The fidelity of light with arbitrary polarizations stored in a warm ⁸⁷Rb atomic vapor at different storage time is studied. The exponential decay of regeneration efficiency with the storage time is observed and a detectable signal at 300-1s storage time is still existed. The storage fidelity at different storage time is well maintained in our experiment.

The highly Ge-doped photosensitive fiber (PSF) has been widely used in the fabrication of fiber Bragg gratings (FBGs). Its birefringence and cladding mode coupling characteristics greatly influence FBG's transmission feature in communication application areas. In this work, a new concept of the PSF is introduced which, along with an optimized birefringence design, a precisely controlled fabrication process, and a cladding mode depressed design, results in a written FBG with -25-dB clad mode-depressed ratio and a polarization mode dispersion value less than 0.045 ps.

A novel scheme is proposed to transform an ultra-short optical pulse to a millimeter-wave frequency-modulated pulse by using the cascaded all-pass cavities (APCs). The envelope waveform of the generated pulse train is calculated, showing effective improvement by APC cascading. The extinction ratio is analyzed with different input pulses, different cavity re°ectivities, and di?erent cascading numbers. It is shown that the cascading does not introduce much effect on the extinction ratio. Two designs by using Gires-Tournois cavity and waveguide ring resonators are proposed to realize the cascaded APC.

The liquid-core fiber with relatively high refractive index difference between the core and cladding is proven to be bending insensitive. The single mode condition and bending loss of the fiber with a mixture of toluene and chloroform as its core material are studied. The results show that the bending loss of this fiber is not only much smaller than the conventional silica single mode fiber but also can be tuned by the temperature and liquid mixture ratio. This kind of fiber may find its potential applications in all-optical network.

A full resolution autostereoscopic three-dimensional (3D) display prototype is developed. It is composed of a time division thin film transistor liquid crystal display panel with an optical controlled birefringence liquid crystal polarization switch and a polarizer parallax barrier. Fast driving circuits operating at 120-Hz frame rate are fabricated. The 3D images on the display have the same resolution as the corresponding two-dimensional images, which is signiˉcantly different from conventional parallax barrier autostereoscopic 3D displays having degraded 3D image resolution.

Image entropy and empirical mode decomposition (EMD) are effective methods for target detection. EMD algorithm is a powerful tool for adaptive multiscale analysis of nonstationary signals. A new technique based on EMD and modified local entropy is proposed in small target detection under sea-sky background. With the EMD algorithm, it is valid to estimate the background and get the target image by removing the background from the original image and segmenting the target based on the modified local entropy method. The data analysis and experiments show the validity of the proposed algorithm.

We propose a method for exaggerating facial expressions derived from exaggeration mappings that transform facial motions into exaggerated motions. The exaggeration mapping of facial motions is defined by non-negative matrix factorization. Three-dimensional facial expressions are simulated using the exaggerating rate as an input value to convey the degree of variation. Experiments show the validity of the exaggeration mapping and facial expression simulations.

System calibration, which usually involves complicated and time-consuming procedures, is crucial for any three-dimensional (3D) shape measurement system based on vision. A novel improved method is proposed for accurate calibration of such a measurement system. The system accuracy is improved with considering the nonlinear measurement error created by the difference between the system model and real measurement environment. We use Levenberg-Marquardt optimization algorithm to compensate the error and get a good result. The improved method has a 50% improvement of re-projection accuracy compared with our previous method. The measurement accuracy is maintained well within 1.5% of the overall measurement depth range.

We observe the morphological change and grain structure of Ni foil when it is ablated with femtosecond laser pulses. Scanning electron microscopy and ˉeld emission transmission electron microscopy are used to study the nature of the morphology and grain structure of nickel foil and determine the essential features. The results indicate that there are many random nanostructures in the center of the ablated region composed of nanocrystalline grains as well as some core-shell structures. The observed morphologies seem to suggest that phase explosion and extremely high cooling rate are the most probable physical mechanisms responsible for the formation of surface nanostructures.

