The performance of three types of InGaAs/InP avalanche photodiodes is investigated for photon counting at 1550 nm in the temperature range of thermoelectric cooling. The best one yields a dark count probability of $% 2.8\cdot 10^{-5}$ per... more
The performance of three types of InGaAs/InP avalanche photodiodes is investigated for photon counting at 1550 nm in the temperature range of thermoelectric cooling. The best one yields a dark count probability of $% 2.8\cdot 10^{-5}$ per gate (2.4 ns) at a detection efficiency of 10% and a temperature of -60C. The afterpulse probability and the timing jitter are also studied. The results obtained are compared with those of other papers and applied to the simulation of a quantum key distribution system. An error rate of 10% would be obtained after 54 kilometers.
The development of a three-electrode trigatron gap with the trigger electrode inside the main electrode is discussed in this paper. Two models of the operation mechanism are proposed to explain the breakdown in the trigatron gap. In... more
The development of a three-electrode trigatron gap with the trigger electrode inside the main electrode is discussed in this paper. Two models of the operation mechanism are proposed to explain the breakdown in the trigatron gap. In addition, a mathematical model was proposed to calculate the breakdown time based on the theoretical analysis. The influence of different parameters on the breakdown time is discussed. Some characteristics in dry air have been experimentally determined such as the influence of the air pressure and the influence of the undervoltage ratio on the spark gap operation. The experimental results show that the operating voltage range between 0.5 and 0.7 might be reasonable. Then, the experimental results and analysis demonstrate that there are three regions divided by two inflection points, and the corresponding values of the undervoltage ratio are threshold values presenting different breakdown processes.
We present a single-photon avalanche diode (SPAD) with a wide spectral range fabricated in an advanced 180 nm CMOS process. The realized SPAD achieves 20 % photon detection probability (PDP) for wavelengths ranging from 440 nm to 820 nm... more
We present a single-photon avalanche diode (SPAD) with a wide spectral range fabricated in an advanced 180 nm CMOS process. The realized SPAD achieves 20 % photon detection probability (PDP) for wavelengths ranging from 440 nm to 820 nm at an excess bias of 4 V, with 30 % PDP at wavelengths from 520 nm to 720 nm. Dark count rates (DCR) are at most 5 kHz, which is 30 Hz/μm2, at an excess bias of 4V when we measure 10 μm diameter active area structure. Afterpulsing probability, timing jitter, and temperature effects on DCR are also presented.
Single-molecule Förster resonance energy transfer (smFRET) is a powerful tool for extracting distance information between two fluorophores (a donor and acceptor dye) on a nanometer scale. This method is commonly used to monitor binding... more
Single-molecule Förster resonance energy transfer (smFRET) is a powerful tool for extracting distance information between two fluorophores (a donor and acceptor dye) on a nanometer scale. This method is commonly used to monitor binding interactions or intra- and intermolecular conformations in biomolecules freely diffusing through a focal volume or immobilized on a surface. The diffusing geometry has the advantage to not interfere with the molecules and to give access to fast time scales. However, separating photon bursts from individual molecules requires low sample concentrations. This results in long acquisition time (several minutes to an hour) to obtain sufficient statistics. It also prevents studying dynamic phenomena happening on time scales larger than the burst duration and smaller than the acquisition time. Parallelization of acquisition overcomes this limit by increasing the acquisition rate using the same low concentrations required for individual molecule burst identification. In this work we present a new two-color smFRET approach using multispot excitation and detection. The donor excitation pattern is composed of 4 spots arranged in a linear pattern. The fluorescent emission of donor and acceptor dyes is then collected and refocused on two separate areas of a custom 8-pixel SPAD array. We report smFRET measurements performed on various DNA samples synthesized with various distances between the donor and acceptor fluorophores. We demonstrate that our approach provides identical FRET efficiency values to a conventional single-spot acquisition approach, but with a reduced acquisition time. Our work thus opens the way to high-throughput smFRET analysis on freely diffusing molecules.
