Evering F C
Department of Electrical Engineering, The Johns Hopkins University, Baltimore, Maryland, USA.
Appl Opt. 1966 Aug 1;5(8):1313-7. doi: 10.1364/AO.5.001313.
Wood's anomalies are investigated by using a microwave spectrometer operating at a wavelength of 3.8 mm. For S-polarization, high surface conductivity, periodicities of 2lambda and 3lambda, and groove depths from lambda/8 to (5lambda)/4, rectangular profile gratings are shown to exhibit anomalies which can be explained by simple interference between the orders due to the incident beam and the orders due to the passing-off order if it is considered as a second beam incident at +/-90 degrees . Artificial passing-off orders are formed, and these permit one to change the natural anomalies from bright to dark and vice versa. Interference of the orders owing to the incident and imposed beams at anomalous angles is demonstrated by measuring the power in each of the overlapping orders separately and comparing the sum of their amplitudes with the value measured at the anomalous angle. For all cases tested the results are satisfactory for either bright or dark anomalies. By adjusting the angle of a second incident beam to calculated values, artificial anomalies, i.e., anomalies at angles of incidence where they do not normally occur, are created. These anomalies cannot be distinguished from their natural counterparts.
利用一台工作波长为3.8毫米的微波光谱仪对伍德异常进行了研究。对于S偏振、高表面电导率、2λ和3λ的周期以及从λ/8到(5λ)/4的槽深，矩形轮廓光栅显示出异常现象，如果将透射级视为以±90度入射的第二束光，则这些异常现象可以通过入射光束的级次与透射级次之间的简单干涉来解释。形成了人工透射级次，这使得人们能够将自然异常从亮变为暗，反之亦然。通过分别测量每个重叠级次的功率，并将它们的振幅之和与在异常角度测量的值进行比较，证明了在异常角度下入射光束和施加光束的级次之间的干涉。对于所有测试的情况，无论是亮异常还是暗异常，结果都令人满意。通过将第二束入射光束的角度调整到计算值，可以产生人工异常，即在通常不会出现异常的入射角处出现的异常。这些异常与自然异常无法区分。
