Silicon Avalanche Photodiode Research Articles

Tunable upconversion photon detector

We introduce a simple approach for a tunable upconversion detector. This scheme is relevant for both single photon detection or anywhere where low light levels at telecom wavelengths need to be detected with a high degree of temporal resolution or where high count rates are desired. A system combining a periodically poled lithium niobate waveguide for the nonlinear wavelength conversion and a low jitter silicon avalanche photodiode is used in conjunction with a tunable pump source. We report more than a tenfold increase in the detectable bandwidth using this tuning scheme.

Enhanced red and near infrared detection in flow cytometry using avalanche photodiodes

Polychromatic flow cytometry enables detailed identification of cell phenotype using multiple fluorescent parameters. The photomultiplier tubes (PMTs) used to detect fluorescence in current instruments limit the sensitivity in the long wavelength spectral range. We demonstrate the flow cytometric applications of silicon avalanche photodiodes (APDs), which have improved red sensitivity and a working fluorescence detection range beyond 1,000 nm. A comparison of the wavelength-dependent performance of the APD and PMT was carried out using pulsed light-emitting diode sources, calibrated test beads, and biological samples. A breadboard flow cytometer test bench was constructed to compare the performance of PMTs and APD detectors. The APD used an additional amplifier stage to match the internal gain of the PMT. The resolution of the APD and PMT was compared for flow cytometry applications using a pulsed light-emitting diode source over the 500-1060 nm spectral range. These measurements showed the relative changes in the signal-to-noise performance of the APD and PMT over a broad spectral range. Both the APD and PMTs were used to measure the signal-to-noise response for a set of six peak calibration beads over the 530-800 nm wavelength range. CD4-positive cells labeled with antibody-conjugated phycoerythrin or 800 nm quantum dots were identified by simultaneous detection using the APD and the PMT. The ratios of the intensities of the CD4- and CD4+ populations were found to be similar for both detectors in the visible wavelengths, but only the APD was able to separate these populations at wavelengths above 800 nm. These measurements illustrate the differences in APD and PMT performance at different wavelengths and signal intensity levels. While the APD and PMT show similar signal-to-noise performance in the visible spectral range, the dark noise of the APD detector reduces the sensitivity at low signal levels. At wavelengths longer than 650 nm, the high quantum efficiency of the APD contributes to better signal-to-noise performance. The APD detector provides enhanced performance in the long wavelength region and may be used to extend the working range of the flow cytometer beyond 1,000 nm.

Avalanche multiplication in amorphous selenium and its utilization in imaging

Amorphous selenium (a-Se) is a well known photoconductor that is currently used in X-ray image detectors and HARP video tubes. Recent advances have made it practical to operate a-Se at extremely high electric fields F, where avalanche multiplication occurs. At sufficiently high fields, the effective quantum efficiency (η∗) (or the overall yield) of the photoconductor can be increased several orders of magnitude above unity and renders avalanche a-Se photoconductors a prospective alternative to vacuum photomultiplier tubes (PMTs) and silicon avalanche photodiodes (APDs). In this work we report our study of η∗ and charge transport for a-Se avalanche photoconductors with different photoconductive layer thicknesses in wide range of F. Our study shows that a-Se is able to produce a gain of ∼1000 with a rise time of ∼1ns, both of which clearly point to the potential (or realized) use of this photoconductor in a variety of imaging applications. Furthermore, our work supports the validity of the so-called modified Lucky drift model to explain the nature of impact ionization and avalanche in this material.

Feasibility study of free-Space quantum key distribution in the mid-infrared

We report on a feasibility study of a free-space Quantum Key Distribution setup operating at a mid-infrared wavelength. Alice sends polarization-coded pseudo-single photons from a Quantum Cascade Laser at 4.6 $\mu$m to Bob, who uses a nonlinear crystal and a Silicon Avalanche Photodiode to perform the detection via Sum Frequency Generation. Theoretical predictions, based on a proof-of-principle experiment, show that, under certain foggy atmospheric conditions, the proposed system is barely affected, whereas other systems operating at standard near-infrared wavelengths would simply not work at all.

