[10p-PB2-1~13] 3.9 Terahertz technologies

[10p-PB2-10] Comparison of Si lens and tapered transmission line as a photoconductive antenna-free space coupler –improvement of laser source and alignment–

〇Osamu Morikawa¹, Katsutoshi Kawano¹, Kohji Yamamoto², Kazuyoshi Kurihara², Fumiyoshi Kuwashima³, Masahiko Tani² (1.JCGA, 2.Univ. Fukui, 3.FUT)

Keywords:V-groove, superfocusing, THz wave

Si lenses are frequently employed for a photoconductive antenna-free space coupler. Recently, tapered transmission lines have been proposed for that purpose. Previously we compared the Si lens and tapered transmission line as the coupler. Focusing of laser beam to the photoconductive gap of the antenna was changed when the Si lens was replaced to the tapered transmission line. Therefore we measured the current induced in the photoconductive antenna when voltage was applied to the antenna and compensate the effect of the change of focusing using the current value. We found that the signal is stronger and the spectral range is wider when we use the Si lens than the tapered transmission line. However, we noticed that the stability of the irradiating laser and the precision of alignment of the antenna chip on the tapered transmission line were insufficient. In this presentation, we compared the Si lens and tapered transmission line using sufficiently stable laser and precise alignment method. We found that the signal was stronger and the spectral range was wider when we used the Si lens than the tapered transmission line.