T-ray topography by time-domain polarimetry

Abstract

We demonstrate a method for substantially improving the axial resolution of terahertz time-of-flight measurements by analyzing the time-dependent polarization direction of an elliptically polarized single-cycle terahertz electromagnetic (T-ray) pulse. We show that, at its most sensitive, the technique has an axial resolution of ∼λ/1000 (<1 μm) with a subsecond measurement time, and very clear T-ray topographic images are obtained. Such a very high axial resolution of the T-ray topography opens the way for novel industrial and biomedical applications such as fine metalworking and corneal inspection in a safe manner.

Experimental Study on Terahertz Imaging Technique in Nondestructive Inspection

“…Because of the unique features, THz imaging technique has been applied widely in environmental monitoring, medical diagnosis, security detection, military radar and nondestructive inspection [6][7][8][9]. Here, the application in nondestructive inspection was introduced particularly.…”

Recent Advances in Birefringence Studies at THz Frequencies

“…This problem was overcome in a recent work [85], where a technique based on the fast mechanical rotation of an EO (110) crystal and lock-in detection was introduced, allowing for a fast and precise determination of the polarization direction of a THz wave. Thus, rotating the EO detector becomes suitable also for polarization imaging applications, as the authors proved in [86], where the method was applied for topographic measurements with extremely high axial resolution.…”

A Real-Time Terahertz Time-Domain Polarization Analyzer with 80-MHz Repetition-Rate Femtosecond Laser Pulses

“…They are also important in many fields of applied science for investigating carrier density and mobility in semiconductors [8,28–30]; local stress and optical axis, probed by terahertz birefringence measurements [31–34] and physiological conditions, probed by reflection polarimetry of human skin [35,36]. In addition, terahertz time-domain polarimetry, which allows us to extract the instantaneous direction of the electric-field (E-field) vectors within a single-cycle of the electromagnetic oscillation, opens new avenues for investigating the surface topography of materials [37] and for separate determination of the optical Faraday and Kerr rotation angles using echo signals [26], a result that cannot be attained with the conventional polarization measurement technique for much higher frequencies.…”