Optical Guiding Research Articles

Design and Simulation of the Solar Optical Guide Lighting and Ventilation System in a Building

With the continuous development of society, power consumption for the lighting and the ventilation in buildings accounts for more and more proportion of the total energy supply. With the aim of relieving the conflict between the fast-growing urbanization and power limitation, a solar optical guide lighting and ventilation (SOGLV) system combining natural lighting and natural ventilation is proposed in this study. The simulations are carried out to analyze the performance of optical guiding at different times by Monte Carlo method. Meanwhile, the performance of ventilation is simulated under different absorbed heat fluxes by Fluent. It is found from the research that the SOGLV system can achieve the goal of lighting and ventilation. The average indoor illumination intensity on the ground floor first increases then decreases within a day. The heat flux on the optical guide pipe wall appears in a block pattern. The maximum velocity is linearly correlated with the average absorbed heat flux on the optical guide wall, ranging from 0.90 m/s to 1.02 m/s.

A GaN‐Based VCSEL with a Convex Structure for Optical Guiding

In this paper, room‐temperature continuous‐wave operation of a GaN‐based vertical‐cavity surface‐emitting laser (VCSEL) with a convex structure for optical guiding is demonstrated. The GaN‐based VCSEL is designed and fabricated with the convex structure containing a 15‐nm step between the center area and the peripheral area of the VCSEL with a Nb2O5 spacer layer. In theory the convex structure with a 1.5% relative refractive index difference between the areas could provide more than 10 high‐order modes. Experimental emission spectra and near field pattern images clearly suggested a multi‐mode operation of the VCSEL with the convex structure. In addition, the VCSEL shows a lower threshold current, 2 mA, and a higher maximum light output power, 0.88 mW, which are superior to those of our standard VCSEL fabricated simultaneously without the convex structure. These results indicate that the optical guiding with the convex structure plays an important role in developments of GaN‐based VCSELs.

Engineering the Lateral Optical Guiding in Gallium Nitride-Based Vertical-Cavity Surface-Emitting Laser Cavities to Reach the Lowest Threshold Gain

In order to improve the current injection in GaN-based blue vertical-cavity surface-emitting lasers (VCSELs) a dielectric aperture is generally used in combination with an indium–tin-oxide (ITO) layer on the top intracavity p-contact layer. The most straightforward way to realize this introduces a depression of the structure near the optical axis and we show, by using a two-dimensional (2D) effective index method and a three-dimensional (3D) coupled-cavity beam propagation method, that this typically results in optically anti-guided structures with associated high optical losses and thus very high threshold gains. Remarkably, the threshold gain reduces with increased negative guiding, which is due to improved lateral confinement and reduction of lateral leakage. Still, moderately positively guided designs should be preferred to avoid the detrimental effect of lateral leakage and high diffraction loss. To ensure positive index guiding, we propose to planarize the structure or introduce an elevation near the optical axis by additional processing, with an associated reduction in threshold material gain from 6000 to 2000 cm-1 for the studied structures.

Optical Guiding of Atoms through a Hollow-Core Photonic Band-Gap Fiber

We demonstrate the first guiding of atoms through a hollow-core photonic band-gap fiber. Rb atoms from a thermal oven source travel through 6.1 and 4.0 cm long fibers with a guiding potential 1/e(2) radius of 3.0 microm. When the photon scattering rate is small, the observed guiding efficiency is greater than 70%. An unexpected low-speed cutoff is attributed to inefficient optical coupling.

Optical Guiding of Trapped Atoms by a Blue-Detuned HollowLaser Beam in the Horizontal Direction

Optical guiding of 85Rb atoms in a magneto-opticaltrap (MOT) by a blue-detuned horizontal hollow laser beam isdemonstrated experimentally. The guiding efficiency and the velocitydistribution of the guided atoms are found to have strong dependence onthe detuning of the guiding laser. In particular, the optimum guidingoccurs when the blue detuning of the hollow laser beam is approximatelyequal to the hyperfine structure splitting of the 85Rbground states, in good agreement with the theoretical analysis based ona three-level model.

高速Zピンチを用いた高強度超短パルスレーザのガイディング

高速Zピンチを用いた高強度超短パルスレーザのガイディング

Room Temperature CW Operation of GaN-Based Blue Laser Diodes by GaInN/GaN Optical Guiding Layers

AbstractGaN-based short wavelength laser diodes are the most promising key device for a digital versatile disk. We have been improving the important points of the laser diodes in terms of optical guiding layers, mirror facets. The continuous wave laser irradiation at room temperature could be achieved successfully by reducing the threshold current to 60 mA (4 kA/cm2). We have tried to apply the multi low temperature buffer layers to the laser diodes for the first time to reduce the crystal defects.

Optical Guiding in the separable beam limit

The nonlinear theory of optical guiding in an FEL amplifier is developed for the case in which the spatial dependence of the current source term in the wave equation can be separated into the product of a function of radius and a function of axial distance. Such a separation can be motivated if either the betatron wavelength is shorter than other lengths of interest (synchroton wavelength, vacuum Rayleigh length) or if the radiation waist exceeds the beam radius. In this limit with the choice of a Gaussian profile for the electron beam density the wave equation can be solved exactly and the radiation field felt by the particles can be expressed as a one-dimensional convolution of the current source.With the given expression for the radiation field, the equations of motion can be solved in the trapped particle regime. Requiring consistency between the particle motion and the fields yields expressions describing nonlinear guided states. The adiabatic evolution of these guided states in the presence of a tapered wiggler is determined by conservation of the electrons' action and total (field + electron beam) energy. Using these relations the growth of the radiation waist as the beam is decelerated can be calculated.

Optical guiding in a free-electron laser.

By use of two-dimensional approximations for the equations that describe a high-gain free-electron laser (FEL) amplifier, and the properties of optical fibers, it is shown that the coherent interaction between the light and the electron beam in an FEL can optically guide the light. In the exponential-gain regime, the FEL performance in the presence of strong diffraction can be simply described by a cubic equation for the complex gain and the dispersion relation for an optical fiber. The phenomenon of optical guiding is illustrated with two-dimensional numerical simulations. The phenomenon has applications to short-wavelength FEL's, to directing of intense light, and to bending of x rays.

Optical Guiding and electro-optic modulation in GaAs epitaxial layers

Single mode TE or TM propagation is demonstrated in an optical waveguide consisting of a high resistivity semiconductor (GaAs) layer (≈ 10 μ) which is sandwiched between a metal film and a lower resistivity semiconductor. A reverse bias applied to the metal-seminconductor Schottky barrier causes an electro-optic retardation (or, in general, phase variation) which can be used for modulation purposes. Amplitude modulation with a “half-voltage” V 1 2 = 84 volts is demonstrated at λ o = 1.15μ with a sample 2.4 mm long.

The Stream Guide, a Simple, Low-Loss Optical Guiding Medium

Heat generated by viscous friction in a high speed gas flow in a pipe causes a transverse refractive index variation that can continuously focus a light beam passing through this pipe. The comparatively simple construction, together with the low losses inherent in gaseous guiding media, makes the stream guide attractive as an optical beam waveguide. This article presents theoretical and experimental results.