在本文中將會介紹以超短脈衝雷射激發兆赫茲電磁輻射之原理與實驗設置，並探討兆赫茲電磁輻射於單晶矽晶圓之穿透特性，研究兆赫茲電磁輻射於平行與聚焦處不同量測位置之差異，以及不同阻值(0.008, 1,11510 W．cm) 矽晶圓對於兆赫茲電磁輻射之穿透影響，由實驗結果得知較佳的量測位置為兆赫茲電磁輻射聚焦處，此處可得到較高的穿透率，此情形可能是由於兆赫茲電磁輻射平行處的非均勻截面電場分布所造成。而影響兆赫茲電磁輻射穿透的重要參數為矽晶圓之電阻係數，由實驗得知電阻係數為0.008 W．cm時，無任何兆赫茲電磁輻射的穿透現象，當電阻係數高於1 W．cm，兆赫茲電磁輻射即有約60% 之穿透。

In this study we investigated terahertz (THz) transmission characteristics on Si wafer samples with various resistivities (0.008, 1, 11510 W．cm) using a THz time-domain spectroscopy (THz-TDS) apparatus. For this THz-
TDS system, there were two testing positions for THz transmission measurements, one provided parallel THz waves for sizable samples with a diameter of about 50 mm, and the other one then focused THz radiation onto a cross-section of about 2 mm diameter where applied to a small-size material. We obtained a higher THz transmission at the focused position for THz waves than the parallel testing position which might be due to a nonuniform cross-section field distribution in the parallel THz beam. Our study of the THz-TDS on Si wafers indicated that there was of about 60% transmission for resistivity larger than 1 W．cm. The related analysis for the complex refractive index of Si samples in THz range will be discussed.