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This paper is to demonstrate the application of modern Engineering Software to improve and advance the mechanical desig processes of a low beam projector headlight. Nowadays, advanced finite element tools are able to run and coupled different physics modules to analyze complex geometries and their material combinations. The particular issue in this study is the light switching mechanism in a headlight structure design. During lighting, the jam of the low beam projector solenoid actuated pivot due to thermal expansions has been distressing the normal operation of the overall headlight structure. A comparison between the original and a new convection enhanced head lamp design is therefore scrutinized. For both cases, heat transfer analysis, where it was included natural convection, conduction, and radiation with a concentrated heat source are proposed in order to obtain the temperature distribution fields at the light switching mechanism. The results were used to run future structural stresses analyses where the average thermal expansion of the crankshaft mechanism was determined.

OBJECTIVE In this study, optical data on color of tongue tips were collected by using a visible reflection spectrum system. Quantitative method of tongue inspection and classification of tongue states including pale, pale red, red and crimson manifestations were investigated. METHODS Chromaticity coordinates of the tongue tips from 98 subjects were calculated on the basis of the visible reflection spectrum. The tongue color was quantified and classified by the visible reflection spectrum in the range from 590 nm to 780 nm, based on the higher red-band energy distribution on the tongue tip color. RESULTS It was found that comparison and analysis of tongue tip color from different samples would be well-suited after spectrum vector normalization, and the difference of tongue tip color between different samples could be observed easily when the tongue tip optical data were sited in CIE 1931 chromaticity diagram. The tongue tip colors were analyzed quantitatively and classified by the spectral energy intensity at the wavelength of 670 nm and (or) spectral energy ratio of red bank from 590 nm to 780 nm. The results of classification showed that there was sound corresponding accuracy with the clinical diagnosis of pale tongue, pale red tongue, red tongue and crimson tongue. CONCLUSION In this study, based on the collection of the information data on tongue tip characteristics with the visible spectrum from 380 nm to 780 nm, the quantitative analysis of tongue inspection for pale tongue, pale red tongue, red tongue and crimson tongue was established. The quantitative value for tongue tip color is an effective method for classification of the condition of the tongue tip, which provides a useful tool for the modernization of tongue inspection in traditional Chinese medicine.

Black silicon, which is obtained by irradiating the surface of a Si wafer with femtosecond laser pulses in the presence of a sulfur-bearing gas, holds great promise in the preparation of high-performance intermediate band silicon solar cells. Using a three-level model, the enhanced usefulness of sunlight of the microstructured silicon was firstly analyzed. A detailed study on the relationship between the light loss, the ionization energy of doped impurities in silicon and the impurity band width were given. Then the effect of the position of intermediate band within the forbidden gap of silicon on the theoretical conversion efficiency for the corresponding solar cell is discussed using the Detailed Balance Theory. Finally problems need to be resolved in making intermediate band solar cells based on femtosecond laser microstructured silicon are pointed out with great emphasis.

According to the principle of light propagation,an automatic measurement system for scattering light survey of meridian and surrounding non-meridian at 808 nm central wavelength was designed and the effect of laser power on light decay rate of tissue were discussed.The diffusion theory of light transporting in biological tissues was used to analyze the experimental results.The results showed that there were statistical differences between meridian and surrounding non-meridian(P0.05).We also found the differences in optical parameters that the average attenuation factor value of pericardium meridian was lower than spleen meridian.In this article,our study showed laser power had no influence on attenuation of light in biological tissues that proved the attenuation is determined by tissue optical characteristics.

This paper critically analyses and simulates the circuit configuration of the integral gated mode single photon detector which is proposed for eliminating the transient spikes problem of conventional gated mode single photon detector. The relationship between the values of the circuit elements and the effect of transient spikes cancellation has been obtained. With particular emphasis, the bias voltage of the avalanche photodiode and the output signal voltage of the integrator have been calculated. The obtained analysis results indicate that the output signal voltage of the integrator only relates to the total quantity of electricity of the avalanche charges by choosing the correct values of the circuit elements and integral time interval. These results can be used to optimize the performance of single photon detectors and provide guides for the design of single photon detectors.

