Wavelength conversion based on degenerate-four-wave-mixing with continuous-wave pumping in silicon nanowire waveguide

We present a comprehensive numerical study on the all-optical wavelength conversion based on the degenerate four-wave-mixing with continuous-wave pumping in the silicon nanowire waveguide. It is well known that the conversion efficiency and the 3-dB bandwidth can be greatly affected by the phase-matching condition. Through proper design of the waveguide cross-section, its dispersion property can be adjusted to satisfy the phase-matching condition and therefore effective wavelength conversion can be achieved in a large wavelength range. Generally, the group velocity dispersion plays a dominant role in the wavelength conversion. However, the fourth-order dispersion takes an important effect on the wavelength conversion when the group velocity dispersion is near the zero-point. Furthermore, the conversion efficiency and the 3-dB bandwidth can also be affected by the interactive length and the initial pump power. Through the numerical simulation, the optimal values for the interactive length and the initial pump power, which are functions of the propagation loss, are obtained to realize the maximum conversion efficiency. (C) 2008 Elsevier B.V. All rights reserved.

Determination of the absorption for incident light propagating parallel through the guest-host polymer film waveguide

Guest host polymer thin films of polymethyl methacrylate (PMMA) incorporated with (4'-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were fabricated by spin coating and then poled by the method of corona-onset poling at elevated temperature. The absorption mechanism of the polymeric film, which is very important for the optical transmission losses and directly relates to the orientation of chromophore NAEC in polymer PMMA, was investigated in detail. From the UV-visible absorption spectra for NAEC/PMMA film before and after being poled, we determined the change of absorption coefficient kappa with the wavelength and approximately calculated the maximum absorption A(parallel tomax) as 3.46 for incident light propagating parallel through the film, i.e. the ordinary polarized light, which cannot be directly measured in the spectro photometer. (C) 2002 Elsevier Science Ltd. All rights reserved.

Tuning the resonant wavelength of long period fiber gratings by etching the fiber's cladding

In this paper the resonant wavelength of a long period fiber grating (LPG) is tuned toward longer wavelength by etching the fiber, For LP04 and LP05 cladding modes', the tuning ranges of 23 and 81 nm are achieved, respectively. Also the dependence of the resonant wavelength on the cladding radius of LPG is theoretically simulated. (C) 2001 Elsevier Science B,V. All rights reserved.

Analysis of output coupling efficiencies for directional emission triangle and square microlasers

Output coupling efficiencies are analyzed for triangular and square microlasers connected with an output waveguide by FDTD simulation. The results show that square resonator with an output waveguide connected to the midpoint of one side can have high output coupling efficiency and a good mode selection.

Experimental investigation of slow light phenomenon in photonic crystal waveguide line defect laser

The guide mode whose frequency locates in the band edge in photonic crystal single line defect waveguide has very low group velocity. So the confinement and gain of electromagnetic field in the band edge are strongly enhanced. Photonic crystal waveguide laser is fabricated and the slow light phenomenon is investigated. The laser is pumped by pulsed pumping light at 980nm whose duty ratio is 0.05%. The active layer in photonic crystal slab is InGaAsP multiple quantum well. Light is transimited by a photonic crystal chirp waveguide in one facet of the laser. Then the output light is coupled to a fiber and the character of laser is analysis by an optical spectrometer. It is found that single mode and multimode happens with different power of pumping light. Meanwhile the plane wave expansion and finite-difference time-domain methods are used to simulate the phenomenon of slow light. And the result of the experiment is compared with the theory which proves the slow light results in lasing oscillation.

Structural optimizations of SOI-based single-mode rib waveguide bends

Effects of structure parameters on bend loss of rib silicon-on-insulator (Sol) bend waveguides have been analyzed by means of effective index method (EIM) and 2D bend loss formula. The simulation results indicate that the bend loss decreases with the increase of bend radius and waveguide width, as well as with the decrease of the step factor of the rib waveguide. Moreover, the optional structure parameters have been found when bend waveguides are single-mode.

