Tham khảo tài liệu 'wave propagation 2010 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 52 Wave Propagation change of sign of any component of vector c . it has three mutually orthogonal symmetry planes coincident with the coordinate planes. However the main property of this surface is that each point of it describes two different conversion reflections o e and e - o. In other words the following assertion is valid If a two-partial wave reflection with the change of the refraction sheet . o - e exists in the geometry under consideration then the other conversion reflection e - o should also be at the same orientations of the boundary B and the reflection plane p and the same refractive index n . Analysis shows that the shape of the mode conversion surface is significantly different for optically positive y 1 and negative y 1 crystals. This is clearly seen from Fig. 4 where surface 73 was constructed numerically at y a and b . Because of symmetry we show only the upper halves c2 0 of the corresponding surfaces from which the quarters 0 p n 2 were cut out for clarity. For an optically positive crystal the conversion surface has the shape of an axially asymmetric torus in which the hole shrinks to the point coincident with the coordinate origin. This surface is a single-sheet one in the sense that the ray along each vector c crosses it once. Fig. 4. Conversion surfaces for an optically positive crystal with y a and an optically negative crystal with y b The conversion surface for a negative crystal is radically different it is a two-sheet one the ray along c crosses it twice the upper half of the surface resembles a mushroom with a cap that descends to the x axis on both sides and a stipe that sharpens downward. To analyze in more detail the geometry of the conversion surfaces of the above two types it is convenient to consider their sections by the c1 0 c2 0 and c3 0 coordinate planes. The section of the conversion surface by the Cl 0 coordinate plane In this section the azimuth p is fixed p n 2 and 3n 2 and solution 73 takes
