A new approach to grating-assisted couplers
29
Citation
13
Reference
10
Related Paper
Citation Trend
Abstract:
A novel approach to the analysis and design of grating-assisted directional couplers is proposed. Power exchange between the waveguides is maximized through phase matching of two power-orthogonal modes of the parallel coupler. It is shown that either complete power transfer or zero crosstalk can be achieved at two different coupling lengths even when the two wavelengths are strongly coupled and/or close to synchronism. An analytical solution to the coupled-mode equations is obtained for the grating of rectangular shape. A grating-assisted coupler made of two slab waveguides is examined as an example to illustrate the salient features of the scheme.< Keywords:
Synchronism
Coupled mode theory
Cite
An analysis of asymmetric directional couplers consisting of two parallel slab waveguides has been performed using the improved coupled-mode theory for multimode waveguides. The use of such couplers for multibranch power dividers has been illustrated, and the expected performances have been discussed, both for a two-branch divider and a three-branch one. One notes in particular the high SNR and efficiency at the end of the coupling region.
Coupled mode theory
Slab
Cite
Citations (5)
We propose and demonstrate the concept of a contra-directional coupler between a W1 and a slotted photonic crystal waveguide. The bandwidth and operating wavelength of such a coupler can be controlled via its geometrical parameters, and power transfer is not periodic unlike in the more familiar codirectional case. Light of specific wavelengths can be extracted from the W1 mode into air slot modes using this design, with W1/slot coupling efficiencies of up to 99±1%, and waveguide extracted coupling efficiencies of up to 51±12% demonstrated experimentally. Combining several of these couplers in series, we demonstrate the spectral filtering functionality on-chip. The device therefore combines the well-known sensing function of the slotted waveguide geometry with the spectrometer function, thus uniting two essential biosensor functions in a monolithic device.
Waveguide
Coupled mode theory
Cite
Citations (6)
Directional couplers based on plasmonic waveguides with nano-scale three channels are designed by utilizing mode coupling effect as well as rib-guiding structure. Longitudinal modal transmission-line theory(L-MTLT) is used for simulating the light propagation and optimizing the design parameters. The designed plasmonic coupler operating as power splitter has nano-scale size of about 200~250 nm width. In order to achieve the desired power splitting ratio, the refractive index of guiding modes is evaluated along the width variation of center channel. Finally, a power splitter based on triple rib directional coupler, which ensures maximum power transfer from one outermost guide to the other outermost guide, is designed.
Splitter
Coupled mode theory
Optical power
Cite
Citations (1)
An ultrashort plasmonic directional coupler based on the hybrid metal-insulator slab waveguide is proposed and analyzed at the telecommunication wavelength of 1550 nm. It is first analyzed using the supermode theory based on mode analysis via the transfer matrix method in the interaction region. Then the 2D model of the coupler, including transition arms, is analyzed using a commercial finite-element method simulator. The hybrid slab waveguide is composed of a metallic layer of silver and two dielectric layers of silica (SiO2) and silicon (Si). The coupler is optimized to have a minimum coupling length and to transfer maximum power considering the layer thicknesses as optimization variables. The resulting coupling length in the submicrometer region along with a noticeable power transfer efficiency are advantages of the proposed coupler compared to previously reported plasmonic couplers.
Transfer-matrix method (optics)
Coupled mode theory
Waveguide
Slab
Cite
Citations (11)
This paper presents an in-depth analysis of highly asymmetric grating assisted directional couplers. The directional coupler consists of a polymer waveguide with dimensions and refractive indices closely matching a single-mode fiber fabricated atop a Ga/sub 0.6/Al/sub 0.4/As/GaAs/Ga/sub 0.4/Al/sub 0.6/As waveguide. The structure is investigated analytically by means of a new orthogonal coupled-mode theory formulated in terms of the Lorentz reciprocity theorem. For the first time, the analysis includes three distinct loss mechanisms, namely, the leakage of power toward the semiconductor substrate, the power lost to radiation modes (mode mismatching), and the grating radiation loss.
Coupled mode theory
Waveguide
Reciprocity
Leakage (economics)
Cite
Citations (10)
This chapter contains sections titled: Introduction Qualitative Description of the Operation of Directional Couplers Marcatili's Improved Coupled-Mode Equations Directional Couplers with Uniform Cross Section and Constant Spacing Switched Δβ Couplers Directional Couplers as Optical Filters Intensity Modulators Based on Directional Couplers Normal Mode Theory of Directional Couplers with Two Waveguides Normal Mode Theory of Directional Couplers with Three or More Waveguides Problems References
Coupled mode theory
Section (typography)
Mode (computer interface)
Propagation constant
Cite
Citations (5)
Coupled-mode theory is widely used for the analysis of directional couplers (see, e.g. Ref. 1) as well as diode laser arrays (see, e.g. Ref. 2). In this type of analysis one usually considers a section consisting of two (or more) parallel waveguides situated close enough so that the power transfer among neighboring guides can occur. However, in many cases, such as in Y-coupled arrays3 or as In directional couplers, where the guides must be brought together before the parallel section and then separated at the output end of the coupler, it is also important to consider nonparallel sections of the device.
Coupled mode theory
Section (typography)
Mode (computer interface)
Cite
Citations (0)
We propose short and robust directional couplers designed by shortcuts to adiabaticity, based on Lewis-Riesenfeld invariant theory. The design of directional couplers is discussed by combining invariant-based inverse engineering and perturbation theory. The error sensitivity of the coupler is minimized by optimizing the evolution of dynamical invariant with respect to coupling coefficient/input wavelength variations. The proposed robust coupler devices are verified with beam propagation simulations.
Coupled mode theory
Beam propagation method
Cite
Citations (55)
Coupled mode theory
Mode coupling
Cite
Citations (32)
A three-waveguide coupler, combining directional and contradirectional coupling between the central and side waveguides, respectively, is discussed. Coupled-mode formalism is used to examine the superposed processes both in synchronism and near synchronism. The nature of the solution is shown to depend on the relative coupling strengths of the individual processes. For stronger contradirectional coupling, the power is divided among the three output ports, at ratios closely related to the ratio of the coupling coefficients, and with a nonperiodic, slowly varying length dependence. The coupler can thus be used as a power divider without the need for a precisely special case where the directional and contradirectional coupling coefficients are equal.< >
Synchronism
Waveguide
Formalism (music)
Coupling strength
Cite
Citations (6)