Reconfigurable Optical Add-Drop Multiplexer Based on Silicon Photonic Wire Waveguide

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Demonstration of high efficient tunable lasing with one photonic crystal W1 waveguide

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Hybrid waveguide-plasmon resonances in gold pillar arrays on top of a dielectric waveguide

We propose a hybrid waveguide-plasmon system consisting of gold pillar arrays on top of a dielectric waveguide. The formation of extraordinary transmissions induced by the hybrid waveguide-plasmon resonances is investigated by rigorous coupled-wave analysis. The characteristics of the hybrid resonances can be predicted by introducing the photonic crystal slab theory. Extremely narrow absorption peaks and the electromagnetically induced transparency-like optical property are demonstrated in our hybrid system. (C) 2010 Optical Society of America

THEORETICAL AND EXPERIMENTAL STUDY OF POLARIZATION CHARACTERISTICS OF POLARIZATION MAINTAINING FIBER BASED ON WAVELENGTH-SWEEPING MODULATION

We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According, to the dependence of the phase difference between two orthogonally polarized modes (denoted Os HE(11)(x) and HE(11)(y)) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the hew length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466-1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244

Mechanical Properties of Short-Isora-Fiber-Reinforced Natural Rubber Composites: Effects of Fiber Length, Orientation, and Loading; Alkali Treatment;and Bonding Agent

A series of short-isora-fiber-reinforced natural rubber composites were prepared by the incorporation of fibers of different lengths (6, 10, and 14 mm) at 15 phr loading and at different concentrations (10, 20, 30, and 40 phr) with a 10 mm fiber length. Mixes were also prepared with 10 mm long fibers treated with a 5% NaOH solution. The vulcanization parameters, processability, and stress-strain properties of these composites were analyzed. Properties such as tensile strength, tear strength, and tensile modulus were found to be at maximum for composites containing longitudinally oriented fibers 10 mm in length. Mixes containing fiber loadings of 30 phr with bonding agent (resorcinol-formaldehyde [RF] resin) showed mechanical properties superior to all other composites. Scanning electron microscopy (SEM) studies were carried out to investigate the fiber surface morphology, fiber pullout, and fiber-rubber interface. SEM studies showed that the bonding between the fiber and rubber was improved with treated fibers and with the use of bonding agent.

Loss characterization in rhodamine 6G doped polymer film waveguide by side illumination fluorescence

We report the position dependent tuning of fluorescence emission from rhodamine 6G doped polymethylmethacrylate film waveguide using a side illumination technique. The transmitted fluorescence as a function of the distance from the point of illumination is measured by translating the waveguide horizontally across a monochromatic light source. This technique has been utilized to characterize the optical loss in dye doped waveguides. We observe that the optical loss coefficients for shorter and longer distances of propagation through the dye doped waveguide are different. At longer distance of propagation a decrease in optical loss coefficient is observed

Effects of mechanical cycling on the bonding of zirconia and fiber posts to human root dentin

Purpose: To evaluate the effect of cyclical mechanical loading on the bond strength of a fiber and a zirconia post bonded to root dentin.Materials and Methods: Forty single-rooted human teeth (maxillary incisors and canines) were sectioned, and the root canals were prepared at 12 mm. Twenty randomly seleced specimens received a quartz fiber post (FRC) (D.T. Light-Post) and 20 others received a zirconia post (ZR) (Cosmopost). The posts were resin luted (All Bond 2 + resin cement Duo-link) and each specimen was embedded in epoxy resin inside a PVC cylinder. Ten specimens with FRC post and 10 specimens with ZR post were submitted to fatigue testing (2,000,000 cycles; load: 50 N; angle of 45 degrees; frequency: 8 Hz), while the other 20 specimens were not fatigued. Thus, 4 groups were formed: G1: FRC+O cycles; G2: FRC+2,000,000 cycles; G3: ZR+O cycles; G4: ZR+2,000,000 cycles. Later, the specimens were cut perpendicular to their long axis to form 2-mm-thick disk-shaped samples (4 sections/specimen), which were submitted to the push-out test (1 mm/min). The mean bond strength values (MPa) were calculated for each tooth (n = 10) and data were submitted to statistical analysis (alpha = 0.05).Results: Two-way ANOVA revealed that the bond strength was significantly affected by mechanical cycling (p = 0.0014) and root post (p = 0.0325). The interaction was also statistically significant (p = 0.0010). Tukey's test showed that the mechanical cycling did not affect the bonding of FRC to root dentin, while fatigue impaired the bonding of zirconium to root dentin.Conclusion: (1) the bond strength of the FRC post to root dentin was not reduced after fatigue testing, whereas the bonding of the zirconia post was significantly affected by the fatigue. (2) Cyclical mechanical loading appears to damage the bond strength of the rigid post only.