An intrinsically stable quantum key distribution system (QKD) with six polarization states encoded by phase modulation is introduced. The encoder and decoder are in the same structures that consist of two polarizing Sagnac interferometers connected in tandem. The six polarization states are determined and distinguished by different sets of phase shifts induced by two respective electrically-driven integrated phase modulators. A mean visibility of interference fringes is kept stable at 97.58% for an hour's performance. Theoretical and experimental analyses show that the proposed QKD system features intrinsically stability immune from environment fluctuation.

By considering higher-order effects, the properties of self-similar parabolic pulses propagating in the microstructured fibre amplifier with a normal group-velocity dispersion have been investigated. The numerical results indicate that the higher-order effects can badly distort self-similar parabolic pulse shape and optical spectrum, and at the same time the peak shift and oscillation appear, while the pulse still reveals highly linear chirp but grows into asymmetry. The influence of different higher-order effects on self-similar parabolic pulse propagation has been analysed. It shows that the self-steepening plays a more important role. We can manipulate the geometrical parameters of the microstructured fibre amplifier to gain a suitable dispersion and nonlinearity coefficient which will keep high-quality self-similar parabolic pulse propagation. These results are significant for the further study of self-similar parabolic pulse propagation.

Au nanorods dispersed in aqueous solution were prepared with the electrochemical method. The absorption spectrum shows two absorption peaks corresponding to the perpendicular and transverse surface plasma resonance absorption of the nanorods. The third-order optical nonlinear properties are investigated by Z-scans. The signs of the nonlinear absorption coefficient and refractive index are reversed as the intensity of incident laser increases, which is due to the shape change of the gold nanoparticles melted by the intense laser pulses.

This study is to present a new scheme for the detection of human meridian system non-invasively. The optical transport properties along the pericardium meridian and a non-meridian path about 1 cm away from the meridian were measured non- invasively on 20 healthy people in vivo. 633 nm, 658 nm and 785 nm red lasers were used for irradiation, and the diffuse light emittances at different points on meridian and non-meridian directions were collected respectively and compared. Our study suggested that the light propagation characteristics along both the meridian and non-meridian directions conformed to the Beer's exponential attenuation law. Statistical analysis of the results suggested that the optical properties of human meridian differ from those of the surrounding tissue ( p < 0.05), and the light attenuation is less when propagating along the pericardium meridian than along the non-meridian direction. These findings not only confirmed the objective existence of acupuncture meridians, but also shed new light on the understanding of meridians.

The evolution of soliton trains in dispersion-shifted fibres (DSFs) in the presence of third-order dispersion (TOD) is investigated. The results show that the collision of neighbouring solitons in the trains can be suppressed by means of a proper TOD, but the maximum transmission distance (or bandwidth) is limited by the increasing soliton separation that results from the TOD. It is also shown that the separation can be suppressed by adjusting the initial phase or amplitude difference between the solitons. These results are helpful to re-establish the potential application of the soliton-based optical-communication systems in DSFs.

A new approach is proposed to enhance supercontinuum (SC) spectrum generation in A dispersion-decreasing optical fibre with a new dispersion profile. The chromatic dispersion D(?,z) is a concave function of wavelengths and has no zero-dispersion wavelengths over the whole or part of the fibre as D(?,z) is positive. A flatter and much broader spectrum can be produced based on the scheme. The general criteria parameters are obtained for characterizing SC shapes in the optical fibres.

The nonlinear effect of two-photon excitation on the imaging property of two-photon confocal microscopy has been analyzed by the two-photon fluorescence intensity transfer function derived in this paper. The two-photon fluorescence intensity transfer function in a confocal microscopy is given. Furthermore the three-dimensional point spread function (3D-PSF) and the three-dimensional optical transfer function (3D-OTF) of two-photon confocal microscopy are derived based on the nonlinear effect of two-photon excitation. The imaging property of two-photon confocal microscopy is discussed in detail based on 3D-OTF. Finally the spatial resolution limit of two-photon confocal microscopy is discussed according to the uncertainty principle.

