Si APD Research Articles

New Crystal Photodiode Combination for Environmental Radiation Measurement

Here, a new design will be introduced to detect radiation in the environment with high efficiency. The designed structure consists of placing ZnS–Si APD and PIN photodiodes at the ends of conventional crystals such as NaI(Tl) and CsI(Tl). Since ZnS is transparent to photons with wavelengths between 340 and 10000 nm, photons coming from the crystals are absorbed directly in the depletion region and generate primary particles. With an increase in the number of generated primary particles, a stronger and cleaner signal is obtained. In the simulation work, the light generated by 30 keV–3 MeV gamma rays in the crystals was obtained using the Geant4 simulation code. The single-particle Monte Carlo technique was used to calculate the photodiode output signal for the crystal emission spectrum. The simulation results showed that the crystals and ZnS–Si photodiode structures formed a good combination. The high quantum efficiency and low excess noise factor make the ZnS–Si structure an excellent choice for scintillating light detection.

Single-photon ranging with hundred-micron accuracy

Single-photon detectors based on avalanche photodiodes and time-correlated single-photon counting technology are widely used in pulsed laser ranging. The ranging accuracy is one of the most important performances of laser ranging. In this work, a laser ranging method based on high-precision single-photon detector is developed to achieve laser ranging for non-cooperative targets with hundred-micron-level ranging accuracy. In the system, a low-time jitter Si APD single photon detector, picosecond pulsed laser and high-precision timing counter are used to reduce the time jitter of the ranging system, and a reference position is added to suppress the influence of delay drift of the system. And a laser interferometer system with a ranging resolution of 1 nm and an accuracy of 0.5 ppm is used to calibrate the distance of each movement of the ranging target. The photon flight time accuracy of 0.5 ps is achieved while the integral time ≥ 3 s. The ranging accuracy of 65 μm@RMS is realized, while the target is 2 m away. This work is one of the highest levels of pulsed time-of-flight ranging, and provides an effective technology for high-precision ranging and imaging of long-range non-cooperative targets.

Design of Thomson scattering diagnostics for the Divertor Tokamak Test (DTT) facility

In the Divertor Tokamak Test (DTT) facility two Thomson scattering (TS) systems are under design for the measurements of Te and ne in the core plasma region and in the divertor respectively. The divertor TS system under study is a conventional TS system based on a Nd:YAG laser source, a fiber optic based light collection system and a set of filter polychromators equipped with Si APD detectors. The laser beam and the collection optics share an aperture between adjacent cassettes of the lower divertor and the scattering signal is collected from a set of scattering volumes close to one of the divertor legs by a collection optics system located under the divertor dome and is carried to the polychromators by fiber optic bundles. The filter polychromators are designed to measure Te as low as 1 eV . Measurements with a spatial resolution of 10 mm are possible, with accuracy limited by the plasma ne and the background light. For the core TS system, two options are under consideration: a conventional system, similar to that designed for the ITER core TS, in which Te and ne are measured along a large fraction of a laser beam crossing the plasma near the equatorial plane and the detection system is again based on fiber optic coupled filter polychromators. The spatial resolution is 5 cm in the central region and 1 cm at the plasma edge. Alternatively a TS system based on the LIDAR concept, previously implemented in JET, is under consideration. Recent advancements in laser and detector technology allow achieving a spatial resolution similar to that of a conventional system, but with a simpler and reliable experimental set-up and possibly at a lower cost.

Sensitive Infrared Photon Counting Detection by Nondegenerate Two-Photon Absorption in Si APD

We report on the sensitive detection of photons at broadband infrared wavelengths based on the nondegenerate two-photon absorption in the Si avalanche photodiodes. The detected 1700~1850 nm infrared photon energy is lower than Si band gap and the energy difference is complemented by a high intensity pump laser field at 1550 nm. It is thus possible to capitalize on the low noise property of large band gap materials for detecting low energy photons. And the linear intensity response of the detector to the incident infrared photons was observed when the power of pump laser was about $12.42\mu $ W, indicating the dominance of nondegenerate two-photon absorption in the infrared photon detection. An enhancement factor of 20 was observed for the incident signal photon numbers of $\sim 0.14\times 10^{\mathbf {6}}$ photons per pulse. We offer an alternative to sensitive detection of infrared light. This may also provide new ideas for broadband infrared photon detection in different applications such as optical comb laser ranging, infrared bio-image and so forth.

