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International SPAD Sensor Workshop (ISSW) - 4-6 Jun 2024 - Trento, Italy - Website

Advances in Imaging and Visualization at the Junction of Physics, Engineering, and Data Science - 9-14 Jun 2024 - Newry. Maine, USA - Website

Sensor+Test - 11-13 Jun 2024 - Nuremberg, Germany - Website 

Smart Sensing - 12-14 Jun 2024 - Tokyo, Japan - Website

SPIE Astronomical Telescopes + Instrumentation - 15-20 Jun 2024 - Yokohama, Japan - Website

Sensors Converge - 24-26 Jun 2024 - Santa Clara, California, USA - Website

International Workshop on Radiation Imaging Detectors - 30 Jun-4 July 2024 - Lisbon, Portugal - Website

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Single Photon Workshop 2024
EICC Edinburgh 18-22 Nov 2024
www.spw2024.org
 

The 11th Single Photon Workshop (SPW) 2024 will be held 18-24 November 2024, hosted at the Edinburgh International Conference Centre.

SPW is the largest conference in the world dedicated to single-photon generation and detection technology and applications. The biennial international conference brings together a broad range of experts across academia, industry and government bodies with interests in single-photon sources, single-photon detectors, photon entanglement, photonic quantum technologies and their use in scientific and industrial applications. It is an exciting opportunity for those interested in these technologies to learn about the state of the art and to foster continuing partnerships with others seeking to advance the capabilities of such technologies.

In tandem with the scientific programme, SPW 2024 will include a major industry exhibition and networking events.
 
Please register your interest at www.spw2024.org
 
Official registration will open in January 2024.
 
The 2024 workshop is being jointly organized by Heriot-Watt University and University of Glasgow.

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In a new paper titled "Design and Characterization of 5 μm Pitch InGaAs Photodiodes Using In Situ Doping and Shallow Mesa Architecture for SWIR Sensing" Jules Tillement et al. from STMicroelectronics, U. Grenoble and CNRS Grenoble write:

Abstract: This paper presents the complete design, fabrication, and characterization of a shallow-mesa photodiode for short-wave infra-red (SWIR) sensing. We characterized and demonstrated photodiodes collecting 1.55 μm photons with a pixel pitch as small as 3 μm. For a 5 μm pixel pitch photodiode, we measured the external quantum efficiency reaching as high as 54%. With substrate removal and an ideal anti-reflective coating, we estimated the internal quantum efficiency as achieving 77% at 1.55 μm. The best measured dark current density reached 5 nA/cm2 at −0.1 V and at 23 °C. The main contributors responsible for this dark current were investigated through the study of its evolution with temperature. We also highlight the importance of passivation with a perimetric contribution analysis and the correlation between MIS capacitance characterization and dark current performance.

Full paper (open access): https://www.mdpi.com/1424-8220/23/22/9219

Figure 1. Schematic cross section of the photodiode after different processes. (a) Photodiode fabricated by Zn diffusion or Be implantation; (b) photodiode fabrication using shallow mesa technique.

Figure 2. Band diagram of simulated structure at equilibrium with the photogenerated pair schematically represented with their path of collection.

Figure 3. Top zoom of the structure—Impact of the N-InP (a) thickness and (b) doping on the band diagram at equilibrium.

Figure 4. Simulated dark current with TCAD Synopsys tools [28]. (a) Shows evolution of the dark current when the InP SRH lifetime is modulated; (b) evolution of the dark current when the InGaAs SRH lifetime is modulated.

Figure 5. Impact of the doping concentration of the InP barrier on the carrier collection.

Figure 6. Simplified and schematic process flow of the shallow mesa-type process. (a) The full stack; (b) the definition of the pixel by etching the P layer and (c) the encapsulation and fabrication of contacts.

Figure 7. SEM views after the whole process. (a) A cross-section of the top stack where the P layer is etched and (b) a top view of the different configuration of the test structures (single in-array diode is not shown on this SEM view).

Figure 8. Schematic cross section of the structure with its potential sources of the dark current.

Figure 9. Dark current measurement on 15 μm pitch in a matrix like environment. The curve is the median of more than 100 single in-array diodes measured.

Figure 10. Dark current measurement of the ten-by-ten diode bundle. This measurement is from process B.

Figure 11. Evolution of the dark current with temperature at −0.1 V. The solid lines show the theoretical evolution of the current limited by diffusion (light blue line) and by generation recombination (purple line). The temperature measurement is performed on a bundle of ten-by-ten 5 μm pixel pitch diodes.

Figure 12. Perimetric and bulk contribution to the global dark current from measurements performed on diodes with diameter ranging from 10 to 120 μm.

