We present the design, fabrication, and full characterisation (sensitivity, beam pattern, and frequency response) of a background limited broadband antenna coupled kinetic inductance detector covering the frequency range from 1.4 to 2.8 THz. This device shows photon noise limited performance with a noise equivalent power of 2.5 × 10^-19W/Hz^1/2 at 1.55 THz and can be easily scaled to a kilo-pixel array. The measured optical efficiency, beam pattern, and antenna frequency response match very well the simulations.

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DESHIMA (Deep Spectroscopic High-redshift Mapper) is an instrument aiming at efficiently making spectroscopic redshift measurements of sub-mm wave galaxies (SMGs), thereby providing about the formation and the evolution of stars and galaxies. The aim of this work is to provide a preliminary study into the design of a wideband leaky lens antenna coupled quasi-optical system within a 1:3 bandwidth. We propose a multi-pixel solution where the virtual sources are located on the lens focal plane. The design is able to provide frequency stable beams to achieve high Gaussian coupling efficiency within the entire bandwidth. We will evaluate the performance of the quasi-optical system design in terms of its Gaussicity and scan loss. The design is specifically targeted at the ASTE telescope located in Atacama, Chile.@en

This contribution presents the design and sub-mm wave measurements of a wideband dual polarized leaky lens antenna coupled to kinetic inductance detector (KIDs) to be specifically used for tightly spaced focal plane arrays. The antenna is planar and composed by two crossed slots, fed by two orthogonal coplanar waveguide (CPW) lines. In transmission, the crossed CPW lines are fed differentially in order to couple the radiation into the slots. The slot antenna feeds a dielectric lens to achieve directive patterns. The main goal of this work is to show the measurement results of the patterns and efficiency, and compare this antenna with its singly polarized version. The measured received power from an incoherent source is increased by a factor of 2 compared to a single-polarized version of the antenna.

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In millimeter and submillimeter-wave radiometric imaging systems, a persistent goal is the increase in the speed of acquisition of the image while maintaining a high sensitivity. Typically, the highest sensitivity is achieved by cryogenically cooling the detectors, specifically in astronomical applications. However, for the purpose of low-cost imaging applications, it is desirable to operate at room temperature. Without cryogenically cooling, the electronic noise introduced by the detectors becomes dominant, making the detectors less sensitive. Resorting to detection architectures containing amplification circuitry might be impractical for implementation in large focal plane arrays (FPAs) fabricated in integrated technologies. This contribution derives the focal plane architecture that maximizes the imaging speed of radiometers operating at room temperature without using any amplification circuitry. It is shown that in such scenario a practical image acquisition speed can still be achieved when a very broad portion of the THz-band is exploited. Ultimately, the imaging speed is maximized when the FPA is undersampled, implying a tradeoff in the size of the optics. The analysis is substantiated by a case study with recently developed wideband leaky lens antenna feeds operating from 200 to 600 GHz.

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This contribution presents the design and measurements of a wideband dual polarized leaky lens antenna. The antenna is composed of two crossed slots fed by two orthogonal microstrips. The crossed microstrips are fed differentially in order to couple the radiation into the slots. Then the slot antenna feeds a dielectric lens to achieve directive patterns. In this work, the proposed leaky lens antenna is optimized to achieve high aperture efficiency with clean symmetric patterns in both polarizations exceeding an octave bandwidth to be used for tightly spaced wideband Focal Plane Arrays (FPAs). The concept is validated by the primary field measurements inside the lens and by the GRASP simulations of the FPA.@en