The production of radiation tolerant vacuum phototriodes and their HV filters for the Compact Muon Solenoid endcap electromagnetic calorimeter

Particle detectors which will operate at the Large Hadron Collider face unprecedented challenges in both the number of active detector elements and in operating without maintenance in a high radiation environment for many years. In the Compact Muon Solenoid (CMS) detector the scintillating crystal electromagnetic calorimeter uses vacuum photodetectors in the endcap where the lifetime neutron and hadron fluence is too high for the silicon avalanche photodiodes used in the barrel. Over 15000 radiation tolerant vacuum phototriodes (VPT) have been now been produced by industry for the endcap calorimeter. The VPT have to operate in an environment which has both a significant lifetime dose (up to 50 kGy) from electrons and gamma rays and a high neutron fluence (up to nearly 10 15 n.cm −2 for E > 100 keV). This paper discusses the steps taken during both the development and production of the VPT to ensure that the response to the scintillation light from the lead tungstate scintillator will not be significantly degraded during the operational lifetime of the experiment. Data from the quality assurance procedures and radiation induced degradation of complete VPT devices is presented. Other components of the endcap calorimeter are also exposed to a similarly intense radiation field. The quality assurance procedure used to select the passive components (resistors and capacitors) used in the high-voltage filter cards is described.

Scintillator strip detector with MRS APD readout for the Super BELLE

We report the results of the tests of 150 detectors consisting of a scintillator strip and a wavelength-shifting fiber, read out by a metal-resistor silicon avalanche photodiode operating in the Geiger mode (MRS APD). Using weak flashes of a Light Emitting Diode we clearly see individual photoelectrons in the amplitude spectra of all MRS APDs. Based on these spectra we determine the gain, the relative quantum efficiency and the cross-talk of the MRS APDs. Using cosmic rays we measure the light yield, the efficiency, the response uniformity and the time resolution of the strips. The first results of the radiation hardness study using a proton beam are presented. The strips are to be installed at the Belle detector as a prototype of the future muon system for the Super B-factory.

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.

A discrete model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode

A new discrete theoretical model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode is developed. It is shown that the spreading resistance in the substrate profoundly affects both the amplitude of a single-photon electrical pulse and the possibility of attaining the steady-state form of the avalanche breakdown excluding the Geiger mode of the photodiode’s operation. The model is employed to interpret the experimental data obtained using test single-photon cells of avalanche photodiodes fabricated on the basis of the 0.25-μm silicon technology with the use of deep implantation to form the region of avalanche multiplication for the charge carriers. Excellent functional properties of the studied type of the single-photon (Geiger) cell are noted. A typical amplitude characteristic of the cell for optical radiation with the wavelength λ = 0.56 μm in the irradiance range of 10−3–102 lx is presented; this characteristic indicates that the quantum efficiency of photoconversion is extremely high.

Observation of the lunar topography by the laser altimeter LALT on board Japanese lunar explorer SELENE

The SELENE Laser Altimeter (LALT) is designed to map the Moon’s topography and will be launched in summer 2007. LALT incorporates Q-switched Cr doped Nd:YAG laser (1064 nm) with an output energy of 100 mJ and 1 Hz repetition frequency for about one year mission period. The laser pulse travels to the Moon’s surface and reflections from the surface are detected by a silicon avalanche photo-diode. The ranging distance is 50–150 km with about 5 m accuracy. Several corrections for accurate ranging data are investigated. The flight hardware has been qualified and passed all the integration tests. A principal goal of the LALT instrument is to obtain a much more detailed lunar topographic map which is superior in global coverage, measurement accuracy and number of data points to previous observations and models. The overall science objectives of LALT are (1) determination of lunar global figure, (2) internal structure and surface processes, (3) exploration of the lunar pole regions, and (4) reduction of lunar occultation data.

Silicon Geiger mode avalanche photodiodes

In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes (GMAP) fabricated by silicon standard planar technology. Low dark count rates, negligible afterpulsing effects, good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields, as telecommunications and nuclear medical imaging.