Figure 13. (a) Capacitance measurement on metal–insulator–semiconductor structure. The measurement starts at 0 V then ramps to +40 V then goes to −40 V and ends at +40 V. (b) A cross section of the MIS structure. The MIS is a 300 μm diameter circle.

Figure 14. Dark current performances compared to the hysteresis measured on several different wafers.

Figure 15. Dark current measurement of a ten-by-ten bundle of 5 μm pixel pitch photodiode. The measurements are conducted at 23 °C.

Figure 16. (a) Schematic test structure for QE measurement; (b) the results of the 3D FDTD simulations conducted with Lumerical to estimate the internal QE of the photodiode.

Figure 18. Current noise for a ten-by-ten 5 μm pixel pitch photodiode bundle measured at −0.1 V.

Figure 19. Median current measurement for bundles of one hundred 3 μm pixel pitch photodiodes under dark and SWIR illumination conditions. The dark blue line represents the dark current and the pink line is the photocurrent under 1.55 μm illumination.

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Product page: https://www.sony-semicon.com/en/products/is/industry/swir/imx992-993.html

Press release: https://www.sony-semicon.com/en/news/2023/2023112901.html

Sony Semiconductor Solutions to Release SWIR Image Sensor for Industrial Applications with Industry-Leading 5.32 Effective Megapixels Expanding the lineup for delivering high-resolution and low-light performance 

The new sensor uses SSS’s proprietary Cu-Cu connection to achieve the industry’s smallest pixel size of 3.45 μm among SWIR image sensors. It also features an optimized pixel structure for efficiently capturing light, enabling high-definition imaging across a broad spectrum ranging from the visible to invisible short-wavelength infrared regions (wavelength: 0.4 to 1.7 μm). Furthermore, new shooting modes deliver high-quality images with significantly reduced noise in dark environments compared to conventional products.

In addition to this product, SSS will also release the IMX993 with a pixel size of 3.45 μm and an effective pixel count of 3.21 megapixels to further expand its SWIR image sensor lineup. These new SWIR image sensors with high pixel counts and high sensitivity will help contribute to the evolution of various industrial equipment.

In the industrial equipment domain in recent years, there has been increasing demand for improving productivity and preventing defective products from leaving the plant. In this context, the capacity to sense not only visible light but also light in the invisible band is in demand. SSS’s SWIR image sensors, which are capable of seamless wide spectrum imaging in the visible to invisible short-wavelength infrared range using a single camera, are already being used in various processes such as semiconductor wafer bonding and defect inspection, as well as ingredient and contaminant inspections in food production.

The new sensors enable imaging with higher resolution using pixel miniaturization, while enhancing imaging performance in low-light environments to provide higher quality imaging in inspection and monitoring applications conducted in darker conditions. By making the most of the characteristics of short-wavelength infrared light, whose light reflection and absorption properties are different from those of visible light, these products help to further expand applications in such areas as inspection, recognition and measurement, thereby contributing to improved industrial productivity.

Main Features
* High pixel count made possible by the industry’s smallest pixels at 3.45 μm, delivering high-resolution imaging

A Cu-Cu connection is used between the indium-gallium arsenide (InGaAs) layer that forms the photodiode of the light receiving unit and the silicon (Si) layer that forms the readout circuit. This design allows for a smaller pixel pitch, resulting in the industry’s smallest pixel size of 3.45 μm. This, in turn, helps achieve a compact form factor that still delivers the industry’s highest pixel count of approximately 5.32 effective megapixels on the IMX992, and approximately 3.21 effective megapixels on the IMX993. The higher pixel count enables detection of tiny objects or imaging across a wide range, contributing to significantly improved recognition and measurement precision in various inspections using short-wavelength infrared light.

* Low-noise imaging even in dark locations possible by switching the shooting mode

Inclusion of new shooting modes enables low-noise imaging without being affected by environmental brightness. In dark environments with limited light, High Conversion Gain (HCG) mode directly amplifies the signal with minimal noise after being converted to an electrical signal from light, thereby relatively reducing the amount of noise downstream. Doing so minimizes the impact of noise in dark locations, leading to greater recognition precision. On the other hand, in bright environments with plenty of light, Low Conversion Gain (LCG) mode enables imaging prioritizing the dynamic range.
Furthermore, enabling Dual Read Rolling Shutter (DRRS) outputs images from the sensor in two distinct types. These images are then composited on the camera to acquire an image with significantly reduced noise.

* Optimized pixel structure for high-sensitivity imaging across a wide range

SSS’s SWIR image sensors employ a thinner indium-phosphorous (InP) layer on top, which would otherwise inevitably absorb visible light, thereby allowing visible light to reach the indium-gallium arsenide (InGaAs) layer underneath, delivering high quantum efficiency even in the visible wavelength. The new products deliver even higher quantum efficiency by optimizing the pixel structure, enabling more uniform sensitivity characteristics across a wide wavelength band from 0.4 to 1.7 μm. Minimizing the image quality differences between wavelengths makes it possible to use the image sensor in a variety of industrial applications and contributes to improved reliability in inspection, recognition, and measurement applications.