In this paper, we report on the enhanced pulse compression due to the interaction between the positive third-order dispersion (TOD) and the nonlinear effect (cross-phase modulation effect) in birefringent fibres. Polarization soliton compression along the slow axis can be enhanced in a birefringent fibre with positive third-order dispersion, while the polarization soliton compression along the fast axis can be enhanced in the fibre with negative third-order dispersion. Moreover, there is an optimal third-order dispersion parameter for obtaining the optimal pulse compression. Redshifted initial chirp is helpful to the pulse compression, while blueshifted chirp is detrimental to the pulse compression. There is also an optimal chirp parameter to reach maximum pulse compression. The optimal pulse compression for TOD parameters under different N-order solitons is also found.

In this paper, we investigate the modulation instability for generating femtosecond pulses in fibres with slowly decreasing dispersion. Higher-order dispersion and higher-order nonlinear effects are taken into account when the continuous wave or quasi-continuous wave evolves into sub-picosecond and femtosecond pulses by modulation instability in the optical fibres. Our research results show that the gain spectrum of the dispersion-decreasing fibres is much wider than that in conventional fibres. The third-order dispersion effect has no contribution to gain spectrum, while the self-steepening effect reduces the maximum value and gain bandwidth and the Raman self-scattering effect widens the extent to which the modulation instability occurs.

A simple and novel strain method is used to change a uniform grating into a linearly chirped grating. Independent tuning of the chirp and the center wavelength of the fiber grating is demonstrated. A 10?Gb?s-1 transmission over 100 km of standard single-mode fiber is realized using this strain method. It is deduced that the product of the maximum dispersion compensation bandwidth and the corresponding dispersion is nearly equal to a constant by numerical simulation.

The nonlinear Schr?dinger equation (NLSE) in erbium-doped fiber (EDF) was obtained. The cross-phase modulation (XPM) in the erbium-doped fiber amplifiers (EDFA) was studied based on this NLSE and the rate equations. A more generalized form of the propagation equation in EDFA was obtained which included the phase shifts the EDFA induced. An analytical expression was given to the XPM in the EDFA. It was found that the XPM in the EDFA dose not change very much with the wavelength except at the neighboring wavelengths (around 1531 nm) where the absorption and emission cross-sections of the erbium ions reach their maxima, and the XPMs have opposite signs on the two sides around 1531 nm. Furthermore, it was found that the XPM increases with the increase of the length of EDF.

A new region where modulation stability occurs in the fibers with minimum group-velocity was found due to the fourth-order dispersion effect. The spectral extent of the region is analyzed and found to be affected by initial input power and the dispersion parameter.

The compression results of picosecond and femtosecond soliton pulses in the dispersion-decreasing fibers are reported in this paper. We found that the high-order dispersion has a great influence on the soliton compression. The expressions of optimum compression factor and optimum fiber length are obtained numerically.

A new method is proposed to compress soliton pulses in the normal dispersive optical fibers through cross-phase-modulation of two pulses. The optimum fiber length for optimum compression is obtained for given values of the pulses and fiber parameters.

OBJECTIVE In this study, to analyze the influence of the brightness value of the supranasal point and the apex nasi on their dominant wavelength and excitation purity according to the spectrocolorimetry data of the supranasal point and the apex nasi in healthy adults that were collected based on optical spectrum colorimetry. METHODS A total of 516 healthy adults were taken as the research subjects. The brightness, dominant wavelength and excitation purity values of the supranasal point and the apex nasi during the complexion inspection of subjects were calculated. This was based on the visible reflection spectrum, and the linear correlation/regression analysis between the brightness Y value and the dominant wavelength or excitation purity value. RESULTS There was no correlation between the brightness Y value and the dominant wavelength of the normal supranasal point and the apex nasi; however, there was negative correlation between the brightness Y value and the excitation purity of the normal supranasal point and apex nasi. CONCLUSION During the complexion inspection, the brightness Y value would not influence the dominant wavelength value, indicating that whiteness and/or blackness would not influence the normal individual complexion. However, the brightness Y value would influence the excitation purity of the supranasal point and the apex nasi, and the degree of saturation should be referred to as the brightness. This research provides a basic reference for diagnosing facial complexion in traditional Chinese medicine.

