Terahertz and Photoelectron Emission from Nanoporous Gold Films on Semiconductors

Junyi Nan; Min Li; Ling Zhang; Shuai Yuan; Boqu He; Heping Zeng

doi:10.3390/nano9030419

Terahertz and Photoelectron Emission from Nanoporous Gold Films on Semiconductors

Nanomaterials (Basel). 2019 Mar 12;9(3):419. doi: 10.3390/nano9030419.

Authors

Junyi Nan¹, Min Li², Ling Zhang³, Shuai Yuan⁴, Boqu He⁵, Heping Zeng^{6

7}

Affiliations

¹ State key laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China. 52162099006@stu.ecnu.edu.cn.
² Shanghai Key Lab of Modern Optical System, School of Optical-Electrical and Computing Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China. minli1220@usst.edu.cn.
³ Shanghai Key Lab of Modern Optical System, School of Optical-Electrical and Computing Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China. lzhang@usst.edu.cn.
⁴ Shanghai Key Lab of Modern Optical System, School of Optical-Electrical and Computing Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China. syuan@usst.edu.cn.
⁵ State key laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China. boquhe@foxmail.com.
⁶ State key laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China. hpzeng@phy.ecnu.edu.cn.
⁷ Shanghai Key Lab of Modern Optical System, School of Optical-Electrical and Computing Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China. hpzeng@phy.ecnu.edu.cn.

Abstract

Efficient terahertz and photoelectron emission were observed from nano-porous gold (NPG) films deposited on an intrinsic gallium arsenide (GaAs) semiconductor substrate stimulated by femtosecond laser with pulse width of 60 fs. Time-domain THz emission and reflection spectroscopy confirmed that the free charges accelerated by irradiated femtosecond laser pulses transferred from the NPG films into the GaAs substrates. Accordingly, charges accumulation was reduced in the NPG films, resulting in a stronger emission of THz pulse than that from NPG films deposited on SiO₂ substrate. Charges injected into the GaAs substrate enforced an observable decrease of the THz refractive index proportional to the intensity of incident light. In comparison, for NPG deposited on glass substrates, laser induced free charges were accumulated in the NPG films, and femtosecond laser pulses irradiating on the NPG films made no changes of the THz refractive index of the glass substrates.

Keywords: localized surface plasmons; nanoporous gold; optical rectification; terahertz radiation.