Product Overview

 

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In this talk, prof. Charbon will review the evolution of solid-state photon counting sensors from avalanche photodiodes (APDs) to silicon photomultipliers (SiPMs) to single-photon avalanche diodes (SPADs). The impact of these sensors on LiDAR has been remarkable, however, more innovations are to come with the continuous advance of integrated SPADs and the introduction of powerful computational imaging techniques directly coupled to SPADs/SiPMs. New technologies, such as 3D-stacking in combination with Ge and InP/InGaAs SPAD sensors, are accelerating the adoption of SWIR/NIR image sensors, while enabling new sensing functionalities. Prof. Charbon will conclude the talk with a technological perspective on how all these technologies could come together in low-cost, computational-intensive image sensors, for affordable, yet powerful quantum imaging

Edoardo Charbon (SM’00 F’17) received the Diploma from ETH Zurich, the M.S. from the University of California at San Diego, and the Ph.D. from the University of California at Berkeley in 1988, 1991, and 1995, respectively, all in electrical engineering and EECS. He has consulted with numerous organizations, including Bosch, X-Fab, Texas Instruments, Maxim, Sony, Agilent, and the Carlyle Group. He was with Cadence Design Systems from 1995 to 2000, where he was the Architect of the company's initiative on information hiding for intellectual property protection. In 2000, he joined Canesta Inc., as the Chief Architect, where he led the development of wireless 3-D CMOS image sensors.
Since 2002 he has been a member of the faculty of EPFL, where is a full professor. From 2008 to 2016 he was with Delft University of Technology’s as Chair of VLSI design. Dr. Charbon has been the driving force behind the creation of deep-submicron CMOS SPAD technology, which is mass-produced since 2015 and is present in telemeters, proximity sensors, and medical diagnostics tools. His interests span from 3-D vision, LiDAR, FLIM, FCS, NIROT to super-resolution microscopy, time-resolved Raman spectroscopy, and cryo-CMOS circuits and systems for quantum computing. He has authored or co-authored over 400 papers and two books, and he holds 24 patents. Dr. Charbon is the recipient of the 2023 IISS Pioneering Achievement Award, he is a distinguished visiting scholar of the W. M. Keck Institute for Space at Caltech, a fellow of the Kavli Institute of Nanoscience Delft, a distinguished lecturer of the IEEE Photonics Society, and a fellow of the IEEE.

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Schon et al from Prophesee published a paper titled "A 320 x 320 1/5" BSI-CMOS stacked event sensor for low-power vision applications" in the 2023 VLSI symposium. This paper presents some technical details about their recently announced GenX320 sensor.

Abstract
Event vision sensors acquire sparse data, making them suited for edge vision applications. However, unconventional data format, nonconstant data rates and non-standard interfaces restrain wide adoption. A 320x320 6.3μm pixel BSI stacked
event sensor, specifically designed for embedded vision, features multiple data pre-processing, filtering and formatting functions, variable MIPI and CPI interfaces and a hierarchy of power modes, facilitating operability in power-sensitive vision
applications.

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ISSCC will be held Feb 18-22, 2024 in San Francisco, CA.

Link to advanced program: https://submissions.mirasmart.com/ISSCC2024/PDF/ISSCC2024AdvanceProgram.pdf

There are several papers of interest in Session 6 on Imagers and Ultrasound. 

6.1 12Mb/s 4×4 Ultrasound MIMO Relay with Wireless Power and Communication for Neural Interfaces
E. So, A. Arbabian (Stanford University, Stanford, CA)

6.2 An Ultrasound-Powering TX with a Global Charge-Redistribution Adiabatic Drive Achieving 69% Power Reduction and 53° Maximum Beam Steering Angle for Implantable Applications
M. Gourdouparis1,2, C. Shi1 , Y. He1 , S. Stanzione1 , R. Ukropec3 , P. Gijsenbergh3 , V. Rochus3 , N. Van Helleputte3 , W. Serdijn2 , Y-H. Liu1,2
 1 imec, Eindhoven, The Netherlands
 2 Delft University of Technology, Delft, The Netherlands
 3 imec, Leuven, Belgium

6.3 Imager with In-Sensor Event Detection and Morphological Transformations with 2.9pJ/pixel×frame Object Segmentation FOM for Always-On Surveillance in 40nm
 J. Vohra, A. Gupta, M. Alioto, National University of Singapore, Singapore, Singapore

