Lin, H.Fumeaux, C.Fischer, B.Abbott, D.2010-12-212010-12-212010Optics Express, 2010; 18(17):17672-176831094-40871094-4087http://hdl.handle.net/2440/62034The 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.en© 2010 Optical Society of AmericaNormal DistributionSpectrum AnalysisInfrared RaysModels, TheoreticalFiber Optic TechnologyTerahertz ImagingCrystallizationEquipment DesignJournal article002010125410.1364/OE.18.0176720002810544000112-s2.0-7795636036733047Fumeaux, C. [0000-0001-6831-7213]Abbott, D. [0000-0002-0945-2674]