Abstract
We present a polarization shaping technique for few-cycle terahertz (THz) waves. For this, N femtosecond laser pulses are generated from a devised diffractive optical system made of as-many glass wedges, which then simultaneously illuminate on various angular positions of a sub-wavelength circular pattern of an indium arsenide thin film, to produce a THz wave of tailor-made polarization state given as a superposition of N linearly-polarized THz pulses. By properly arranging the orientation and thickness of the glass wedges, which determine the polarization and its timing of the constituent THz pulses, we successfully generate THz waves of various unconventional polarization states, such as polarization rotation and alternation between circular polarization states.
Highlights
Ultrafast pulse shaping technique has enabled on-demand generation of visible light of arbitrary waveforms, making significant contributions in many research areas including laser spectroscopy [1], quantum control of non-linear processes [2], and magnetic spin state control [3], to list a few
Polarization has gradually become an important control parameter, and the polarization state shaping of optical frequency wave, which has been pursued with the help of well-developed optical devices and components, such as optical gratings, or liquid crystal devices [4], is succesfully applied for spintronics [5] and photo-biochemistry [6]
There have been attempts to achieve the circular polarization of THz frequency waves by combining a couple of linearly-polarized THz waves [13]; or by passive optical components, such as prisms [14], Fresnel rhombs [15], achromatic wave plates [16]
Summary
Ultrafast pulse shaping technique has enabled on-demand generation of visible light of arbitrary waveforms, making significant contributions in many research areas including laser spectroscopy [1], quantum control of non-linear processes [2], and magnetic spin state control [3], to list a few. Polarization has gradually become an important control parameter, and the polarization state shaping of optical frequency wave, which has been pursued with the help of well-developed optical devices and components, such as optical gratings, or liquid crystal devices [4], is succesfully applied for spintronics [5] and photo-biochemistry [6]. This undeveloped frequency region has attracted a great deal of interest [7, 8]. THz frequency waves of controlled polarization state are relevant in use for many fundamental studies. The material waves of which the frequency belongs to THz region include the spin wave of magnetic materials and the vibrational waves of circularly dichroic biological molecules [9,10,11]. The scope of THz-version of polarization state shaping is rather limitted to a few simple polarization states
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