6.4 A Resonant High-Voltage Pulser for Battery-Powered Ultrasound Devices
 I. Bellouki1 , N. Rozsa1 , Z-Y. Chang1 , Z. Chen1 , M. Tan1,2, M. Pertijs1
 1 Delft University of Technology, Delft, The Netherlands
 2 SonoSilicon, Hangzhou, China

6.5 A 0.5°-Resolution Hybrid Dual-Band Ultrasound Imaging SoC for UAV Applications
 J. Guo1 , J. Feng1 , S. Chen1 , L. Wu1 , C-W. Tsai1,2, Y. Huang1 , B. Lin1 , J. Yoo1,2
 1 National University of Singapore, Singapore, Singapore
 2 The N.1 Institute for Health, Singapore, Singapore

6.6 A 10,000 Inference/s Vision Chip with SPAD Imaging and Reconfigurable Intelligent Spike-Based Vision Processor
 X. Yang*1 , F. Lei*1 , N. Tian*1 , C. Shi2 , Z. Wang1 , S. Yu1 , R. Dou1 , P. Feng1 , N. Qi1 , J. Liu1 , N. Wu1 , L. Liu1
 1 Chinese Academy of Sciences, Beijing, China 2 Chongqing University, Chongqing, China
 *Equally Credited Authors (ECAs)

6.7 A 160×120 Flash LiDAR Sensor with Fully Analog-Assisted In-Pixel Histogramming TDC Based on Self-Referenced SAR ADC
 S-H. Han1 , S. Park1 , J-H. Chun2,3, J. Choi2,3, S-J. Kim1
 1 Ulsan National Institute of Science and Technology, Ulsan, Korea
 2 Sungkyunkwan University, Suwon, Korea
 3 SolidVue, Seongnam, Korea

6.8 A 256×192-Pixel 30fps Automotive Direct Time-of-Flight LiDAR Using 8× Current-Integrating-Based TIA, Hybrid Pulse Position/Width Converter, and Intensity/CNN-Guided 3D Inpainting
 C. Zou1 , Y. Ou1 , Y. Zhu1 , R. P. Martins1,2, C-H. Chan1 , M. Zhang1
 1 University of Macau, Macau, China
 2 Instituto Superior Tecnico/University of Lisboa, Lisbon, Portugal

6.9 A 0.35V 0.367TOPS/W Image Sensor with 3-Layer Optical-Electronic Hybrid Convolutional Neural Network
 X. Wang*, Z. Huang*, T. Liu, W. Shi, H. Chen, M. Zhang
 Tsinghua University, Beijing, China
 *Equally Credited Authors (ECAs)

6.10 A 1/1.56-inch 50Mpixel CMOS Image Sensor with 0.5μm pitch Quad Photodiode Separated by Front Deep Trench Isolation
 D. Kim, K. Cho, H-C. Ji, M. Kim, J. Kim, T. Kim, S. Seo, D. Im, Y-N. Lee, J. Choi, S. Yoon, I. Noh, J. Kim, K. J. Lee, H. Jung, J. Shin, H. Hur, K. E. Chang, I. Cho, K. Woo, B. S. Moon, J. Kim, Y. Ahn, D. Sim, S. Park, W. Lee, K. Kim, C. K. Chang, H. Yoon, J. Kim, S-I. Kim, H. Kim, C-R. Moon, J. Song
 Samsung Semiconductor, Hwaseong, Korea

6.11 A 320x240 CMOS LiDAR Sensor with 6-Transistor nMOS-Only SPAD Analog Front-End and Area-Efficient Priority Histogram Memory
 M. Kim*1 , H. Seo*1,2, S. Kim1 , J-H. Chun1,2, S-J. Kim3 , J. Choi*1,2
 1 Sungkyunkwan University, Suwon, Korea
 2 SolidVue, Seongnam, Korea
 3 Ulsan National Institute of Science and Technology, Ulsan, Korea
 *Equally Credited Authors (ECAs)
 

Imaging papers in other sessions: 

17.3 A Fully Wireless, Miniaturized, Multicolor Fluorescence Image Sensor Implant for Real-Time Monitoring in Cancer Therapy
 R. Rabbani*1 , M. Roschelle*1 , S. Gweon1 , R. Kumar1 , A. Vercruysse1 , N. W. Cho2 , M. H. Spitzer2 , A. M. Niknejad1 , V. M. Stojanovic1 , M. Anwar1,2
 1 University of California, Berkeley, CA
 2 University of California, San Francisco, CA
 *Equally Credited Authors (ECAs)

33.10 A 2.7ps-ToF-Resolution and 12.5mW Frequency-Domain NIRS Readout IC with Dynamic Light Sensing Frontend and Cross-Coupling-Free Inter-Stabilized Data Converter
 Z. Ma1 , Y. Lin1 , C. Chen1 , X. Qi1 , Y. Li1 , K-T. Tang2 , F. Wang3 , T. Zhang4 , G. Wang1 , J. Zhao1
 1 Shanghai Jiao Tong University, Shanghai, China
 2 National Tsing Hua University, Hsinchu, Taiwan
 3 Shanghai United Imaging Microelectronics Technology, Shanghai, China
 4 Shanghai Mental Health Center, Shanghai, China

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Miyauchi et al from Brillnics and  Tohoku University published a paper titled "Analysis of Light Intensity and Charge Holding Time Dependence of Pinned Photodiode Full Well Capacity" in the IISW 2023 special issue of the journal Sensors.

