tailieunhanh - Model-Based Design for Embedded Systems- P70

Model-Based Design for Embedded Systems- P70: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 676 Model-Based Design for Embedded Systems 0 1 2 3 . a is the period of the diffractive grating and 0 is in radians. In the special case of a square well when light is diffracted by a grating with a displacement of A 4 a A 2 optical path difference after reflection all the optical power is diffracted from the even modes into the odd modes 45 . In the first simulation the standard operation of the GLV is verified. We assume an incident plane wave of green light Agreen 520 nm striking the grating with the square-well period defined by the ribbon width and no gap. We simulate the GLV in both cases that is when all the ribbons are on the same plane and when the alternating ribbons are moved downward a distance of A 4. In this example the light is reflected off of the grating and propagated 1000 gm to an observation plane. A bounding box of 400 x 400 gm is used with N equal to 2048. Intensity contours of the observation plane are presented in Figure and b. When the grating is moved into the down position all of the optical power is not transferred into the expected odd far-field diffractive modes. This is seen in the center of Figure as small intensity clusters are scattered between the 1st modes. This scattering is a near-field effect and demonstrates that in this system light propagating 1000 gm is not in the far field. If a designer used a tool propagating with the Fraunhofer far-field approximations these scattering effects would not be detected. For example when running the same simulation on LightPipes 46 a CAD tool using the Fraunhofer approximation for optical propagation only the far-field pattern of light diffracted into the 1st and 3rd modes is seen as presented in Figure . When comparing this result to Figure it is shown that far-field approximation is not valid for this propagation distance. Through this example we have shown that using the angular frequency technique we achieve the full Rayleigh-Sommerfeld accuracy while .