An ultra narrow linewidth fiber laser is presented, which is composed of a ring cavity laser and a linewidthnarrowing module. The fiber laser is introduced in detail and the single mode operation of the laser is verified. Using a revised self-heterodyne detection method, experimental data of the laser linewidth against the pump power are presented. The narrowest linewidth is measured to be 109 Hz, whereas the output power is 1.1 mW.

The design of a tunable metal-coated long-period fiber grating (LPFG) filter based on the material dispersion consideration is presented. The tuning of the resonant wavelength can be achieved by heating the metal layer. Based on the coupled mode theory, the influences of the material dispersion on the transmission spectrum of the metal-coated LPFG are studied. There is a special grating period for a specific cladding mode; when the grating period is less than or equal to the special grating period, the material dispersion has weak influence on the resonant wavelength. Under such condition, the attenuation band depth corresponding to the specific cladding mode has excellent stability while the temperature changes, thus improving the filtering performances of the tunable loss filter. Further, experimental results demonstrate the validity and feasibility of the proposed tunable filter.

The human visual system processes lightness constancy to estimate reflectance under complex viewing conditions. We focus on the underlying reason the human visual system is conscious of haze, and discuss the single-image haze-removal problem based on lightness constancy from the beginning of haze illusion. Following the basic principle and model of "atmospheric transfer function", we bring about a simple dehazing paradigm by estimating two values using bilateral filtering. Practical investigation of parameters and design are analyzed in detail. Furthermore, a novel quantitative standard haziness presents itself naturally during the estimation process. Comparative study and objective evaluation demonstrate that the proposed method is fast and effective, yielding high-contrast and vivid haze-free images.

Two comprehensive evaluation metrics, image perceptual quality based on target detectability (PQTD) and perceptual quality based on scene understanding (PQSU), are proposed to measure image quality for visible and infrared color fusion images of typical scenes. A psychophysical experiment is performed to explore the relationship between conventional quality attributes and the proposed evaluation metrics. The prediction models for PQTD and PQSU are derived by multiple linear regression statistical analyses. Results show that the variation of PQTD can be predicted by sharpness and perceptual contrast between the target and background, and that color harmony and sharpness can predict PQSU. The proposed evaluation metrics and their prediction models provide a foundation for further developing objective quality evaluation of color fusion images.

We propose and demonstrate broadband Brillouin slow light using a multiple-longitudinal-mode tunable fiber laser as Brillouin pump. A tunable broadband Brillouin pump with a tuning range from 1 520 to 1 555 nm is generated using a fiber ring laser with a semiconductor optical amplifier (SOA) as its gain medium. The pump spectrum consists of a large number of longitudinal modes separated by 6 MHz. The 3-dB bandwidth is about 11.5 GHz, and its fluctuation is less than 100 MHz within the tuning range. An 8-Gb/s data signal can be delayed by up to 83.0 ps (bit error rate < 10 9) at 17-dBm pump power.

We demonstrate experimentally the application of a phase error detection method in the coherent beam combination (CBC) of a laser array. The method is based on the Hartmann micro-lens array. Both the piston and tilt errors can be detected and corrected simultaneously by combining this method with adaptive optics-correcting technology. The far-field intensity pattern of the combined beam has high energy concentration and good beam quality. The power encircled in the main lobe of the far-field pattern is 41.3%, and the contrast of the pattern reaches 81.8%. Experimental results show the great potential of the Hartmann phasing method for use in the CBC of a large number of laser beams.

A novel, compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser is developed. A diode-end-pumped pair of Nd:YLF slabs and an intracavity-frequency-doubled configuration are adopted to increase conversion efficiency. Using 49.8-mJ incident pump pulse energy at 500-Hz repetition rate, the laser obtains 11-mJ pulse energy and 5.5-W average output power at 527-nm wavelength, achieving an optical–optical conversion efficiency of 22%. The pulsewidth is less than 15 ns, and the beam quality factors are M2x=1.28 and M2y=1.12.

In this manuscript, coherent polarization beam combining of four polarization-maintained fiber amplifiers is demonstrated. In each fiber amplifier, two cascaded fiber amplification stages are used to boost the output power to watt level. The compact and robust single-frequency dithering technique is employed in the active phase-locking of the four laser beams. When the system is in the closed loop, the phase noise can be suppressed effectively for long-time observation. The experimental results show that the combining efficiency of the whole system is as high as 95%.

Two series of Yb3+-doped silica glasses (YA and YAP) are fabricated using the sol-gel method, and their spectroscopic properties are investigated. The longest fluorescence lifetime of 0.96 ms is obtained in YAP2 and YAP3 glasses. The emission cross-section (emi) and emi × of Yb3+ in the YAP1 glass are 1.00 pm2 and 0.94 pm2·ms, respectively. Co-doping with Al and P decreases the hydroxyl group content in the glasses because of the reduction in non-bridging oxygen content. The lowest OH content in the YAP3 glass is 9.6 ppm.

The upconversion luminescences of YAlO3:Er3+ phosphor co-doping with different Gd3+ concentrations are investigated under the excitation of 980- and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd3+ ions for Y3+ sites changes the local symmetry of Er3+, leading to the improvement of upconversion efficiency.

