本研究係以傳輸線理論計算與以有限時域差分法(finite-difference-time-domain method)為基礎之數值模擬，針對橫電(transverse electric, TE)極化波於光頻率範圍內入射二維「金屬－介電質」多層結構進行探討。兩者之計算結果均顯示於特定條件下具有極低反射之現象。其成因為電磁波會於高折射率材料內部形成導波模態。由導波理論可知電磁波於導波層兩介面間所累積之總相位變化，決定其是否於導波層內形成導波模態。因所累積之相位受到導波層厚度與折射率之影響，故反射率會隨著導波層厚度及折射率呈現週期性變化。除此之外，在相同結構下，入射波長越大則等效折射率越低，故形成導波模態之入射角度亦越小。此外，金屬厚度除了對TE波之反射率造成影響，亦影響反射率之角度頻譜中之半高全寬角度。金屬厚度越厚時，產生導波模態之入射角越小，且角度頻譜之半高全寬角度亦較小；反之，金屬厚度較薄時，產生導波模態所需之入射角則較接近 ，而其半高全寬角度會較大。但金屬厚度亦有其限制，若金屬厚度大於60 nm將使得電磁波無法進入導波層內部，自然亦無法形成導波模態。 This thesis employs the transmission line theory and a commercial software package based on Finite-Difference-Time-Domain method to investigate the transverse electric (TE) wave incidence upon two-dimensional planar metal-dielectric multilayered structures at optical frequencies. Results from both approaches show that a minimum reflectance could occur due to the resonant coupling between the incident electromagnetic wave and a guided mode in the high-index layer. From the guided-wave theory, since the phase accumulated by the wave at two boundaries in the guiding layer determines the guidance condition, the resonant coupling is largely affected by the thickness and refractive index of the high-index layer. It changes with the thickness and refractive index of the high-index layer periodically. In addition, under the same structure, since the effective index becomes smaller when the operating wavelength is increased, a smaller incident angle is required to excite the guided mode. On the other hand, metal thickness also affects the full-width-at-half-maximum (FWHM) angle of the reflectance. If the metal thickness becomes thicker, the incident angle required for the resonant coupling gets closer to the critical angle and the FWHM angle is smaller. On the contrary, the required incident angle is closer to when the thickness of the metal is decreased and the corresponding FWHM angle increases. Nevertheless, when the thickness of the metal is large than 60 nm, the TE resonant coupling vanishes.
