Novel micropixel avalanche photodiodes (MAPD) with super high pixel density

In this study, we present the gamma-ray detection performance of LYSO, YSO(Ce) and BGO scintillators read out by a 9 ch. micropixel avalanche photodiode (MAPD) array with a high pixel density (PD) and photon detection efficiency (PDE). The array with an active area of 11.5 × 11.5 mm2 was assembled using single MAPDs with an active area of 3.7 × 3.7 mm2. It had a single output signal and was developed for gamma spectroscopy. Breakdown voltage measurements were carried out for each channel, as a result of which the optimal operating voltage for the array was found. The linearity range and energy resolution for each crystal were determined in the energy range from 30 to 1770 keV . The high pixel density of the array allowed to achieve good linearity in the studied energy range.

Helium and hydrogen atom detection in the recycling gas using optical measurements on an ASDEX pressure gauge

We report here on a potentially significant improvement in the design of neutral pressure gauges of the so-called ASDEX-type which were first used in the Axially Symmetric Divertor EXperiment (ASDEX). Such gauges are considered state-of-the-art and are in wide use in fusion experiments, but they nonetheless suffer from a relatively high failure rate when operated at high magnetic field strengths for long times. This is therefore a significant concern for long-pulse, high-field experiments such as Wendelstein 7-X (W7-X) and ITER. The new design is much more robust. The improvement is to use a LaB6 crystal instead of a tungsten wire as the thermionic emitter of electrons in the gauge. Such a LaB6 prototype gauge was successfully operated for a total of 60 h in B = 3.1 T, confirming the significantly improved robustness of the new design and qualifying it for near-term operation in W7-X. With the LaB6 crystal, an order of magnitude reduction in heating current is achieved, relative to the tungsten filament based gauges, from 15-20 A to 1-2 A. This reduces the Lorenz forces and the heating power by an order of magnitude also and is presumably the reason for the much improved robustness. The new gauge design, test environment setup at the superconducting magnet, and results from test operation are described.

The Multi-Pixel Photon Counter (MPPC), which is also called a silicon photomultiplier (SiPM)1,2, is one promising candidate for automotive light detection and ranging (LIDAR)3. Due to high internal gain around 106, photon counting is possible and satisfies long range measurement. Compared to photo diodes (PDs) and avalanche photo diodes (APDs), read-out circuits for MPPCs are very simple because no external amplifier is needed. Conventional MPPCs have been developed for targeting blue scintillation light around 400 nm for positron emission tomography (PET) and high energy physics experiments. In this paper we report new near-infrared (NIR)-enhanced MPPCs whose development targets include 905 nm laser light for automotive LIDAR systems. Conventional MPPCs have a p-on-n structure and show 2% photon detection efficiency (PDE) at 905 nm. Our newly developed n-on-p MPPC achieved 7% PDE without greatly changing the impurity concentration profile of the depletion layer. This n-on-p MPPC has been released as an NIRenhanced MPPC: S13720-1325CS. For further improvement of NIR sensitivity, we tried several silicon wafers and process conditions of p-n junction profiles. Even though dark noise and the voltage range have to be modified, the latest sample shows 11% PDE, suggesting potential for further sensitivity improvement.

The design of a photodetector unit of a new Shashlyk EM calorimeter for COMPASS II

Silicon photomultiplier (SiPMs) is a photon counting device that consists of single photon avalanche diodes (SPADs) arrays being operated at a Geiger mode and has been widely used in many kinds of application including high-energy physics, confocal laser scanning microscopy (CSLM), flow cytometry, and light detection and ranging (LiDAR) instead of photomultiplier tube (PMT). Trench structures basically places at the boarder of every SPAD to guard optical and electrical crosstalk. However, illuminating photons to the trench region restricted the performance of SiPM such as photon detection efficiency (PDE) and timing performance because it does not absorb photon sufficiently. Our previous work demonstrated that guiding incident photons into the photo sensitive area of SPADs using metalens array resulted in improvement of the performance of the SiPM. However, performance is expected to fluctuate due to misalignment caused by slight vibration because metalens and SiPMs are separated configuration. Guaranteeing a good alignment between the metalens and SiPM has been necessary for practical applications. Here, we demonstrate the completely monolithic integration of a metalens with its corresponding SPAD to provide stable PDE improvement while maintaining the compact and flatness of the optical device. Furthermore, we investigated the crosstalk and dark-current comparing with a reference SiPM without the metalens for investigating the negative effect of integrating metalens with the SiPM. From the results of sophisticated investigation, we show the more practical approach toward the improving overall performance of the SiPM not only the PDE and timing performance but also crosstalk and dark current. Finally, we will show our next perspective and progress towards near infrared application.