Direct photon-counting scintillation detector readout using an SSPM

Gamma-ray detector technologies, capable of providing adequate energy information, use photomultiplier tubes (PMTs) or silicon avalanche photodiodes to detect the light pulse from a scintillation crystal. A new approach to detect the light from scintillation materials is to use an array of small photon counting detectors, or a “detector-on-a-chip” based on a novel “Solid-state Photomultiplier” (SSPM) concept. A CMOS SSPM coupled to a scintillation crystal uses an array of CMOS Geiger photodiode (GPD) pixels to collect light and produce a signal proportional to the energy of the radiation. Each pixel acts as a binary photon detector, but the summed output is an analog representation of the total photon intensity. We have successfully fabricated arrays of GPD pixels in a CMOS environment, which makes possible the production of miniaturized arrays integrated with the detector electronics in a small silicon chip. This detector technology allows for a substantial cost reduction while preserving the energy resolution needed for radiological measurements. In this work, we compare designs for the SSPM detector. One pixel design achieves maximum detection efficiency (DE) for 632-nm photons approaching 30% with a room temperature dark count rate (DCR) of less than 1 kHz for a 30-μm-diameter pixel. We characterize after pulsing and optical cross talk and discuss their effects on the performance of the SSPM. For 30-μm diameter, passively quenched CMOS GPD pixels, modeling suggests that a pixel spacing of approximately 90 μm optimizes the SSPM performance with respect to DE and cross talk.

Photon counting timing uniformity–unique feature of the silicon avalanche photodiodes K14

The paper reports on detailed tests of active area uniformity of three different single photon avalanche detectors (SPADs). Relative sensitivity, timing jitter, and relative detection delay have been measured for a series of points across the detection area; the resulting spatial profiles have been plotted and analysed. Unique features have been found in the case of silicon-based K14 SPADs: their active area is extremely uniform, especially with respect to the detection delay, in contrast to the remaining two SPADs, which exhibit significant fluctuations of the delay. The perfect uniformity of the K14 SPADs enables the detector to maintain its high temporal resolution of 40 ps FWHM even for large detection areas of 200 µm diameter.

Observation of Nuclear Excitation of 19F by Synchrotron Radiation

Fluorine (F) has the lowest atomic number and atomic weight of the members of the halogen family. Only the isotope with atomic weight 19 is stable. Fluorine is the most electronegative element and the most chemically energetic of the nonmetallic elements. The reactivity of the element fluorine is so high that chemical processes take place at about 500 C; a good sample is the reaction of fluorine and uranium dioxide leading to the production of uranium hexafluoride. F nuclei with a nuclear spin of 1/2 and a 100% natural abundance presents favourable nuclear magnetic resonance (NMR) characteristics. The application of the F NMR to metabolic studies of fluoropyrimidine drugs in clinical use; such as the anticancer drug 5-fluorouracil in human biofluids, have emphasized the usefulness of the technique for the quantitative detection of novel and unexpected metabolites. The use of synchrotron radiation as a source for nuclear resonant scattering experiments has led to many new studies of physical problems such as nuclear Bragg scattering, nuclear forward scattering, and nuclear inelastic scattering that can not be investigated satisfactorily with radioactive sources in the conventional Mossbauer spectroscopy. The unique characteristics of synchrotron radiation are the collimation, the polarization, the pulsed nature, and the high brilliance. The discrimination between the scattering from electrons and the scattering from nuclei has been solved by taking advantage of the instantaneous character of the atomic prompt nonresonant scattering compared with the relatively long lifetime of the nuclear excited states. Avalanche photodiodes allow the observation of delayed events after a few nanoseconds, even in the presence of a huge prompt background. High-resolution monochromators allow us to select energy and tune by energy bands of the order of 1meV width. The third generation synchrotron radiation storage rings, ESRF, APS, and SPring-8, were constructed and equipped with beamlines dedicated to nuclear resonance scattering experiments. The nuclear resonance scattering of synchrotron radiation has been experimentally observed in various nuclei, i.e., Ta (6.21 keV), Tm (8.41 keV), Kr (9.4 keV), Fe (14.41 keV), Eu (21.54 keV), Sm (22.49 keV), Sn (23.88 keV), Dy (25.65 keV), K (29.83 keV), and Sb (37.13 keV). The use of parentless Mossbauer isotopes, e.g., K, has become a reality. Other isotopes such Ni (67.41 keV), Au (77.35 keV), and Gd (79.51 keV) with high-transition energies above 50 keV have been excited and their fluorescence decay has been detected. Excitation energies above 100 keV of nuclei have not yet been reported. In this paper, we report the observation of the F nuclear excitation (109.89 keV) by the use of synchrotron radiation. The experiment was performed at the undulator beamline (BL09XU) at SPring-8. The undulator gap was tuned such that the seventeenth harmonic of the undulator radiation corresponds to the F resonance energy for the transition from the 1=2þ ground state to the 109.89 keV 1=2 excited state. Figure 1 shows our optics and detecting system for the F nuclear excitation and deexcitation. The double-crystal monochromator operates with diamond (333) reflection, while the X-rays from diamond (111) reflection were eliminated using a Ge(111) crystal. X-ray pulses with a time width of 50 ps [full width of half maximum (FWHM)] excited the F nuclei, using a several-bunch operation of the storage ring. The system with a silicon avalanche photodiode (APD) recorded the time spectra of -rays emitted from the 109.89 keV 1=2 state of the F nuclei. The details of the fast counting system with the APD detector were reported by Kishimoto. The APD has a 4 2 array of 3 5 0:15mm pixels and a depletion layer 150 mm thick. An efficiency of 0.6% at 100 keV was estimated, corresponding to absorption in 150-mm-thick silicon. The time resolution is 1.3 ns (FWHM). The APD was mounted under the sample. We used a fast amplifier to obtain fast negative pulses of the APD outputs, which were processed with a constant fraction discriminator (CFD). The outputs from the CFD were used as the start signals into a time-toamplitude converter (TAC). The veto signals into the CFD and the stop signals into the TAC were supplied through some divider and delay modules by 508.58MHz signals from the accelerator. The time spectra were recorded by the TAC and a multichannel analyzer. The prompt radiation outputs were inhibited during the first 5 ns by veto signals. Delayed signals started to be detected after the first 5 ns of the prompt radiation. For the study of the first excited level of the F nuclei, a lithium fluoride sample (LiF, 20 20 10mm) was used as a scattering sample. Figure 2 shows the time dependences of