Abstract
In this paper, the light intensity and charge holding time dependence of pinned photodiode (PD) full well capacity (FWC) are studied for our pixel structure with a buried overflow path under the transfer gate. The formulae for PDFWC derived from a simple analytical model show that the relation between light intensity and PDFWC is logarithmic because PDFWC is determined by the balance between the photo-generated current and overflow current under the bright condition. Furthermore, with using pulsed light before a charge holding operation in PD, the accumulated charges in PD decrease with the holding time due to the overflow current, and finally, it reaches equilibrium PDFWC. The analytical model has been successfully validated by the technology computer-aided design (TCAD) device simulation and actual device measurement.

Open access: https://doi.org/10.3390/s23218847

Figure 1. Measured dynamic behaviors of PPD.

Figure 2. Pixel schematic and pulse timing for characterization.

Figure 3. PD cross-section and potential of the buried overflow path.

Figure 4. Potential and charge distribution changes from PD reset to PD saturation.

Figure 7. Potential and charge distribution changes from PD saturation to equilibrium PDFWC.

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Link: https://www.sony.com/lr/electronics/interchangeable-lens-cameras/ilce-9m3

Sony recently announced a full-frame global shutter camera which was featured in several press articles below:

PetaPixel https://petapixel.com/2023/11/07/sony-announces-a9-iii-worlds-first-global-sensor-full-frame-camera/

DPReview https://www.dpreview.com/news/7271416294/sony-announces-a9-iii-world-s-first-full-frame-global-shutter-camera

The Verge https://www.theverge.com/2023/11/7/23950504/sony-a9-iii-mirrorless-camera-global-shutter-price-release

From Sony's official webpage:

[This camera uses the] Newly developed full-frame stacked 24.6 MP Exmor RS™ image sensor with global shutter [...] a stacked CMOS architecture and integral memory [...] advanced A/D conversion enable high-speed processing to proceed with minimal delay. [AI features are implemented using the] BIONZ XR™ processing engine. With up to eight times more processing power than previous versions, the BIONZ XR image processing engine minimises processing latency [...] It's able to process the high volume of data generated by the newly developed Exmor RS image sensor in real-time, even while shooting continuous bursts at up to 120 fps, and it can capture high-quality 14-bit RAW images in all still shooting modes. [...] [The] α9 III can use subject form data to accurately recognise movement. Human pose estimation technology recognises not just eyes but also body and head position with high precision. 

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The deadline for the 2024 ISSW on December 8, 2023 is fast approaching! Paper submission portal is now open!

The 2024 International SPAD Sensor Workshop will be held from 4-6 June 2024 in Trento, Italy.

Paper submission

Workshop papers must be submitted online on Microsoft CMT. Click here to be redirected to the submission website. You may need to register first, then search for the "2024 International SPAD Sensor Workshop" within the list of conferences using the dedicated search bar.

Paper format

Kindly take note that the ISSW employs a single-stage submission process, necessitating the submission of camera-ready papers. Each submission should comprise a 1000-character abstract and a 3-page paper, equivalent to 1 page of text and 2 pages of images. The submission must include the authors' name(s) and affiliation, mailing address, telephone, and email address. The formatting can adhere to either a style that integrates text and figures, akin to the standard IEEE format, or a structure with a page of text followed by figures, mirroring the format of the International Solid-State Circuits Conference (ISSCC) or the IEEE Symposium on VLSI Technology and Circuits. Examples illustrating these formats can be accessed in the online database of the International Image Sensor Society.

The deadline for paper submission is 23:59 CET, Friday December 8th, 2023.

Papers will be considered on the basis of originality and quality. High quality papers on work in progress are also welcome. Papers will be reviewed confidentially by the Technical Program Committee. Accepted papers will be made freely available for download from the International Image Sensor Society website. Please note that no major modifications are allowed. Authors will be notified of the acceptance of their abstract & posters at the latest by Wednesday Jan 31st, 2024.
 
Poster submission 

In addition to talks, we wish to offer all graduate students, post-docs, and early-career researchers an opportunity to present a poster on their research projects or other research relevant to the workshop topics . If you wish to take up this opportunity, please submit a 1000-character abstract and a 1-page description (including figures) of the proposed research activity, along with authors’ name(s) and affiliation, mailing address, telephone, and e-mail address.

