Geometry parameter optimization of large cross-sectional S-shaped bent rib waveguides for silicon based optical switches

地址: Chinese Acad Sci, Inst Semicond, State Key Lab Integrated Optoelect, Beijing 100083, Peoples R China

Novel folding 8x8 silicon-based optical matrix switch with tapered waveguides and self-aligned corner mirrors

Novel folding 8 x 8 matrix switches based on silicon on insulator were demonstrated. In the design, single-mode rib waveguides and multimode interferences are connected by optimized tapered waveguides to reduce the mode coupling loss between the two types of waveguides. The self-aligned method was applied to the key integrated turning mirrors for perfect positions and low loss of them. A mixed etching process including inductively coupled plasma and chemical etching was employed to etch waveguides and mirrors, respectively. The compact size of the device is only 20 x 3.2 mm(2). The switch element with high switching speed and low power consumption is presented in the matrix. The average insertion loss of the matrix is about -21 dB, and the excess loss of one mirror is measured of -1.4 dB. The worst crosstalk is larger than 21 dB. Experimental results illuminate that some of the main characteristics of optical matrix switches are. developed in the modified design, which is in accord with theoretic analyses.

A highly efficient beam propagation method for modeling step-index waveguides with tilt interface

Based on a new finite-difference scheme and Runge-Kutta method together with transparent boundary conditions (TBCs), a novel beam propagation method to model step-index waveguides with tilt interfaces is presented. The modified scheme provides an precies description of the tilt interface of the nonrectangular waveguide structure, showing a much better efficiency and accuracy comparing with the previously presented formulas.

Accurate mode analysis of ultraviolet-written channel waveguides

The transfer matrix method combined with the effective index method is adopted to model the silica-based channel waveguide patterned by UV writing. The effective indexes of the graded index channel waveguides with different dimension are calculated. The maximal error of the effective index is less than 3 x 10(-5). By this method, the number of the guided mode and the dimension range to guide certain modes can be obtained easily. Finally, the dimension range to guide a single mode is presented. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

New finite-difference scheme for simulations of step-index waveguides with tilt interfaces

A new finite-difference scheme is presented for the second derivative of a semivectorial field in a step-index optical waveguide with tilt interfaces. The present scheme provides an accurate description of the tilt interface of the nonrectangular structure. Comparison with previously presented formulas shows the effectiveness of the present scheme.

Simple method for estimating minimum bend radii of SOI single mode curved rib waveguides

A simple method based on the effective index method was used to estimate the minimum bend radii of curved SOI waveguides. An analytical formula was obtained to estimate the minimum radius of curvature at which the mode becomes cut off due to the side radiative loss.

Comparison of modal gain and material gain for strong guiding slab waveguides

The relations between the gain factor, defined as the ratio of modal gain to material gain, and the optical confinement factor are discussed for the TE and TM modes in slab waveguides. For the TE modes, the gain factor is larger than the optical confinement factor, due to the zigzag propagation of the modal light ray in the core layers. For the TM modes, the existence of a nonzero electric field in the propagation direction results in a more complicated relation of the gain factor and the confinement factor. For an air-Si-SiO2 strong slab waveguide, the numerical results show that the modal gain can be larger than the material gain and the higher-order transverse mode can have an even larger modal gain than the fundamental mode, The efficiency of waveguiding photodetectors can be improved by applying the modal gain or loss characteristics in strong waveguides.

Measurement of the optical transmission modes and losses of the poled guest-host polymer NAEC/PEK-c planar waveguides

The polyetherketone (PEK-c) guest-host polymer planar waveguides doped with (4'-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The waveguide films were poled by corona-onset poling at elevated temperature (COPET), and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. By using the prism-in coupling method, the dark-line spectrum given by the reflected intensity versus the angle of incidence have been obtained, and the optical transmission losses of mth modes have been measured for the poled polymer waveguides at lambda = 632.8 nm. The measurement result showed that the optical loss of the fundamental mode is less than 0.7 dB cm(-1) for the TE polarization. (C) 2000 Elsevier Science Ltd. All rights reserved.

Oscillatory magneto-conductance in quantum waveguides with lateral multi-barrier structures

The magneto-transport properties of a narrow quantum waveguide with lateral multibarrier modulation are investigated theoretically. It is found that the magnetoconductance as a function of Fermi energy or magnetic field exhibits square-wave-like oscillations. In the presence of magnetic field, the edge states are formed near each barrier and the boundaries. Therefore, the number of edge states increases with the number of lateral barriers, leading to the increase of the propagating modes. On the other hand, owing to the tunneling effect a pair of edge states around the barrier region with opposite moving directions may be coupled and formed a circulating localized state, leading to the quenching of the related propagating states. The resulting dispersion relation exhibits oscillation structures superimposed on the bulk Landau levels. These novel conductance characteristics may provide potential applications to the fabrication of new quantum devices.

