INTEGRATED NANOSTRIP DIPOLE ANTENNAS FOR COHERENT 30 THZ INFRARED RADIATION

We report on the experimental study of infrared nanostrip dipole anten nas which are connected to thin-film nanometer Ni-NiO-Ni diodes. The i ntegrated Ni-NiO-Ni diodes are used to detect 30THz (almost-equal-to 1 0 mum) CO2-laser radiation. The diodes are deposited on 385 mum silico n substrates which are covered with a layer of 1.6 mum SiO2 on both si des. We have found that in low-power applications 1.6 mum of SiO2 yiel ds excellent quarter-wave matching layers for wavelengths centered at lambda0 = 10.8 mum. By this method 79% of the incident CO2-laser radia tion is transmitted into the Si substrate compared to 48% without SiO2 layer. The use of SiO2 quarter-wave matching layers considerably impr oves the efficiency of infrared nanostrip dipole antennas. This has be en confirmed by the study of the laser-induced response of the Ni-NiO- Ni diode detectors as a function of the length L of the dipole antenna . Thus, we have observed that the laser-induced response strongly incr eases for shorter antennas and exhibits a distinct maximum at L = 2.8 +/- 0.3 mum. For the first time, we have investigated the 30 THz radia tion patterns of nanostrip dipole: antennas of different lengths. On t his occasion, we have observed that the radiation pattern changes when the length L of the dipole antenna is varied. This observation indica tes that antenna currents propagate on the nanostrip dipole antenna.