Abstract: An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

Abstract: An apparatus and method for transmitting data in an aqueous medium is provided. The apparatus, comprising a transmitter having one or a plurality of LED transmitting components, which is configured, when immersed in an aqueous medium, to transmit light in a blue or green light wavelength, and a receiver configured, when immersed in the aqueous medium, to receive light in the wavelength of the transmitter.

Abstract: A method and apparatus for detecting fiducial marking on a material are disclosed. The fiducial marking is characterized by the ability to absorb light in a first wavelength range and to fluoresce in a second wavelength range that is outside the first wavelength range. An excitation source is configured to direct light at the material in the first wavelength range, to cause the fiducial marking material absorb the light in the first wavelength range and to fluoresce in the second wavelength range. A detection device is located at a predetermined site and is configured to optically examine the material at the predetermined detection site, to determine whether fluorescence from the fiducial marking which is in the second wavelength range is detected at the predetermined detection site.

Abstract: A method and apparatus for detecting fiducial marking on a material are disclosed. The fiducial marking is characterized by the ability to absorb light in a first wavelength range and to fluoresce in a second wavelength range that is outside the first wavelength range. An excitation source is configured to direct light at the material in the first wavelength range, to cause the fiducial marking material absorb the light in the first wavelength range and to fluoresce in the second wavelength range. A detection device is located at a predetermined site and is configured to optically examine the material at the predetermined detection site, to determine whether fluorescence from the fiducial marking which is in the second wavelength range is detected at the predetermined detection site.

Abstract: A ytterbium-doped solid state laser including a resonant cavity formed by an input mirror and an output mirror; and a gain medium within the resonant cavity, the gain medium being made of a ytterbium-doped host material having a ytterbium ion doping level and a thickness sufficient to yield single longitudinal mode laser operation when the resonant cavity is pumped by an external light source.