A complete module for single-photon counting and timing is demonstrated in a single chip. Features comparable with or better than commercially available macroscopic modules are obtained by integration of an active-quenching and active-reset circuit in complementary metal-oxide semiconductor technology together with a single-photon avalanche diode (SPAD). The integrated SPAD has a 12-microm-diam...

The first single-photon avalanche diode (SPAD) image sensor fully integrated on flexible substrate is reported. The design consists of an array of 1024 quenched pixels with CMOS readout and addressing circuitries. The flexible substrate was made compatible with sol-gel polymer, which will be used to imprint microlenses by quartz mold to improve fill factor. The SPAD pixel can operate both in fr...

We present a resonant-cavity-enhanced Single Photon Avalanche Diode (SPAD) fabricated on a reflecting siliconon-insulator (SOI) substrate. The substrate incorporates a two period distributed Bragg reflector fabricated using a commercially available double-SOI process. The resonant-cavity-enhanced (RCE) SPAD detectors have peak photon detection efficiencies ranging from 41% at 780nm to 32% at 85...

Recently, considerable attention has been placed upon exploiting the negative-feedback effect in accelerating the quenching time of the avalanche current in passively quenched single-photon avalanche-diode (SPAD) circuits. Reducing the quenching time results in a reduction in the total charge generated in the SPAD, thereby reducing the number of trapped carries; this, in turn, can lead to impro...

Single-molecule Förster resonance energy transfer (smFRET) techniques are now widely used to address outstanding problems in biology and biophysics. In order to study freely diffusing molecules, current approaches consist in exciting a low concentration (<100 pM) sample with a single confocal spot using one or more lasers and detecting the induced single-molecule fluorescence in one or more spe...

The quantum yield of photosystem II, determined by chlorophyll fluorescence and the quantum yield of CO2 uptake, determined from gas exchange, are two physiologically important measurements in clarifying the response to environmental stress. Both measurements, however, require an accurate assessment of leaf light absorption in the photosynthetically active radiation wavelength range (400–700 nm...

Use of physiological parameters as fast tools to screen for drought tolerance in sugarcane: Drought is one of the major limitations to plant productivity worldwide. Identifying suitable screening tools and quantifiable traits would facilitate the crop improvement process for drought tolerance. In the present study, we evaluated the ability of four relatively physiological parameters (variable-t...

BACKGROUND This study examines whether leaf spectra can be used to measure damage to cassava plants from whitefly (Bemisia tabaci), and the potential to translate measurements from leaf to landscape scale in eastern Africa. Symptoms of the cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) viruses, and sooty mould (SM) blackening of lower leaves from whiteflies feeding on the ...

Iron deficiency in plants is caused by a low availability of iron in the soil, and its main visual symptom is leaf yellowing due to a decrease in chlorophyll content, along with a reduction in plant growth and fruit quality. Foliar sprays with Fe compounds are an economic alternative to the treatment with expensive synthetic Fe-chelates applied to the soil, although the efficacy of foliar treat...