External bias dependent dynamic terahertz propagation through BiFeO₃ film

Abstract

Interactions of Terahertz radiations with matter can lead to the realization of functional devices related to sensing, high-speed communications, non-destructive testing (NDT), 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 THz to 1 THz frequency range) because of the variation in electric field from 0 kV/cm to 600 kV/cm. Further, we have captured signatures of the hysteretic nature of polarization switching in BiFeO3 film through non-contact THz-TDS technique, similar trends are observed in SS-PFM (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 BiFeO3 film. 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.

New insights into APCVD grown monolayer MoS2 using time-domain terahertz spectroscopy

“…S4 34 . To satisfy the need of highly resistive substrate in order to nullify the conductive losses in substrate 35 for THz-TDS measurements, the sapphire substrate has been chosen for growth of monolayer MoS 2 . The already optimized growth parameters have been used for growth on sapphire substrate as discussed in the experimental part.…”

Electronically triggered tunable terahertz signal observed in LPCVD grown single layer graphene

“…Arrangement of four parabolic mirrors in the THz-TDS setup is designed in such a way that the emitting THz beam is focussed to pass through the SLG sample before detecting at the receiver end. 15,[43][44][45] A dry N 2 atmosphere was maintained throughout the experiment to minimize the environmental effect such as humidity while recording the true THz responses as precisely as possible. 46 The study of SLG in the THz regime is motivated by an appropriate intraband energy gap of SLG when compared with single THz photon energy (4.1 meV for 1 THz).…”

Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization

“…A metasurface array of 1 cm × 1 cm is fabricated that maintains homogeneous excitation of the device. The obtained time-domain data is converted to frequency domain by deploying the Fast Fourier Transform (FFT) algorithm [60]. The observed transmission amplitude is normalized with respect to the silicon substrate, identical to the one used as substrate in metasurface fabrication.…”