P-polarization high reflectors are deposited by e-beam from hafnia and silica. 1-on-1 and N-on-1 tests at 1064-nm wavelength with P-polarization at 45° incidence are carried out on these samples. Microscope and scanning electron microscope are applied to investigate the damage morphologies in both 1-on-1 and N-on-1 tests. It is found that the laser damage threshold is higher in N-on-1 tests and nodular defect is the main inducement that leads to the damage because nodular ejection with plasma scalding is the typical damage morphology. Similar damage morphology observed in the two tests indicates that the higher laser damage threshold in N-on-1 test is attributed to the mechanical stabilization process of nodular defects, owing to the gradually increased laser fluence radiation. Based on the typical morphology study, some process optimizations are given.

We present a flat-top laser beam generation scheme using coherent beam combining of hexagonally arranged Gaussian lasers. To produce a beam with a flat-top profile, we optimize the amplitude and phase of each unit laser using the least-square method. Simulation results show that with 13 unit lasers, a beam with the flatness of less than 1% in the optimizing region can be achieved. The main lobe contains over 95% of the total power. The scheme requires no external beam shaping element and has the potential to be designed for high-power applications.

The phase noises of a 10-m polarization-maintaining (PM) fiber and a 10-W PM fiber amplifier are experimentally measured. The results indicate that the 10-m PM ˉber with similar phase noise could be used to investigate the architecture of master oscillator power ampliˉer coherent combination. A seven-element hexagonal ˉber coherent array is developed to investigate the far-ˉeld distribution and phase controlling technique of a coherently combining ˉber laser array. A hexagonal prism is designed as the combining and splitting component to achieve a ˉll factor of 0.66. The hill climbing method is employed to detect and lock the element phase.

We demonstrate a high power single-frequency fiber laser. By using phosphate glass fiber as its gain media, the laser can achieve high output power of 100 mW in centimeter-long linear cavity. Single-frequency single-polarization operation with <5 kHz linewidth and 65-dB signal-to-noise ratio (SNR) is realized by using external cavity polarization feedback technology.

In order to estimate the position and orientation of an object with a single camera, a novel measurement method based on pinhole camera model with five reference points is presented. Taking the specially designed planar target with the monocular vision system, the projection line of the reference points is built. According to the projection model, the coordinates of the reference points in the camera coordinate system are estimated with the least-squares algorithm. Thus the position and orientation of the target are worked out. Experimental result shows that the measurement precision of angle is less than 0.2°, and that of displacement is less than 0.1 mm.

Robust non-intrusive eye location plays an important role in vision-based man-machine interaction. A modified Hausdor? distance based measure to localize the eyes is proposed, which could tolerate various changes in eye pose, shape, and scale. To eliminate the e?ects of the illumination variations, an 8-neighbour-based transformation of the gray images is proposed. The transformed image is less sensitive to illumination changes while preserves the appearance information of eyes. All the localized candidates of eyes are identified by back-propagation neural networks. Experiments demonstrate that the robust method for eye location is able to localize eyes with di?erent eye sizes, shapes, and poses under different illuminations.

LiLuF₄ single crystals co-doped with thulium (5%) and holmium (0.5%), having large size, intact shape, and high optical quality, are successfully grown by the Czochralski technique. Absorption and fluorescence spectra of the crystal are measured. The absorption spectrum shows that the main absorption band locates at near 686 and 792 nm and the °uorescence spectrum peaks at 2.05 \mu m. At room temperature, the as-grown Tm, Ho: LiLuF₄ single crystals are end-pumped by a fiber-coupled laser diode system with pumping wavelength of 795 nm under CW operations. A power of 50 mw continuous laser output at 2.05 \mu m wavelength is achieved. Meanwhile an obvious green light is detected.

A novel Tm^³⁺/Er^³⁺/Yb^³⁺ triply-doped glass ceramics containing BaF2 nano-crystals are successfully prepared. Fluoride nanocrystals BaF2 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. The intense blue (476 nm), green (543 nm), and red (656 nm) emissions of the glass ceramics are simultaneously observed at room temperature under 980-nm excitation, and the emission luminescence intensity increases signiˉcantly compared with the precursor glass, which is attributed to the low phonon energy of °uoride nanocrystals when rare-earth ions are incorporated into the precipitated BaF2 nanocrystals. Under 980-nm excitation at 400 mW, the international commission on illumination (CIE) chromaticity coordinate (X = 0.278, Y = 0.358) of the tridoped oxy°uoride glass ceramics' upconversion emissions is close to the standard white-light illumination (X = 0.333, Y = 0.333). The results indicate that Tm^³⁺/Er^³⁺/Yb^³⁺ triply doped glass ceramics can act as suitable materials for potential three-dimensional displays applications.

