Matter-wave interference in an axial triple-well optical dipole trap

This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by -37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth -0.5 μK and volume -74 μm^3 are suitable to trap and manipulate an atomic Bose-Einstein condensation （BEC）. Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.

Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

Based on simple analytical equations, short circuit current density （Jsc） of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of Jsc; and obvious oscillatory behaviour of Jsc was observed as a function of thickness. At the same time, the influence of the carrier lifetime on Jsc also cannot be neglected. When the carrier lifetime is relatively short, Jsc only increases at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and Jsc behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.

Analysis of the Interference Signal of the Distributed Optical Fiber Sensing Based on DSP

In this paper, the author analyzes characteristics and extracting method of interference signal of the distributed optical fiber sensing. In the distributed optical fiber sensing, realizing alarm and positioning function only through the cross-correlation operation will increase the load of the system, can make misinformation rate of the system be improved greatly. Therefore, before the localization algorithm, adding a interference signal feature recognition is very necessary, can reduce unnecessary operation loss and reduce the load of the system, also reducing the number of the false positives.

Interference of selective higher-order modes in optical fibers

The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally. It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber (SMF) to the LP0m modes in step-index multimode fibers (MMFs) with different parameters, one can selectively generate higher-order modes and construct all-fiber interferometers. The research presented in this paper forms a basis of a new type of fiber devices with potential applications in fiber sensing, optical fiber communications, and optical signal processing.

Effects of optical interference and annealing on the performance of poly(3-hexylthiophene):fullerene based solar cells

In this paper, the effects of optical interference and annealing on the performance of P3HT：PCBM based organic solar cells are studied in detail. Due to the optical interference effect, short circuit current density （Jsc） shows obvious oscillatory behaviour with the variation of active layer thickness. With the help of the simulated results, the devices are optimized around the first two optical interference peaks. It is found that the optimized thicknesses are 80 and 208 nm. The study on the effect of annealing on the performance indicates that post-annealing is more favourable than pre-annealing. Based on post-annealing, different annealing temperatures are tested. The optimized annealing condition is 160℃ for 10 min in a nitrogen atmosphere. The device shows that the open circuit voltage Voc achieves about 0.65V and the power conversion efficiency is as high as 4.0 % around the second interference peak.

Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed InGaN/GaN quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily.

Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback

This paper proposes a theoretical analysis for the characteristics of an external cavity Nd：YAG laser with feedback of multiple-beam interference, which is induced by the multi-reentrance of the light from the external Fabry-Perot cavity. The theoretical model considers the multiple beam interference of the external Fabry-Perot cavity. It is found that the optical feedback signals are distorted to pulse waveforms instead of the sinusoidal ones in conventional feedback. The experimental results are in good agreement with the theoretical analysis. The obtained theoretical and experimental results can advance the development of a laser feedback interferometer.

An Optical Path Length Modulator for Laser Diode Self-Mixing Interference

Transparent liquid flattening or stretching realizes optical path length modulation. A flat thin seal transparent cavity, one flank is an electromagnetic driving membrane and is filled over with transparent liquid. Vibration of the membrane makes the liquid compressing or stretching, changes the liquid layer thickness, i.e. the optical path length of light through the liquid layer. The liquid layer compressed is equivalent to increase membrane tension. The membrane has higher resonant frequency. The cavity diameter 10 mm modulation frequency is about 18 kHz.

Performance analysis of a hybrid optical CDMA/DWDM system against inter-symbol interference and four wave mixing

This paper reports the implementation and theoretical model for analyzing an optical CDMA/DWDM hybrid system to reduce two major problems,the Inter-Symbol Interference(ISI)and the Four-Wave Mixing(FWM)effects and improve the performance of optical subscriber access networks by using Zero Cross-Correlation(ZCC)optical codes,which helps to reduce the effect of the Multiple Access Interference(MAI).A squeezing method is used in the proposed hybrid system to completely suppress the ISI.In this method,the sequence interval of the signature code is squeezed into a duration of less than one-bit.The hybrid system is capable of accommodating 120 optical CDMA users carried by only 10 DWDM wavelengths spaced by 0.2 nm with 60 Gb/s/wavelength transmitted over 105.075 km of optical fiber.The result shows that the optimum interval of the code sequence is a quarter(i.e.,25%)of the bit duration.Moreover,the results reveal that the CDMA technology based on the spread spectrum is capable of increasing the nonlinear tolerance of the proposed hybrid system as the energy of bits is distributed over the chip sequence code.Also,the number of ones/weight and the positions between them have a significant effect on the performance of the proposed hybrid system.