Aims. Future astrophysics and cosmic microwave background space missions operating in the far-infrared to millimetre part of the spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and efficient low-noise and low-power readout systems. We have developed a demonstrator system suitable for such applications. Methods. The system combines a 961 pixel imaging array based upon Microwave Kinetic Inductance Detectors (MKIDs) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. We evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 GHz and 20% fractional bandwidth. Results. The overall system has an excellent sensitivity, with an average detector sensitivity (NEPdet) =3 × 10-19 W/Hz measured using a thermal calibration source. At a loading power per pixel of 50 fW we demonstrate white, photon noise limited detector noise down to 300 mHz. The dynamic range would allow the detection of ~1 Jy bright sources within the field of view without tuning the readout of the detectors. The expected dead time due to cosmic ray interactions, when operated in an L2 or a similar far-Earth orbit, is found to be <4%. Additionally, the achieved pixel yield is 83% and the crosstalk between the pixels is <-30 dB. Conclusions. This demonstrates that MKID technology can provide multiplexing ratios on the order of a 1000 with state-of-the-art single pixel performance, and that the technology is now mature enough to be considered for future space based observatories and experiments.@en

Microwave kinetic inductance detectors (MKIDs) promise high sensitivity, combined with device simplicity and intrinsic multiplexibility. We demonstrate in this paper the realization of an imaging system consisting of an array of 961 antenna-coupled MKIDs that is read out using a single pair of coax cables and an analogue-digital back-end with a 2 GHz readout bandwidth. We measure the optical NEP of the central pixels of the array and find NEP = 510 -19 w/Vhz. The electrical NEP is measured for all pixels, giving NEP = 3.3 ± 1.310 -19 W/VHz for 85% of the pixels. We further obtain an instantaneous dynamic range of a factor 1000 and a cosmic ray dead time of 0.5% in the lab, resulting in 25% dead time when operated in a spacecraft at L2.@en

We present the development of background limited kinetic inductance detectors (KIDs) for THz astronomy applications to be used in space based observatories. The THz radiation is coupled to the KID via a leaky wave antenna covering the frequency range from 1.4 to 2.8 THz. We have developed a hybrid niobium titanium nitride/aluminium (NbTiN/Al) KID, fabricated on a silicon (Si) substrate, in which the leaky wave antenna and absorbing section of the KID are fabricated on a suspended silicon nitride (SiN) membrane. The radiation is coupled to the leaky wave antenna with a Si lens placed on top of it at a distance of 3μm. We observe photon noise limited performance both in the phase and amplitude readout simultaneously. Both the optical efficiency and the antenna beam patterns have been measured with excellent agreement with the simulations, and the measured FTS shows a large frequency range (over an octave), only limited by the optical filters placed in the setup.@en

This paper presents the design and measurements of a wideband dual polarized leaky lens antenna suitable for tightly spaced focal plane arrays. The antenna is composed of two crossed leaky slots fed by two orthogonal microstrips to realize the dual-polarization operation. The crossed microstrips are fed differentially in order to couple the radiation into the slots. The slots are then coupled to a dielectric lens to achieve directive patterns suited for feeding large Focal distance to Diameter ratio reflectors. In this paper, the proposed leaky lens antenna is optimized to achieve high aperture efficiency with clean symmetric patterns in both polarizations exceeding an octave bandwidth. The concept is validated by the measurements of the primary fields inside the lens and with GRASP simulations of the focal plane array.@en

Microwave Kinetic Inductance Detectors (MKIDs) are becoming a very promising candidate for next generation imaging instruments for the far infrared. A MKID consists of a superconducting resonator coupled to a feed-line used for the readout. In the devices presented here radiation coupling is achieved by coupling the MKID directly to planar antenna. The antenna is placed in the focus of an elliptical lens to increase the filling factor and to match efficiently to fore-optics. In this paper we present the design and the optical performance of MKIDs optimized for operation at 350 GHz. We have measured a device consisting of 14 pixels, characterized the coupling efficiency, antenna-lens frequency response and beam pattern and compared these to theoretical simulations. The optical efficiency has been measured by means of a black body radiator mounted in an ADR cryostat, through the variation of the black body temperature a variable illumination of each pixel (from 0.1 fW to 2 pW) is achieved. The frequency response and beam pattern have been directly measured in a He3 cryostat directly via the cryostat window and without the use of intermediate optics.@en