We present the measurement of the third-order nonlinearity of Bi₂O₃-B₂O₃-BaO glasses using the single Z-scan method with femtosecond laser pulses at 750-850 nm. Both third-order nonlinear refraction \gamma and two photon absorption coefficient \beta are investigated. The \gamma shows an increasing tendency with increasing BaO content, and the largest value is estimated to be 7.2×10^-14 cm²/W, which is as large as those of chalcogenide glasses. The dependence of \beta on the normalized photon energy is studied.

The electronic structures and optical properties of both the perfect CsI crystal and the crystal containing a pair of V^1-_Cs-V¹⁺_I are calculated using CASTEP code with the lattice structure optimized. The calculated results indicate that the optical symmetry of the CsI crystal coincides with the lattice structure geometry of the CsI crystal. The absorption spectrum of the CsI crystal containing a pair of V^1-_Cs-V¹⁺_I also does not occur in the visible and near-ultraviolet range. It reveals that the existence of the pair of V^1-_Cs-V¹⁺_I in CsI crystal has no visible effects on the optical properties of the CsI crystal.

The emission properties of 2 \mu m region fluorescence of Tm^³⁺-Ho^³⁺ co-doped tellurite glasses are investigated. Introducing F^- ions to the composition of tellurite glasses plays a positive effect on the 2 \mu m emission. A maximum intensity of 2 \mu m emission is achieved when 1.5-mol% Tm₂O₃ and 1-mol% Ho₂O₃ concentration are doped in the glasses. The emission cross section and gain coefficient of the ⁵I₈-⁵I₇ transition of Ho^³⁺ are calculated. The emission cross section has a maximum of 1.29×10^-20 cm² at 2048 nm wavelength. The results indicate that Tm^³⁺-Ho^³⁺ co-doped tellurite glasses are suitable for 2 \mu m application.

Singlet oxygen (¹O₂) is widely considered to play a major role in photodynamic therapy (PDT), and thus an increasing attention has been focused on the direct detection of ¹O₂ near-infrared luminescence around 1270 nm for PDT dosimetry. A new sensitive detection system is developed to directly measure the temporal and spectral resolved ¹O₂ luminescence spectra. The triplet state and ¹O₂ lifetimes of Rose Bengal as a model photosensitizer in different solvents are determined, and the obtained results agree well with the published data. Our detection system has the potential application in ¹O₂ luminescence-based PDT dosimetry.

Based on the technique of the symmetry reduction, we find the asymptotic self-similarity analytical resolutions from the constant coefficient Ginzburg-Landau equation considering both in°uences of the third-order dispersion and gain dispersion on the evolution of pulses. We have obtained the self-similar pulse amplitude function, phase function, strict linear chirp function, and the e?ective temporal pulse width. Numerical simulations show qualitative agreement with these theoretical results.

The pulse profile influence of excitation light on the two-photon absorption coefficient \beta is theoretically and numerically studied. Based on Gaussian spatial and temporal laser, we obtain an expansion formula of energy transmission. As compared with a plain beam and a pulse beam that is rectangular in time but Gaussian in space, the relative deviations of \beta turn out to be about 214% and 47%, respectively. These differences indicate that a smaller \beta may be obtained than the real one in usual nonlinear transmission. Our result suggests that by taking real pulse profile into account, a more exact \beta can be derived in energy transmission measurement.

Numerical calculations based on the transfer matrix method are carried out, and the results of band gap with resonance peaks are obtained. The electron beam lithography technology (EBL) and induction coupling plasma (ICP) etching are used to make the photonic crystal (PC) structures, and from several scanning electron microscope images, the PC structures are observed with features closing to the design. In order to create the tiny PC structures in the right places of the waveguide by the EBL technology at different time, some alignment markers are deposited on the chip, which are made of gold that deposited on titanium for its good adhesion to the underlying Si. An optical testing bed is designed for measurement of the optical characterization of PC structures. Through the analysis of the measured data, \Delta \lambda value of 0.8 nm is obtained and for the centre frequency of 1547 nm, a very high quality factor value of 1933 can be obtained. The 3-nm difference represents only a 0.2% error from the theoretical centre.

