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In recent space missions, acquisition of electric power is quite important. Wireless or beaming energy transmissions using a microwave or laser beam have been attracting many interests. Although laser beams are more advantageous in directionality than microwaves, there are mainly two obstacles in constructing a laser transmitter. Firstly, a high power laser beam must be collimated well. Secondly, the high power and lightweight laser facility must be feasible economically. In general, with the increase in power and size of a laser oscillator, it becomes more expensive and difficult to oscillate in a single transverse mode. An arrayed laser is one of the solutions to overcome these obstacles. For the development of an arrayed laser beam system, it is important to know its combined diffraction pattern, and geometric parameters of the array, which strongly influence the pattern, should be optimized. In this paper, a detailed analysis has been performed on coherent combinations of diffraction-limited Gaussian beams. Far-field patterns of rectangular-symmetric arrays were calculated with various geometric parameters such as the number of array elements and the ratio of their pitch to the minimum spot size of an element Delta/w(sub 0). As a result, far-field patterns of arrays were evaluated in terms of a main lobe radius W(sub ML) and an energy fraction of the beam that is contained in the main lobe eta(sub ML). W(sub ML) and eta(sub ML) represent a radius of a receiver and a transmission energy efficiency, respectively. For a constant Delta/w(sub 0), both W(sub ML)/W(sub n) and eta(sub ML) were found insensitive to the number of array elements, where W(sub n) is the radius of a Gaussian beam having emission area equivalent to the array. In other words, a radius of a receiver is independent of the number of array elements but depends on total emission area of the array. This also suggests that an array composed of small diode lasers can be utilized like a large-aperture laser if it has a large total emission area. On the other hand, the dependence on Delta/w(sub 0) was found critical. For any number of array elements, both W(sub ML)/W(sub n) and eta(sub ML) were decreased with Delta/w(sub 0). On the basis of these results, the feasibility of high power energy transmission by phased array lasers has been discussed. 1 GW power can be transmitted from a 5.5 x 5.5 m coherent laser diode array with Delta/w(sub 0) = 2.2 to 11-m-diameter receiver at a distance of 40,000 km with the transmission efficiency of 80 percent. (It was assumed that the transmitter consists of 25,000 x 25,000 laser diodes of the wavelength 808 nm, and the output power of the element laser is 2 W with a 100-micrometer-radius aperture.) If the beams are incoherent, a 200-km-diameter receiver will be required for same conditions. Therefore, coherent combination of laser beams is essential especially for a laser diode array., 資料番号: AA0045915017