Generation of frequency-tunable terahertz electromagnetic waves from coherent longitudinal optical phonon-plasmon coupled modes

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K13341
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Applied materials
• Research Institution: Osaka City University
• Principal Investigator: NAKAYAMA Masaaki 大阪市立大学, 大学院工学研究科, 教授 (30172480)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: コヒーレント縦光学フォノン－プラズモン結合モード / テラヘルツ電磁波 / 時間分解テラヘルツ分光法 / テラヘルツ周波数可変性 / GaAsエピタキシャル構造

Outline of Final Research Achievements

We measured systematically terahertz (THz) electromagnetic waves in undoped GaAs/n-type GaAs and undoped GaAs/p-type GaAs epitaxial structures with time-domain THz spectroscopy. From the Fourier transform of the time-domain signals, it was found that there are two THz bands, the frequencies of which markedly depend on an excitation power. From the analysis of the excitation-power dependence based on a theory for the carrier-density dependence of the frequency of the longitudinal optical phonon-plasmon coupled (LOPC) mode, we revealed that the above two THz bands correspond to the lower and upper branches of the coherent LOPC mode and that the frequency is determined by the photogenerated electron density in the undoped GaAs layer. Consequently, we have demonstrated the generation of frequency-tunable THz electromagnetic waves from the coherent LOPC mode.

Free Research Field

半導体光物性