The measurement of aircraft and vehicle Laser Radar Cross Section (LRCS) is of crucial importance for the detection system evaluation and the characteristic research of the laser scattering. A brief introduction of the measuring theory of the laser scattering from the full-scale aircraft and vehicle targets is presented in this paper. By analyzing the measuring condition in outfield test, the laser systems and test steps are designed for full-scale aircraft and vehicle LRCS and verified by the experiment in laboratory. The processing data error 7% below is obtained of the laser radar cross section by using Gaussian compensation and elimination of sky background for original test data. The study of measurement and analysis proves that the proposed method is effective and correct to get laser radar cross section data in outfield test. The objectives of this study were: (1) to develop structural concepts for different LRCS fuselage configurations constructed of conventional materials; (2) to compare these findings with those of aircrafts or vehicles; (3) to assess the application of advanced materials for each configuration; (4) to conduct an analytical investigation of the aerodynamic loads, vertical drag and mission performance of different LRCS configurations; and (5) to compare these findings with those of the aircrafts or vehicles.
Laser Diodes (LDs) are becoming increasingly attractive as small and reliable laser-beam sources,
with applications that include pumping of solid-state lasers, materials processing, and medicine. However,
because of the poor beam quality of its output beam, which affects its direct applications, thus people pay
much attention on how to shape the beam of the high power laser diode bar effectively. In this paper some
typical beam shaping methods, shaping principles, key techniques and shaping effects are discussed. Based on
geometric optical analysis, the collimation properties of the off-axis light wave through a cylindrical lens and
elliptical cylindrical lens are separately analyzed in detail by rays tracing formulas, the collimation effects of
them are also made a comparison.
Beam quality is very important in laser technology and its application. In practice a good beam quality evaluating method can indicate which beam is good and which laser is suitable. Therefore evaluating beam quality is of huge significance. Because the beam of laser diode has many characteristics differ from other lasers, such as the angle of the beam is too big, and the angle in the direction parallel to the junction plane disagrees with it in the perpendicular direction, a new quality parameter Q(θ,ω,d) for evaluating beam quality of laser diode is given. The difficulty of collimation is well expressed by use of Q. The smaller the value of Q is, the more easily the beam is collimated.
The propagation characteristics of Hermite-cosine-Gaussian beams passing through an ABCD optical system with hard-edge aperture is studied, by means of expansion of the window’s function of the hard-edge aperture into a finite sum of complex Gaussian functions, the approximate analytical propagation equations of laser beams are derived. This method is superd in its reduction of computing time, together with the convenience it furnished in analyzing physically the propagation properties of laser beams.
Based on the analysis of the beam output characteristics of laser diodes, using the generalized Collins integral, the propagation characteristics of Hermite-Gaussian beams passing through a gradient index lens is studied. The analytical expressions of intensity distribution is derived and numerical examples is illustrated. it furnished in analyzing physically the propagation properties of the beams of laser diodes.
A screwdriver-like fiber end to couple the light power of laser diode array(LDA) into multimode fiber is presented. The coupling efficiency formula of such coupling system is given, and the numerical evaluation show that the theoretical coupling efficiency could be as high as 83% without an antireflection coating on the fiber end face. This method can be easily fabricated and has large tolerance.