Two-dimensional (2D) slab photonic crystal waveguides (PCWGs) on silicon-on-insulator (SOI) wafer were designed and fabricated. Full photonic band gap, band gap guided mode, and index guided mode were observed by measuring the transmission spectra. Mini-stop-bands in the PCWG were simulated with different structure parameters. Coupling characteristics of PCWG were investigated theoretically considering the imperfections during the fabrication process. It was found that suppressing power reservation effect can realize both short coupling length and high coupling efficiency.

We project a compact T-branch beam splitter with a micron scale using a two-dimensional (2D) photonic crystal (PC). For TE polarization, one light beam can be split into two sub-beams along opposite directions. The propagating directions of the two splitting beams remain unchanged when the incident angle varies in a certain range. Coupled-mode theory is used to analyze the truncating interface structure in order to investigate the energy loss of the splitter. Simulation results and theoretical analysis show that choosing an appropriate location of the truncating interface (PC-air interface) is very important for obtaining high efficiency due to the effect of defect modes. The most advantage of this kind of beam splitter is being fabricated and integrated easily.

We propose a new type of two-dimensional (2D) photonic crystal L-shaped bent waveguides based on ring resonators with an acceptable bandwidth. The proposed structure mechanism is based on coupling between a waveguide and a ring resonator. This structure is designed and verified by finite-difference time-domain (FDTD) computation. Our simulation using this method gets over 90% output.

A novel fabrication method of multi-core photonic crystal fibers is proposed on the basis of a fiber-embedded technique. A taper tower is used to modify the structures of the fiber preform, and four steps of fiber fabrication and different structures of fiber samples are given. The mode structures and beating characteristics of a photonic crystal fiber sample with two successive cores are investigated in detail with the help of a supercontinuum light source, a charge-coupled device (CCD) camera, and an optical spectrum analyzer. The test results show a clear beating phenomenon between two orthotropic polarization modes with a 2.8-nm peak interval in wavelength.

Recent advances in quantum dots (QDs) for classical and non-classical light sources are presented. We have established metal organic chemical vapor deposition (MOCVD) technology for InAs-based Q D lasers at 1.3 \mm and achieved ultralow threshold in Q D lasers with photonic crystal (PhC) nanocavity. In addition, single photon emitters at 1.55 \mum, GaN-based single photon sources operating at 200 K, and high- PhC nanocavity have been demonstrated.

The dynamics of nonlinear processes in quantum dot (QD) semiconductor optical amplifiers (SOAs) are investigated. Using small-signal measurements, the suitabilities of cross-gain and cross-phase modulation as well as four wave mixing (FWM) for wavelength conversion are examined. The cross-gain modulation is found to be suitable for wavelength conversion up to a frequency of 40 GHz.

Chip-scale integration of optoelectronic devices such as lasers, waveguides, and modulators on silicon is prevailing as a promising approach to realize future ultrahigh speed optical interconnects. We review recent progress of the direct epitaxy and fabrication of quantum dot (QD) lasers and integrated guided-wave devices on silicon. This approach involves the development of molecular beam epitaxial growth of self-organized QD lasers directly on silicon substrates and their monolithic integration with amorphous silicon waveguides and quantum well electroabsorption modulators. Additionally, we report a preliminary study of long-wavelength (>1.3 \mum) Q D lasers grown on silicon and integrated crystalline silicon waveguides using membrane transfer technology.

The basic propagation properties of the silica and silicon subwavelength-diameter hollow wire waveguides have been investigated by comparison. It shows that the silica and silicon subwavelength-diameter hollow wire waveguides have some interesting properties, such as enhanced evanescent field in the cladding, enhanced intensity in the hollow core, and large waveguide dispersion. For the different confinement ability, the enhanced field in the hollow core and cladding of the silica subwavelength-diameter hollow wire is much stronger than that of the silicon one for the same size.

Slow and fast light in quantum-well (QW) and quantum-dot (QD) semiconductor optical amplifiers (SOAs) using nonlinear quantum optical effects are presented. We demonstrate electrical and optical controls of fast light using the coherent population oscillation (CPO) and four wave mixing (FWM) in the gain regime of QW SOAs. We then consider the dependence on the wavelength and modal gain of the pump in QW SOAs. To enhance the tunable photonic delay of a single QW SOA, we explore a serial cascade of multiple amplifiers. A model for the number of QW SOAs in series with variable optical attenuation is developed and matched to the experimental data. We demonstrate the scaling law and the bandwidth control by using the serial cascade of multiple QW SOAs. Experimentally, we achieve a phase change of 160° and a scaling factor of four at 1 GHz using the cascade of four QW SOAs. Finally, we investigate CPO and FWM slow and fast light of QD SOAs. The experiment shows that the bandwidth of the time delay as a function of the modulation frequency changes in the absorption and gain regimes due to the carrier-lifetime variation. The tunable phase shift in QD SOA is compared between the ground- and first excited-state transitions with different modal gains.