The deadline for poster submission is 23:59 CET, Friday December 8th, 2023.

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Li et al. present a new THz imaging technique for defect detection in a recent paper in the journal Nature Communications. The paper is titled "Rapid sensing of hidden objects and defects using a single-pixel diffractive terahertz sensor".

Abstract: Terahertz waves offer advantages for nondestructive detection of hidden objects/defects in materials, as they can penetrate most optically-opaque materials. However, existing terahertz inspection systems face throughput and accuracy restrictions due to their limited imaging speed and resolution. Furthermore, machine-vision-based systems using large-pixel-count imaging encounter bottlenecks due to their data storage, transmission and processing requirements. Here, we report a diffractive sensor that rapidly detects hidden defects/objects within a 3D sample using a single-pixel terahertz detector, eliminating sample scanning or image formation/processing. Leveraging deep-learning-optimized diffractive layers, this diffractive sensor can all-optically probe the 3D structural information of samples by outputting a spectrum, directly indicating the presence/absence of hidden structures or defects. We experimentally validated this framework using a single-pixel terahertz time-domain spectroscopy set-up and 3D-printed diffractive layers, successfully detecting unknown hidden defects inside silicon samples. This technique is valuable for applications including security screening, biomedical sensing and industrial quality control. 

Paper (open access): https://www.nature.com/articles/s41467-023-42554-2

News coverage: https://phys.org/news/2023-11-hidden-defects-materials-single-pixel-terahertz.html

CMOS SPAD Sensors for Solid-state LIDAR

 
In the realm of engineering and material science, detecting hidden structures or defects within materials is crucial. Traditional terahertz imaging systems, which rely on the unique property of terahertz waves to penetrate visibly opaque materials, have been developed to reveal the internal structures of various materials of interest.

This capability provides unprecedented advantages in numerous applications for industrial quality control, security screening, biomedicine, and defense. However, most existing terahertz imaging systems have limited throughput and bulky setups, and they need raster scanning to acquire images of the hidden features.

To change this paradigm, researchers at UCLA Samueli School of Engineering and the California NanoSystems Institute developed a unique terahertz sensor that can rapidly detect hidden defects or objects within a target sample volume using a single-pixel spectroscopic terahertz detector.
Instead of the traditional point-by-point scanning and digital image formation-based methods, this sensor inspects the volume of the test sample illuminated with terahertz radiation in a single snapshot, without forming or digitally processing an image of the sample.

Led by Dr. Aydogan Ozcan, the Chancellor's Professor of Electrical & Computer Engineering and Dr. Mona Jarrahi, the Northrop Grumman Endowed Chair at UCLA, this sensor serves as an all-optical processor, adept at searching for and classifying unexpected sources of waves caused by diffraction through hidden defects. The paper is published in the journal Nature Communications.

"It is a shift in how we view and harness terahertz imaging and sensing as we move away from traditional methods toward more efficient, AI-driven, all-optical sensing systems," said Dr. Ozcan, who is also the Associate Director of the California NanoSystems Institute at UCLA.

This new sensor comprises a series of diffractive layers, automatically optimized using deep learning algorithms. Once trained, these layers are transformed into a physical prototype using additive manufacturing approaches such as 3D printing. This allows the system to perform all-optical processing without the burdensome need for raster scanning or digital image capture/processing.

"It is like the sensor has its own built-in intelligence," said Dr. Ozcan, drawing parallels with their previous AI-designed optical neural networks. "Our design comprises several diffractive layers that modify the input terahertz spectrum depending on the presence or absence of hidden structures or defects within materials under test. Think of it as giving our sensor the capability to 'sense and respond' based on what it 'sees' at the speed of light."

To demonstrate their novel concept, the UCLA team fabricated a diffractive terahertz sensor using 3D printing and successfully detected hidden defects in silicon samples. These samples consisted of stacked wafers, with one layer containing defects and the other concealing them. The smart system accurately revealed the presence of unknown hidden defects with various shapes and positions.
The team believes their diffractive defect sensor framework can also work across other wavelengths, such as infrared and X-rays. This versatility heralds a plethora of applications, from manufacturing quality control to security screening and even cultural heritage preservation.

The simplicity, high throughput, and cost-effectiveness of this non-imaging approach promise transformative advances in applications where speed, efficiency, and precision are paramount.

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Oripov et al. from NIST and JPL recently published a paper titled "A superconducting nanowire single-photon camera with 400,000 pixels" in Nature.

