High-Responsivity ZnS Schottky Barrier Photodiode Array for Ultraviolet Imaging

A different approach,using the molecular beam epitaxy (MBE)-grown ZnS-based Schottky photodiode technology,is applied to fabricate an 8×8 photodiode array.The micro-processing procedures of this photodiode array including standard photolithography,a number of metallisation,wet-chemical etching and SiO_2 deposition for insulation are developed.The detector is characterized to have a cutoff wavelength at 340 nm and the photo-responsivity measurements on the pixels result an ultraviolet (UV) response as high as 0.15 A/W,corresponding to an external quantum efficiency of 55% in the visible-blind spectral ranging from 400 down to 250nm.Imaging tests indicate that this array is able to capture the intensity profile of a given UV light source with reasonably good capability.

Post-processing Free Quantum Random Number Generator Based on Avalanche Photodiode Array

Quantum random number generators adopting single negligible dead time of avalanche photodiodes （APDs） photon detection have been restricted due to the non- We propose a new approach based on an APD array to improve the generation rate of random numbers significantly. This method compares the detectors＇ responses to consecutive optical pulses and generates the random sequence. We implement a demonstration experiment to show its simplicity, compactness and scalability. The generated numbers are proved to be unbiased, post-processing free, ready to use, and their randomness is verified by using the national institute of standard technology statistical test suite. The random bit generation efficiency is as high as 32.8% and the potential generation rate adopting the 32× 32 APD array is up to tens of Gbits/s.

Spatially modulated scene illumination for intensity-compensated two-dimensional array photon-counting LiDAR imaging

Photon-counting LiDAR using a two-dimensional(2D)array detector has the advantages of high lateral resolution and fast acquisition speed.The non-uniform intensity profile of the illumination beam and non-uniform quantum efficiency of the detectors in the 2D array deteriorate the imaging quality.Herein,we propose a photon-counting LiDAR system that uses a spatial light modulator to control the spatial intensity to compensate for both the non-uniform intensity profile of the illumination beam,and the variation in the quantum efficiency of the detectors in the 2D array.By using a 635 nm peak wavelength and 4 mW average power semiconductor laser,lab-based experiments at a 4.27 m stand-off distance are performed to verify the effectiveness of the proposed method.Compared with the unmodulated method,the standard deviation of the intensity image of the proposed method is reduced from 0.109 to 0.089 for a whiteboard target,with an average signal photon number of 0.006 per pixel.

Bias-free operational monolithic symmetric-connected photodiode array

We have designed and fabricated zero-bias operational two-element symmetric-connected photodetector arrays(SC-PDAs).The designed SC-PDAs have higher saturation currents,larger RF power,and better frequency responses than the single photodetector(PD)under zero bias.The bias-free SC-PDA with 15μm diameter of each PD demonstrated a 3 d B bandwidth of 19.4 GHz at 0.5 m A.The RF saturation photocurrent and maximum RF output power of the SC-PDA with 40μm,50μm,and 60μm diameters under zero bias are over9.31 m A and-5.86 d Bm at 3 GHz,14.52 m A and 1.17 d Bm at 1 GHz,and 13.72 m A and-1.76 d Bm at 1 GHz,respectively.

Short Range Laser Rangefinder Employing False Target Rejection

Till now a laser rangefinder has been used to find the range of a stationary target or the variations and deformities of a plane surface like in the manufacturing processes.New concept in the design of a laser rangefinder for a moving target is described.It is based on triangulation method of ranging and combines with a threefold false target rejection circuit to eliminate the possibility of false target indication due to light reflected by any obstruction in the line of sight of laser source and the target. The false target rejection is done twice through hardware and once through software.

Signal Acquisition and Processing Method Using Sector SSPA

Self scanning photodiode array (SSPA) is a kind of solid state imaging sensor. The signal processing method using a special sector SSPA was investigated. Based on the principle and characteristics of SSPA, a signal acquisition and processing method controlled by computer was introduced. The amplification of weak signal, the matching of time sequence, the fast peak holding with low leakage, the high speed A/D conversion and nonlinear correction were discussed. This method can acquire the peak signal of every ring of sector SSPA with high accuracy and in real time. It can be used to detect the distribution of space light energy.

