Jana Arun, Rane Shreeya, Roy Choudhury Palash, Roy Chowdhury Dibakar
Ecole Centrale School of Engineering, Mahindra University, Hyderabad, Telangana 500043, India.
Nanotechnology. 2022 May 17;33(32). doi: 10.1088/1361-6528/ac6bb2.
Interactions of terahertz radiations with matter can lead to the realization of functional devices related to sensing, high-speed communications, non-destructive testing, spectroscopy, etc In spite of the versatile applications that THz can offer, progress in this field is still suffering due to the dearth of suitable responsive materials. In this context, we have experimentally investigated emerging multiferroic BiFeO3 film (∼200 nm) employing terahertz time-domain spectroscopy (THz-TDS) under vertically applied (THz propagation in the same direction) electric fields. Our experiments reveal dynamic modulation of THz amplitude (up to about 7% within 0.2-1 THz frequency range) because of the variation in electric field from 0 to 600 kV cm. Further, we have captured signatures of the hysteretic nature of polarization switching in BiFeOfilm through non-contact THz-TDS technique, similar trends are observed in switching spectroscopy piezoresponse force microscope measurements. We postulate the modulation of THz transmissions to the alignment/switching of ferroelectric polarization domains (under applied electric fields) leading to the reduced THz scattering losses (hence, reduced refractive index) experienced in the BiFeOfilm. This work indicates ample opportunities in integrating nanoscale multiferroic material systems with THz photonics in order to incorporate dynamic functionalities to realize futuristic THz devices.
太赫兹辐射与物质的相互作用可促使实现与传感、高速通信、无损检测、光谱学等相关的功能器件。尽管太赫兹能带来多种应用，但由于缺乏合适的响应材料，该领域的进展仍受到阻碍。在此背景下，我们利用太赫兹时域光谱技术（THz - TDS），在垂直施加（太赫兹沿相同方向传播）电场的条件下，对新兴的多铁性BiFeO₃薄膜（约200纳米）进行了实验研究。我们的实验表明，由于电场从0变化到600 kV/cm，太赫兹振幅在0.2 - 1太赫兹频率范围内出现了动态调制（高达约7%）。此外，我们通过非接触太赫兹时域光谱技术捕捉到了BiFeO薄膜中极化切换的滞后特性的信号，在切换光谱压电响应力显微镜测量中也观察到了类似趋势。我们推测太赫兹传输的调制是由于铁电极化畴（在施加电场下）的排列/切换，导致BiFeO薄膜中太赫兹散射损耗降低（因此，折射率降低）。这项工作表明，将纳米级多铁性材料系统与太赫兹光子学集成有大量机会，以便纳入动态功能来实现未来的太赫兹器件。
