金属开口谐振环结构的太赫兹波吸收特性

Terahertz absorbing properties of different metal split-ring resonators

太赫兹调制器、滤波器、吸收器是太赫兹波应用领域的关键器件,而金属开口谐振环是这些器件的常用结构。通过仿真及实验的手段,系统地比较了不同亚波长金属开口谐振环结构的太赫兹波吸收特性。设计并制备两种不同形式的亚波长金属谐振环,利用时域有限差分(FDTD)的模拟方法与光泵浦太赫兹探测(OPTP)的实验方法,分析了电磁波入射谐振环时,TM与TE模式下的太赫兹透射特性。发现在TM模式下,吸收峰峰值均反比于谐振环的等效电容值与等效电感值。而在TE模式下,由于偶极子振荡长度相同导致了两种谐振环吸收峰峰值相近。此外,改变外部光激励条件时实验结果表明TM模式下,单开口环比双开口环对光激励更敏感:泵浦光功率为5 m W相比无泵浦光时,单开口环透射率增加了80%,而双开口环透射率仅增加了43%。

Terahertz modulator, filters and absorbers are the key parts of terahertz application, while the metal split ring is the common structure of these applications. Comparisons of terahertz absorbing properties, which were caused by different structures of subwavelength metal split ring resonator, were studied by simulation and experiment. Two split ring resonators which had different split gap types were fabricated. By using Finite Difference Time Domain（FDTD） simulation and Optical Pump Terahertz Probe （OPTP） experimental methods, the terahertz transmittance curves of TM mode and TE mode were investigated when the electromagnetic waves were perpendicular to the samples. The analysis found that in TM mode, the frequency of the absorption peak was inversely proportional to the value of the effective inductance and the effective capacitance. But in TE mode, the similar resonance frequency of the two SRRs were caused by the same length of dipole resonance. In addition, when optical excitation power changed, the experimental result indicates that one-gap SRR is more sensitive than two-gap SRR in TM mode. As the pump light power up to 5 mW, the resonance frequency transmittance of one-gap SRR raised 80% than the pump light condition at 0 mW. But, two-gap SRR only raised 43% when the light condition changed from 0 mW to 5 mW.