Extraction and Determination of Three Chlorophenols by Hollow Fiber Liquid Phase Microextraction - Spectrophotometric Analysis, and Evaluation Procedures Using Mean Centering of Ratio Spectra Method

A method termed hollow fiber liquid phase microextraction (HF-LPME) was utilized to extract three chlo- rophenols, 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6- trichlorophenol (2,4,6-TCP), separately from water. The extracted chlorophenols were then separated, identified, and quantified by UV-Vis spectrophotometry with photodiode array detection (UV-Vis/DAD). In the study, experimental con-ditions such as organic phase identity, acceptor phase volume, sample agitation, extraction time, acceptor phase NaOH concentration, donor phase HCl concentration, salt addition, and UV absorption wavelength were optimized. The statistical parameters of the proposed method were investigated under the selected con-ditions. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) was calculated. The results showed that the proposed method is simple, rapid, accurate and precise for the analysis of ternary mixtures.

Simultaneous determination of 20 food additives by high performance liquid chromatography with photo-diode array detector

An efficient and accurate analytical method was developed for the simultaneous determination of 20 synthetic food additives, including three sweeteners,seven food colorants,nine synthetic preservatives and caffeine,by high performance liquid chromatography （HPLC） with photodiode array detector（PDA）.This method permits the detection of food additives at very low concentrations（0.005-0.150μg/mL）.The applicability was verified by the determination of food additives present in various foodstuffs.

Chemical compounds as well as antioxidant and litholytic activities of Arbutus unedo L. leaves against calcium oxalate stones

Objective: The present study aimed to quantify and identify the bioactive compounds of the Arbutus unedo L. leaves in order to evaluate both their antioxidant properties and litholytic activities against calcium oxalate stones.Methods: This survey was carried out using hydroalcoholic extract(E.FA) and infusion(I.FA) of A. unedo leaves. The quantification of phenolic compounds, flavonoids, flavonols and anthocyanins was done by spectrophotometric methods and identification of chemical components was performed by ultraperformance liquid chromatography with photodiode array and electrospray ionization tandem mass spectrometry. Antioxidant activity was measured using the 1,1-diphenyl-2-picrylhydrazyl(DPPH)method and by the ferric reducing/antioxidant power(FRAP) assay. Litholytic activity of E.FA and I.FA was studied using a special model that resembles circuitry of the urinary system.Results: E.FA showed greater antioxidant efficacy than I.FA(P < 0.05). Its higher efficiency was shown via the values of median inhibitory concentration, which was close to(76.14 ± 0.91) mg/mL for E.FA versus(202.64 ± 5.77) lg/mL for I.FA using the DPPH method, and(53.77 ± 0.81) lg/mL for E.FA versus(236.86 ± 31.90) lg/mL for I.FA, using FRAP method. I.FA exhibited significantly higher litholytic activity compared to E.FA(P < 0.05), with dissolution values of 31.03% ± 0.63% versus 14.55% ± 0.65%, respectively.Conclusion: Overall, the results suggest that the A. unedo is rich in bioactive compounds, and possesses antioxidant and litholitic abilities that are worthy of further study.

Simultaneous Analysis of Indapamide and Related Impurities in Sustained-Release Tablets by a Single-Run HPLC-PDA Method

The contents of indapamide and related impurities in generic indapamide sustained-release tablets were simultaneously detected by a single-run high performance liquid chromatography equipped with photodiode array detector(HPLC-PDA)method for the quality control in this paper.The results showed the method had a good selectivity and was validated through linearity,limits of detection and quantification,recovery,and precision.The linear ranges of indapamide,2-methyl-1-nitroso-2,3-dihydro-1H-indole(impurity A,ImA),4-chloro-N-(2-methyl-1H-indol-1-yl)-3-sulphamoyl-benzamide(impurity B,ImB)and 4-chloro-3-sulfamoylbenzoic acid(impurity 1,Im1)were 0.028-1.80μg/mL(R=0.99995),0.060-1.20μg/mL(R=0.9996),0.0324-1.20μg/mL(R=0.99985)and 0.060-1.20μg/mL(R=0.9997)with detection limits of 0.0093,0.012,0.012 and 0.006μg/mL,respectively.ImA and Im1 were not detectable in the generic drug.The content of indapamide was 96.7%of the labeled amount with a relative standard deviation(RSD)of 1.30%,and the percentage of ImB relative to the labeled amounts of indapamide was 0.106%with an RSD of 1.82%.The content of other unspecified impurities all met the reference quality standards.The results provided references for the quality control and the quality standard study of generic indapamide sustained-release tablets.