Abstract
Photoconductive antennas (PCAs), as a popular terahertz (THz) radiation source, have been widely used in spectroscopy, material characterization, biological imaging and detection of hazardous materials. However, PCAs have a relatively low energy conversion efficiency from femtosecond laser pulses to THz radiation which often limits the signal-to-noise ratio and bandwidth of THz imaging and spectroscopy systems. To address these limitations, here we report a THz photoconductive antenna emitter with all-dielectric nanopillars integrated on top of the SI-GaAs substrate to increase the generated photocarriers, which achieves a broadband and frequency insensitive THz power enhancement factor around 1.25 at frequencies 0.05 - 1.6 THz. Our results reported here provide a new method for increasing the THz power of PCAs, which paves the way for the subsequent researches of next-generation PCAs.
Highlights
Photoconductive antennas (PCAs) have always been widely used by the research community because of number of advantages, such as compact in size, low cost, fiber technology compatible and room temperature operation
The radiated THz power of PCAs is at a level that does not meet the rapidly growing demand in the field of THz science and technology
We propose and demonstrate a dielectric nanopillars assisted PCA transmitter having a nearly uniform THz power enhancement factor in a broad bandwidth
Summary
Photoconductive antennas (PCAs) have always been widely used by the research community because of number of advantages, such as compact in size, low cost, fiber technology compatible and room temperature operation. Improving THz efficiency of PCAs has always been a challenging task [1,2,3,4,5,6,7] To address this problem, the O’Hara firstly integrated a split ring resonator into the electrodes of a PCA transmitter [8]. We propose and demonstrate a dielectric nanopillars assisted PCA transmitter having a nearly uniform THz power enhancement factor in a broad bandwidth. 17, the optical absorption improvement is due to the multiple beam inference instead of Mie or plasmonic resonances, which permits to fabricate the nanopillars by dry etching the substrate itself, preventing the complex dielectric layer growth process and the unknown metal-semiconductor contact problems encountered in previous nano-structure assisted PCAs As we present in ref. 17, the optical absorption improvement is due to the multiple beam inference instead of Mie or plasmonic resonances, which permits to fabricate the nanopillars by dry etching the substrate itself, preventing the complex dielectric layer growth process and the unknown metal-semiconductor contact problems encountered in previous nano-structure assisted PCAs
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