Search

Decreasing the widths and thicknesses of thin metal stripes can effectively increase the propagation distance of long-range surface plasmon polaritons, but at the cost of significant reduction on the overall mode confinement, which fundamentally limits the packing density in nanophotonic integration. By utilizing the coupling between the dielectric waveguide and plasmonic modes, we propose a silicon-based 3-D hybrid long-range plasmonic waveguide that not only supports long-range propagation, but also has compact modal size. Our simulation result shows that a propagation distance of 696 μm with an ultrasmall modal area of 0.0013 μm2 can be simultaneously achieved at 1.55 μ m. [ABSTRACT FROM PUBLISHER]

We present the results of an experimental study of waveguide tapers realized in LiNbO3 using the soft-proton-exchange process and the waveguide segmentation technique. Measurements show that they can be favorably introduced between the nonlinear or electrooptic part of the components, which require strong mode confinement to increase efficiency, and the coupling section with a standard optical fiber, which requires low mode confinement in order to have low coupling losses. These tapers allow almost lossless mode-shape transformation. Preliminary results show that they allow reducing the coupling losses by up to 0.7 dB, thus proving the practical interest of the approach. [ABSTRACT FROM PUBLISHER]

A variable optical attenuator was demonstrated by using a thermooptic cutoff modulator in polymers. It combined horizontally and vertically tapered waveguide structures to improve both the attenuation efficiency and the fiber coupling. The rib height of the waveguides in the input and output region was chosen to achieve minimum fiber coupling loss. For the waveguide in the active region with the electrodes, the rib height was reduced and the width was tapered in order to enhance the attenuation performance by weakening the mode confinement. The two waveguides with different rib heights were connected smoothly by employing a vertical taper, which was realized by utilizing two steps of reactive ion etching with a shadow mask. Then a fiber coupler built in a silicon block was attached directly to the output end of the device. A fraction of the main attenuator output was tapped and fed back to the electrical driver to achieve constant output regardless of variations in input light power and polarization. The measured insertion loss of the attenuator was 2.5 dB at 1550 nm. The dynamic range was more than 20 dB with an electrical power consumption of 160 mW. And the optical response time was faster than 1.5 ms. The effect of polarization on the attenuation was reduced to 0.1 dB by employing a continuous electronic feedback control. The wavelength uniformity was as small as 0.3 dB over the range from 1530 to 1560 nm. Finally, the attenuator was successfully used to regulate channel powers within 0.4 dB in a wavelength division multiplexed transmission system [ABSTRACT FROM PUBLISHER]

Mode confinement to low-index "defect" regions of a two-dimensional square photonic lattice has been studied as a means to realize single-spatial-mode vertical-cavity surface-emitting lasers (VCSELs). A selective etching process with two-step metal-organic chemical vapor deposition is used to fabricate the low-index defect VCSELs. A device with a 9-mum-wide aperture demonstrates 2.9-mW continuous-wave (CW) output power. The near diffraction-limited single-lobe far-field and high-resolution spectral analyses confirm single fundamental defect mode emission. Comparison studies between pulsed and CW operation indicate that thermal effects have a significant impact on the modal performance of the devices. Single-mode emission with more than 8 mW of peak pulsed power has been observed with short pulsewidth operation (0.1 mus, 2%). Improvements in thermal management are required to achieve higher CW single-mode emission in these devices [ABSTRACT FROM PUBLISHER]