Single-mode, long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the near- to mid-infrared covering the wavelength range from 1.3 to 2.3 \mum are presented. This wide spectral emission range opens applications in gas sensing and optical interconnects. All these lasers are monolithically grown in the InGaAlAs-InP material system utilizing a buried tunnel junction (BTJ) as current aperture. Fabricated with a novel high-speed design with reduced parasitics, bandwidths in excess of 10 GHz at 1.3 and 1.55 \mum have been achieved. Therefore, the coarse wavelength division multiplexing (CWDM) wavelength range of 1.3 to 1.6 \mum at 10 Gb/s can be accomplished with one technology. Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated. One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning. Micro-electro-mechanical system (MEMS) tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity. All these devices feature continuous-wave (CW) operation with typical single-mode output powers exceeding 1 mW. The operation voltage is around 1－1.5 V and power consumption is as low as 10－20 mW. Furthermore, we have also developed VCSELs based on GaSb, targeting at the wavelength range from 2.3 to 3.0 \mum. The functionality of tunable diode laser spectroscopy (TDLS) systems is shown by presenting a laser hygrometer applying a 1.84-\mum VCSEL.

This paper reviews the progress on nano-aperture vertical-cavity surface-emitting lasers (VCSELs). The design, fabrication, and polarization control of nano-aperture VCSELs are reviewed. With the nano-aperture evolving from conventional circular and square aperture to unique C-shaped, H-shaped, I-shaped, and bowtie-shaped aperture, both the near-field intensity and near-field beam confinement from nano-aperture VCSELs are significantly improved. As a high-intensity compact light source with sub-100-nm spot size, nano-aperture VCSELs are promising to realize many new near-field optical systems and applications.

We have seen a lot of unique features off vertical cavity surface emitting lasers (VCSELs), such as low power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years and they are now the key devices in local area networks using multi-mode optical fibers. In addition, new functions on VCSELs have been demonstrated. In this paper, the recent advances of VCSEL photonics will be reviewed, which include the wavelength engineering and the athermal operation based on microelectro mechanical system (MEMS) technologies. Also, this paper explores the potential and challenges for new functions of VCSELs, including high-speed control of optical phase, slow light devices, plasmonic VCSELs, and so on.

In this letter, poly(vinylidene difluoride) (PVDF)/(Y0.97Eu0.03)2O3 rare-earth nanocomposites were prepared by a simple co-precipitation method, and their morphology, structure, and optical properties were investigated. The scanning electron microscope (SEM) images showed that the (Y0.97Eu0.03)2O3 rare-earth nanoparticles formed 50 nm-2 \mum aggregates in PVDF matrices. X-ray diffraction (XRD) curves indicated the incorporation and structure preserving of (Y0.97Eu0.03)2O3 nanoparticles in PVDF matrices. Photoluminescence (PL) spectra of the nanocomposite showed a characteristic red light emission at 612 nm, which was attributed to the intrinsic emission of (Y0.97Eu0.03)2O3 nanoparticles. Optical band gap (Eg) of the nanocomposite exhibited a decreasing trend with the increase of (Y0.97Eu0.03)2O3 content in PVDF matrices within the experimental dosage range.

The response time and transmittivity of the magnetic fluid (MF) for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to 6.47%. It was found that the transmittivity decreased with increasing concentration under a given magnetic field, and the evolution time was changed with different concentrations. Moreover, the light intensity decreased rapidly at the beginning and then became stable when the magnetic field was applied.

The properties of terahertz (THz) radiation pulses emitted by a metallic, large aspect ratio carbon nanotube antenna have been studied both in the THz waveforms and field distribution. The peak THz field up to 2.66 and 1.26 kV/cm are observed at the probe points. The proposed antenna is designed to operate for dual frequency applications from 2.36 to 2.58 THz and from 7.27 to 7.5 THz for less than dB return loss.