A new family of photodetectors with a Discrete Amplification (DA) mechanism allows the realization of very high gain and low excess noise factor in the visible and near infrared spectral regions and offers an alternative to conventional photomultiplier tubes and Geiger mode avalanche photodetectors. These photodetectors can operate in linear detection mode with gain-bandwidth product in excess of 4X10¹⁴ and in photon counting mode with count rates up to 10⁸ counts/sec. Potential benefits of this technology over conventional avalanche photodetectors include ultra low excess noise factor, very high gain, and lower reset time (<< 1 μs). In the photon counting mode, the devices can be operated in the non-gated mode under a constant dc bias. Because of its unique characteristics of self-quenching and self-recovery, no external quenching circuit is needed. We present the discrete amplification design approach used for the development of a solid state photomultiplier in the near infrared wavelength region. The demonstrated device performance far exceeds any available solid state photodetectors in the near infrared wavelength range. The measured devices have the following performance characteristics: gain > 2X10⁵, excess noise factor < 1.05, rise time < 350ps, fall time < 500ps, dark current < 2X10⁶ cps, operating voltage < 60V. These devices are ideal for researchers in the field of deep space optical communication, spectroscopy, industrial and scientific instrumentation, Ladar/Lidar, quantum cryptography, night vision and other military, defence and aerospace applications.

We developed the novel photon counter, named multipixel photon counter (MPPC). It is solid state photon counter using Geiger-mode APD and self-quenching resistance. It has many features like low bias voltage operation, high gain and insensitive to magnetic fields. We have fabricated the three kinds of MPPC, which are 40 times 40, 20 times 20, and 10 times 10 pixels segmented from 1 mm times 1 mm total active area. The gain, dark count rate, photon detection efficiency (PDE) and time resolution are measured and confirmed that MPPC has large potential as the new photon detection device.

Single-photon detector (SPD) as an essential building block for detecting and counting photons, plays a fundamental role in quantum technologies. In this work, we propose an efficient workflow of modeling SPDs based on emerging one-dimensional materials, i.e. nanowires, utilizing avalanche breakdown in reverse biased condition. Comparing to another extensively studied platform, superconducting nanowire SPDs, avalanche nanowire device is demonstrated in this work to promise comparable performance (e.g. high photon detection efficiency (PDE) and and low dark count rate (DCR)) but without working at extreme cryogenic temperature (4K). The proposed workflow explored to maximize computational workload and balancing between time-consuming drift-diffusion simulation and fast script-based post-processing, and in timely convergence we were able to predict a suite of key performance metrics for single-photon SPDs, including breakdown voltage, PDE, DCR, and time resolution.

After developing various kinds of photodetectors such as phototubes, photomultiplier tubes, image pick up tubes, solid state photodetectors and a variety of light sources, we also started to develop integrated systems utilizing new detectors or imaging devices. These led us to the technology for a single photon counting imaging and detection of picosecond and femtosecond phenomena. Through those experiences, we gained the understanding that photon is a paste of substances, and yet we know so little about photon. By developing various technology for many fields such as analytical chemistry, high energy physics, medicine, biology, brain science, astronomy, etc., we are beginning to understand that the mind and life are based on the same matter, that is substance. Since humankind has so little knowledge about the substance concerning the mind and life, this makes some confusion on these subjects at this moment. If we explore photonics more deeply, many problems we now have in the world could be solved. By creating new knowledge and technology, I believe we will be able to solve the problems of illness, aging, energy, environment, human capability, and finally, the essential healthiness of the six billion human beings in the world.

