Nonlinear wave propagation in a 1D photonic crystal containing single-negative layers is investigated using the multiple-scale method. In this approach, the electric field is decomposed into a slowly varying envelope function and a fast Bloch-like function to obtain the analytic expressions of the effective parameters of an equivalent medium. The periodic structure has an equivalent left-handed medium for the envelope function. Gap soliton formation is discussed and compared with that associated with the Bragg gap.

A temperature-compensated fiber optic Fabry-Perot accelerometer (FOFPA) formed by symmetrically bonding an all-silica in-line fiber Fabry-Perot etalon (ILFFPE) and a piezoelectric ceramic unimorph actuator (PCUA) to two surfaces of a silica cantilever is reported. The all-silica ILFFPE with feedback-controlled cavity length by the PCUA simultaneously senses acceleration and temperature. The results indicate that the fabricated FOFPA system simultaneously senses acceleration and temperature with active temperature compensation. The nonlinearity of the output voltage to acceleration is less than 0.65%. The nonlinearity of the control voltage to temperature is 1.75%. Furthermore, the maximum deviation of the sensitivity with temperature compensation at a temperature range from 25 to 50 oC is 0.025 V/g.

In this letter, two kinds of continuous wavelength-tunable light sources are achieved and investigated experimentally using a self-seeding reflective semiconductor optical amplifier (RSOA). Over 40 single mode wavelengths with 100 GHz spacing are generated by setting the parameters of the wavelength selective switch. The peak power of each wavelength reaches over 0.2 dBm with the signal-to-noise ratio (SNR) > 35 dB. The proposed schemes are appropriate for multi-wavelength-tunable light sources; the maximum number of wavelengths generated can reach to 4.

A method to fabricate fiber Bragg grating (FBG) in an optical microfiber (OM) from a conventional photosensitive fiber is proposed in this letter. The cladding of a conventional photosensitive fiber is etched to 17 \mu m. The etched fiber is drawn to an OM 6 μm in diameter. The photosensitivity of the fabricated OM is effectively reserved. A FBG in the OM (MFBG) is successfully fabricated using a KrF excimer laser at a fluence of 400 mJ/cm2 through a phase mask with a pitch of 1 089.3 nm. The reflectivity of the FBG is approximately 10%, and the 3-dB spectrum bandwidth is 0.13 nm. The concentration of brine is measured by immersing the MFBG in the liquid, and the minimum detectable refractive index variation can reach 7.2 \times 10^{-5} at a refractive index value of 1.33.

One-dimensional (1D) integral imaging based on parallax images' virtual reconstruction is proposed. The 1D integral imaging contains parallax images' capture process, parallax images' virtual reconstruction process, and 1D elemental image array's generation process. A pixel mapping algorithm is deduced to implement the last two processes; a 1D elemental image array is generated by the mapping of pixels on the parallax images obtained using a 1D camera array. The proposed 1D integral imaging can capture the 1D elemental image array of a real three-dimensional (3D) scene.

A compact bi-directional (BiDi) triplexer using grating-assisted multimode interference (MMI) coupler is proposed based on silicon nanowire waveguides.Because of the high index contrast between silicon and silicon dioxide, the size of the structure is greatly reduced with a footprint of 2.5 \times 911 (\mu m). Asymmetrical ports are introduced in the MMI structure to satisfy the bandwidth requirements of the industrial standards ITU-T G.983.3-dB bandwidths of 100, 22, and 15 nm are obtained for the wavelengths of 1 310, 1 490, and 1 550 nm, respectively. The device can be readily fabricated using a commercial CMOS process.

Selective area growth (SAG) is performed to fabricate monolithically integrated distributed feedback (DFB) laser array by adjusting the width of a SiO2 mask. A strain-compensated-barrier structure is adopted to reduce the accumulated strain and improve the quality of multi-quantum well materials. Varying the strip width of the SAG masks, the DFB laser array with an average channel spacing of 1.47 nm is demonstrated by a conventional holographic method with constant-pitch grating. The threshold current from 14 to 18 mA and over 35-dB side mode suppression ratio (SMSR) are obtained for all DFB lasers in the array.