Multiple Quantum Barrier Nano-avalanche Photodiodes - Part II: Excess Noise Characteristics

Background: Excess noise characteristics of Multiple Quantum Barrier (MQB) nanoscale avalanche photodiodes (APDs) based on Si~3C-SiC heterostructures have been studied in this part of the paper. The multiplication gain and Excess Noise Factor (ENF) of the MQB APDs have been calculated by varying the number of Quantum Barriers (QBs). Methods: The numerically calculated ENF values of MQB APDs have been compared with the ENF of Si flat conventional APDs of similar dimensions and it is observed that the use of QBs leads to significant reduction in ENF of the APDs under similar biasing and illumination conditions. Results: The enhanced ratio of hole to electron ionization rates in MQB structures as compared to the bulk Si APD structure has been found to be the primary cause of improvement in the noise performance of the MQB nano-APDs. Conclusion: Finally, the numerically calculated ENF of Si flat APD has been compared with the experimentally measured ENF of a commercially available Si APD and those are found to be in good agreement; this comparison validates the simulation methodology adopted by the authors in this paper.

Evaluating the Radiation Effects on the Characteristics of the Silicon Avalanche Photodiode with Protons

Silicon avalanche photodiode (Si APD) plays important roles in high sensitive optical detecting applications, such as remote sensing, radiation detection and optical communication etc. However, in the space, the Si APD would unavoidably suffer radiation damage, which would degrade the Si APD performance, like dark current, responsivity and gain etc. Here, we report the results of Si APD radiation tests with protons to evaluate their radiation hardness properties and suitability for space missions. With this motivation, samples have been radiated using 50 MeV protons with maximum does 1E12 p(proton)/cm2 The test results show that the Si APD dark current increment is negligible when the radiation dose is below 1E11 p/cm2, ∼10 nA, satisfying most nanowatt level detecting applications. As the radiation dose further increases to 1E12 p/cm2, the Si APD breakdown voltage has a measureable decrement, which subsequently increases the dark current and gain. And through over two years’ in-orbit test, the Si APD dark current keeps below 1 nA, while the responsively is ∼4.9 A/W.

Характеристики кремниевого лавинного фотодиода для ближнего ИК-диапазона

Sensitivity in 400 – 1150 nm spectral range, dark current and dynamic characteristics have been tested of a developed silicon avalanche photodiode with an active diameter of 1.5 mm. Developed Si APD possesses: photosensitivity 80-85 A/W in 900 - 1010 nm spectral range, 1.5 nA dark current, rise and fall time less than 2.5 ns with a bias voltage of 350 v.

Noise Analysis of Trans-impedance Amplifier (TIA) in Variety Op Amp for use in Visible Light Communication (VLC) System

VLC is a complex system with lots of challenges in its implementation. One of its problems is noise that originated from internal and external sources (sunlight, artificial light, etc). Internal noise is originated from active components of analog front-end (AFE) circuit, which will be discussed in this paper, especially on the trans-impedance amplifier (TIA) domain. The noise characteristics of AFE circuit in VLC system has been analyzed using the variety of available commercial Op Amp and different types of the photodiode (Si, Si-PIN, Si APD). The approach of this research is based on analytical calculus and simulation using MATLAB®. The results of this research show that the main factor that affecting the noise is en, the feedback resistor (Rf), and junction capacitor in the photodiode (Cj). Besides that, the design concept of multi channel TIA (8 channel) using IC Op Amp, with consideration of pin number of each Op Amp, supply needs, the initial value of Rf, converter to 8-DIP and feedback capacitor (Cf) channel, also discussed in this paper.

ICESat/GLAS Altimetry Measurements: Received Signal Dynamic Range and Saturation Correction.