Recent experimental work on semiconductor-based harmonically mode-locked lasers geared toward low noise applications is reviewed. Active, harmonic mode-locking of semiconductor-based lasers has proven to be an excellent way to generate 10... more
Recent experimental work on semiconductor-based harmonically mode-locked lasers geared toward low noise applications is reviewed. Active, harmonic mode-locking of semiconductor-based lasers has proven to be an excellent way to generate 10 GHz repetition rate pulse trains with pulse-to-pulse timing jitter of only a few femtoseconds without requiring active feedback stabilization. This level of timing jitter is achieved in long fiberized ring cavities and relies upon such factors as low noise rf sources as mode-lockers, high optical power, intracavity dispersion management and intracavity phase modulation. When a high finesse etalon is placed within the optical cavity, semiconductor-based harmonically mode-locked lasers can be used as optical frequency comb sources with 10 GHz mode spacing. When active mode-locking is replaced with regenerative mode-locking, a completely self-contained comb source is created, referenced to the intracavity etalon.
This work presents the results of short circuit tests recently conducted on PFMA1 [1], a 150 kJ Mather-type Plasma Focus [2] designed to run at a repetition rate of 1 Hz for two hours at a time. PFMA1 is operated at 30 kV, with a 350 F... more
This work presents the results of short circuit tests recently conducted on PFMA1 [1], a 150 kJ Mather-type Plasma Focus [2] designed to run at a repetition rate of 1 Hz for two hours at a time. PFMA1 is operated at 30 kV, with a 350 F capacitor bank of 32 parallel capacitors. It is equipped with a custom designed
In recent years a growing number of applications demands always better timing resolution for Single Photon Avalanche Diodes. The challenge is pursuing the improved timing resolution without impairing the other device characteristics such... more
In recent years a growing number of applications demands always better timing resolution for Single Photon Avalanche Diodes. The challenge is pursuing the improved timing resolution without impairing the other device characteristics such as quantum efficiency and dark counts. This task requires a clear understanding of the physical mechanisms necessary to drive the device engineering process. Past studies state that in Si-SPADs the avalanche injection position statistics is the main contribution to the photon-timing jitter. However, in recent re-engineered devices, this assumption is questioned. For the purpose of assessing for good this contribution we developed an experimental setup in order to characterize the photontiming jitter as a function of the injection position by means of TCSPC measurements with a laser focused on the device active area. Results confirmed not only that the injection position is not the main contribution to the photon-timing jitter but also evidenced a radial dependence never observed before. Furthermore we found a relation between the photon-timing jitter and the specific resistance of the devices. To characterize the resistances we studied the avalanche current density distribution in the device active area by imaging the photo-luminescence due to hot-carrier emission.
This paper describes a new technique which allows measuring time-varying noise of (analog-to-digital) A/D converters more accurately than may be possible with traditional test equipment. A previous work demonstrated that the effects of... more
This paper describes a new technique which allows measuring time-varying noise of (analog-to-digital) A/D converters more accurately than may be possible with traditional test equipment. A previous work demonstrated that the effects of the quantization and nonlinearities on the jitter measurement may be overcome by measuring the noise distribution function. This paper presents a dual-channel technique based on the measurement
Rapid Single Flux Quantum (RSFQ) logic is well-known for its ultra-high switching speed and extremely low power consumption. In this paper, we present two original experiments to demonstrate that it's also a reliable technology and its... more
Rapid Single Flux Quantum (RSFQ) logic is well-known for its ultra-high switching speed and extremely low power consumption. In this paper, we present two original experiments to demonstrate that it's also a reliable technology and its reliability is sufficient even for such a large-scale system as a proposed petaflops-scale HTMT computer. We have measured the bit error rate (BER) for a circular register of inverters representing a critical path of a 64-bit integer adder, and timing jitter in a 200 Josephson junction (JJ) long transmission line, imitating a branch of a clock distribution tree, both being important and representative building blocks of the HTMT computer. For the adder critical path we have demonstrated the highest clock frequency of 17 GHz, latency of 860 ps and BER of 10-19 for 3.5 μm technology of HYPRES, Inc. The value of timing jitter was 200 fs per JJ for 1.5 μm technology of TRW, Inc. These figures are in good agreement with our simulations