We present the birefringence measurements induced in K9 specimen by cracks produced by 1 064-nm Nd:YAG laser. The birefringence data are converted into units of stress, permitting the estimation of residual stress near cracks. The laser parameters and characterization of the optical material influence the value of residual stress. Residual stress in optical materials can affect fracture; thus, this factor should be considered in any formulation that involves enhanced damage resistance of optical components used in laser-induced damage experiments. The probability of the initial damage and the direction of the energy dissipation in cracks determine the residual stress distribution. Moreover, thermal-stress coupling enlarges the asymmetry of residual stress distribution. Therefore, the physical mechanism of asymmetric damage is useful for understanding the nature of optical materials under high-power laser irradiation.

The manipulation of the subpulse number, pulse delay, and pulse energy distribution of an ultrafast laser enables electron dynamics control by changing absorptions, excitations, ionizations, and recombinations of electrons, which can result in smaller, cleaner, and more controllable structures. This letter experimentally reveals that ablation sizes and recasts can be controlled by shaping femtosecond pulse trains to adjust transient localized electron dynamics, material properties, and corresponding phase change mechanisms.

In this letter, numerical simulation and experimental study of a radial-slab solid-state laser are presented. The laser includes four crossing-slabs pumped by four Xe flashlamps. The numerical simulation of coherent intensity in the near field and the far field indicates that the laser with the structure can improve the quality of output beam compared with incoherent beam combination. The radial-slab solid-state laser is fabricated, and initial experiments are carried out at a pulse repetition of 1 Hz. Nine beams in the near field and one combined beam in the far field are obtained in our initial experiment. The experimental results are consistent with the numerical analysis in the coherent condition. The results show that coherent beam combination is obtained by this laser.

Theoretical simulation and experiments based on a prism beam expander and an echelle grating are conducted to study the dependence of linewidth and pulse energy on incidence angle and slit width. With a larger prism incident angle or narrower slit width, the linewidth becomes narrower while the laser pulse energy becomes lower. However, the pulse energy can be improved by optimally designing the prism beam expander. In addition, a subpicometer linewidth ArF laser is obtained with a double-prism beam expander and an echelle grating.

An efficient 1 319-nm Nd:YAG single-frequency laser is demonstrated in a diffusion-bonded nonplanar ring oscillator (NPRO) with an undoped end. The thermal model of diffusion-bonded NPRO is generated to analyze the temperature field and thermal focal length. A stable single-frequency output power of up to 1.55 W is obtained at 1 319 nm.

A short distributed feedback fiber laser with a nearly unidirectional output is fabricated and tested. The short fiber laser is made of a polarization-dependent phase-shift grating fabricated with a vertically polarized 244-nm ultraviolet (UV) laser. A single \pi phase-shift is introduced to a 2-cm grating at a specified position by directly moving the phase mask during UV beam scanning. Test results show that the laser has a single polarization longitudinal mode with 2.6-mW pump threshold. The backward-to- forward output power ratio is approximately 30:1. The relative intensity noise is –88 dB/Hz, and the linewidth is approximately 10 kHz at 75-mW 980-nm pumping. The unidirectional output and short dimension of this short fiber laser make it very useful in sensing applications, especially in multiplexed sensing applications.

A large-aperture Nd:YAG thin-disk laser directly cooled by liquid is end-pumped by two spatial self-organized laser diode arrays. The pump coupling efficiency reaches as high as 93%. Without any complex pump coupling components, the structure becomes simplified and compact. By optimizing the incident angle of the pump beam, a pump power density of 578 W/cm2 is achieved with a pump uniformity of 5.52%. Up to 1 346-W peak output power with a slope efficiency of 54.9% is obtained when pumping with a long pulse. The near-field pattern of the laser output is uniform.

A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition (PIC) of the active region (AR) and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.