Measurement of Optic Axis Direction Based on Interference Fringe Method

In order to conquer the defect in low precision and small range for measuring optic axial angle based on conoscopic interference method, interference fringe method is proposed. It is not the distance deviating from melatope but fringe numbers to decide optic axial angle. Fringe numbers are divided into integer portion and decimal fraction portion, the decimal fraction portion is calculated by non-linear interpolation method and integer portion is determined by the relative placement of interference fringes in the principal section. Extremum arithmetic of digit image is proposed and can be used to determine the interference fringes conveniently and precisely. After different niobate crystals were measured, the result shows that measurement range of optic axial angle is increased efficiently and measurement error is reduced to 0.1°.

Tapered Multimode Interference Combiners for Coherent Receivers

A new tapered multimode interference （MMl）-based coherent lightwave combiner is reported. A comprehensive theoretical analysis of mode behaviors in the tapered MMI waveguide is presented, and the output characteristics of the tapered MMI combiners with various structures are demonstrated. The combiner is fabricated on a silicon-on-insulator （SO1） substrate. Due to its advantages of having no end-facet reflection,easy extension to a multi-port configuration, high tolerance for fabrication errors, and compact size, the tapered MMI is a good candidate for a coherent lightwave combiner to be used in large-scale photonic integrated circuits.

Measurement of refrative index based on fiber Mach-Zehnder interference

In order to detect the refractive index of liquid with high precision,based on modular interference,Mach-Zehnder optical fiber refractive rate sensor was studied.Sensor structure is composed of ordinary single-mode fiber and multimode fiber,according to the singlemode multimode singlemode sequence to fuse together,and the fused optical fiber is used to process the taper.As a result,the diameter of the sensing head is about 10μm.Experimental results show that,as liquid refractive index increases range from 1.33 to 1.35,the loss peak of the transmission spectrum will shift to long wave direction.

Combined Transmission Interference Spectrum of No Core Fiber and BP Neural Network for Concentration Sensing Research

To investigate wavelength response of the no core fiber（NCF）interference spectrum to concentration,a three-layer back propagation（BP）neural network model was established to optimize the concentration sensing data.In this method,the measured wavelength and the corresponding concentration were trained by a BP neural network,so that the accuracy of the measurement system was optimized.The wavelength was used as the training set and got into the input layer of the three layer BP network model which is used as the input value of the network,and the corresponding actual concentration value was used as the output value of the network,and the optimal network structure was trained.This paper discovers a preferable correlation between the predicted value and the actual value,where the former is approximately equal to the latter.The correlation coefficients of the measured and predicted values for a sucrose concentration were 1.000 89 and 1.003 94;similarly,correlations of0.999 51 and 1.018 8 for a glucose concentration were observed.The results demonstrate that the BP neural network can improve the prediction accuracy of the nonlinear relationship between the interference spectral data and the concentration in NCF sensing systems.

Characteristics of the propagation of partial discharge ultrasonic signals on a transformer wall based on Sagnac interference

The acoustic emission(AE)method has been widely recognized for the detection of incipient insulation fault phenomenon(partial discharge,PD)in power transfomiers,nevertheless,the installation and placement of AE sensors should be taken into full consideration.In this manuscript,a three-dimensional multiphysics model was established and simulated to research the characteristics of the propagation in the transformer wall.Furthermore,a piezoelectric transducer was used to detect PD ultrasonic signals and verify the simulation results in the laboratory.To ensure the accuracy of the detection,an optical fiber sensor based on the Sagnac interference principle was designed and adopted.The variation of the amplitude of the ultrasonic signal with distance reveals the characteristics of the ultrasonic signal propagating in the transformer wall.The distribution of sound pressure on the upper and lower surfaces of the simulation model proved that ultrasonic waves propagate in the form of symmetrical Lamb waves in the transformer wall.Moreover,the amplitude of the AE attenuates due to absorption and refraction loss,and local fluctuations on account of acoustic interference.Thus,a stable signal detected by an AE sensor does not represent the absence of PD in a transfomier.To improve the reliability of AE detection,it is proposed in this manuscript that repeated movement of the AE sensor is necessary to obtain a suitable measurement position.Similarly,it is necessary to adjust the position of the AE sensor in order to locate the PD source well.In addition,this study is expected to provide a theoretical analysis and a fiber sensor to address the problem of sensor placement in AE detection.

