2 School of Physics, Huazhong University of Science and Technology, Wuhan, People's Republic of China
3 Singapore Synchrotron Light Source, National University of Singapore, Singapore 117576, Singapore
4 Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
5 Authors to whom any correspondence should be addressed.
Branchlike nano-electrode structures were found to improve the THz emission intensity of a photomixer by approximately one order of magnitude higher than that of a photomixer with one row of nano-electrodes separated by the same 100 nm gap. The enhancement is attributed to a more efficient collection of generated carriers, which is in turn due to a more intense electric field under the branchlike nano-electrodes' structures. This is coupled with an increased number of effective areas where strong tip-to-tip THz field enhancements were observed. The optical-to-THz conversion efficiency of the photomixers with the new branchlike nano-electrodes was found to be 10 times higher. The more efficient THz photomixer will greatly benefit the development of continuous-wave THz imaging and spectroscopy systems.