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Underwater wireless communication stands as a captivating and swiftly progressing domain in recent. To support higher data rate and higher bandwidth applications, there is significant attention towards underwater acoustics along with Visible Light Communication (VLC) technology. Underwater sensor networking serves as the backbone of oceanic exploration efforts. Based on the traffic load and underwater environmental conditions, an appropriate communication link can be selected to achieve higher data rate. Acoustics supports communication over longer distances with lower data rate. Despite offering higher data rates, Visible Light Communication (VLC) faces limitations in terms of communication range, proving to be relatively short compared to other methods. A seamless transition is anticipated during data transmission and reception by employing Light Emitting Diodes (LEDs) and photo detectors on the optical-acoustic channel, bridging the gap between acoustic and optical communication methods. Utilizing MIMO-based Enhanced Reverse Polarity Orthogonal Frequency Division Multiplexing (MIMO-ERPO-OFDM) in Underwater Optical Communication (UWOC) proves to be a superior approach, achieving a high throughput of 19.9 Mbps and a lower Bit Error Rate (BER) of 10− 1. [ABSTRACT FROM AUTHOR]

Three small molecules furnished with a planar core, (5,6-bis(octyloxy) benzo[c][1,2,5] thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl), and two wings, thieno [3,2-b]indole or carbazoles, were synthesized and used as sensing layer to make photo-detectors. The devices can detect photons at a wavelength band of 300-700 nm and exhibit a sensitive photo-response under on/off modulation. Near UV (405 nm) and visible (532 nm) laser beam were the light source in this work. The corrected responsivity reached up to 498 mA W-1 at 532 nm and 411 mA W-1 at 405 nm. Laser induced photo-current escalation was observed and investigated. For longer molecules, the photo-current was easy to be constant than the shorter reference counterpart. This special photo response mechanism was studied by alternating current impedance spectroscopy (IS) measurements and X-ray diffraction (XRD) exprements. Possible relations between molecular weight and various figures of merit for photo detectors were discussed. [ABSTRACT FROM AUTHOR]

Aerosol effects evaluation on Earth’s radiation budget demands knowledge of its concentration, spatial, and temporal distribution. Therefore, long-term measurements of aerosol properties in different regions of Earth are very important. In this paper, indium nitride (InN)- and indium oxynitride (InNO)-based photodiodes calibration was realized. A pyranometer was used in this paper. Calibrated InN and InNO Schottky photodiodes will be used for aerosol detection. According to the calibration tests, it was found that the most suitable sensors for the continuation of an aerosol statistical study in the atmosphere are those made with the InNO deposited with oxygen 10% and 20%; their correlation coefficient values are almost one. Besides, their measures do not reach the saturation point. In future, we intend to use these devices in a quantitative study of aerosols present in the center of a large city, to get a sense of human interference in the atmosphere composition and its consequences. [ABSTRACT FROM PUBLISHER]

Multifunctional materials are a new class of thin films and coatings. These materials show interesting characteristics for application in many scientific areas, in special electronic and photonic technologies. These characteristics include sensitivity for thermal, light, mechanical, chemical and other influences, high resistivity, high electrical isolation and transparence in visible range. Recently it was obtained a new oxide type that combines oxygen, nitrogen and indium: the indium oxynitride. In this work, we study the deposition of indium oxynitride by reactive sputtering for application in photoconductor sensors. The deposition processes were performed in a home build magnetron sputtering system, using a four-inch pure In target, nitrogen and oxygen as process gases. The pressure was kept constant at 10 mtorr and the RF power (13.56 MHz) was constant at 250 W. The photoconductors were made with these thin films. The photoelectric detectors were analyzed by IxV (current versus voltage) analyses. The IxV analysis presented a low leakage current (10-8 A). The photoelectric effect was observed from the difference between the case with emitted light and dark currents. It increased around 140 times, under illumination of a halogen lamp. The Hall Effect measurements indicated that the films were n-type semiconductors. The increase in the oxygen concentration added in the plasma, promoted the change in the character of these thin films from conductor to semiconductor material.