High energy ion implantation enhanced intermixed quantum well structures and their absorption characteristics in passive optical waveguides

We have shown that high energy ion implantation enhanced intermixing (HE-IIEI) technology for quantum well (QW) structures is a powerful technique which can be used to blue shift the band gap energy of a QW structure and therefore decrease its band gap absorption. Room temperature (RT) photoluminescence (PL) and guided-wave transmission measurements have been employed to investigate the amount of blue shift of the band gap energy of an intermixed QW structure and the reduction of band gap absorption, Record large blue shifts in PL peaks of 132 nm for a 4-QW InGaAs/InGaAsP/InP structure have been demonstrated in the intermixed regions of the QW wafers, on whose non-intermixed regions, a shift as small as 5 nm is observed. This feature makes this technology very attractive for selective intermixing in selected areas of an MQW structure. The dramatical reduction in band gap absorption for the InP based MQW structure has been investigated experimentally. It is found that the intensity attenuation for the blue shifted structure is decreased by 242.8 dB/cm for the TE mode and 119 dB/cm for the TM mode with respect to the control samples. Electro-absorption characteristics have also been clearly observed in the intermixed structure. Current-Voltage characteristics were employed to investigate the degradation of the p-n junction in the intermixed region. We have achieved a successful fabrication and operation of Y-junction optical switches (JOS) based on MQW semiconductor optical amplifiers using HE-IIEI technology to fabricate the low loss passive waveguide. (C) 1997 Published by Elsevier Science B.V.

High Q microring resonator in silicon-on-insulator rib waveguides - art. no. 68380J

A high quality (Q) factor microring resonator in silicon-on-insulator rib waveguides was fabricated by electron beam lithography, followed by inductively coupled plasma etching. The waveguide dimensions were scaled down to submicron, for a low bending loss and compactness. Experimentally, the resonator has been realized with a quality factor as high as 21,200, as well as a large extinction ratio 12.5dB at telecommunication wavelength near 1550nm. From the measured results, propagation loss in the rib waveguide is determined as low as 6.900/cm. This high Q microring resonator is expected to lead to high speed optical modulators and bio-sensing devices.

High efficiency fiber to waveguide optical coupler in silicon-on-insulator-based slot waveguides - art. no. 68310R

We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed coupler can be used in chip-to-chip communication.

SOI submicron rib waveguides: Design, Fabrication and Characterization

We present detailed design, fabrication, and characterization issues of submicron rib waveguides based on silicon-on-insulator. The waveguides fabricated by EBL and ICP processes have propagation loss of 1.8dB/mm and bend loss of 0.14dB/90 degrees for bends with radius of 5 mu m.

Investigations on oxide-free InGaAlAs waveguides grown by narrow stripe selective MOVPE

Oxide-free InGaAlAs waveguides have been grown on the InP substrates patterned with pairs of SiO2 mask stripes using narrow stripe selective MOVPE. The mask stripe width is varied from 0 to 40 pm, while the window region width between a pair of mask stripes is fixed at 1.5, 2.5 and 3.5 mu m, respectively. Smooth surface s and flat interfaces are obtained in the selectively grown InQaAlAs waveguides. There exhibit strong dependences of the thickness enhancement ratio and the photoluminescence (PL) spectrum on the mask stripe width and the window region width for the InGaAlAs wavegwdes. A large PL peak wavelength shift of 79 nm and a PL full width of at half maximum (FWHM) of less than 64 meV are obtained simultaneously. Some possible interpretations for our investigations are presented by considering both the migration effect from a masked region (MMR) and the lateral vapor diffusion effect (LVD).

Growth mechanism of InGaAlAs waveguides by narrow stripe selective MOVPE

Growth mechanism of InGaAlAs waveguides by narrow stripe selective MOVPE has been studied. Both the InGaAlAs bulk waveguides and the InGaAlAs MQW waveguides were successful grown on the patterned substrates at optimized growth conditions. The mask stripe width varied from 0 to 40 mu m, while the window region width between a pair of mask stripes was fixed 2.5 mu m. These selectively grown waveguides were covered by specific InP layers, which can keep the InGaAlAs waveguides from being oxidized during the fabrication of devices. In particular, there exhibit strong dependences of the photoluminescence (PL) spectrum on the mask stripe width for the samples. The results were explained in considering both the migration effect from a masked region (MMR) and the lateral vapor diffusion effect (LVD).