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Browsing by Author "Huang, Ping"

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    Helicity-dependent terahertz emission spectroscopy of topological insulator Sb2Te3 thin films
    (2017-11-06)
    Tu, Chien-Ming
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    Chen, Yi-Cheng
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    Huang, Ping
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    Chuang, Pei-Yu
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    Lin, Ming-Yu
    We report on helicity-dependent terahertz emissions that originate from the helicity-dependent photocurrents in topological insulator Sb2Te3 thin films due to ultrafast optical excitation. The polarity of the emitted terahertz radiation is controlled by both the incident angle and the helicity of optical pulses. Using an unprecedented decomposition-recombination procedure in the time domain, the signals of the Dirac fermions are fully separated from bulk contributions. These results provide insights into the optical coupling of topological surface states and open up opportunities for applying helicity-dependent terahertz emission spectroscopy in spintronics.
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    Helicity-Dependent Terahertz Radiation from Topological Insulator Sb2Te3 Thin Film by Femtosecond Optical Excitation
    (2016)
    Tu, Chien-Ming
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    Chen, Yi-Cheng
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    Huang, Ping
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    Chuang, Pei-Yu
    ;
    Lin, Ming-Yu
    We report on terahertz radiation from topological insulator (TI)Sb2Te3 thin film under ultrafast optical excitation with different helicity. Polarity-reversals of the emitted THz radiation were observed as the helicity of optical pulses reversed. The observed phenomena are coincident with the characteristics of the helicity-dependent photocurrent on TIs. Our work demonstrates the potential applications of surface photocurrents on TIs for opto-spintronics devices.
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    THz emission from organic cocrystalline salt: 2, 6-diaminopyridinium-4-nitrophenolate-4-nitrophenol
    (2016-03-07)
    Tu, Chien-Ming
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    Chou, Li-Hsien
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    Chen, Yi-Cheng
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    Huang, Ping
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    Rajaboopathi, M.
    We report few-cycle THz pulses emission from a novel organic crystal 2,6-diaminopyridinium-4-nitrophenolate-4-nitrophenol (DAP(+)NP(-)NP). The observed amplitude of the THz electric field from a DAP(+)NP(-)NP crystal is comparable with that from a ZnTesingle crystal under the same optical pumping conditions. Both the waveform and spectra of the THz radiation from DAP(+)NP(-)NP are similar to those from ZnTe. We conclude that a high quality DAP(+)NP(-)NP crystal would be a high potential candidate in THz generation and applications. (C) 2016 Optical Society of America