Enhancing near-infrared avalanche photodiode performance by femtosecond laser microstructuring

A processing technique using femtosecond laser pulses to microstructure the surface of a silicon avalanche photodiode (APD) has been used to enhance its near-infrared (near-IR) response. Experiments were performed on a series of APDs and APD arrays using various structuring parameters and poststructuring annealing sequences. Following thermal annealing, we were able to fabricate APD arrays with quantum efficiencies as high as 58% at 1064 nm without degradation of their noise or gain performance. Experimental results provided evidence to suggest that the improvement in charge collection is a result of increased absorption in the near-IR.

External Synchronization of 160-GHz Optical Beat Signal by Optical Phase-Locked Loop Technique

We have synchronized a 160-GHz optical beat signal with a 40-GHz reference optical pulse train by using an optical phase-locked loop (OPLL). The OPLL consists of an optical beat signal source, comprising a pair of three-electrode distributed feedback laser diodes that works as a voltage controlled oscillator, and an all-optical phase detector based on the two-photon absorption in a silicon avalanche photodiode. Phase-locking operation is confirmed through phase-error measurement and cross-correlation trace measurement. The residual timing jitter of the 160-GHz optical beat signal relative to the reference pulse train, in the bandwidth of 80 MHz, is measured to be as small as 126 fs

Signal fluctuation in neutron-irradiated silicon Avalanche Photodiodes

Light from PbWO 4 crystals in the barrel part of the CMS electromagnetic calorimeter will be detected by Avalanche Photodiodes (APDs). The crystal-APD system has to operate reliably in a high radiation environment. In the present paper, APD signal variation with wavelength and gain fluctuations for PbWO 4 scintillation light was investigated as a function of the neutron fluence. Calculations were made with a single-particle Monte Carlo simulation technique. The results show that the neutron fluence has an influence on the APD signal during 10 years CMS operation.

Avalanche photodiodes for electromagnetic calorimeters

Hamamatsu S8148 silicon avalanche photodiode (APD) working in proportional mode has been chosen as readout device for the PbWO 4 crystals in the barrel of the CMS electromagnetic calorimeter (ECAL). High hadron fluences strongly affect the main parameters of both the scintillation crystals and the silicon detectors. In this work, we offer a new zinc sulfide–silicon (ZnS–Si) isotype heterojunction APD structure that is able to operate in high-radiation levels. A Monte Carlo simulation code has been performed in order to compare the Hamamatsu S8148 and the ZnS–Si APD structures for the photons emitting from PbWO 4 crystal during 10 years of CMS operation. Based on this work, the performance of these two APD structures has been investigated.

