Abstract

In order to support the communication needs of our society, carrier frequencies for wireless communication networks in the terahertz frequency range will be an almost forced choice [1]. For instance, the technology of choice to encode high-frequency data signals onto a terahertz carrier is still an open issue [2]. In this work, we investigate the transfer of a gigahertz modulation from an optical carrier at telecom wavelengths to terahertz carrier. Two telecom lasers modulated in amplitude at microwave frequency Ω illuminates an ultrafast ion-irradiated In_0.53Ga_0.47As photomixer[3]. The cw terahertz emission generated by the photomixer is analyzed by using a Fourier transform infrared spectrometer and a Si bolometer. The terahertz spectra corresponding to the photomixer emission are shown in Fig. 1(a) (plain lines), for ω_THZ=0.35 THz to ω_THZ =1.25 THz. Dotted lines illustrate the spectra exhibiting only the carrier frequency ω_THZ when no modulation is applied. The signature of transfer of the microwave modulation of the driving lasers onto the terahertz carrier is the appearance of microwave shifts (or sidebands) at ω= ω_THZ + Ω and ω= ω_THZ + Ω,. The relative heights of the lower and upper sidebands are ~0.19 and ~0.16 respectively, for all the tested carrier frequencies .

© 2009 IEEE