A new method for increasing laser induced damage threshold (LIDT) of dielectric antireflection (AR) coating is proposed. Compared with AR film stack of H2.5L (H:HfO2, L:SiO2 on BK7 substrate, SiO2 interfacial layer with four quarter wavelength optical thickness (QWOT) is deposited on the substrate before the preparation of H2.5L film. It is found that the introduction of SiO2 interfacial layer with a certain thickness is effective and flexible to increase the LIDT of dielectric AR coatings. The measured LIDT is enhanced by about 50%, while remaining the low reflectivity with less than 0.09% at the center wavelength of 1064 nm. Detailed mechanisms of the LIDT enhancement are discussed.

Guided mode resonant filters (GMRFs) for authentication application with low sideband reflection at and azimuthal angles were designed. Using rigorous coupled-wave analysis, the diffractive characteristics of this kind device with different illumination angles, groove depths, and thicknesses of cover SiO2 layer were investigated. The structure of GMRF which satisfies the requirements for authentication applications was obtained. Illuminated at 30\circ for a definite polarization mode, the filter presents symmetrical reflectance shape, low sideband reflectance, two separate reflectance peaks, and definite full-width at half-maximum (FWHM) at 0\circ and 90\circ azimuthal angles.

Propagation properties of polarized four-petal Gaussian beams along the optical axis of uniaxially anisotropic crystals were investigated. Based on the paraxially vectorial theory of beam propagation, analytic expressions of the diffraction light field were obtained. The effects of the anisotropy on the polarization properties of the diffracted four-petal Gaussian beams have also been explained by numerical method. The results elucidate that the linear polarization state and the symmetry of the incident beams cannot be kept during propagation in anisotropic crystals.

A novel pre-collimating scheme in laser-focused chromium (Cr) atomic deposition is presented. It consists of three apertures, which are one main pre-collimating aperture at centre and two probing apertures with uniform dimension at both sides of the central one. The calculations show that the Cr atomic beam is divided into three parts accordingly after going through this scheme, and the full-width at half-maximum (FWHM) of each part decreases while the peak value increases after one-dimensional (1D) Doppler laser collimation, subsequently. Compared with that before laser collimation, the central part does not have displacement, but each part of the other two has the same displacement to the centre after laser collimation. These phenomena which are agreed with experiment prove that the novel pre-collimating scheme is a feasible means to solve the problem which we cannot observe the collimation of Cr atomic beam after substrate in laser-focused deposition with a pre-collimating scheme of only one aperture, because the atoms will be obstructed completely by the substrate.

It is well known that a light spot of sub-wavelength will diverge in all directions. In this letter, A method is presented for generating sub-wavelength (0.44\lambda) longitudinally polarized beam, which propagates without divergence over lengths of about 2\lambda in free space. This is achieved by a high numerical aperture (NA) lens axicon that utilizes spherical aberration to duplicate the performance of an axicon and to create an extended focal line.

We present a grating model of two-dimensional (2D) rigorous coupled wave analysis (RCWA) to study top diffraction gratings on light-emitting diodes (LEDs). We compare the integrated-transmission of the non-grating, rectangular-grating, and triangular-grating cases for the same grating period of 6 \mum, and show that the triangular grating has the best performance. For the triangular grating with 6-\mm period, the LED achieves the highest light transmission at 6-m grating bottom width and 2.9-\mum grating depth. Compared with the non-grating case, the optimized light transmission improvement is about 74.6%. The simulation agrees with the experimental data of the thin polymer grating encapsulated flip-chip (FC) GaN-based LEDs for the light extraction improvement.

We report experimental results on enhanced light transmission through double-layered (Ag/Au) metallic hole arrays within a skin-depth. Zero-order transmission spectrums are characterized as a function of Ag film's thickness, which extends from \delta/15, \delta/6 to approximately \delta, where \delta is a skin-depth. In contrast with other reported results (Refs.[11-13]) in single-layered metallic hole arrays, our experimental results show much more dramatic properties of transmission process dependent on sub- thickness. It is shown that there is no negligible transmission enhancement at \delta/16. At \delta/6, much higher transmission efficiency can be achieved. With film's thickness being close to \delta, the transmission efficiency declines contrarily. Simultaneously, the corresponding resonant peak also slightly moves toward the shorter wavelength. It is proposed that the coupling of surface plasmon polaritons (SPPs) at Ag/Au interface within is involved in the process.

A dielectric multi-layered structure is studied in this letter. It is found that at some frequency ranges, the equal-frequency contours (EFCs) are almost flat for one polarization but still curve for the other. Based on this property, we propose a novel polarization beam splitter.