Showing papers on "Equilibrium mode distribution published in 1996"

Adiabatically tapered periodic segmentation of channel waveguides for mode-size transformation and fundamental mode excitation.

Abstract: We report modeling, fabrication, and characterization of tapered waveguides, using periodically segmented annealed proton exchange in LiNbO3. For a taper transforming the 1/e full width (intensity) mode size from 6.0 μm × 4.4 μm to 2.0 μm × 1.3 μm, 0.4-dB excess loss was observed. The large, slightly elliptical mode can ease coupling to single-mode fibers and circular free-space beams. The same taper structure was used to excite a highly multimoded (13 modes) waveguide with more than 95% of the power stably launched into the lowest-order mode. This function is useful for nonlinear waveguide devices, such as difference-frequency generators, in which modes at highly disparate wavelengths interact.

Dispersion compensation based on dual-mode optical fiber with inhomogeneous profile core

Abstract: It is well known that the first higher order mode of optical fibers exhibits large negative waveguide dispersion by operating close to its cutoff wavelength. By using this dispersion, the positive dispersion in conventional 1.3 /spl mu/m zero dispersion optical fibers for 1.55 /spl mu/m signal light can be compensated. In this paper, we focus on the dispersion compensation technique using the first higher order mode in a dual-mode optical fiber, which supports both the fundamental LP/sub 01/ and first higher order LP/sub 11/ modes. Numerical calculations show that the waveguide dispersion of the first higher order mode is very sensitive to the refractive-index profile of optical fibers. In addition, it is demonstrated that a directional coupler composed of a single-mode fiber and a dual-mode fiber operates as a mode converter, which converts the signal light from the LP/sub 01/ mode to the LP/sub 11/ mode.

LSM and LSE mode dielectric waveguide having propagating and non-propagating regions

Abstract: A dielectric waveguide has a dielectric member disposed between a pair of parallel conductor flat surfaces, such that a propagating region and a non-propagating region are formed. The spacing between the conductor flat surfaces in the non-propagating region is determined to be smaller than that in the propagating region. The above-mentioned spacings and the dielectric constant of the dielectric member are determined such that the cut-off frequency of the LSM 01 mode propagating through the propagating region is lower than the cut-off frequency of the LSE 01 mode and that electromagnetic waves of both the LSM 01 mode and the LSE 01 mode are cut-off in the non-propagating region, so that any transmission loss attributable to a mode conversion between the LSM 01 mode and LSE 01 mode occurring at, for example, a bend of the waveguide is eliminated so as to facilitate production of the waveguide having a desired bend angle and radius of curvature.

Polarization mode coupled single mode waveguide

Abstract: A single mode optical waveguide having reduced polarization mode dispersion and a method of making such a waveguide is disclosed. Perturbations (6, 8) are introduced into the waveguide core (4) to couple power between the two polarization modes. A model calculation shows that the perturbation length may be of the order of the correlation length. The inventive waveguide is robust in that polarization mode dispersion is reduced even if perturbations (6, 8) are impressed on the fiber after manufacture.

A gratingless wavelength stabilized semiconductor laser

Abstract: A single frequency laser structure is obtained by coupling a high order mode of a semiconductor waveguide to a low index polymer waveguide. The device does not require a grating or regrowth, emits in a mode compatible with optical fibers, and may be immune to catastrophic mirror damage. The epilayers of the semiconductor waveguide use quarterwave reflectors to support a mode with a low enough effective index to phase match to the polymer waveguide. The coupling between the two waveguides is highly frequency selective and therefore stabilizes the wavelength. Preliminary structures emit in a single longitudinal and spatial mode, have 30 dB of sidemode suppression, and emit about 6 mW into a fiber compatible mode.

Surface-wave-like mode in slot line

Abstract: Propagation properties of the surface-wave-like mode in slot line are investigated with the spectral domain analysis. This surface-wave-like mode is an odd dominant mode with a magnetic wall symmetric plane placed at the center of the slot. Its field distribution is similar to that of the TM/sub 0/ mode supported by the surrounding structure. It exists in the lower frequency regime and evolves into a nonphysical and nonspectral real mode in the higher frequency regime. Unlike other surface-wave-like modes in planar transmission line, the surface-wave-like mode in slot line does not evolve into a leaky mode.

Extra-short He-Ne lasers based on mode split

Abstract: An extra-short He-Ne laser (shorter than 100mm) does not work well because there is likely no longitudinal mode in the lasing bandwidth sometimes and the output power rises and falls deeply from time to time.A method to solve this problem has been presented and investigated.A piece of quartz crystal plate appropriately designed is used as a cavity mirror of a He-Ne laser,which has a longitudinal mode spacing larger than the lasing bandwidth to make the equal-spacing mode split.In other words,the number of longitudinal modes is doubled and the actual mode spacing is reduced to the half of that without mode split.Therefore,there is always at least one mode operating in the lasing bandwidth and the power is stable at any room temperature.Such a laser with 85mm cavity length and 0.24mW output power has been made.

Single mode tapered polymer waveguides for mode conversion

Abstract: We have developed a tapered polymer waveguide that performs a 2-dimensional mode transformation to convert the laser diode mode into the fiber mode. The waveguide was designed by modeling and computer optimization. The input and output waveguide structures were designed and optimized separately, under the assumption that by adiabatically tapering the waveguide and using a longitudinal grading of the index, we can fabricate a waveguide which correctly links the input structure to the output structure.

Application of the coupled mode theory to eigenvalue problems of graded‐index optical fibers

Abstract: The propagation constant and the modal field distribution for guided modes of an arbitrary graded-index optical fiber have been calculated with the use of the coupled mode theory. The infinitely extended parabolic profile fiber is taken as an ideal waveguide, and an arbitrary radially inhomogeneous optical fiber can be viewed as a perturbation. Its modal field can be expanded in terms of a complete set of ideal waveguide modes. Eigenvalues and modal fields are then obtained from coupled mode equations that have been transformed into a set of linear equations. Numerical results have been presented and compared with exact values. © 1996 John Wiley & Sons, Inc.

Mode coupling and interference in large mode volume waveguide and slab CO2 lasers

Abstract: Influence of mode coupling and interference effects on the mode structure of CO2, waveguide and slab laser generation both for large scale empty waveguide resonator with flat and curved mirrors and when properties of active medium are counted has been investigated.