Recent developments on Silicon Photomultipliers (SiPMs) have shown that they are particularly adequate to detect fast signal due to low-intensity light. Fondazione Bruno Kessler (FBK) has optimized these sensors for the Near-Ultraviolet Cherenkov light emitted by high energy gamma-ray showers in the atmosphere. The FBK high density SiPMs (NUV-HD) have been extensively characterized in the laboratories of the Italian Institute of Nuclear Physics (INFN) in view of equipping the focal plane camera of the Schwarzschild–Couder Telescope prototype (pSCT) in the framework of the Cherenkov Telescope Array (CTA). Here we report the performances of the 6 × 6 mm 2 SiPMs based on 40 × 40 μm 2 cells, in terms of gain and signal-to-noise ratio. We compare the results obtained on devices from the latest generation and grown on different substrates in order to choose the most suitable sensor for the pSCT camera. [ABSTRACT FROM AUTHOR]

The Italian Institute of Nuclear Physics (INFN) is currently involved in the R&D for the integration of Fondazione Bruno Kessler (FBK) Silicon Photomultipliers (SiPM) in the focal plane camera for the prototype of the Schwarzschild–Couder Telescope (pSCT) proposed to integrate the Cherenkov Telescope Array (CTA) observatory. High density FBK SiPMs optimized for the detection of Near Ultraviolet Cherenkov light (NUV-HD) will be used to equip the camera, coupled to the TARGET-7 readout electronics. A first production of 9 INFN modules is being tested and will be installed on the focal plane of the pSCT camera. Each module consists of 64 6 mm × 6 mm pixels, based on 40 μ m × 40 μ m microcells, arranged in 16-pixel matrices. The front-end electronics is based on the TARGET-7 ASIC, a 16-channel chip for sampling and digitization of the signal. Here we report measurements of the performances of the complete readout chain, including results regarding homogeneity in terms of gain and signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

Various spurious effects limit the effectiveness of Photomultipliers when used in low-light-level coincidence counting experiments. One of these effects is afterpulses from light emission in the Photomultiplier. Here we present a study on the light emission in Photomultipliers using a variety of methods. First we image the light emission directly. Second we characterize the light emission spectrum. Finally we investigate the time resolved light emission. In particular we find that, not only the dynodes “glow,” but also the support structure emits light. A fluorescent effect is found. The experiments performed help to understand the fundamental effects of light emission and afterpulses in Photomultipliers. [ABSTRACT FROM PUBLISHER]

We present an avalanche photodiode (APD) with separate absorption and multiplication zone. The APD is fabricated in a 0.35-μm CMOS process using an epitaxial wafer. Due to its thick detection zone, this concept offers a high dynamic quantum efficiency and thus a high resulting dynamic responsivity. Measurements using a 670-nm laser source demonstrate a maximum responsivity of 1.8· 104 A/W at 5 nW and a maximum bandwidth of 1.02 GHz at 5-μW illumination power. A maximum responsivity bandwidth product of 269.7 GHz· A/W was found at 35 V reverse bias voltage and 5-nW optical power. [ABSTRACT FROM PUBLISHER]

Abstract: The lifetime of the most recent generation micro-channel plate (MCP) PMTs of BINP, Hamamatsu (R10754X) and PHOTONIS (XP85112) is being studied in a simultaneous measurement. We find that the new techniques applied to reduce the aging of the photocathode of the MCP-PMTs has significantly increased the lifetime. Dark count rate, gain and quantum efficiency of the tubes are given as a function of the integrated anode charge. Several times the quantum efficiency was also measured across the surface of the photocathode. At this point of the ongoing measurements the best MCP-PMT turns out to be the XP85112 with its MCP surfaces coated by an atomic layer to reduce the outgassing of the lead glass. This tube shows no aging after an integrated anode charge of 2.1C/cm2 which is more than an order of magnitude better than that of previous generation MCP-PMTs. [Copyright &y& Elsevier]

The applicability of single-mode fibers from the viewpoint of transmitted optical power limitation due to scattering and noise processes is studied. To deal with this applicability of fibers and consequently with lightwave systems performance, several parameters should be taken into consideration. The most important parameters affecting the performance of amplified optical networks are: channel frequency separation, total channel numbers, the maximum allowable signal power, the maximum transmission length, and the receiver sensitivity degradation. The effects of amplified spontaneous emission (ASE) noise, avalanche photodiode (APD) noise, thermal noise, and interference (crosstalk) for optical code division multiple access direct detection (OCDMA/DD) are examined. One such scheme is an optical orthogonal code division multiple access (OOCDMA) system. In this paper, performance of amplified lightwave systems employing both conventional M-ary Quadrature Amplitude Modulation Subcarriers Multiple Intensity Modulation / Direct Detection (M-ary QAM-SCM-IM/ DD) and OCDMA/DD schemes have been analyzed. The analysis also incorporates the influence of code rates (weights) on the system performance. It is observed from analysis that for a given number of users, performance of OCDMA networks improves with the increase in the code weight. Furthermore, use of large code weight will give rise to better performance, but less number of simultaneous supportable users. On the other hand use of small code weight leads to a poor performance, but in this case the number of supportable users are large. Also, it is found that coding can increase the total channel number and eliminate error floor under a given bit error rate and receiver sensitivity. These systems employing optical amplifier have been studied and investigated. It is found that coding can increase the total channel number and eliminate error floor under a given bit error rate and receiver sensitivity. A performance comparison of QAM and OCDMA systems reveals that OCDMA can accommodate a larger number of subscribers and more simultaneous users than QAM. [ABSTRACT FROM AUTHOR]