Objective Using the data from normal tongue and lip colors of normal people which were collected by the visible reflection spectrum, we analyzed the colorimetric parameters of tongue and lip colors. Methods In this study, 516 healthy students aging from 19 to 26 from the colleges and universities of Guangdong Province of China were taken as research subjects. After collecting the data of tongue and lip colors of the 516 subjects using visible reflectance spectroscopy, CIE XYZ tristimulus values as defined by the International Commission on Illumination in 1964 were calculated, and the colorimetric parameters of the normal tongue and lip colors were obtained, such as the CIE 1964 chromaticity coordinate, brightness, dominant wavelength and excitation purity. Results The results of CIE 1964 chromaticity diagram calculated on the visible reflection spectrum showed that the normal tongue color chromaticity coordinate x(10) was 0.341 3±0.008 5 and y(10) was 0.332 6±0.005 1, and the normal lip color chromaticity coordinate x(10) was 0.357 7±0.009 2 and y(10) was 0.338 3±0.005 7; the brightness Y values of the normal tongue color and lip colors were 17.96±3.78 and 19.78±3.72, the dominant wavelength values of the normal tongue color and lip color were (626.3±51.6) nm and (600.4±18.2) nm, and the excitation purity values of the normal tongue color and lip color were 0.083±0.031 and 0.144±0.036, respectively. Conclusion Application of the visible reflection spectrum is a standard way to collect colorimetric data for inspection of the complexion. The investigation of chromaticity coordinates, brightness, dominant wavelength and excitation purity of the normal tongue and lip colors may offer the basic reference for diagnosing morbid complexion on the tongue and lip colors in traditional Chinese medicine.

We investigate the adiabatic enhanced compression of ultrashort pulses from a distributed feedback laser operated at 1550 nm in fibres with slowly decreasing dispersion (FSDD). High-quality pulse compressions from 4.4 ps down to 1.1 ps in a 100 m FSDD and from 4.4 ps down to 830 fs in a 500 m FSDD are obtained. The Raman self-frequency shift of femtosecond pulses in the compression is observed. Theoretical analyses are in good agreement with experimental results.

We report on the enhanced pulse compression due to the interaction of positive third-order dispersion and cross-phase-modulation effects in birefringent fibres. Polarization soliton compression along the slow axis can be enhanced in birefringent fibres with positive third-order dispersion, and the polarization soliton compression along the fast axis can be enhanced in fibres with negative third-order dispersion. Moreover, the third-order dispersion parameter can be optimized to obtain the optimal pulse compression.

The influence of the third-order dispersion (TOD) on the polarization mode dispersion (PMD) is investigated. It is found that the TOD effect destroys orthogonal polarization modes in optical birefringent fibres. A new method is proposed to compensate for the PMD by means of cascading the fibres with the positive and negative TOD. This has proven to be practicable in long transmissions.

Starting from our definition of apodization profile functions, we discover the optimal profiles and the characteristics of defined apodization functions in sidelobe suppression. It is shown by numerical analysis that the optimal grating length is 45?mm to compensate for dispersion induced by 100?km fibres and the smoothness of the ripples in time-delay characteristics is related to the defined parameters.

A novel idea is proposed to suppress the soliton self-frequency shift of femtosecond soliton pulse in dispersion-decreasing fibers. The expression of the soliton self-frequency shift as a function of the pulse width and the fiber dispersion parameter is derived. The numerical simulation is also given, and is in agreement with analytical results.

According to performance requirement of high precision temperature control system used in single-photon detector, the signal-to-noise improvement ratio (SNIR) achieved by digital averaging used in it is analyzed, and the functional relation between SNIR and average times, sampling period, length of sampling time and bandwidth of band limited white noise is given. Aiming at practical application, on condition that the total sampling time is limited, the influences of average time and sampling period on the SNIR of the system are calculated respectively, the expression of SNIR is given and the optimal sampling time is defined.

