Design and performance of a dual polarizing detector system for broadband astronomical spectroscopy at submillimeter wavelengths

Abstract

The design and performance of a dual polarizing bolometer detector system for use with a polarizing Fourier transform spectrometer to conduct broadband astronomical spectroscopy at submillimeter wavelengths is presented. The system features a fully differential electronics design which virtually eliminates common mode noise. The optical design efficiently rejects unwanted radiation, both spectrally and spatially, while minimizing the effects of resonant optical cavities. The system is cooled by an efficient, closed cycle He4–3He refrigerator which is cycled under computer control. The noise performance of the system is determined from analysis of electrical, optical, and spectral measurements, and the results are compared with a theoretical bolometer model.

SCUBA-2 Fourier transform spectrometer (FTS-2) commissioning results

“…This requires observing a point source at several points spanning the FOV with reasonable S/N, which is not feasible given the current noise performance. We expect the spectral line frequency accuracy to be a very small fraction of a resolution element as has been achieved with previous similar instruments 17 , but the instrumental line shape still remains to be characterized. This requires measurement of narrow isolated lines with a linear bolometer setup, which rules out the use of the atmospheric lines in the single-port mode.…”

Terahertz detection using electro-optic effect in a ZnTe layered structure

“…Here, (1) χ is the linear electric susceptibility whereas (2) χ and (3) χ are the second and third-order electric susceptibilities, respectively. The last two parameters lead to nonlinear effects.…”

“…The terahertz frequency range (0.1-10 THz) has been mainly used for spectrometery and astronomical applications [1] where detectors are commonly of the bolometer type operating in liquid helium temperature [2]. In the recent years, this frequency range has been considered for other applications such as imaging, medical diagnosis, and communications [3]- [5].…”

Far-infrared sensor for cirrus (FIRSC): an aircraft-based Fourier-transform spectrometer to measure cloud radiance

“…The 300-mK bolometer temperature is achieved by use of a closedcycle dual-stage 4 He- 3 He refrigerator. 5,10 The polarizer ͑POL͒ is at the focus of the lens located at the interferometer output, and its aperture of 5 mm at the focal distance of 180 mm defines the instantaneous field of view for the instrument. From the polarizer the reflected and the transmitted polarized signal components are reimaged to the apertures of the feedhorns that hold the final bandpass-limiting filters.…”

“…With matched detectors this complementary modulation can be used differentially to eliminate common mode noise. 5 In our case the two channels are independently optimized to span different spectral ranges.…”