Accession Number : ADP008225

Title :   Theory of Square Meander-Type Couplers,

Corporate Author : HEINRICH-HERTZ-INST FUER NACHRICHTENTECHNIK BERLIN G M B H (GERMANY F R)

Personal Author(s) : Nolting, H.-P.

Report Date : APR 1992

Pagination or Media Count : 4

Abstract : Experimental results on the square meander or grating-assisted co-directional coupler have been published recently. The device was employed as a passive wavelength sensitive multiplexer/demultiplexer and as part of a tunable laser. Theoretical analyses were based on a coupled mode method, but no method to calculate the coupling efficiency from a first principles approach, including the case of strong coupling, has been published so far to the best of our knowledge. As will be shown in this paper, a standard coupled mode approach which is based on the eigenmode of the isolated waveguides, cannot be used for this device. Instead we will describe a method to calculate the period length and the coupling length as a function of the waveguide and grating architecture by using mode matching theory at the boundaries of the grating and mode propagation in the constant waveguide sections in between. This way the exact grating and waveguide architecture is taken into account. This approach is straight forward and leads to a deeper understanding of the physical behavior of the device. A few examples shall demonstrate the usefulness of this calculation method for the design of square meander type couplers. For simplicity we neglect the feeding branches in a first approach, but they can be added in an easy way at a later stage. In an asymmetric coupler most of the energy of the two fundamental modes (even or odd mode, E sub e and E sub o) is concentrated into one of the two waveguides. So energy exchange of waves from one waveguide to the other can be described as coupling from one fundamental mode to the other.

Descriptors :   *TUNABLE LASERS, *WAVEGUIDES, *WAVEGUIDE COUPLERS, BOUNDARIES, COUPLINGS, EFFICIENCY, ENERGY TRANSFER, EXCHANGE, FUNCTIONS, LASERS, MATCHING, PROPAGATION, THEORY, GERMANY.

Subject Categories : Lasers and Masers
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE