The angle spectrum of inputting optical signals is received by the input surface of arrayed waveguides . whereas the diffraction process of light beam outputed in slab waveguide is a process of " composing frequency and generating image " . the reason that fraunhofer diffractive pattern can be gained on outputting waveguide surface is that output ends of arrayed waveguide distribute on the arch structure which leads bent phase factor to offset the quadratic phase factor in fresnel diffraction 输入平板波导内光束的衍射过程是“分频成谱”的过程，在阵列波导的输入面接收到的是输入光信息的角谱；而输出平板波导内光束的衍射过程则是“合频成像”的过程，正是由于阵列波导输出口排列分布在圆弧形结构上，其弯曲位相因子消去了菲涅耳衍射中的二次位相因子，从而在输出波导面上能够得到夫琅和费衍射图样。
