Bandwidth of a 4.7 THz beam multiplexer based on Fourier grating
Y. Gan (Rijksuniversiteit Groningen, SRON–Netherlands Institute for Space Research)
B. Mirzaei (TU Delft - ImPhys/Optics, SRON–Netherlands Institute for Space Research)
J. R.G. Silva (SRON–Netherlands Institute for Space Research, Rijksuniversiteit Groningen)
W. Laauwen (SRON–Netherlands Institute for Space Research)
F. F.S. Van Der Tak (Rijksuniversiteit Groningen, SRON–Netherlands Institute for Space Research)
J. R. Gao (SRON–Netherlands Institute for Space Research, TU Delft - ImPhys/Optics)
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Abstract
We present an analysis of the bandwidth of an asymmetric 8-beam Fourier grating as the beam multiplexer for a 4.7 THz local oscillator used in a heterodyne receiver. We take the grating designed for NASA GUSTO balloon observatory as an example to address the bandwidth question although it does not need to operate over a wide frequency range. By illuminating the grating at different frequencies from 4.445 to 5.045 THz, we simulated the changes of its performance in three aspects using COMSOL Multiphysics: diffraction efficiency, power uniformity, and the angular distribution of the output beams. These parameters can affect the coupling efficiency between the output beams of the grating and the beams of a mixer array. The bandwidth of the grating is found to be 230 GHz, corresponding to 4.9% of the operating frequency, which is sufficient for many applications.