Low-efficiency is an important issue in "plug and play" quantum key distribution system for practical application. The inefficient reasons of system and the current solutions are analyzed. And then a new quantum key distribution scheme with multi-wavelength pulses is proposed, in which a broadband optical source and the WDMs are combined to generate the optical pulses with four wavelengths. Moreover, the WDMs can also be used as a filter to extract the signal in the proposed scheme. Compared with other schemes, this scheme is highly stable, more securate and independent of the response speed of the control systems. The scheme can be used in high efficiency "plug and play" quantum key distribution system in practice.

Black silicon, produced by irradiating the surface of a silicon wafer with femtosecond laser pulses in the presence of a sulfur-bearing gas, is widely believed to be a potential material for efficient multi-intermediate-band silicon solar cells. Taking chalcogen as an example, we analyse the loss of sunlight for silicon with two impurity bands and we find that loss of the sunlight can be minimized to 0.332 when Te0(0.307 eV) and Te+(0.411 eV) are doped into microstructured silicon. Finally, problems needed to be resolved in analysing the relationship between conversion efficiency of the ideal four-band silicon solar cell and the position of the introduced two intermediated bands in silicon according to detailed balance theory are pointed out with great emphasis.

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.

In this paper are analyzed the characteristics of the single photon detector (SPD) with using coaxial cables as reflection lines to cancel transient spikes noises, particularly,the characteristics of variations in bias voltage of the avalanche photodiode (APD) and output signal. Based on the theoretical analyses,the principle of the timing relation between single photon pulses and the two gate pluses is discussed. Also, the condition and the effect of transient spikes cancellation are achieved. And the minimal detecting period is obtained. Finally,we conduct some experiments to verify our theory. In our experiment,the noise rejection ratio is 25.1dB. The results accord with our theory satisfactorily. Our results will be helpful in designing and optimizing single photon detectors.

A flashlamp-pumped Cr:LiSAF laser system with a voltage controlled Q-switch structure in the cavity is designed. A dual-wavelength and dual-pulse tunable laser output is gained. The relation of laser output behavior with input energy is studied experimentally. The output is dual-pulsed with the energy of the 32 mJ/pulse producing the total output energy of 64 mJ and the pulse width is about 27 ns at 850 nm. Then, we use one LBO crystal as the frequency doubling crystal to obtain a dual wavelength (448.1 nm and 449.15 nm) and dual pulse laser. The output for one wavelength is about 10.3 mJ and the line width is less than 0.02 nm.

We investigated by time-of-flight technique the slow light and superluminal effects in high-quality three-dimensional （3D） colloidal photonic crystals （PCs） with opal structure, fabricated by pressure controlled isothermal vertical deposition technique. They produce high transmission in the pass bands and sharp band edges due to low volume density of defects and dislocations. The variation of the group velocity across the short-wavelength band edge was measured. Group velocity as low as 0.43c was observed near the band edge while group velocity as high as 1.34c was found in the band gap. We have also simulated the transportation of ultrashort pulses through 3D PCs and compared the simulation results with the experimental ones.

A new circuit model for using the avalanche photodiodes to detect infrared single photon is proposed, which combines the requirements of a single photon detector control circuit and features of the electric pulses generator by transient process of transmission lines. The simulation results are given for the new circuit model and the emphasis is laid on the analysis of the feasibility of the circuit model in using the gate mode scheme of the avalanche photodiodes to detect infrared single photon and the influence of each electrical component on the performance of the circuit model. Finally, optimal parameters of the electrical components and the gate-mode with the quenching circuit model are demonstrated.

A free-space quantum key distribution system is demonstrated experimentally which makes use of polarized coherent short laser pulses and the differential phase shift scheme with a Faraday-Michelson interferometer. The system features low noise, high stability and low bit-error rate. In the proposed experimental scheme, polarizated short laser pulse of several nanoseconds duration is made to transmit through the free space to decrease noise and a low bit-error rate less than 6% is achieved.

