Channel spacing halving and multi-channel apodisation of sampling fiber Bragg grating (SFBG) based on moire effect are demonstrated, which are realized by stretching and double exposure in fabrication of the SFBG. The experiment and theoretical analysis showed that the channel spacing could be halved when the period of moire grating was four times of the period of sampling and the initial phase difference of two exposures was even times of π. The multi-channel apodisation could be realized when the period of moire fringe was twice the length of SFBG and the initial phase difference of two exposures was odd times of π. A novel method to control the initial phase difference of two exposures is presented in this paper. Usingthis technique, we fabricated two SFBGs with channel spacing of 50 and 100 G by a same phase mask and an apodized SFBG with channel spacing of 100 G.

The advantages of using nonlinear optical loop mirror (NOLM) to compress pulse with slight amplitude fluctuation and reflected energy loss are analyzed in theory. Experimentally the NOLM is placed in an actively mode-locked erbium-doped fiber ring laser to form a figure-eight actively and passively modelocked fiber laser. 12 ps mode-locked pulses centered at 1.543 μm were obtained with the modulation frequency of 2.498748700 GHz. 3.715 mW output power is achieved with 50 mW pump power.

In this paper, the Yb-doped superfluorescent fiber source (SFS) with cascaded broad fiber Bragg gratings (FBGs) are reported. The spectral properties of this SFS with cascaded broad FBGs are described and compared with that without cascaded broad FBGs. The experimental results have shown that cascaded broad FBGs can increase the output of some special wave bands.

In this paper, a simple label eraser employing Gaussian apodized fiber Bragg grating (FBG) for all optical label swapping (AOLS) networks is proposed. Relying on the analysis of the payload through multi-stage erasers, this kind of eraser significantly improves the cascadability in comparison with the traditional fiber-loop mirror (FLM) eraser. The influences of the residual labels on the intermediate swapping node labels through the eraser are also investigated. It is shown that the power penalty is only less 1 dB when the optical power ratio of residual label to the new label signal arrives at -8 dB. The influence is negligible due to the sharp notch filtering effect of the Gaussian apodized FBG.

The properties of ultra-short dense dispersion-managed soliton (DDMS) in optical fiber links are investigated. They show some excellent characters, such as, reducing pulse's breathing extent greatly, facing fewer mutual interactions and tolerating larger local dispersion. In general, DDMS is more stable than a conventional dispersion-managed soliton in high-capacity systems. Excessively dense dispersion compensation is more suitable for systems with weak nonlinear effect.

A novel MEMS variable optical attenuator (VOA), which has completely different attenuation mechanism from those in literatures, is proposed and demonstrated in this paper. The basic operation principle is that the optical power coupled between two initially aligned single-mode fibers will be continuously attenuated while the end of one of the fibers is deflected from the initial position. A micromachined solenoid type inductor with a U-shaped permalloy magnetic core is used to attract the deflectable fiber that has a permalloy coat on its end. To fabricate the multi-layer three-dimensional inductive component, a new UV-LIGA process for thick photoresists is developed, combining advantages of both SU-8 and AZ-4000series photoresists. The inductive component is approximately 1.7 mm×1.3 mm×50 μm in size and has a low resistance value (~2.1 Ω). The whole size of the VOA before packaging is 30 mm×2 mm×0.6 mm. The first prototype shows less then 3-dB insertion loss at 0-dB attenuation and nearly 40-dB attenuation range with less than 20 mW electrical input power at wavelength 1550 nm.

This paper presents a novel approach of visual inspection for texture surface defects. The approach uses artificial immune theory in learning the detection of texture defects. In this paper, texture defects are regards as non-self, and normal textures are regarded as self. Defect filters and segmentation thresholds used for defect detection are regarded as antibodies. The clonal selection algorithm stemmed from the natural immune system is employed to learn antibodies. Experimental results on textile image inspection are presented to illustrate the merit and feasibility of the proposed method.

In this paper, an optical system for in-plane remote displacement measurement is brought forward. The remarkable characteristic of this optical system is to use a big aperture lens to focus the waists of two Gauss beams on a scatter which have been expanded and collimated, so good laser Doppler signals and high measurement accuracy are achieved. The experiments prove that the measurement system consisting of this optical system, a lock-in amplifier and a digital filter can be used to measure the in-plane displacement of scatters in distance of 50 m with the relative accuracy of 1%.

In this paper, a narrow-band tunable external-cavity semiconductor laser with the Littman set-up is reported. The laser system consists of a semiconductor laser, a blazed grating and an external mirror. Its sideband suppression ratio over 20 dB was obtained. Conveniently tuning in wavelength region of 797.38-807.26 nm was achieved. The laser is operating in single frequency with narrow linewidth smaller than 0.06 nm. The output beam has good directional stability when tuned.

As the output power of a chemical oxygen iodine laser (COIL) increases, the output laser beam instability appears as the far-field beam spot drift and deformation for the large Fresnel number unstable resonator. In order to interpret this phenomenon, an output beam mode simulation code was developed with the fast Fourier transform method. The calculation results show that the presence of the nonuniform gain in COIL produces a skewed output intensity distribution, which causes the mirror tilt and bulge due to the thermal expansion. With the output power of COIL increases, the mirror surfaces, especially the back surface of the scraper mirror, absorb more and more heat, which causes the drift and deformation of far field beam spot seriously. The initial misalignment direction is an important factor for the far field beam spot drifting and deformation.

