Broadband and tunable terahertz absorption via photogenerated carriers in undoped silicon

• 作者: Jie Li Jitao Li Chenglong Zheng Longhai Liu Zhen Yue Hang Xu Xuanruo Hao Fuyu Li Tingting Tang Yating Zhang Jianquan Yao
• 来源期刊: 中国科学：物理学 力学 天文学（英文版）
• 年，卷（期）: 2022,（1）
• 所属期刊栏目: Article
• 页码范围: 14-21
• 页数: 8页
• 语种: 英文

摘要

Terahertz absorbers based on doped silicon have achieved broadband and high-efficiency absorption due to their high con-centration of carriers.However,their tunable performance is obviously insufficient.Here,we propose a new scheme for active terahertz absorption based on undoped silicon with a metamaterial antireflection layer,which realizes both strong absorption and ultrahigh modulation depth.Benefiting from the weak absorption and high transmission of undoped silicon for 1064-nm continuous wave,uniformly distributed carriers across the entire thickness of the absorber are excited,and efficient free carrier absorption of the terahertz wave is obtained.We use only a 500-μm thick absorber and achieve absorption greater than 90％ in the range of 0.58 to 1.92 THz,with a peak value of 99％.More important,the absorber can be switched between two working states ofnonabsorption and high-efficiency absorption by changing the pump power,which means the modulation depth reaches 100％.This simple and high-performance implementation scheme provides a new idea for the design of terahertz tunable absorbers.