This paper reports progress on a type of ultrafast photoconductive source that can be driven at 1550 nm but exhibits the robustness of GaAs (e.g., low-temperature-grown GaAs) driven at 780 nm. The approach is GaAs doped heavily with Er (≈4x1020 cm-3 or 2% atomic-Er-to-Ga fraction) such that ErAs nanoparticles form spontaneously during epitaxial growth by MBE. The nanoparticles are mostly spherical with a diameter of a few nm while the packing density is estimated as high as ~2.2x1019/cm3. Yet, the Er-doped GaAs epilayer maintains excellent structural quality and smooth surface morphology. A photoconductive switch coupled to a 4-turn square spiral antenna is fabricated and characterized. At least ~40 μW average THz power is generated when the device is biased at 75 V and pumped with a 1550-nm 90-fs-short pulsed laser having average power ~85 mW. This research is significant for 1550-nm-technologycompatible, cost-effective THz sources.
W-D. Zhang, A. Mingardi, E. R. Brown, A. Feldman, T. Harvey, and R. P. Mirin, "Ultrafast photoconductive devices based upon GaAs:ErAs nanoparticle composite driven at 1550 nm," Proc. SPIE 10193, Ultrafast Bandgap Photonics II, 1019308 (Presented at SPIE Defense + Security: April 10, 2017; Published: 8 May 2017); https://doi.org/10.1117/12.2262647.
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