Abstract
Arrayed hexagonal metal nanostructures are used to maximize the local current density while providing effective thermal management at the nanoscale, thereby allowing for increased emission from photoconductive terahertz (THz) sources. The THz emission field amplitude was increased by 60% above that of a commercial THz photoconductive antenna, even though the hexagonal nanostructured device had 75% of the bias voltage. The arrayed hexagonal outperforms our previously investigated strip array nanoplasmonic structure by providing stronger localization of the current density near the metal surface with an operating bandwidth of 2.6 THz. This approach is promising to achieve efficient THz sources.
Highlights
A photoconductive antenna (PCA) can produce terahertz (THz) bandwidth pulses by the generation of photocarriers in the antenna gap using a femtosecond laser [1, 2]
The main advantage of the nanoplasmonic structure for detection is to create a fast sweep out time, and thereby allow for the usage of a low-cost high-mobility long carrier lifetime substrate like semi-insulating GaAs [18, 20,21,22], as opposed to other less common substrates with short carrier lifetimes [23,24,25,26,27,28,29,30,31]
Even though the voltage is higher for the 5 μm gap structure, the local bias field is higher in the nanoplasmonic structures, due to the smaller gaps
Summary
A photoconductive antenna (PCA) can produce terahertz (THz) bandwidth pulses by the generation of photocarriers in the antenna gap using a femtosecond laser [1, 2] Such THz waves (0.3~10 THz) have applications in security, imaging [3,4,5,6,7,8,9,10,11], near-field scanning microscopy and spectroscopy [12,13,14,15,16]. We demonstrate that both the bias field and the carrier density can be increased in a nanoplasmonic structure by reducing heat generation and effectively removing heat generated near the metal nanostructures. The main roles of the nanostructured metal are to localize the current density near the metal to reduce heat generation while maximizing THz emission and ensuring that the heat that is generated is efficiently removed
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