Abstract: DIRC Cherenkov detectors will be the main devices for separation at the PANDA experiment at FAIR. Due to their advantageous properties in terms of time resolution and especially inside magnetic fields micro-channel plate photo multipliers (MCP-PMTs) are very attractive sensor candidates. In this paper we present the investigation of several types of multi-anode MCP-PMTs. The darkcount rate, the behavior inside a magnetic field of up to 2T, the time resolution, the gain homogeneity and crosstalk of multi-pixel MCP-PMTs were found to be well suitable for the PANDA requirements. Even the rate capability of the latest models from Burle-Photonis and Hamamatsu is satisfactory. Although a big step forward was accomplished with these recently available MCP-PMTs, the lifetime is still not sufficient for the photon densities expected for the PANDA DIRCs. [Copyright &y& Elsevier]

SiPM photo detectors are nowadays commonly used in many applications. For large size telescopes like MAGIC or the future Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) project, a pixel size of some square centimeters is needed. An analog amplifier and sum stage was built and characterized. A large and compact SiPM matrix prototype, with the associated focusing optics, was assembled into a monolithic light detector with an active area of 3 cm 2 . The performance of the electronics is tailored for Imaging Atmospheric Cherenkov Telescopes (IACT) applications, with fast signal and adequate signal-to-noise ( S / N ) ratio. [ABSTRACT FROM AUTHOR]

The generation of sub-millimeter waves and terahertz signals is a difficult challenge, and a few approaches are being studied by several groups. We are investigating the approach of heterodyning two optical signals in a uni-traveling-carrier photo detector, which has been identified as the device of choice for very high frequencies. In this paper we present a novel analytical model, which was developed as a design tool for the above device. The model was validated by designing, fabricating and testing a new 100 GHz photo detector. In addition, performance limits for the UTC traveling wave photo detector are calculated by the new model, and it is shown that this device has the potential of delivering more than 1 mW of power at frequencies approaching 1 THz. [ABSTRACT FROM AUTHOR]

Abstract: The deterioration of the sensitivity of amorphous silicon strip photo detectors (‘ALMY’ sensors) under long-term illumination has been studied with collimated laser beams of different wavelengths and intensities. The high position sensitivity of the ALMY sensors allows for the precise localization of the illumination point and for monitoring of the local sensitivity degradation with respect to the rest of the non-illuminated sensor area. [Copyright &y& Elsevier]

A concept for single optical photon detection promises high quantum efficiency and large area sensitivity while restricting the avalanche region to a very narrow ("point-like") region of the device. This is accomplished by combining the principle of drift diode with an avalanche structure situated close by the electron collection electrode on the wafer surface opposite to the large area radiation entrance window placed on the fully depleted bulk. Extensive simulations demonstrate the validity of this concept. [ABSTRACT FROM AUTHOR]

A simple technique for detecting adjustable contrast in a visual scene is presented. The circuit elements can be used to detect contrast in any array of sensors or processing elements where spatial relationships among neighboring elements define contrast or the presence of an edge. This technique eliminates the need for a differential pair, thereby allowing more than two inputs to be compared for contrast in a single processing step. The circuit elements first smooth erroneous edges in the array through the use of a resistive network, then, the mean (scaled by an adjustable amount) of a pixel and its neighbors is compared to the harmonic mean of the same pixels to detect the presence of contrast within the pixel neighborhood. Comparison between the mean and harmonic mean allows the detection of contrast to be scale-invariant as long as the transistors remain in subthreshold operation. This circuit offers the massively parallel processing inherent to focal plane processing within an 18% fill factor in a 2 μm process, 6.8 μW typical power dissipation per element, and 0.67 ms response time at low power subthreshold operation. Results for a proof of concept, 8×8 array of pixels with light inputs, as well as a purely electronic input, 4×4 array are presented. [ABSTRACT FROM AUTHOR]