Bismuth (Bi)-doped materials have attracted a great deal of attention because of their broadband nearinfrared (near-IR) emission around the wavelength utilized in telecommunications. In this study, broad near-IR emission band from 1 100 to 1 650 nm is generated in the Bi-doped 90GeS2-10Ga2S3 glass and glass-ceramics under 820 nm of light excitation. Based on the analysis of the absorption and emission spectra, the origin of this broadband emission is ascribed to the Bi^{2-}_{2} dimers. The precipitation of \beta-GeS2 nanocrystals drastically enhances the emission intensity and lifetime of Bi-doped chalcogenide glass.

Three-dimensional-ordered Yb/Er co-doped Bi2Ti2O7 inverse opal, powder, and disordered reference samples are prepared and their upconversion (UC) emission properties and mechanisms are investigated. Significant suppression of UC emission is detected when the photonic band-gaps overlap with Er3+ UC green emission bands. Interestingly, green and red UC emissions follow a two-photon process in the powder sample but a three-photon one in the inverse opal.

We investigate the nonlinear behaviors of light recognized as chaos during the propagation of Gaussian laser beam inside a nonlinear polarization maintaining and absorption reducing (PANDA) ring resonator system. It aims to generate the nonlinear behavior of light to obtain data in binary logic codes for transmission in fiber optics communication. Effective parameters, such as refractive indices of a silicon waveguide, coupling coefficients (), and ring radius ring (R), can be properly selected to operate the nonlinear behavior. Therefore, the binary coded data generated by the PANDA ring resonator system can be decoded and converted to Manchester codes, where the decoding process of the transmitted codes occurs at the end of the transmission link. The simulation results show that the original codes can be recovered with a high security of signal transmission using the Manchester method.

The nonlinear optical (NLO) and optical limiting (OL) properties of three new structures of organic NLO guest–host Poly(N-vinylcarbozole)/disperse orange 3 (PVK/DO3), PVK/disperse orange 13 (PVK/DO13), and PVK/disperse orange 25 (PVK/DO25) as a solution at different concentrations and as a thin-film sample are studied using continuous wave z-scan system at 532 nm. The open-aperture z-scan data of the NLO materials in the solution and thin-film samples displayed two-photon and saturable absorptions, respectively. The PVK/DO13 exhibites the largest and best values of the nonlinearities, such as n2, \beta, (3), compared with those of PVK/DO3 and PVK/DO25. This nonlinearity increases as the concentration increases. The results indicate that these NLO materials are good candidates for optical switching and OL devices.

Enhancing the photoluminescence and depressing the background emission are important problems in rare earth ion-doped materials. In this letter, the two-photon absorption (TPA) probability in a Pr3+ ion system is enhanced by a factor of 12.3 by a \pi-phase step scanning of ultrashort laser pulses. This level is significantly higher than that achieved by a transform-limit pulse. However, the laser intensity of shaped pulse is reduced to 37% of the initial transform-limited pulse. In this method, the TPA probability can also be reduced to 58%. Furthermore, the effect of the shift of the intermediate energy level and the bandwidth of final states on TPA probability is discussed.

A 5-bit photonic analog-to-digital conversion under a sampling rate of 10 Gs/s is experimentally demonstrated. In the experiment, the birefringence walk-off in the scheme is compensated, and 16 high-extinction ratio optical transfer functions with different phase shifts are obtained. A 1-GHz sinusoidal analog signal is sampled and quantized by optical processing, and the effective number of bits obtained is 4.17.

The optical properties and plasmon resonance coupling of double coaxial gold nanotube arrays are investigated. The results show that the optical transmission is highly tunable by varying the thicknesses of the inner and outer nanotubes, the separation between the inner and outer nanotubes, and the dielectric parameters inside, between, and outside the two nanotubes. The shorter-wavelength transmission bands are very sensitive to the modification of the wall thickness of the outer nanotube, the separation, and the dielectric parameters between the double nanotubes. The dipole and multipolar plasmon modes are excited in our model. However, for small separation and refractive index, the dipole normal mode has a leading function in the transmission properties. Compared with the dipolar modes, the contribution of higher-order modes becomes larger as the parameters increase.