Chopra Nishtha, Lloyd-Hughes James
Department of Physics, University of Warwick, Coventry, West Midlands CV4 7AL, U.K.
ACS Photonics. 2025 Jan 11;12(2):917-924. doi: 10.1021/acsphotonics.4c01934. eCollection 2025 Feb 19.
A dual-beam THz spectrometer is reported that substantially reduces the influence of systematic errors in THz time-domain spectroscopy such as those caused by variations in femtosecond laser power or the environmental temperature and humidity. Dual THz beams with single-cycle waveforms were generated simultaneously using a dual-pixel interdigitated photoconductive antenna, allowing the simultaneous acquisition of sample and reference data in the spectrometer using the same optical components. A low-aberration optical geometry ensured diffraction-limited spatial profiles for both beams despite their off-axis propagation and was validated experimentally by measuring frequency-dependent beam profiles and theoretically via physical optics calculations. Although the experimental amplitudes and absolute phase spectra of both beams were very similar, we further provided a correction procedure to eliminate these small differences. The robustness of the dual-beam spectrometer design was evaluated by measuring the complex transmission of a thin plastic sheet after intentionally introducing a change in the relative humidity of the THz beam path. The dual-beam THz spectrometer was effective at removing systematic errors in the amplitude and phase by simultaneously measuring the two THz beams under the same conditions.
报道了一种双光束太赫兹光谱仪，该光谱仪可大幅降低太赫兹时域光谱中系统误差的影响，比如由飞秒激光功率变化或环境温度和湿度引起的系统误差。使用双像素叉指式光电导天线同时产生具有单周期波形的双太赫兹光束，这使得光谱仪能够使用相同的光学组件同时采集样品和参考数据。一种低像差光学结构确保了两束光尽管离轴传播但仍具有衍射极限的空间分布，通过测量频率相关的光束分布进行了实验验证，并通过物理光学计算进行了理论验证。尽管两束光的实验幅度和绝对相位光谱非常相似，但我们进一步提供了一种校正程序来消除这些微小差异。通过在有意改变太赫兹光束路径的相对湿度后测量薄塑料片的复透射率，评估了双光束光谱仪设计的稳健性。双光束太赫兹光谱仪通过在相同条件下同时测量两束太赫兹光束，有效地消除了幅度和相位中的系统误差。