As photon detection is a major issue in any high-energy astronomy instrumentation, many space missions combined photomultiplier tubes (PMTs) with scintillators, for converting incoming high-energy photons into visible light, which in turn is converted in an electrical pulse. The silicon photomultipliers (SiPM), instead of PMTs which are bulky, fragile, and requiring a high-voltage power supply of up to several thousand volts, seem to be an encouraging alternative in the space field. We started a R&D program to assess the possibility of using SiPMs for space-based applications in the domain of high-energy astronomy. We already presented some results of the detector characterization to study the SiPM performance in a representative space environment, namely at low temperature and low pressure. For this purpose, we developed a dedicated vacuum chamber with a specific mechanical and thermal controlled system. After measuring dark current, dark count rate and PDE (Photon Detection Efficiency), we performed a first campaign of irradiation tests at UCL (Belgium) in order to understand the susceptibility of SiPM to radiation damage on two selected detectors (Ketek and SensL references) with a high level of fluence. Finally we led a new proton irradiation campaign based on several lower levels of fluence and two energies for further study. We then present the results of dark current measurements of irradiated SensL detectors.

Studies on a silicon-photomultiplier-based camera for Imaging Atmospheric Cherenkov Telescopes

Innovative airglow instrument based on constant photon count control

Background Currently, a wide variety of silicon photomultipliers (SiPMs) are available, each designed for specific applications in fields such as science, medicine, and industry. Advances in production technology have led to the development of more sensitive and efficient photodiodes, which are critical for applications requiring precision, such as medical imaging. Methods A research group has been working on designing a highly sensitive photodiode to enhance the capabilities of next-generation PET-MRI scanners. This involves integrating micropixel avalanche photodiodes (MAPDs) to improve image resolution. The chosen design features deep-immersion MAPDs with a pixel size of 12 microns and a density of 1000 pixels per square millimeter, allowing for high-detail photon detection. The 4x4 mm2 active area is optimized to balance sensitivity and size for high-resolution medical imaging. To produce these photodiodes, the group has outlined a production plan involving 20-inch silicon wafers grown using multiple techniques to enhance material properties. The Malaysian Institute of Microelectronic Systems (MIMOS), renowned for its expertise in optical microelectronics, was selected as the production center. With MIMOS' state-of-the-art facilities, the project aims to meet stringent medical diagnostics standards. Results The experimental results demonstrated that the MAPD-3NM photodiode achieved an amplification factor 1.8 times greater than the MAPD-3NK under optimal conditions. Its overvoltage range increased by 100%, reaching 4 V, enhancing photon detection and amplification. The MAPD-3NM also showed a significant reduction in dark current, about 3.5 times lower than the MAPD-3NK, improving performance in low-light environments. Additionally, the MAPD-3NM had a capacitance of 200 pF compared to 176 pF for the MAPD-3NK, contributing to its superior performance. These improvements make the MAPD-3NM more efficient and sensitive for scientific and medical applications. Conclusions This project represents a major advancement in photodetector technology for medical diagnostics, aiming to develop more accurate and efficient PET-MRI scanners that enhance patient outcomes with improved imaging capabilities.

InGaAs/InP single-photon detectors (SPDs) are the key devices for applications requiring near-infrared single-photon detection. The gating mode is an effective approach to synchronous single-photon detection. Increasing gating frequency and reducing the module size are important challenges for the design of such a detector system. Here we present for the first time, to the best of our knowledge, an InGaAs/InP SPD with 1.25GHz sine wave gating (SWG) using a monolithically integrated readout circuit (MIRC). The MIRC has a size of 15 mm×15 mm and implements the miniaturization of avalanche extraction for high-frequency SWG. In the MIRC, low-pass filters and a low-noise radio frequency amplifier are integrated based on the technique of low temperature co-fired ceramic, which can effectively reduce the parasitic capacitance and extract weak avalanche signals. We then characterize the InGaAs/InP SPD to verify the functionality and reliability of the MIRC, and the SPD exhibits excellent performance with 27.5% photon detection efficiency, a 1.2kcps dark count rate, and 9.1% afterpulse probability at 223K and 100ns hold-off time. With this MIRC, one can further design miniaturized high-frequency SPD modules that are highly required for practical applications.