A Reexamination of Deep Diffused Silicon Avalanche Photodiode Gain and Quantum Efficiency

Traditionally the measured gain of an avalanche photodiode (APD) has been considered the product of two parameters. The electron multiplication process being one and the quantum efficiency (QE) the other. The multiplication process is often considered wavelength dependent and the QE being bias independent. We propose a new examination of these related parameters where the APD gain is considered intrinsic, defined as being the amount of electron multiplication each photoelectron undergoes based only on the applied bias and is thus independent of the incident photon wavelength, and where the QE, which can be defined as the number of generated photoelectrons per number of incident photons, is considered intrinsic being a function of not only wavelength, but also bias. This is a more logical, and physically real, perspective of APD behavior. We introduce a technique to measure the intrinsic gain and the intrinsic QE of deep diffused silicon APDs. Once the intrinsic gain vs. bias of the APD is measured, it becomes possible to use this measurement as an absolute parameter. With the intrinsic gain known, we show how the intrinsic QE of an APD, for a given wavelength, changes as a function of bias. We show that when the APD is operated from the low to high gain regime, light at 400 nm to 800 nm experiences an increase in QE. These fundamental, dynamic and operational properties of APDs are critical when considering the wavelength(s) that are of interest for a given application

Two-photon absorption for optical clock recovery in OTDM networks

The authors describe the design and performance of an ultrafast optical clock recovery system that is based on two-photon absorption (TPA) in a silicon avalanche photodiode. Unlike many other optical clock recovery techniques, the system is shown to be polarization insensitive, broadband, low jitter, and scalable to high data rates. Moreover, the system is simple, economical, and suitable for integration with silicon electronics. Successful operation of the system is reported for speeds up to 80 Gb/s and transmission distances up to 840 km using a recirculating loop. The authors introduce a new dithering detection scheme that dramatically improves the dynamic range and decreases polarization and wavelength dependence, without introducing an additional timing jitter. The system achieves a dynamic range of 10 dB and optical bandwidth exceeding 35 nm

Rationale for the Combination of Nuclear Medicine with Magnetic Resonance for Pre-clinical Imaging

Multi-modality combinations of SPECT/CT and PET/CT have proven to be highly successful in the clinic and small animal SPECT/CT and PET/CT are becoming the norm in the research and drug development setting. However, the use of ionizing radiation from a high-resolution CT scanner is undesirable in any setting and particularly in small animal imaging (SAI), in laboratory experiments where it can result in radiation doses of sufficient magnitude that the experimental results can be influenced by the organism's response to radiation. The alternative use of magnetic resonance (MR) would offer a high-resolution, non-ionizing method for anatomical imaging of laboratory animals. MR brings considerably more than its 3D anatomical capability, especially regarding the imaging of laboratory animals. Dynamic MR imaging techniques can facilitate studies of perfusion, oxygenation, and diffusion amongst others. Further, MR spectroscopy can provide images that can be related to the concentration of endogenous molecules in vivo. MR imaging of injected contrast agents extends MR into the domain of molecular imaging. In combination with nuclear medicine (NM) SPECT and PET modalities in small animal imaging, MR would facilitate studies of dynamic processes such as biodistribution, pharmacokinetics, and pharmacodynamics. However, the detectors for nearly all PET and SPECT systems are still based on vacuum tube technology, namely: photomultiplier tubes (PMT's) in which the signal is generated by transporting electrons over a substantial distance within an evacuated glass tube, making them inoperable in even small magnetic fields. Thus the combination of SPECT or PET with MR has not been practical until the recent availability of semiconductor detectors such as silicon avalanche photodiodes (APD's) for PET and CdZnTe (CZT) detectors for SPECT coupled with the availability of high-density low noise ASIC electronics to read out the semiconductor detectors. The strong advantage of these technologies over PMT's is their insensitivity to magnetic fields which makes their use in co-axial multi-modality nuclear medicine/magnetic resonance instrumentation possible.