The optical probe in tonometers is a key component in measuring the flattened diameter or area of the ocular cornea. A new kind of optical probe for the direct measurement of the flattened area of the ocular cornea is presented. The optical probe uses the cone prism with a modulating flake of light intensity as its measuring body. The test results on simulated eyeballs with different radii of curvature of the ocular cornea show that there is a linear relation between the flattened area of the ocular cornea and the normalized current. The optical probe, which is more compact compared with existing optical probes and easily configured with its coaxiality of optical parts, may be an excellent probe for constructing a low-cost, miniaturized applanation tonometer.

The interaction of multi-channel surface acoustic waves (SAWs) and a guided optical wave in fiber is studied, and the corresponding coupled wave equations are derived. A novel two-channel SAW all-fiber acousto-optic modulator is designed, fabricated, and tested. The theoretical analysis is supported by the experimental results.

The light propagation within an absorbing medium and the reflection and refraction at the interface of two absorbing media are studied. By using the unit vectors denoting the planes of constant field amplitude and constant phase respectively, the light propagation and attenuation are described by the effective refractive indices which depend on both the complex refractive index of the medium and the angle between the unit vectors. With the expression for the light propagation, the corresponding Snell's law and the expression of Fresnel coefficients are obtained, which can be applied to describe the re°ection-refraction event at the interface between an arbitrary combination of transparent and absorbing media.

We present the moments formalism theory to study the deflection of the slow signal light in the cold atomic media, which is under the condition of the Gaussian control laser and electromagnetically induced transparency. Deflection, the interesting phenomenon on quantum coherence, is testified by analytic and numerical methods. Results show that, as the signal light propagating in the medium, there would be an observable deflection before the general diffraction. Influences of the coupling intensity on deflection phenomenon and the beam waist of the signal light in the medium are also investigated.

The evolution of stress in evaporated SiO₂, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures (thin film deposition, stopping deposition, cooling, venting the vacuum chamber, and exposing coated optics to the atmosphere) is put forward. Further investigations into the subprocedures reveal their features. During the deposition stage, the stresses are usually compressive and reach a stable state when the deposited film is thicker than 100 nm. An increment of compressive stress value is observed with the decrease of residual gas pressure or deposition rate. A very low stress of -20 MPa is formed in SiO₂ films deposited at 3×10^-2 Pa. After deposition, the stress increases slightly in the compressive direction and is subject to the stabilization in subsequent tens of minutes. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours. An initial discussion of these behaviors is given.

The influence on the level of amplified spontaneous emission (ASE) contrast resulting from the different seed pulse energies has been experimentally studied in a 10-TW-level femtosecond Ti:sapphire chirped pulse amplification laser. It is found that, with the seed pulse energy increasing, the ASE pedestal is suppressed more efficiently, and the ASE contrast is improved with a saturable tendency. The measurement of ~2×10^-8 ASE contrast in the range of more than 50 ps before the main pulse is achieved in the laser.

The phase shifts of the extinction and refractive index gratings to the illumination pattern are revealed in doped polymethyl methacrylate (PMMA). The dynamic process of these shifts is studied via two-wave coupling at 351 nm. It is shown that these shifts are from the strain and the shrinkage inside the sample and accompanied with the photo-repolymerization process during the building process of the holographic grating. Such shifts will cause obvious energy exchange between the two recording beams and enough attention should be paid to the nonlocal property of the holographic gratings of the material in the application.

Accurate small animal surface reconstruction is important for full angle non-contact fluorescence molecular tomography (FMT) systems. In this letter, an optimal surface reconstruction method for FMT is proposed. The proposed method uses a line search method to minimize the mismatch between the reconstructed three-dimensional (3D) surface and the projected object silhouette at different angles. The results show that the mean mismatches of the 3D surfaces generated on three live anesthetized mice are all less than two charge coupled device (CCD) pixels (0.154 mm). With the accurately reconstructed 3D surface, in-vivo FMT is also performed.