Parallel photoreactor development with enhanced photon efficiency and reproducibility based on laws of optics

A lab-scale parallel photoreactor model has been developed for broad applications in organic chemistry.Position,angle,and distance in the reactor are systematically optimized for achieving high reproducibility under the guidance of the Inverse Square Law and Lambert’s Cosine Law,which were first applied in the design of the photoreactor.Improvement of photon efficiency is realized via 3-point irradiation and broad-band light reflector of aluminum.Photon flux is measured with an optical power meter with its display and adjustment suggested being integrated into the photoreactor for the first time.

A new photon kinetic-measurement based on the kinetics of electron-hole pairs in photodegradation of textile wastewater using the UV-H_2O_(2FS)-TiO_2 process

Actual textile wastewater and synthesized wastewater containing various textile dyes were photocatalytic degraded by the UVH2O2Fs-TiO2 process in an aimular-flow photocatalytic reactor. In this process, a photon kinetic-measure was adopted to obtain constant rates of dyes decomposition. It was theorized that, by illumination at different UV frequencies, the electrons within the semiconductor were excited from the valence band to the conduction band, yielding the formation of electron-hole pairs which are the pre-requisites for photocatalysis. CPT （critical photonic time） exposure required to cause 90% of vibrations between the double and single bonds along the molecular chain of the dyes to be oxidized, was taken to measure the photocatalytic activities. The CPTs varied with the frequencies of the UV spectral areas. The derivatization of CPT from the first-order kinetic law was presented.

Calculation method of quantum efficiency to TiO_2 nanocrystal photocatalysis reaction

The quantum yield is an important factor to evaluate the efficiency of photoreactor. This article gives an overall calculation method of the quantum efficiency( Φ ) and the apparent quantum efficiency( Φ a) to the TiO 2/UV photocatalysis system. Furthermore, for the immobility system (IS), the formulation of the faction of light absorbed by the TiO 2 thin film is proposed so as to calculate the quantum efficiency by using the measured value and theoretic calculated value of transmissivity (T). For the suspension system(SS), due to the difficulty to obtain the absorption coefficient ( α ) of TiO 2 particulates, the quantum efficiency is calculated by means of the relative photonic efficiency ( ζ r) and the standard quantum yield ( Φ standard ).

Recent strategies to enhance the efficiency of hematite photoanodes in photoelectrochemical water splitting

Photoelectrochemical(PEC)water splitting is one of the most promising approaches toward achieving the conversion of solar energy to hydrogen.Hematite is a widely applied photoanode material in PEC water splitting because of its appropriate band structure,non-toxicity,high stability,and low cost.Nevertheless,its relatively low photochemical conversion efficiency limits its application,and enhancing its PEC water splitting efficiency remains a challenge.Consequently,increasing efforts have been rendered toward improving the performance of hematite photoanodes.The entire PEC water splitting efficiency typically includes three parts:the photon absorption efficiency,the separation efficiency of the semiconductor bulk,and the surface injection efficiency.This review briefly discusses the recent advances in studies on hematite photoanodes for water splitting,and through the enhancement of the three above-mentioned efficiencies,the corresponding strategies toward improving the PEC performance of hematite are comprehensively discussed and summarized.

Numerical analysis of In_(0.53) Ga_(0.47) As/InP single photon avalanche diodes

A rigorous theoretical model for Ino.53Gao.47As/InP single photon avalanche diode is utilized to investigate the dependences of single photon quantum efficiency and dark count probability on structure and operation condition. In the model, low field impact ionizations in charge and absorption layers are allowed, while avalanche breakdown can occur only in the multiplication layer. The origin of dark counts is discussed and the results indicate that the dominant mechanism that gives rise to dark counts depends on both device structure and operating condition. When the multiplication layer is thicker than a critical thickness or the temperature is higher than a critical value, generation-recombination in the absorption layer is the dominative mechanism; otherwise band-to-band tunneling in the multiplication layer dominates the dark counts. The thicknesses of charge and multiplication layers greatly affect the dark count and the peak single photon quantum efficiency and increasing the multiplication layer width may reduce the dark count probability and increase the peak single photon quantum efficiency. However, when the multiplication layer width exceeds 1 μm, the peak single photon quantum efficiency increases slowly and it is finally saturated at the quantum efficiency of the single photon avalanche diodes.

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures （CCSs） in two-dimensional （2D） photonic crystals （PCs） are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain （FDTD） method, and the results show that within a very short coupling distance of about 3λ, where ）, is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.

Enhancement of light extraction efficiency in OLED with two-dimensional photonic crystal slabs

Light extraction efficiency of organic light emitting diode （OLED） based on various photonic crystal slab （PCS） structures was studied. By using the finite-difference time-domain （FDTD） method, we investigated the effect of several parameters, including filling factor and lattice constant, on the enhancement of light extraction efficiency of three basic PCSs, and got the most effective one. Two novel designs of ＂interlaced＂ and ＂double-interlaced＂ PCS structures based on the most effective basic PCS structure were introduced, and the ＂interlaced＂ one was proved to be even more efficient than its prototype. Large enhancement of light extraction efficiency resulted from the coupling to leaky modes in the expended light cone of a band structure, the diffraction in the space between columns, as well as the strong scattering at indium-tinoxide/glass interfaces.

Preliminary results for the design,fabrication,and performance of a backside-illuminated avalanche drift detector

The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier （SiPM） has gradually become an alternative to the photomultiplier tube （PMT） in many applications in high-energy physics, astroparticle physics, and medical imaging because of its high photon detection efficiency （PDE）, good resolution for single-photon detection, insensitivity to magnetic field, low operating voltage, compactness, and low cost. However, primarily because of the geometric fill factor, the PDE of most SiPMs is not very high; in particular, for those SiPMs with a high density of micro cells, the effective area is small, and the bandwidth of the light response is narrow. As a building block of the SiPM, the concept of the backside-illuminated avalanche drift detector （ADD） was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons, even ultraviolet light and X-ray light, and because the avalanche multiplication region is very small, the ADD is beneficial for the fabrication of large-area SiPMs. However, because of difficulties in design and fabrication, no significant progress had been made, and the concept had not yet been verified. In this paper, preliminary results in the design, fabrication, and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.

Efficient generation of non-classical photon pairs in a hot atomic ensemble

We demonstrate the generation of non-classical photon pairs in a warm S-Rb atomic vapor （＇ell with no buffer gas or polarization preserving coatings via spontaneous four-wave mixing. We obtain the photon pairs with a 1/e correlation time of 40 ns and the violation of Cauchy-Sehwartz inequality by a factor of 23 - 3. This provides a convenient and efficient method to generate photon pair sources based on an atomic ensemble.