Effects of optical axis direction on optical path difference and lateral displacement of Savart polariscope

A simple method is applied to calculating the optical path difference （OPD） of a plane parallel uniaxial plate with an arbitrary optical axis direction. Then, the theoretical expressions of the OPD and lateral displacement （LD） of Savart polariscope under non-ideal conditions are obtained exactly. The variations of OPD and LD are simulated, and some important conclusions are obtained when the optical axis directions have an identical tolerance of ／pm 1^{{／circ}}. An application example is given that the tolerances of optical axis directions are gained according to the spectral resolution tolerances of the stationary polarization interference imaging spectrometer （SPIIS）. Several approximate formulae are obtained for explaining some conclusions above. The work provides a theoretical guidance for the optic design, crystal processing, installation and debugging, data analysis and spectral reconstruction of the SPIIS.

Impact of the spatial coherence on self-interference digital holography

Owing to the unique feature that the signal and reference waves of self-interference digital holography(SIDH)contain the same spatial information from the same point of object,compared with conventional digital holography,the SIDH has the special spatial coherence properties.We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH.Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH,and the impact extent of the spatial coherence depends substantially on the recording distance of hologram.The theoretical conclusions are supported well by numerical simulation and optical experiments.

Identification of Phases in Aluminide Coatings by Means of Interference Layer Metallography

Interference layer metallography was used to identify the phases present in the aluminide coating on superalloy IN738LC. They are: two intermetallic aluminides NiAl and Ni_3Al, y-solid solution and a Cr-rich solid solution, two sulphides M_(23)C_6 and MC, and two sulphides (Al,Cr)_3S_4 and (Cr,Ti)_3S_4. ZnS and ZnSe are proposed to be vapor deposited onto the surface of the specimen to get good colour contrast and good light-dark contrast. The refractive index and absorption coefficient of all these phases have been detemined.

Simulation of the Physical Performance of Optical Packet Switching Nodes

A graphical and visual simulation system for the study of optical packet switching (OPS) nodes is accomplished. With the simulation system, the effect on physical performance-bit error rate (BER) due to a variety of factors such as the crosstalk parameters of OPS nodes, number of cascaded OPS nodes, length of optical output buffer, traffic load and fluctuation of amplitude of optical signals are evaluated. Reliability of the simulation system is proved by the analytical results obtained in all the above cases.

A STUDY OF INTERFACES OF COMPOSITES BY MEANS OF OPTICAL FIBRE SENSING TECHNTIQUE

Fibre stress of glass fibre reinforced polymeric copmosites on load is determined by using optical fibre as model fiber and by means of laser interference method. In addition, the origination of fibre stress during moulding process of composites and the relation between fiber stress of loaded composites and external stress are examined. The experiments show that fibre stress is related to molecular structure of inter facial materials and structure of inter facial layers. When stress is transferred from matrix to fibre, each inter facial layer has different stress gradient and deformability. This property can be characterized by introducing an inter facial stress transfer coefficient k to the two-phase model.

The 650-nm variable optical attenuator based on polymer/silica hybrid waveguide

Visible light variable optical attenuators（VOA） are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber（POF） transmission systems.In this paper, a polymer/silica hybrid waveguide thermo–optic attenuator based on multimode interference（MMI） coupler is designed and fabricated to operate at 650 nm. The single-mode transmission condition, MMI coupler, and transition taper dimensions are optimized through the beam propagation method. Thermal analysis based on material properties provides the optimized heater placement angle. The fabricated VOA presents an attenuation of 26.5 dB with a 21-mW electrical input power at 650 nm. The rise time and fall time are 51.99 and 192 μs, respectively. The time–stability measurement results prove its working reliability.