Focus and Alignment Tolerance in a Photoconductive Terahertz Source
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- Paz-Martínez, G., Garduño-Mejía, J., Kolokoltsev, O.V. et al. J Infrared Milli Terahz Waves (2015) 36: 830. doi:10.1007/s10762-015-0185-1
Robust coupling between a pulsed laser beam and a photoelectric circuit is an important issue in the development of miniaturized, integrated, and embedded terahertz instrumentation. Here, we present a study of the effect of varying the focus and alignment parameters of an excitation laser pulse on the emission characteristics of a standard Hertzian-dipole type terahertz photoelectric source. The objective is to quantify the tolerance of a terahertz time-domain spectroscopy system, and we study the variation of peak amplitude, waveform, phase, and energy distribution as a function of excitation position and defocus. We find that a terahertz source can be made relatively tolerant to variations in focus, alignment, and details of the geometry of the photoelectric system, providing a window for a more robust field operation.