Characteristics dependence of the silicon photoelectronic multipliers on temperature

The characteristics dependence on the ambient temperature for three types of silicon photoelectronic multipliers have been studied in this research. The prototypes of Si-photoelectronic multipliers with a p+–p–n+ structure produced by JSC Integral (Republic of Belarus), serially produced silicon photoelectronic multipliers KETEK РМ3325 and ON Semi FC 30035 have been used as objects of research. We present the setup diagram and research technique. Measurements of the photocurrent magnitude versus the illumination intensity, calculations of the critical and threshold intensities, and the dynamic range have been performed. We also present the photocurrent dependences on the illumination intensity at different ambient temperatures. As it was found, these dependences have a linear section, the length of which characterizes the critical intensity value, and the inclination angle of the linear section to the intensity axis characterizes the photodetector sensitivity to optical radiation. It has been determined that the temperature increase leads to an increase in the critical intensity value and to a decrease in the sensitivity value. We present the dependences of the threshold intensity on the overvoltage at different ambient temperatures. The dependence of the threshold intensity on overvoltage is most strongly pronounced when the supply voltage is below the breakdown voltage. It was found that the threshold intensity is increased with the temperature increase and the threshold intensity dependence on the temperature is the same for all investigated photodetectors. It was found that the dynamic range value is decreased with the temperature increase, which is caused by a more significant change in the threshold intensity as compared to the critical one. The results given in this article can be applied when developing and designing the tools and devices for recording optical radiation based on silicon photoelectronic multipliers.

Photoresponse properties of Au/(CoFe2O4-PVP)/n-Si/Au (MPS) diode

Photo-response properties of the Au/(CoFe2O4-PVP)/n-Si (MPS) diode were investigated using current-voltage (I-V) measurements achieved under dark and various illumination conditions. The experimental results showed that the MPS diode has a good response to the illumination. Especially, in reverse-bias region, photocurrent (Iph) increases with increasing illumination intensity (P) due to the formation of electron–hole pairs. The double-logarithmic Iph-P plot has a good relation with 1.27 slope and such high value of slope indicates a lower density of the unoccupied trap level. This indicates that the diode exhibits a good photoconductive and photovoltaic behavior. The photo-to-dark current ratio confirms the photo-sensitivity of the diode. Thermionic emission (TE) theory was used to determine the diode electronic parameters such as saturation current (I0), ideality factor (n) and barrier height (ΦB0) and their values were calculated from the measured I-V data. Moreover, the ΦB0 and series resistance (Rs) were extracted from an alternative method suggested by Norde. All these parameters (ΦB0, n, Rs, and I0) decrease with increasing illumination intensity and there is a good linear correlation between ΦB0 and n as ΦB0 (n) = 4.72x10− 2n + 0.5464 eV. As a results, the fabricated MPS diode due to the excellent photo-response can be used for photovoltaic applications.

Phototransistor: The Story So Far

The research paper prospects the theory of phototransistor ranging from the history of the device to its application in the real world. The research paper deep dives into the characteristics of the phototransistor while discussing its dependence on bias drive, bias voltage, and illumination intensity. The research paper includes a comparative study between the various types of phototransistors based on optical gain, spectral range, and efficiency. It also concludes the best illumination method for the phototransistor based on the optical gain parameter.

Optimization of Preparation Conditions for Side-Emitting Polymer Optical Fibers Using Response Surface Methodology

Polymer optical fibers (POFs) were used for preparing side-emitting polymer optical fibers (SPOFs), which were processed with acetone and n-hexane combined in selected proportions by a solvent treatment method. The effects of the volume ratio of acetone to n-hexane and treatment time on response variable factors were investigated. The center composite design (CCD) based response surface methodology (RSM), a quadratic model, and a two-factor interaction model were developed to relate the preparation variables of illumination intensity, breaking strength, and rigidity. According to analysis of variance (ANOVA), the factors affecting the optimization of each response factor were determined. The predicted values after process optimization were found to be highly similar to the experimental values. The optimal conditions for the preparation of SPOF were as follows: the volume ratio of acetone to hexane was 1.703, and the treatment time was 2.716 s. The three response variables of SPOF prepared under the optimal conditions were: illumination intensity 19.339 mV, breaking strength 5.707 N, and rigidity 572.013 N·mm2.

Sources of widefield fluorescence from the brain

Widefield fluorescence microscopy is used to monitor the spiking of populations of neurons in the brain. Widefield fluorescence can originate from indicator molecules at all depths in cortex and the relative contributions from somata, dendrites, and axons are often unknown. Here, I simulate widefield illumination and fluorescence collection and determine the main sources of fluorescence for several GCaMP mouse lines. Scattering strongly affects illumination and collection. One consequence is that illumination intensity is greatest ~300–400 µm below the pia, not at the brain surface. Another is that fluorescence from a source deep in cortex may extend across a diameter of 3–4 mm at the brain surface, severely limiting lateral resolution. In many mouse lines, the volume of tissue contributing to fluorescence extends through the full depth of cortex and fluorescence at most surface locations is a weighted average across multiple cortical columns and often more than one cortical area.