Summary

We have demonstrated that the THz radiation generated from oxygen ion-implanted GaAs and LT-GaAs with dipole antenna structure under pulsed and CW mode. In our studies, we compared the emission properties of the LT-GaAs and GaAs implanted with oxygen multi-implants dosage concentrations

13 2

2.5 10 ions/cm× (500 keV & 800 keV ), 4 10 ions/cm× ^{13 2} (1200 keV ) and annealing temperature ( 550℃ for 60s).

From the result of electric measurement, oxygen-ion-implanted GaAs has higher increasing ratio when we bias at higher voltage, although oxygen-ion- implanted GaAs has higher dark current than low temperature grown GaAs.

From the result of THz radiation characteristics, the pulse THz peak power of oxygen ion implanted GaAs is 5.2mW, and that of the LT-GaAs is 3.6mW. It’s almost 1.5 times the LT-GaAs. And we also measure the highest CW THz power of oxygen ion implanted GaAs is 2.268μW and for low temperature grown GaAs is 1.268μW. It’s about 1.8 times the low temperature grown GaAs. The oxygen ion implanted GaAs has higher THz power both in pulse and CW mode and there

is no saturation effect in both pulse and CW mode. But low temperature grown GaAs has saturation effect in CW mode in our experiment. We also measurement the frequency bandwidth of both materials, the bandwidth of both materials are 1THz measured by pulse (TDS) and CW (photomixing). The results show that this kind of material is suitable for high power under both pumping sources THz radiation generation.

5.2 Future work

We have successfully demonstrated the THz radiation characteristics of two different materials (oxygen-ion-implanted and LT-GaAs) in pulse and CW mode.

For the laser sources, we can replace our system to an external-cavity dual-wavelength laser diode. Because of the common-mode rejection effect and less mode-hopping the linewidth of beating frequency will become smaller than using two independent laser diodes. According to the recent study, they use interdigitated-fingner antenna structure to enhance CW THz power and optimize their fabricated conditions. And also traveling-wave structure could be used to maintain the bandwidth. So we can improve our emitters by optimizing the conditions of implant dosage and annealing temperature for high frequency purpose, or we can try to adopt other antenna structures to increase the bandwidth.

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