Abstract: For the past 50 years, superconducting detectors have offered exceptional sensitivity and speed for detecting faint electromagnetic signals in a wide range of applications. These detectors operate at very low temperatures and generate a minimum of excess noise, making them ideal for testing the non-local nature of reality, investigating dark matter, mapping the early universe and performing quantum computation and communication. Despite their appealing properties, however, there are at present no large-scale superconducting cameras—even the largest demonstrations have never exceeded 20,000 pixels. This is especially true for superconducting nanowire single-photon detectors (SNSPDs). These detectors have been demonstrated with system detection efficiencies of 98.0%, sub-3-ps timing jitter, sensitivity from the ultraviolet to the mid-infrared and microhertz dark-count rates, but have never achieved an array size larger than a kilopixel. Here we report on the development of a 400,000-pixel SNSPD camera, a factor of 400 improvement over the state of the art. The array spanned an area of 4 × 2.5 mm with 5 × 5-μm resolution, reached unity quantum efficiency at wavelengths of 370 nm and 635 nm, counted at a rate of 1.1 × 105 counts per second (cps) and had a dark-count rate of 1.0 × 10^−4 cps per detector (corresponding to 0.13 cps over the whole array). The imaging area contains no ancillary circuitry and the architecture is scalable well beyond the present demonstration, paving the way for large-format superconducting cameras with near-unity detection efficiencies across a wide range of the electromagnetic spectrum.

Link: https://www.nature.com/articles/s41586-023-06550-2

a, Circuit diagram of a bus and one section of 50 detectors with ancillary readout components. SNSPDs are shown in the grey boxes and all other components are placed outside the imaging area. A photon that arrives at time t0 has its location determined by a time-of-flight readout process based on the time-of-arrival difference t2 − t1. b, Oscilloscope traces from a photon detection showing the arrival of positive (green) and negative (red) pulses at times t1 and t2, respectively.

a, Histogram of the pulse differential time delays Δt = t1 − t2 from the north bus during flood illumination with a Gaussian spot. All 400 detectors resolved clearly, with gaps indicating detectors that were pruned. Inset, zoomed-in region showing that counts from adjacent detectors are easily resolvable and no counts were generated by a pruned detector. b, Plot of raw trow and tcol time delays when flood illuminated at 370 nm. c, Zoomed-in subsection of the array with 25 × 25 detectors. d, Histogram of time delays for a 2 × 2 detector subset with 10-ps bin size showing clear distinguishability between adjacent detectors.

a, Count rate versus optical attenuation for a section of detectors biased at 45 μA per detector. The dashed purple line shows a slope of 1, with deviations from that line at higher rates indicating blocking loss. b, System jitter of a 50-detector section. Detection delay was calculated as the time elapsed between the optical pulse being generated and the detection event being read out.

News coverage: https://www.universetoday.com/163959/a-new-superconducting-camera-can-resolve-single-photons/

A New Superconducting Camera can Resolve Single Photons

Researchers have built a superconducting camera with 400,000 pixels, which is so sensitive it can detect single photons. It comprises a grid of superconducting wires with no resistance until a photon strikes one or more wires. This shuts down the superconductivity in the grid, sending a signal. By combining the locations and intensities of the signals, the camera generates an image.

The researchers who built the camera, from the US National Institute of Standards and Technology (NIST) say the architecture is scalable, and so this current iteration paves the way for even larger-format superconducting cameras that could make detections across a wide range of the electromagnetic spectrum. This would be ideal for astronomical ventures such as imaging faint galaxies or extrasolar planets, as well as biomedical research using near-infrared light to peer into human tissue.

These devices have been possible for decades but with a fraction of the pixel count. This new version has 400 times more pixels than any other device of its type. Previous versions have not been very practical because of the low-quality output.

In the past, it was found to be difficult-to-impossible to chill the camera’s superconducting components – which would be hundreds of thousands of wires – by connecting them each to a cooling system.
According to NIST, researchers Adam McCaughan and Bakhrom Oripov and their collaborators at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the University of Colorado Boulder overcame that obstacle by constructing the wires to form multiple rows and columns, like those in a tic-tac-toe game, where each intersection point is a pixel. Then they combined the signals from many pixels onto just a few room-temperature readout nanowires.

The detectors can discern differences in the arrival time of signals as short as 50 trillionths of a second. They can also detect up to 100,000 photons a second striking the grid.
McCaughan said the readout technology can easily be scaled up for even larger cameras, and predicted that a superconducting single-photon camera with tens or hundreds of millions of pixels could soon be available.

In the meantime, the team plans to improve the sensitivity of their prototype camera so that it can capture virtually every incoming photon. That will enable the camera to tackle quantum imaging techniques that could be a game changer for many fields, including astronomy and medical imaging.

