Abstract
We demonstrate a method to create arbitrary terahertz (THz) polarization profiles by exploiting the magnetic field-dependent emission process of a spintronic source. As a proof-of-concept, we show that by applying a specific magnetic field pattern to the source, it is possible to generate a quadrupole-like THz polarization profile. Experimental measurements of the electric field at the focus of the THz beam revealed a polarity flip in the transverse profile of the quadrupole-like mode with a resulting strong, on-axis longitudinal component of 17.7 kV cm−1. This represents an order of magnitude increase in the longitudinal component for the quadrupole-like profile compared to a linear polarization, showing an example of how the magnetic field patterning of a spintronic source can be exploited to obtain desirable THz polarization properties. This unique ability to generate any desired THz polarization profile opens up possibilities for schemes such as rotatable polarization spectroscopy and for efficient mode coupling in various waveguide designs. Furthermore, the strong longitudinal fields that can be generated have applications in areas including intra-subband spectroscopy of semiconductors, non-diffraction limited THz imaging, and particle-beam acceleration.
Highlights
Experimental measurements of the electric field at the focus of the THz beam revealed a polarity flip in the transverse profile of the quadrupole-like mode with a resulting strong, on-axis longitudinal component of 17.7 kV cmÀ1
We demonstrate the ability to generate highfield strength THz radiation with arbitrary polarization profiles without the use of complex optical components
We report on the application of a magnetic field pattern to a spintronic emitter placed between two magnets of either aligned or opposing polarity, which after excitation of the emitter by a femtosecond laser pulse results in the generation of THz radiation with either linear or quadrupole-like polarization, respectively
Summary
Experimental measurements of the electric field at the focus of the THz beam revealed a polarity flip in the transverse profile of the quadrupole-like mode with a resulting strong, on-axis longitudinal component of 17.7 kV cmÀ1.
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