亚波长铌酸锂波导产生THz特性研究(特邀)  

Terahertz Characteristics Generated by Subwavelength Lithium Niobate Waveguides(Invited)

作　　者：张泽亮 马若斌 李星佑 卢瑶 吴强[2] 刘伟伟[1] Zhang Zeliang;Ma Ruobin;Li Xingyou;Lu Yao;Wu Qiang;Liu Weiwei(Institute of Modern Optics,Nankai University,Tianjin 300350,China;School of Physics,Nankai University,Tianjin 300071,China)

机构地区：[1]南开大学现代光学研究所,天津300350 [2]南开大学物理科学学院,天津300071

出　　处：《光学学报》2024年第17期338-345,共8页Acta Optica Sinica

基　　金：国家自然科学基金(12074198);中央高校基本科研业务费(63243166)。

摘　　要：基于铌酸锂棱镜产生强太赫兹(THz)源的频谱中心频率通常难以调制,这限制了其在可调谐多波长方面的应用。通过实验实现了一种基于铌酸锂波导的可调谐THz源,通过控制铌酸锂波导厚度控制波导发射THz频谱的中心频率,实现可调谐单频THz波输出。基于叉指型阵列光电导天线检测铌酸锂波导,产生THz信号,提升系统信噪比。与传统片上电光取样系统相比,本文系统的信噪比提升10倍。Objective Terahertz(THz)waves hold significant application potential in fields such as spectroscopy,integrated optics,and imaging.With the advancement of high-power femtosecond laser technology,lithium niobate crystals and waveguides have emerged as efficient,high-beam quality,and stable THz sources for generating THz radiation.Notably,the tilted-pulse-front method has led to significant progress in generating strong THz radiation from lithium niobate crystals.However,the spectral center frequency of strong THz sources generated by lithium niobate prisms is typically challenging to modulate,limiting their use in tunable multi-wavelength applications.We present a tunable THz source based on a lithium niobate waveguide,wherein the waveguide’s thickness is controlled to modulate the central frequency of the emitted THz spectrum,achieving tunable single-frequency THz wave output.In addition,we utilize an interdigital photoconductive antenna to detect the THz signals generated by the lithium niobate waveguide,enhancing the system’s signal-to-noise ratio.Methods The experimental setup involves a laser with a wavelength of 800 nm,a pulse width of 35 fs,and a repetition rate of 500 Hz.A cylindrical lens with a focal length of 70 mm is used to modulate the laser beam into a line laser mode suitable for transverse excitation.Two off-axis mirrors with a focal length of 101.1 mm are used to collect the THz waves generated by the lithium niobate waveguide.An interdigital photoconductive antenna is used to collect the far-field THz signals,with a wide-angle silicon lens that efficiently collects elliptical THz spots,ensuring high detection efficiency without the need for additional optical components.Results and Discussions In the transverse excitation mode,by comparing the time-domain and spectral characteristics of THz waves generated by lithium niobate waveguides of varying thicknesses and lengths,the following conclusions are drawn.1)The center frequency of THz waves generated by the lithium niobate waveguide is affect

关 键 词：铌酸锂波导 窄带太赫兹波产生 光电导天线 高信噪比 太赫兹时域光谱系统 

分 类 号：O437[机械工程—光学工程]