Terahertz (THz) technology is one of emerging technologies that will change our life. A lot of attractive applications in security, medicine, biology, astronomy, and non-destructive materials testing have been demonstrated already. However, the realization of THz emitters and receivers is a challenge because the frequencies are too high for conventional electronics and the photon energies are too small for classical optics. As a result, THz radiation is resistant to the techniques commonly employed in these well established neighbouring bands.

https://www.degruyter.com/document/doi/10.2478/s11772-011-0033-3/pdf

Terahertz detectors and focal plane arrays

In the paper, issues associated with the development and exploitation of terahertz (THz) radiation detectors are discussed. The paper is written for those readers who desire an analysis of the latest developments in different type of THz radiation sensors (detectors), which play an increasing role in different areas of human activity (e.g., security, biological, drugs and explosions detection, imaging, astronomy applications, etc.). The basic physical phenomena and the recent progress in both direct and heterodyne detectors are discussed. More details concern Schottky barrier diodes, pair braking detectors, hot electron mixers, and field-effect transistor detectors. Also the operational conditions of THz detectors and their upper performance limits are discussed.

https://www.degruyter.com/downloadpdf/j/oere.2010.18.issue-1/s11772-009-0029-4/s11772-009-0029-4.xml

THz radiation sensors

SCUBA-2 is a submillimeter camera being built for the James Clerk Maxwell Telescope in Hawaii. Bringing CCD style imaging to the submillimeter for the first time, with over 10 000 pixels, it will provide a revolutionary improvement in sensitivity and mapping speed. We present results of the first tests on a prototype 1280 pixel SCUBA-2 subarray; the full instrument will be made up of eight such subarrays. The array is made up of transition edge sensor TES detectors, with Mo/Cu bilayers as the sensing element. To keep the number of wires reasonable, a multiplexed readout is used. Unlike previous TES arrays, an in-focal plane multiplexer configuration is used, in which the multiplexing elements are located beneath each pixel. To achieve the required performance, the detectors are operated at a temperature of approximately 120 mK. We describe the results of a basic electrical and optical characterization of the array, demonstrating that it is fully operational. Noise measurements were made on several pixels and gave a noise equivalent power below 2.5 10 17 WH Z 0.5 , within the requirements for SCUBA-2. The construction of the testbed used to carry out these measurements is also described. © 2007 American Institute of Physics. DOI: 10.1063/1.2436839

http://www.science.uwaterloo.ca/~jkycia/Publications/papers/RSI78_024502.pdf

Electrical and optical measurements on the first SCUBA-2 prototype 1280 pixel submillimeter superconducting bolometer array.

SCUBA-2, which replaces SCUBA (the Submillimeter Common User Bolometer Array) on the James Clerk Maxwell Telescope (JCMT) in 2006, is a large-format bolometer array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two dc-coupled, monolithic, filled arrays with a total of ~10,000 bolometers. It will offer simultaneous imaging of a 50 sq-arcmin field of view at wavelengths of 850 and 450 microns. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimeter interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors operating at 120 mK for performance limited by the sky background photon noise. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes. Electrical connections are made through indium bump bonds to a SQUID time-domain multiplexer (MUX). We give an overview of the SCUBA-2 system and an update on its status, and describe some of the technological innovations that make this unique instrument possible.

/pdf/an-update-on-the-scuba-2-project-bewe47ka16.pdf

An update on the SCUBA-2 project

We are developing cryogenic readout circuits for the array of superconducting tunneling junctions (STJs) at 
submillimeter wavelength SISCAM (Superconductive Imaging Submillimeter-wave CAMera). A current conceptual 
design of SISCAM will employ a direct hybrid array system just like CMOS image sensors widely used at optical and 
infrared wavelength. Because of relatively large impedance of the STJ fabricated by RIKEN (~10 MΩ in a dark 
condition), it requires readout preamplifier with low current noise. Therefore, it is not suitable for the STJ to use a 
readout system by Superconductive Quantum Interferences Devices as for Transition Edge Sensor. Instead, we selected 
capacitive transimpedance amplifier (CTIA) using a SONY n-type GaAs Junction Field Effect Transistor (JFET). 
However, the CTIA has not been used as the readout of the STJ. Therefore, we measured the photocurrent of the STJ by 
the CTIA with Silicon JFETs and by transimpedance amplifier (TIA), which is a conventional readout for the STJ, in the 
same bias condition, and confirmed both results are in good agreement. Additionally, we report development of readout 
integrated circuits with GaAs JFETs. In order to design the CTIA circuit with the GaAs JFETs, we fabricated the 
independent GaAs JFETs and matched pairs of them. We measured electrical characteristics of these GaAs JFETs at the 
cryogenic temperatures less than 4.2 K. We demonstrated performance of an operational amplifier fabricated with the 
GaAs JFETs measuring a differential amplifier with the dual GaAs JFET, and additionally estimate amplifier gain, offset 
voltage, and power consumption of the CTIA by the circuit simulation using the PSPICE. In consequence, the expected 
performance fulfills the requirements for the readout amplifier of the STJs except for the noise performance.

Progress on GaAs cryogenic readout circuits for SISCAM

SCUBA-2 is a second generation, wide-field submillimeter camera under development for the James Clerk Maxwell Telescope. With over 12,000 pixels, in two arrays, SCUBA-2 will map the submillimeter sky ~1000 times faster than the current SCUBA instrument to the same signal-to-noise. Many areas of astronomy will benefit from such a highly sensitive survey instrument: from studies of galaxy formation and evolution in the early Universe to understanding star and planet formation in our own Galaxy. Due to be operational in 2006, SCUBA-2 will also act as a "pathfinder" for the new generation of submillimeter interferometers (such as ALMA) by performing large-area surveys to an unprecedented depth. The challenge of developing the detectors and multiplexer is discussed in this paper.

/pdf/scuba-2-developing-the-detectors-1k2shuw8ub.pdf

SCUBA-2: Developing the Detectors

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SCUBA-2: Developing the Detectors