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Experiments on laser-rock-fluid interactions have been carried out by using pulsed CO and CO 2 lasers which irradiated rocks typical for oil field: sandstone, limestone, shale and granite. Energy fluence and laser intensity on rock surface were up to 1.0 kJ/cm 2 and 10 7 W/cm 2 , respectively. The dependencies of specific energy consumption (i.e. energy per volume needed for rock excavation) on energy fluence, the number of pulses, saturated fluid, rock material and irradiation conditions have been obtained for various rock samples. The dependencies of momentum transferred to the rock on energy fluence for dry rocks and rocks with surface saturated by water or mineral oil have been measured. High-speed photography procedure has been used for analyzing laser plasma plume formation on a rock surface. Infrared spectra of reflectivity and absorption of rocks before and after irradiation have been measured.

The results of the first year of a Gas Research Institute funded research program to study laser-rock-fluid interaction will be presented. The overall purpose of this research is to determine the feasibility, costs, benefits, and the environmental impact of using laser technology to drill and complete oil and gas wells. When drilling and completing petroleum wells, many rock types (sandstone, limestone, dolomite, granite, shale, salt, concrete) and fluids (fresh water, salt water, oil, hydrocarbon gas, drilling fluids) must be penetrated by the laser. The Free-Electron Laser (FEL) technology is attractive because of the ability to tune the laser to different wavelengths. Laser energy absorbed by rocks is related to the wavelength of the laser source. The mechanisms of rock destruction (spalling, melting and vaporization) are therefore a function of the wavelength. The ability to transmit laser energy over long distances (up to 5000 m or 15,000 ft) is also a function of wavelength. Results of tests conducted at the U.S. Air Force and the U.S. Army's high power laser facilities are presented. The challenges ahead to advance a fundamental change in the methods currently used to drill and complete petroleum wells are discussed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A compact optical crosspoint switch is being fabricated at the University of Colorado. It consists of two identical smart pixels arrays (SPAs) which face one another. The arrays communicate using 64 optical channels in both forward and reverse directions. Each channel uses a vertical-cavity surface-emitting laser (VCSEL) which is collimated using a microlens. The collimated beam is routed to the appropriate photodetector on the facing array using a Fourier computer generated hologram (CGH). Each VCSEL has a separate hologram associated with it, allowing space variant interconnection between the facing arrays. Each SPA has an 8 by 8 array of VCSELs adjacent to an 8 by 8 array of photodetectors and smart pixel circuitry. These are integrated with the microlenses and holograms and packaged to form a compact and stable system, occupying several cm3. At present each smart pixel has several logic gates, but an optically similar system with approximately 1000 gates per pixel is under development. This type of interconnection is suited to board-to-board applications, and potentially offers high speed, low cost, high density bi-directional connections. The fabrication of the switch incorporates several novel integration techniques.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A series of optoelectronic processing systems is under development at the Optoelectronic Computing System Center (OCSC) at the University of Colorado. The demonstrations consist of two facing optoelectronic modules that communicate with each other using bidirectional free-space optical channels. An analysis of the fabrication tolerances required for correct operation of these systems is presented. An overview of the system and the techniques used for fabrication is given, along with the tolerances achieved in practice. A comparison with theoretical results indicates the critical alignments within the system. Methods to obtain the alignments required for larger systems are discussed.