The matrix eigenvalue method is used to analyze a laser resonator composed of diffraction optical elements. The results show that this type of resonator can separate fundamental mode and high order modes effectively. The output beams can be designed for different requests.

Diode-laser pumped monolithic single-frequency non-planar ring laser has the advantages of compactness, reliability and high efficiency. But when the pump power is high enough, the thermal effect will be serious and the high-order transverse modes will appear. Therefore the single-mode output power is limited. In this paper, the mechanism of generating the high-order transverse modes in the monolithic unidirectional non-planar ring cavity is analyzed using ray tracing method. The calculated results are in agreement with the experiments.

A pulsed Nd:YAG laser is used in multi-layer cladding on ZM6 Mg base alloys. The microstructure is studied with an optical microscope and a scanning electron microscope (SEM). The composition within the layer was determined by electron probe microanalysis (EPMA). X-ray diffraction (XRD) was also used to investigate the phase of constitutes of the cladding zone. The results show that microstructure in solidified cladding layer changes much when treated by high energy laser beam. The microstructure of the ZM6 alloy consists of α-Mg and Mg9Nd, while the L-ZM6 of α-Mg, Mg9Nd and α-Zr. The depth of the cladding is over 1 mm. Many fine particles were found to be distributed homogeneously throughout the matrix and the columnar grain grows along substrate.

A method of measuring thermal diffusivity of materials at room temperature by photothermal reflection technique is described. An intensity-modulated Ar+ laser beam is used as incident light. The beam is focused to about 1 mm diameter spot and illuminates the sample surface. HgCdTe infrared detector is used to receive photothermal signal. Using this technique, the photothermal signals are experimentally measured as the function of different frequencies. The thermal diffusivities can be obtained by fitting the experimental data. On the other hand, the thermal diffusivities of one-way composite and orthogonalsymmetric arranged composites Al2O3/Al are measured in transverse, longitudinal and arbitrary directions. The results show that the diffusivity of one-way material decreases with the increase of the measurement angle; the diffusivity of orthogonally arranged material almost keeps the same when measurement angle changes.

Stainless steel-doped SrTiO3 thin films were fabricated by laser molecular beam epitaxy (L-MBE). Nonlinear optical property of the thin film was measured by the single beam Z-scan technique at the wavelength of 532 nm. Two two-phonon absorption coefficient and nonlinear refractive index were determined to be 9.37×10^(-7) m/W and 1.55×10^(-6) esu, respectively. The merit figure T was calculated to be 1.8, satisfying condition T < 2 for an optical switch. The thin film has a very promising prospect for the applications in optical device.

The infrared stimulated radiation of 1D2-->3F2 and 1D2-->3H6 transitions in Pr3+:Y2SiO5 (YSO) via pulsed laser pumping has been observed. The threshold energy, temperature dependence and divergence angle for the stimulated radiation are also measured.

The technique of fluorescence spectroscopy is applied to study thioredoxin reductase (TrxR) in the cells of human brain. Experimental results show that, by the violet light emitting diode (LED, λmax=407 nm) light irradiation, TrxR is able to emit three striking spectral bands (528-582 nm; 588-660 nm; 683-700 nm). The fluorescence intensity is linear to the concentration of TrxR. The spectrum of denatured TrxR is rather different from that of organized TrxR, which reflects the structure change between denatured TrxR and organized TrxR. Furthermore, physical and biochemical mechanisms of fluorescence production for LED light-induced TrxR spectra and its characteristics are analyzed. This paper may be useful to better understand the structure of TrxR, and to provide new spectroscopic information to improve the resolution for this kind of biology structure.

In this letter, we report on, for the first time, the successful femtosecond micro-fabrication of continuous waveguide-like channels in the photorefractive polymer consisting of the nonlinear chromophore 2,5-dimethyl-4-(p-nitrophenylazo)anisole (DMNPAA), the photosensitive compound 2,4,7-trinitro-9-flourenone (TNF), and the plasticiser N-ethylcarbazole (ECZ) all doped in the polymer matrix poly(methyl methacrylate) (PMMA). These channels are caused by the change in refractive index as a result of the localised heating of the polymer and therefore have an important potential for micro-photonic devices in future.

Continuous-wave blue light at 429 nm from a second harmonic process has been investigated at room temperature with Potassium Niobate (KNbO3) crystal. Optimum parameters for nonlinear conversion in our designing single-resonant, external ring cavity pumped by the Ti:sapphire laser are established. 39% of maximum overall conversion efficiency is obtained and factors that limit the conversion efficiency is discussed.

The present letter finds the complete set of exact solutions of the time-dependent generalized Cini model by making use of the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation and, based on this, the general explicit expression for the decoherence factor is therefore obtained. This study provides us with a useful method to consider the geometric phase and topological properties in the time-dependent quantum decoherence process.

Optic parameters, such as the probabilities of radiative and non-radiative transition and the crossrelaxation probability between Yb3+ and Ho3+ ions in Yb,Ho:YAG crystal, are calculated on the basis of Judd-Ofelt and Dexter theories. The energy up-conversion process is analyzed by solving the transition rate-equations. The results show that (1) the intensity of the green fluorescence relates to the square of the concentration of the active ions; (2) the intensity increases with the concentration of sensitive ions as well, but the increasing rate goes rather too slow; (3) the efficiency of the energy up-conversion relates with the speed of the energy up-conversion and the quantum efficiency of the transiting from upper levelto lower level.