The Terahertz (THz) band is the portion of the spectrum that covers a frequency range from 300 GHz to 3 THz. The potential of this band has been proven for numerous type of applications including medical imaging, non-destructive testing, space observation, spectroscopy and security screening, thanks to its good compromise between the spatial resolution and penetration. Most of these applications demand for high spatial and range resolution of the images, as well as fast acquisition time. To fulll such requirements, focal plane arrays (FPAs) need to comprise a large number of elements and be able to operate over broad bandwidths. Moreover, fabrication of the FPAs with thousands of antenna elements becomes a real issue at such frequencies due to the fabrications constraints and immense manufacturing costs. This doctoral thesis consists of two parts: Part I focuses on the design of the lens antennas using a multiple feed per lens scenario, specically aiming at imaging for security and the telecommunication systems as potential applications. The aim of the study is to design integrated lens antennas to achieve frequency stable radiation characteristics either to obtain an ecient reflector illumination or to be used directly as an imager over a wideband operation, typically more than one octave. In the literature, double slot antennas have been widely proposed as an ecient lens feeder, yet they are able to operate within a very narrow bandwidth, in the order of 10 - 15%. Due to its wideband characteristics connected array of leaky slot antenna concept has been used as a lens feeder. Depending on the application type, two dierent approaches have been implemented to achieve frequency independent lens radiation: A coherently fed connected leaky slot array based design with a traditional extended hemi-spherical lens for phased array antenna applications and an integrated double shell lens based design where each source element is associated to an independent beam for telecommunication and security systems. Part II of the thesis focuses on a single feed per lens scenario, specifically aiming at Terahertz (THz) astronomy applications. Such applications mostly require antennas consist of multi-pixels with large operational bandwidths. Many of the sub-mm wave instruments done for this kind of applications are envisioned to have large format focal plane arrays (FPA) that are based on single beam per feed and tight sampling and are coupled to reflector systems with large F/D ratios. Future satellite based, astronomic THz radiometers will be most likely based on cryogenically cooled detectors to reach the highest sensitivities, will consist of tens of thousands receivers to provide a broad eld of view and could address simultaneously a broad portion of the THz band. Several type of reflector feeds have been proposed in the literature including the Vivaldi antennas, horn antennas and the eleven antennas. These antennas, however, are typically optimized to maximize the reflector illumination eciencies as a single reflector feed. As a result, they suer from the feed taper eciency which is crucial to characterize the total system performance for tightly packed FPAs. No need to mention about the feasibility issues when it comes to the fabrication of the thousands of array elements with the manufacturing techniques available nowadays in sub-mm band. Integrated lens antennas, on the other hand, are widely used in sub-mm band since they allow the integration of the antenna and the detector on the same chip. Space instruments based on cryogenic power detectors often use focal plane arrays based on dielectric lenses. In the literature, the most commonly used lens feed is a double slot antenna, which typically operates in a bandwidth much less than one octave and with single polarization. Sinuous and spiral antennas have been also proposed as wideband lens antenna solutions. However, the fabrication of the feeding lines integrated to the antenna becomes challenging at sub-mm band since they have to be extremely tiny in order not to disturb the radiated elds. To overcome these issues, we propose a highly ecient, dual-polarized wideband leaky lens antenna design that can be integrated to planar feeding lines on the same chip. To our knowledge, the proposed design is the only practical wideband dual polarized antenna solution presently available at sub-mm wave frequencies which lends itself as an extremely useful alternative for next generation sub-mm wave space astronomical instruments.@en

We propose an array of connected leaky-wave slots as feed of an extended hemispherical dielectric lens, for broadband
imaging applications. Simulations of the entire structure, including array and lens, are performed by combining a spectral
Green’s function approach and an accelerated physical optics method. The antenna characteristics are investigated over a 4:1
bandwidth parametrically varying the feed off-axis distance (x/R, y/R) and the lens extension length (L). Measurements from
prototype demonstrator are also presented to validate the method of analysis.@en