A fully integrable avalanche photodiode fabricated in a 0.35- \(\mu \) m standard high-voltage CMOS process is presented. The device achieves a high unamplified responsivity ( \(M=1\) ) of 0.41 A/W and a maximum responsivity ( \(M=6.6 \,{\cdot }\, 1 0^{4}\) ) of \(2.7 \,{\cdot }\, 10^{4}\) A/W for 5-nW optical power using a 670-nm laser source. The maximum bandwidth of 850 MHz was measured at 500-nW and 5- \(\mu \) W optical power which results in a responsivity bandwidth product of 17.4-GHz \(\,\cdot \,\) A/W for a gain of \({M=50}\) . [ABSTRACT FROM AUTHOR]

The barrel-Time-of-Flight detector is one of the outer layers of the multi-layer design of the PANDA target spectrometer. PANDA, which is being built at the FAIR facility, will use cooled antiprotons on a fixed Hydrogen or nuclei target, to study broad topics in hadron physics. The detector is designed to achieve a time resolution below 100 ps and provides the interaction times of events as well as the particle ID. The B-TOF is designed with a minimal material budget in mind mainly consisting of 5 mm thin plastic scintillator tiles read out by a serial connection of 4 SiPMs. The signal transmission is embedded in large 16 layer PCB in micro strip lines. We will first review the detector concept which is described in the TDR then some more recent developments, with a study of different PCB layouts for signal transmission, the readout with the TOFPET2 ASIC and its performance and presenting the results of a study on the influence of the scintillator thickness on the time resolution. [ABSTRACT FROM AUTHOR]

This paper presents a monolithic avalanche diode array designed in a commercial AMS 350 nm high-voltage CMOS (HV-CMOS) process. This monolithic detector comprises a single photon avalanche diode (SPAD), active quenching circuit and readout electronics. The SPAD consists of a p+ diffusion/n-well junction surrounded by a shallow p-well acting as a guard ring to prevent edge breakdown. The monolithic detector has a matrix of 20 × 15 pixels. The size of one SPAD pixel is 38 × 92 μ m 2. One pixel defined as SPAD and readout electronics has a total size of 115 × 111 μ m 2 with a fill factor = 24.3% and a chip size of about 2.8 × 2.6 mm2. [ABSTRACT FROM AUTHOR]

The paper describes various multi-channel ASICs designed by OMEGA laboratory and WEEROC company to readout SiPM or MPPC-based detectors used in particle physics or astrophysics experiments. [ABSTRACT FROM AUTHOR]

The CuO doped carbon thin films were produced by using electrochemical deposition and the surface characteristics of the photodiodes were investigated using the scanning electron microscopy and infrared (IR) spectroscopy. Illumination behaviours and current – voltage (I–V) characteristics were assessed. Diodes show rectifying characteristics, where reverse current at backward bias region showed increasing characteristics with increasing illumination intensities. I–V characteristics curves were used to calculate the ideality factor (n) and barrier height (Φ B); the average ideality factor and barrier height were found as 3.74 and 0.51 eV, respectively. Moreover, capacitance – voltage (C–V) and conductance – voltage (G - V) curves were assessed. Capacitance values showed a decreasing trend with increasing frequency. C adj and G adj characteristics were evaluated and the density of interface states (D it) and series resistance (R s) were calculated using C–V and G - V curves. Detailed investigation of CuO doped amorphous carbon photodiodes (CuO-a:C) revealed that photodiodes exhibited quite good solar sensitive and photoresponsive properties. Overall performance of the photodiodes indicates that CuO-a:C diodes have great potential to be used as a photodetector in optoelectronic devices and their applications. • CuO doped carbon photodiodes were produced. • Structural properties were chacaterized. • Surface properties were characterized. • I–V, I - t and C–V chracterizations were performed. • D it and Rs values were calculated. [ABSTRACT FROM AUTHOR]

The Barrel-Time-of-Flight detector is one of the outer layers in the multi-layer design of the P ̄ anda target spectrometer, covering a polar angle region of 22 ° < θ l a b < 150 °. P ̄ anda , which is being built at the FAIR facility, will use cooled antiprotons on a Hydrogen or nuclei target, to study a variety of topics in hadron physics. The detector is a scintillating tile hodoscope with an SiPM readout. A single unit consists of a 90 × 30 × 5 mm 3 fast plastic scintillator tile and 3 × 3 mm 2 SiPM photosensors on both ends. Four SiPMs are connected in series to overcome the limited sensor size of a single SiPM sensor and to improve the time resolution drastically (100 ps to 50 ps). While the P ̄ anda experiment is equipped with DIRC detectors for PID of faster particles, the Barrel TOF complements the setup by providing additional PID information with a π /K separation of 4 sigma up to the Cherenkov threshold. [ABSTRACT FROM AUTHOR]