The CirPAD, a circular 1.4 M hybrid pixel detector dedicated to X-ray diffraction measurements at Synchrotron SOLEIL

One of the challenges of all synchrotron facilities is to offer the highest performance detectors for all their specific experiments, in particular for X-ray diffraction imaging and its high throughput data collection. In that context, the DiffAbs beamline, the Detectors and the Design and Engineering groups at Synchrotron SOLEIL, in collaboration with ImXPAD and Cegitek companies, have developed an original and unique detector with a circular shape. This detector is based on the hybrid pixel photon-counting technology and consists of the specific assembly of 20 hybrid pixel array detector (XPAD) modules. This article aims to demonstrate the main characteristics of the CirPAD (for Circular Pixel Array Detector) and its performance – i.e. excellent pixel quality, flat-field correction, high-count-rate performance, etc. Additionally, the powder X-ray diffraction pattern of an LaB6 reference sample is presented and refined. The obtained results demonstrate the high quality of the data recorded from the CirPAD, which allows the proposal of its use to all scientific communities interested in performing experiments at the DiffAbs beamline.

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample.

Demonstration of thermal modulation using nanoscale and microscale structures for ultralarge pixel array photothermal transducers

Large-pixel-array infrared emitters are attractive in the applications of infrared imaging and detection. However, the array scale has been restricted in traditional technologies. Here, we demonstrated a light-driven photothermal transduction approach for an ultralarge pixel array infrared emitter. A metal-black coating with nanoporous structures and a silicon (Si) layer with microgap structures were proposed to manage the thermal input and output issues. The effects of the nanoscale structures in the black coating and microscale structures in the Si layer were investigated. Remarkable thermal modulation could be obtained by adjusting the nanoscale and microscale structures. The measured stationary and transient results of the fabricated photothermal transducers agreed well with the simulated results. From the input view, due to its wide spectrum and high absorption, the black coating with nanoscale structures contributed to a 5.6-fold increase in the temperature difference compared to that without the black coating. From the output view, the microgap structures in the Si layer eliminated the in-plane thermal crosstalk. The temperature difference was increased by 340% by modulating the out-of-plane microstructures. The proposed photothermal transducer had a rising time of 0.95 ms and a falling time of 0.53 ms, ensuring a fast time response. This method is compatible with low-cost and mass manufacturing and has promising potential to achieve ultralarge-array pixels beyond ten million.

Towards multipixel THz Schottky diode detector with a single RF output line

We propose the design of a dual-pixel array of Schottky diodes. Each diode is fixed between the bow-tie antenna arms on top of a SI-GaAs membrane acting as a waveguide backshort for efficient coupling of the antenna to the feedline of high-directivity horn. The detector utilizes a single RF output line: microwave reflectometer is used for the readout. The pixels are equipped with dual-mode resonator filters to eliminate the cross-talk. We evaluate the design proposed via numerical simulation and performance tests of the array subunits: NEP of 300 pW/Hz0.5 and dynamic range of 24 dB are demonstrated at 137.5 GHz.

Area-Efficient Post-Processing Circuits for Physically Unclonable Function with 2-Mpixel CMOS Image Sensor

In order to realize image information security starting from the data source, challenge–response (CR) device authentication, based on a Physically Unclonable Function (PUF) with a 2 Mpixel CMOS image sensor (CIS), is studied, in which variation of the transistor in the pixel array is utilized. As each CR pair can be used only once to make the CIS PUF resistant to the modeling attack, CR authentication with CIS can be carried out 4050 times, with basic post-processing to generate the PUF ID. If a larger number of authentications is required, advanced post-processing using Lehmer encoding can be utilized to carry out authentication 14,858 times. According to the PUF performance evaluation, the authentication error rate is less than 0.001 ppm. Furthermore, the area overhead of the CIS chip for the basic and advanced post-processing is only 1% and 2%, respectively, based on a Verilog HDL model circuit design.

Imaging biological tissue with high-throughput single-pixel compressive holography

Single-pixel holography (SPH) is capable of generating holographic images with rich spatial information by employing only a single-pixel detector. Thanks to the relatively low dark-noise production, high sensitivity, large bandwidth, and cheap price of single-pixel detectors in comparison to pixel-array detectors, SPH is becoming an attractive imaging modality at wavelengths where pixel-array detectors are not available or prohibitively expensive. In this work, we develop a high-throughput single-pixel compressive holography with a space-bandwidth-time product (SBP-T) of 41,667 pixels/s, realized by enabling phase stepping naturally in time and abandoning the need for phase-encoded illumination. This holographic system is scalable to provide either a large field of view (~83 mm2) or a high resolution (5.80 μm × 4.31 μm). In particular, high-resolution holographic images of biological tissues are presented, exhibiting rich contrast in both amplitude and phase. This work is an important step towards multi-spectrum imaging using a single-pixel detector in biophotonics.