Comparison of coherent and incoherent laser beam combination for tactical engagements

Abstract

Abstract. The performance of a multibeam laser system is evaluated for coherent and incoherent beam combination under tactical scenarios. For direct comparison, identical aperture geometries are used for both, coherent or incoherent, combination methods. The analysis assumes a multilaser source coupled with a conventional 0.32 m diameter, on-axis, beam director. Parametric analysis includes variations over residual errors, beam quality, atmospheric effects, and scenario geometry. Analytical solutions from previous results are used to evaluate performance for the vacuum case, providing an upper bound on performance and a backdrop for organizing the multitude of effects as they are analyzed. Wave optics simulations are used for total system performance. Each laser in the array has a wavelength of 1.07 μm, 10 kW (25 kW) output power, and Gaussian exitance profile. Both tracking and full-aperture adaptive optics are modeled. Three tactical engagement geometries, air to surface, surface to air, and surface to surface, are evaluated for slant ranges from 2.5 to 10 km. Two near-median atmospheric profiles were selected based upon worldwide climatological data. The performance metric used is beam propagation efficiency for circular target diameters of 5 and 10 cm. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).

Modeled and measured image-plane polychromatic speckle contrast

“…[1][2][3][4][5][6][7] However, even at shorter tactical ranges, HEL tracking requirements are very demanding. 8 Yet little published research exists regarding the potential tracking advantages of active (laser) illumination and the resulting detrimental speckle effects at tactical ranges. 9,10 Potential advantages of active illumination include eliminating dependence upon target emission and reflection of natural light, increasing signal-to-noise ratio (SNR), and increasing resolution over longer wavelength thermal imaging.…”

Simulation of deep turbulence compensation for a laser phased array

“…This choice was made to keep the geometry similar to a 6 element array which was studied earlier. [4] In the present case, this results in 2.3 cm diameter sub-apertures placed on about 2.5 cm centers. The 2 cases simulated here are all for a 10 km range, which is considered a tactically interesting distance, reasonably possible for a variety of engagements.…”

“…Fiber laser phased array systems offer potential advantages in size, weight, efficiency, and scalability over more conventional designs, plus the promise of new capabilities and features such as electronic beam steering, distributed apertures, conformal apertures, and graceful degradation. [1,2,3,4] The next sections lay out the simulation in detail, present example cases, and conclude with a discussion of the results obtained. The methodology section details the hypothetical physical parameters of the array simulated, the mapping of these parameters into the simulation space, and the construction and operation of the components of the simulation.…”

Simulation of array tilt effects in laser phased arrays

“…Van Zandt discusses tactically interesting phased -and unphased -arrays further. [8] For an array of this size, we can expect many waves of phase difference between sub-aperture wavefronts on initial assembly. In operation if mounted on an aircraft or other moving platform, many waves of drift between these phases can also be expected in the absence of some active control scheme.…”