리튬나이오베이트 기판의 분극 반전 기술을 이용하여 5.5 GHz대역의 SSB(Single Sideband) 광변조기를 설계 및 제작하였다. 분극 반전을 통해 광이 인가받는 유효전계가 마흐젠더 두 도파로에서 $90^{circ}$ 위상차를 갖도록 할 수 있었다. 제작된 광변조기는 5.8 GHz의 중심주파수로, 1.9 V DC 인가 시 약 33 dB의 USB 억제율을, -10.6 V 인가 시 약 25 dB의 LSB 억제율을 나타내었다. 또한 2.5 GHz의 대역폭에서 15 dB 이하의 Sideband 억제율을 보이고 있다.
A single sideband(SSB) modulator operating at 5.5 GHz was fabricated by polarization inversion techniques. The dimension of domain inversion in a $LiINbO_3$ Mach-Zehnder structure was precisely controlled so that the RF signal applied on two Mach-Zehnder arms gives rise to $90^{circ}$ effective phase difference. The single sideband suppression was maximized by optimization of the polarization status of the optical input and by the DC bias value. The fabricated device showed the center frequency of 5.8 GHz and the maximum sideband suppression of 33dB, where the bandwidth of 15 dB sideband suppression ranged over a 2.5 GHz span. The optical phase delay could be regulated by the DC bias voltage, fur example, the enhanced optical modulation sideband was distinctively switched from the upper sideband to the lower sideband by changing the DC bias voltage from 1.9 V to -10.6 V.