We discuss theoretically how supercontinuum spectra produced from high-order harmonic generation processes in a synthesized same-color laser field is optimized by adjusting the chirp parameter of the controlling pulse. Furthermore, a 40-attosecond isolated pulse with an effective bandwidth of 121 orders is obtained from He+ ion when the chirp rate ratio of pulses has a small value. The numerical results show that the efficiency of single as pulse generation is enhanced, and the quantum paths are controlled successfully. Our simulation shows that the produced pulses with high signal-to-noise ratio are obtained straightforwardly without any phase compensation. These results are explained using the classical approach.

Different electro-optic effects, such as Kerr effect, Pockels effect induced by the electric field or strain, and plasma dispersion effect exist in silicon. Experimentally distinguishing these effects is necessary for designing silicon-based electro-optic devices. According to their different polarization dependencies and frequency responses, these effects are measured and distinguished successfully via a transverse electro-optic modulation experiment based on the near-intrinsic silicon sample. The results indicate that Pockels effect induced by the electric field or strain is primary among these effects in the near-intrinsic silicon sample.

Using the thermal field dynamics theory to convert the thermal state into a "pure" state in doubled Fock space, we find that the average value of e^{fa+a} under squeezed thermal state (STS) is just the generating function of Legendre polynomials. Based on this remarkable result, the normalization and photon-number distributions of m-photon added (or subtracted) STSs are conviently obtained as the Legendre polynomials. This new concise method can be expanded to the entangled case.

We cool 85Rb atoms in an integrating sphere directly from a vapor background using diffuse light generated by multiple reflections of laser beams in the inner surface of the integrating sphere. We compare and analyze the different features of cold 85Rb atoms and cold 87Rb atoms in diffuse light cooling, which are important in applying 85Rb and 87Rb isotopes in many experiments on testing fundamental physics.

The perturbation theory of matrices is applied to ray transfer matrices (RTMs) to describe an optical component with aberration. A quantitative description of the perturbation extent corresponding to aberration strength is provided using condition numbers and absolute errors for the perturbed RTM. An application to a single small aberration is presented, and the results are compared with those of the diffraction theory of aberrations.

A miniature, broadband, astigmatism-corrected Czerny-Turner spectrometer is proposed. Theories of the broadband astigmatism correction using freeform cylindrical lens are thoroughly analyzed. Comparisons of the freeform cylindrical lens method with those of titling cylindrical lens or wedge cylindrical lens methods are also described. Results show the better spectrometer performance with the new optical design over a broadband spectral range from 300 to 800 nm.

Using the time-dependent theory, we calculate the random-laser emission spectra in a two-dimensional strongly disordered medium. The calculation results show that in low dimensional systems, such as thinfilm disordered media and planar waveguides, the larger the difference of the refractive indices between the scattering and background media, the smaller the lasing threshold. We also reveal the existence of multimode survival and mode competition. We experimentally obtain the emission spectra of a dye solution with Al particles doped at different pumping energies, and the experimental results agree well with the calculated ones.

A spinel LiMn2O4 is investigated via Raman spectroscopy at 514.5-nm excitation and X-ray diffraction. The dependence of Raman spectra on the different irradiated laser powers is determined and found to be different from that at 632.8-nm excitation. Based on our extensive analysis, our experimental results can be attributed to the laser heating effect, which reduces the Mn4+ cation concentration in the local area. Consequently, the decrease in average Mn valence in the local area unavoidably induces the Jahn-Teller effect and local lattice distortion, which accounts for the evolution of the measured Raman spectra of spinel LiMn2O4.

Based on the floating reference theory, a new method for extracting the net analyte signal (NAS) is proposed. The noise background subspace is spanned by spectra at the floating radial reference point, and then, the spectra at the measurement point are projected on the subspace. Thereafter, the glucose concentrations in intralipid solutions are investigated through Monte Carlo simulation and experiments, and the partial least squares (PLS) models with and without NAS analysis are built. The root mean square errors of calibration and prediction reach to 28.87% and 27.33%, respectively. The results confirm the existence of information induced by glucose concentration variations as well as the validity of the floating reference theory.

A Chinese skin colour database is established based on measurements taken from nine bodies areas of 202 Chinese individuals to move towards accurate skin colour reproduction. The colour appearance of each skin point is predicted, and a comprehensive colour gamut for Chinese skin is determined. A consistent colour shift between facial and arm colours is identified, in which facial colour tends to be more reddish, more colourful, and darker than arm colour. Moreover, Chinese females are found to have lighter, paler, and more yellowish skin than Chinese males. Variations in Chinese skin colour are quantified, and body area differences and gender differences are shown to have significant effects on Chinese skin colour.

Based on the configuration of surface plasmon resonance (SPR) sensor, the SPR sensor model is set up, and the thermo-properties of various parts in the model are discussed. The thermo-characteristics of SPR spectra in wavelength interrogation and angular interrogation are investigated. Results show that thermo-optic and dispersion effects in the model deteriorate the sensitivity of SPR sensor, especially the thermo-optic effects. Mathematical expression is established to describe the resonance wavelength or angle, which is dependent of temperature. It demonstrates that the thermo-property of sensing medium excites the fluctuation of resonance wavelength or angle more intensely than that of the substrate or metal film in 1–2 orders. Our theoretical research is consistent with the previous experimental results.