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The 2023 workshop on Radiation Effects on Optoelectronic Detectors and Photonics Technologies (RADOPT) will be co-organised by CNES, UJM, SODERN, ISAE-SUPAERO AIRBUS DEFENCE & SPACE, THALES ALENIA SPACE in Touluse, France on November 29 and 30, 2023.

After the success of RADOPT 2021, this second edition of the workshop, will continue to combine and replace two well-known events from the Photonic Devices and IC’s community: the “Optical Fibers in Radiation Environments Days -FMR” and the Radiation effects on Optoelectronic Detectors Workshop, traditionally organized every-two years by the COMET OOE of CNES.

The objective of the workshop is to provide a forum for the presentation and discussion of recent developments regarding the use of optoelectronics and photonics technologies in radiation-rich environments. The workshop also offers the opportunity to highlight future prospects in the fast-moving space, high energy physics, fusion and fission research fields and to enhance exchanges and collaborations between scientists. Participation of young researchers (PhD) is especially encouraged.

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Kim et al. from imec and coauthors from universities in Belgium and Korea recently published a paper titled "A Thin-Film Pinned-Photodiode Imager Pixel with Fully Monolithic Fabrication and beyond 1Me- Full Well Capacity" in MDPI Sensors. This paper describes imec's recent thin film pinned photodiode technology.

Open access paper link: https://www.mdpi.com/1424-8220/23/21/8803

Abstract
Thin-film photodiodes (TFPD) monolithically integrated on the Si Read-Out Integrated Circuitry (ROIC) are promising imaging platforms when beyond-silicon optoelectronic properties are required. Although TFPD device performance has improved significantly, the pixel development has been limited in terms of noise characteristics compared to the Si-based image sensors. Here, a thin-film-based pinned photodiode (TF-PPD) structure is presented, showing reduced kTC noise and dark current, accompanied with a high conversion gain (CG). Indium-gallium-zinc oxide (IGZO) thin-film transistors and quantum dot photodiodes are integrated sequentially on the Si ROIC in a fully monolithic scheme with the introduction of photogate (PG) to achieve PPD operation. This PG brings not only a low noise performance, but also a high full well capacity (FWC) coming from the large capacitance of its metal-oxide-semiconductor (MOS). Hence, the FWC of the pixel is boosted up to 1.37 Me- with a 5 μm pixel pitch, which is 8.3 times larger than the FWC that the TFPD junction capacitor can store. This large FWC, along with the inherent low noise characteristics of the TF-PPD, leads to the three-digit dynamic range (DR) of 100.2 dB. Unlike a Si-based PG pixel, dark current contribution from the depleted semiconductor interfaces is limited, thanks to the wide energy band gap of the IGZO channel material used in this work. We expect that this novel 4 T pixel architecture can accelerate the deployment of monolithic TFPD imaging technology, as it has worked for CMOS Image sensors (CIS).

Figure 1. Pixel cross-section for the monolithic TFPD image sensor (a) 3 T and (b) 4 T (TF-PPD) structure (TCO: transparent conductive oxide, HTL: hole transport layer, PG: photogate, TG: transfer gate, FD: floating diffusion). Electric potential and signal readout configuration for 3 T pixel (c) and for 4 T pixel (d). Pixel circuit diagram for 3 T pixel (e) and for the 4 T pixel (f).

Figure 2. I-V characteristic of QDPD test structure (a) and of IGZO TFT (b), a micrograph of the TF-PPD passive pixel array (c), and its measurement schematic (d). Band diagrams for the PD (e) and PG (f).

Figure 3. Silvaco TCAD simulation results; (a) simulated structure, (b) lateral potential profile along the IGZO layer, and (c) potential profile when TG is turned off and (d) on.

Figure 4. Signal output vs. integration time with different VPG and VTG values with the illumination. Signal curves with the fixed VTG (−1 V), varying VPG (−4~−1 V) (a), the same graphs for the fixed VPG (−2 V), and different VTGs (−6.5~−1 V) (b).

Figure 4. Signal output vs. integration time with different VPG and VTG values with the illumination. Signal curves with the fixed VTG (−1 V), varying VPG (−4~−1 V) (a), the same graphs for the fixed VPG (−2 V), and different VTGs (−6.5~−1 V) (b).

Figure 5. (a) Pixel output vs. integration time for different pixel pitches. (b) FWC comparison between estimation and measurement.

Figure 6. FWC comparison by different pixel fill factors. Pixel schematics for different shapes (a), and FWC by different pixel shapes and pitches (b).

Figure 7. Potential diagram describing FWC increase by the larger VPG (a), and FWC vs. VPG (b).

Figure 8. Passive pixel dark current (a) and Arrhenius plots (b) for the QDPD test structure and the passive pixel.

Figure 9. FWC vs. pixel area. A guideline showing the FWC density per unit area for this work (blue) and a trend line for the most of CISs (red).

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