstract: There is provided a casing for packaging a preassembled optical fibre-coupled optoelectronic device assembly. The casing comprises a can having an integrated snout pipe section and an opening extending from the top wall of the can to the snout pipe section for receiving an optical fibre such that the optical fibre can be fitted through the opening into the snout pipe section and so pass through the snout pipe section to the exterior of the casing with the optoelectronic device housed within the can. The opening may be sealed with a removable wall section. Alternatively, when the opening is sufficiently narrow, with solder alone.

Abstract: A pumping module for use in a solid state laser comprises an annular array of laser diode segments (10) forming a passage (24), each segment (10) comprising an extended body supporting a laser diode array (17) that extends along the longitudinal axis of the segment (10) for directing light into the passage (24) from an inner face (12) of the annular array, wherein adjacent side faces of any two segments (10) in the annular array are in sealing engagement. The inner faces (12) of the array of segments (10) form a continuous surface so that coolant can flow between a laser rod and the segments (10) to reduce localized heating.

Abstract: The present invention provides a novel technique based on gray scale mask patterning (110), which requires only a single lithography and etching step (110, 120) to produce different thickness of SiO2 implantation mask (13) in selected regions followed by a one step IID (130) to achieve selective area intermixing. This novel, low cost, and simple technique can be applied for the fabrication of PICs in general, and WDM sources in particular. By applying a gray scale mask technique in IID in accordance with the present invention, the bandgap energy of a QW material can be tuned to different degrees across a wafer (14). This enables not only the integration of monolithic multiple-wavelength lasers but further extends to integrate with modulators and couplers on a single chip. This technique can also be applied to ease the fabrication and design process of superluminescent diodes (SLDs) by expanding the gain spectrum to a maximum after epitaxial growth.

Abstract: A pumping module for use in a solid state laser comprises an annular array of laser diode segments (10) forming a passage (24), each segment (10) comprising an extended body supporting a laser diode array (17) that extends along the longitudinal axis of the segment (10) for directing light into the passage (24) from an inner face (12) of the annular array, wherein adjacent side faces of any two segments (10) in the annular array are in sealing engagement. The inner faces (12) of the array of segments (10) form a continuous surface so that coolant can flow between a laser rod and the segments (10) to reduce localized heating.

Abstract: A method for sensing and analyzing topographic properties of an aspheric test element is disclosed. The principle of the measurement technique is to immerse the element under test into a container filled with liquid crystal. A polarized plane wave passes through front and back precisely processed glass plates of the container sandwiched between a polarizer and an analyzer. The two side plates are not transited by the plane wave of light but are deposited with conductive layers in order to generate an electrical field between them. This DC (direct current) external electrical field is supplied to help to align the molecular direction of the liquid crystal. In a thus-induced desired configuration, the molecular direction of liquid crystal is aligned to be perpendicular to the incident plane wave front. As the plane light wave propagates through the liquid crystal in the container, it will be divided into ordinary and extraordinary beams. These two beams will create interference behind the analyzer.

Abstract: The present invention provides a novel technique based on gray scale mask patterning (110), which requires only a single lithography and etching step (110, 120) to produce different thickness of SiO2 implantation mask (13) in selected regions followed by a one step IID (130) to achieve selective area intermixing. This novel, low cost, and simple technique can be applied for the fabrication of PICs in general, and WDM sources in particular. By applying a gray scale mask technique in IID in accordance with the present invention, the bandgap energy of a QW material can be tuned to different degrees across a wafer (14). This enables not only the integration of monolithic multiple-wavelength lasers but further extends to integrate with modulators and couplers on a single chip. This technique can also be applied to ease the fabrication and design process of superluminescent diodes (SLDs) by expanding the gain spectrum to a maximum after epitaxial growth.