Phase drift caused by environment is the main source of quantum bit error rate and instability in the double M-Z interferometer quantum key distribution(QKD) system. The phase drift consists of both high-frequency and low-frequency vibrations, the former, which is due to environment noise, is usually conducted via the atmosphere and can be isolated by technological measures (e.g. using foamed-plastics wrapping or rubber pillow ), the latter comes from building-vibration, which vibrates slowly with a serious impact on M-Z interferometer, with a period of 3±0.32 min (min level). A novel real-time tracking and compensation method for phase drift caused by low-frequency vibration is proposed. With the improved scheme, the QKD system based on double M-Z interferometers can operate stably for 24 hours, and key exchange with an error below 6% over 75 kilometers has been achieved in the lab.

We propose and demonstrate an improved differential phase shift key distribution scheme. Alice uses a pulsed laser source and two cascaded fiber loops to get coherent pulses, then modulates them randomly under differential phase shift scheme, which compensates for the random polarization mode dispersion and phase shift. An interferometer made up of two Faraday mirrors is employed to detect single photon under gate mode. In one-way transmission, QKD is free from Trojan attack. Our experiment at setup can work stably for a long time (at least 24h) with an error ratio of 3%. The stable scheme is efficient, economical and favorable for practical application.

Compared with the photonic crystal (PC) structures composed of Si circular, the PC structrures composed of triangular lattice of air holes in a dielectric slab are more easily fabricated and integrated. The tunability of directional band gap in a two-dimensional photonic crystal of air holes in a semiconductor matrix is demonstrated numerically, using the plane wave expansion calculation. Numerical simulations show that the photonic crystal band gaps are modulated by nematic liquid crystals infiltrated in the air holes. Then the band gap can be controlled easily under the influence of the external electric field. So the results can serve as a field-sensitive polarizer. These results are in agreement with that of Liu. However, the tunable field-sensitive polarizer based on the phenylacetylene liquid crystals instead of 5CB liquid crystals has the wider frequency range. Moreover, the transmission spectrum of the photonic crystal infiltrated by liquid crystal is analyzed, using finite difference time domain (FDTD) method. Numerical simulations show that the shift of the spectrum modulated by liquid crystal can be used to design a novel switch.

A method that can generate all kinds of nonorthogonal polarization states is induced for long distance and high bit rate generation quantum key distribution. T he polarization states are synthesized by two linearly polarization states contr olled by phase modulator. The modulator is allowed to produced non-quarter_wave phase delay so that can compensate the influence of birefrmgence during transmis sion throuogh the fiber. The structures of the encoder and the decoder based on the method are also described that can effectively reduce the bit error rate.

The imaging theory of nonlinear second harmonic generation (SHG) and third harmonic generation (THG) in confocal microscopy is presented in this paper. The nonlinear effect of SHG and THG on the imaging properties of confocal microscopy has been analyzed in detail by the imaging theory. It is proved that the imaging process of SHG and THG in confocal microscopy, which is different from conventional coherent imaging or incoherent imaging, can be divided into two different processes of coherent imaging. The three-dimensional point spread functions (3D-PSF) of SHG and THG confocal microscopy are derived based on the nonlinear principles of SHG and THG. The imaging properties of SHG and THG confocal microscopy are discussed in detail according to its 3D-PSF. It is shown that the resolution of SHG and THG confocal microscopy is higher than that of single- and two-photon confocal microscopy.

A novel method that can lead to bright optical pulse compression in the normal-dispersion regime of single mode fiber is proposed.It consists of copropagating a bright pulse with a intense pulse pair in a single mode fiber.Various cases of the bright pulse compression are studied numerically under realistic practical conditions.We found that, as compared with the previous compression method,this method is not only of more practical use but also can achieve better compression of the bright pulse.

The spectral and spatial features of the coherent Raman emission (stimulated scattering and/or four-wave mixing) emission from the multimode GeO 2 -doped and P 2 O 5 -doped glass fibers have been studied experimentally. The spectral structures are obviously different for the two kinds of optical fiber samples; however the 10 times reduction of the beam size of the highest-order Stokes SRS component can be observed for both samples due to the Raman self-focusing processes. The refractive index changes induced by the multi-wave mixing with Raman resonance play an important role in these processes.