Modelling of sub-wavelength THz sources as Gaussian apertures.
The THz emission point on a nonlinear electro-optical crystal for generating broadband THz radiation is modeled as a radiating Gaussian aperture. With the wavelengths of the infrared pump beam being much smaller than the wavelength components of the generated THz pulse, a THz sub-wavelength radiating aperture with Gaussian profile is effectively created. This paper comprehensively investigates Gaussian apertures in focused THz radiation generation in electro-optical crystals and illustrates the breakdown of the paraxial approximation at low THz frequencies. The findings show that the shape of the radiation pattern causes a reduction in detectable THz radiation and hence contributes significantly to low signal-to-noise ratio in THz radiation generation. Whilst we have demonstrated the findings on optical rectification in this paper, the model may apply without a loss of generality to other types of apertures sources in THz radiation generation.
Lin
Hungyen
H
School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia. hlin@eleceng.adelaide.edu.au
Fumeaux
Christophe
C
Fischer
Bernd Michael
BM
Abbott
Derek
D
D003460:Crystallization / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation / Q000379:methods*; D007259:Infrared Rays; D008962:Models, Theoretical; D016011:Normal Distribution; D013057:Spectrum Analysis / Q000295:instrumentation / Q000379:methods*; D055069:Terahertz Imaging / Q000295:instrumentation / Q000379:methods*