THz Imaging Using Uncooled Wideband Direct Detection Focal Plane Arrays

Berkel, Sven van; Yurduseven, Ozan; Freni, A.; Neto, A.; Llombart, Nuria

doi:10.1109/tthz.2017.2736338

Cited by 31 publications

(34 citation statements)

References 40 publications

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“…The sensitivity of a passive imager can be related to the ability of the system in detecting variations in the temperature of a distributed incoherent source, [15], [51]. Thus, it is related to the power received from a distributed source, , with an average temperature, , and angular dimension much larger than the beam of the reflector (imager point spread function).…”

Section: Distributed-source Responsementioning

confidence: 99%

Reception Power Pattern of Distributed Absorbers in Focal Plane Arrays: A Fourier Optics Analysis

Llombart

Dabironezare

Carluccio

et al. 2018

IEEE Trans. Antennas Propagat.

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Passive imaging cameras at millimeter and submillimeter wavelengths are currently entering a new era with the development of large format arrays of direct detectors. Several of these arrays are being developed with bare absorbing meshes without any antenna coupling (lens or horn) structures. The design of such arrays is typically done resorting to geometrical considerations or basic broadside plane wave incidence analysis. This paper presents a spectral technique for the analysis of such focal plane arrays in reception using Fourier Optics, which is valid also for moderately skewed incident angles. The analysis constitutes a step improvement with respect to previously used methods by providing an accurate and efficient way to estimate the point-source angular response and the throughput from a distributed incoherent source of an absorbing mesh in the focal plane of a quasi-optical component (e.g. a parabolic reflector or lens). The proposed technique is validated with full-wave simulations. After presenting the analysis, the paper compares the performance of arrays of bare absorber in the focal plane of a quasi-optical component to those of corresponding antenna based arrays. It is found that absorbers lead to a comparable trade-off, in terms of spill-over and focusing efficiency, only for very tight samplings. For larger samplings, the focusing efficiency of absorbers is significantly lower than the one for antennas.

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Section: Distributed-source Responsementioning

confidence: 99%

Reception Power Pattern of Distributed Absorbers in Focal Plane Arrays: A Fourier Optics Analysis

Llombart

Dabironezare

Carluccio

et al. 2018

IEEE Trans. Antennas Propagat.

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“…The sensitivity of the imager can be estimated as its noise equivalent temperature difference (NETD), which determines the ability of the system in detecting variations in the temperature of the source. The expression of NETD for the absorbers in the focal plane can be expressed as [23]…”

Section: A Focal Plane Configurationmentioning

confidence: 99%

“…Therefore, the angular integral in (2) can be simplified to Ω s . By normalizing by the term ℎ Ω s , one can then derive an expression for an effective point spread function, similar to what it presented in [23] for single mode antennas, as follows:…”

Section: B Incoherent Point-source Responsementioning

confidence: 99%

A Dual-Band Focal Plane Array of Kinetic Inductance Bolometers Based on Frequency-Selective Absorbers

Dabironezare

Hassel

Gandini

et al. 2018

IEEE Trans. THz Sci. Technol.

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Passive imaging cameras at sub-millimeter wavelengths with large format focal plane arrays are being developed as the next generation of security screening systems. In this contribution, a dual-band focal plane array (FPA) for security imagers at submillimeter wave frequencies is presented. The detectors are based on bolometric superconducting kinetic inductance resonators, which allows the development of large FPAs at medium cooled temperatures. Two frequency selective absorber (FSA) sets coupled to superconductive resonator lines are designed to implement a dual color security imager. The performance of the dual band imager is evaluated using spectral analysis approach that combines Fourier optics with a Floquet mode field representation. The geometry of the unit cells is based on a Jerusalem cross configuration and the designed FSAs show a stable angular response and a rejection 1 to 3 of the undesired bandwidth. The detectors in the dual band FPA are distributed over a hexagonal grid to maximize their physical size and then improve their sensitivity. The effective point spread function of the imager coupled to a black body point source over a wide frequency band (1:6) was demonstrated experimentally with excellent agreement to the one estimated by using the proposed spectral technique.Index Terms-Sub-mm wavelengths, focal plane array, frequency selective absorber, incoherent source.

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“…For single mode and single polarized antenna, this normalized throughput becomes Ω/ 2 = 1 2 as described in [14], [4], except for the fact of 2. Therefore, in [4], [13] and [18] the term 2 is called the optical coupling efficiency since it is always smaller than 1. In case of multi-mode detectors, the normalized throughput can be larger than one [14], which makes the use of the term optical efficiency improper.…”

Section: B Normalized Optical Throughputmentioning

confidence: 99%

“…The value of the aperture efficiency is, for a single moded device, given by the product between the radiation and focusing (taper) efficiencies [18], except for the polarization factor 2. In the proposed single-mode device the value of the radiation efficiency is only 47%.…”

mentioning

confidence: 99%

Incoherent Detection of Orthogonal Polarizations via an Antenna Coupled MKID: Experimental Validation at 1.55 THz

Yurduseven

Bueno

Yates

et al. 2018

IEEE Trans. THz Sci. Technol.

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There is an increasing demand for large format detector arrays with large bandwidths and high antenna efficiencies for future THz astronomical radiometric applications. For direct detection instruments, it is also desired to have antennas with dual polarization reception in order to increase the received power from incoherent sources, thereby improving the observing speed of the instrument. The main goal of this work is the validation of the incoherent detection of two orthogonal polarizations by a leaky lens antenna, coupled to a single Microwave Kinetic Inductance Detector (MKID). Depending on the absorbed power over a distributed transmission line, the resonant frequency of the MKID changes. The proposed antenna is composed of two crossed leaky wave slots feeding a silicon extended hemispherical lens. The slots are coupled to four aluminum (Al) coplanar waveguide (CPW) lines that incoherently absorb the incoming THz radiation. The antenna and the power absorbing CPW lines are embedded inside the MKID, allowing an efficient radiation detection at THz frequencies where no lossless superconductors are available. The proposed dual-polarized device absorbs power incrementally over four different CPWs incoherently and is therefore simulated in reception (deriving a plane-wave response) similarly to what is done in distributed absorbers. We compare numerically and experimentally the proposed dual-polarized leaky lens coupled MKID and its single polarization counterpart and show that the dual polarized device receives twice as much power as the single-polarized one. Eventually, the dual-polarized device, when used with air-bridges, provides the same angular selectivity and twice the throughput of the single-polarized one.

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THz Imaging Using Uncooled Wideband Direct Detection Focal Plane Arrays

Cited by 31 publications

References 40 publications

Reception Power Pattern of Distributed Absorbers in Focal Plane Arrays: A Fourier Optics Analysis

Reception Power Pattern of Distributed Absorbers in Focal Plane Arrays: A Fourier Optics Analysis

A Dual-Band Focal Plane Array of Kinetic Inductance Bolometers Based on Frequency-Selective Absorbers

Incoherent Detection of Orthogonal Polarizations via an Antenna Coupled MKID: Experimental Validation at 1.55 THz

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