NASA's Ice, Cloud, and land Elevation Satellite (ICESat), which operated between 2003 and 2009, made the first satellite-based global lidar measurement of Earth's ice sheet elevations, sea-ice thickness and vegetation canopy structure. The primary instrument on ICESat was the Geoscience Laser Altimeter System (GLAS), which measured the distance from the spacecraft to Earth's surface via the roundtrip travel time of individual laser pulses. GLAS utilized pulsed lasers and a direct detection receiver consisting of a silicon avalanche photodiode (Si APD) and a waveform digitizer. Early in the mission, the peak power of the received signal from snow and ice surfaces was found to span a wider dynamic range than planned, often exceeding the linear dynamic range of the GLAS 1064-nm detector assembly. The resulting saturation of the receiver distorted the recorded signal and resulted in range biases as large as ~50 cm for ice and snow-covered surfaces. We developed a correction for this "saturation range bias" based on laboratory tests using a spare flight detector, and refined the correction by comparing GLAS elevation estimates to those derived from Global Positioning System (GPS) surveys over the calibration site at the salar de Uyuni, Bolivia. Applying the saturation correction largely eliminated the range bias due to receiver saturation for affected ICESat measurements over Uyuni and significantly reduced the discrepancies at orbit crossovers located on flat regions of the Antarctic ice sheet.

Enhanced solar-blind ultraviolet single-photon detection with a Geiger-mode silicon avalanche photodiode

Solar-blind ultraviolet detection is of great importance in astronomy and industrial and military applications. Here, we report enhanced solar-blind ultraviolet single-photon detection by a normal silicon avalanche photodiode (Si APD) single-photon detector with a specially designed photon-collecting device. By re-focusing the reflected photon from the Si chip surface on the detection area by the aluminum-coated hemisphere, the detection efficiency of the Si APD at 280 nm can be improved to 4.62%. This system has the potential for high-efficiency photon detection in the solar-blind ultraviolet regime with low noise.

Radiation tolerance of opto-electronic components proposed for space-based quantum key distribution

Plasma in low earth orbit can damage electronic components and potentially jeopardize scientific missions in space. Predicting the accumulated damage and understanding components’ radiation tolerance are important in mission planning. In this manuscript, we report on the observed radiation tolerance of single photon detectors and a liquid crystal polarization rotator. We conclude that an uncooled Si APD could continue to operate from more than a month up to beyond the lifetime of the satellite depending on the orbit. The liquid crystal polarization rotator was also unaffected by the exposed dosage.

A charge-integration readout circuit with a linear-mode silicon avalanche photodiode for a photon-number resolving detector

A charge-integration readout circuit for a photon-number resolving detector for visible or near-infrared wavelength is presented. In the scheme, photons are converted into electric carriers by a Si APD operating in the linear mode. To read the small number of photo-carriers generated by the Si APD, a charge-integration readout circuit is used. The entire circuit operates at 77 K. The main noise of the readout circuit is attributed to dielectric polarization noise, which is dominant at the operating temperature. The noise of the readout circuit was reduced to 3.0 electrons averaged by a period of 40 ms.

Synchronous single-photon counting using an Si avalanche photodiode at room temperature

We have successfully demonstrated photon counting using an Si APD at room temperature. A wide dynamic range of 43 dB has been achieved with the synchronous single-photon counting (SSPC) technique.

Reliability of Light Emitters and Detectors for Optical Fiber Communication Systems

Life test results on light emitters and detectors showed promisingly long lifetimes for short and long wavelength optical fiber communication systems. Data are presented on 0.85 μm AIGaAs LD's and LED's, Si APD's and p-i-n-PD's, 1.3 μm InGaAsP LD's and LED's, and Ge APD's and PD's. Degradation mechanisms and counteractions are also discussed.

2-bit 1 Gsample/s electrooptic guided-wave analog-to-digital converter

An electrooptic analog-to-digital converter which uses a pulsed GaAlAs diode laser for sampling, a LiNbO 3 Ti-indiffused-waveguide interferometric array for conversion, a Si APD, and a special 1 GHz Si integrated circuit for digital processing has been demonstrated at 1 Gsample/s. Individual bit channels of this 2-bit device have been tested by a beat-frequency technique with a 499.2 MHz test signal. This represents the highest frequency conversion of an analog waveform reported to date.

S/N performance of an AlGaAs laser preamplifier and a linear repeater system

Baseband signal-to-noise-ratio characteristics in an AlGaAs laser preamplifier and a linear repeater system were studied theoretically and experimentally. The AlGaAs laser preamplifier improved the minimum detectable power by 1.6 dB over the level achieved by direct detection with an Si APD. 37 dB regenerative repeater gain was experimentally obtained in the system with two optical repeaters at 100 Mbit/s data rate.